MULTI-CELL COx ELECTROLYZER STACKS

Abstract

Various COx electrolyzer multi-cell architectures are provided, including various frame, flow field, gas diffusion layer, and repeat unit designs that may be particularly useful in the context of multi-cell COx electrolyzer cells.

Description

RELATED APPLICATIONS

[0001] An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in its entirety and for all purposes.BACKGROUND

[0002] COx electrolyzers offer a potential route for converting or reducing COx gas, e.g., CO or CO2, into one or more desired carbon-based byproducts, such as industrial chemicals or fuels, thereby allowing for waste COx gas that would normally be released into the atmosphere to instead be converted into industrially useful products.

[0003] Background and contextual descriptions contained herein are provided solely for the purpose of generally presenting the context of the disclosure. Much of this disclosure presents work of the inventors, and simply because such work is described in the background section or presented as context elsewhere herein does not mean that such work is admitted prior art.SUMMARY

[0004] Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims.

[0005] One or more embodiments provide a COx electrolyzer apparatus capable of converting or reducing COx gas into one or more desired byproducts.

[0006] One or more embodiments provide a frame capable of facilitating fluid flow in a COx electrolyzer apparatus.

[0007] One or more embodiments provide a COx electrolyzer apparatus capable of constraining expansion of a plurality of COx electrolyzer cells in an axial direction in an operational state of the COx electrolyzer apparatus.

[0008] Additional aspects will be set forth in the detailed description which follows, and, in part, will be apparent from the disclosure, or may be learned by practice of the inventive concepts.

[0009] According to some embodiments, a COx electrolyzer apparatus (“apparatus”) includes a first end assembly, a second end assembly, a plurality of separator plates, and a plurality of COx electrolyzer cells (“cells”). The second end assembly is coupled to the first end assembly via a plurality of tensioning members. The plurality of COx electrolyzer cells (“cells”) are interposed between the first and second end assemblies and arranged in a stack along an axial direction. Each cell among the cells includes an instance of first components and an instance of second components. The first components include a membrane electrode assembly (“MEA”), a cathode frame, and a cathode flow field. The MEA has a cathodic part, an anodic part, and a separator between the cathodic part and the anodic part. The cathode frame is adjacent to the cathodic part. The cathode flow field is at least partially disposed in a first opening in the cathode frame. The second components include an anode frame adjacent to the anodic part of the MEA and an anode flow field at least partially disposed in a second opening in the anode frame. The cathode and anode frames of adjacent cells among the cells are coupled to one another via a corresponding plurality of frame fasteners with a separator plate among the separator plates interposed therebetween. The frame fasteners are different from the tensioning members.

[0010] In some embodiments, the first components may further include a cathode gas diffusion layer (GDL) adjacent to the cathode frame and covering the cathode flow field. The cathode GDL and the cathode flow field may be configured to guide a flow of gaseous COx across the first opening in a first direction transverse to the axial direction and in a distributed manner with respect to at least a second direction transverse to each of the axial and first directions. The second components may further include an anode porous transport layer (PTL) adjacent to the anode frame and covering the anode flow field. The anode PTL and the anode flow field may be configured to guide a flow of anolyte across the second opening in a third direction transverse to the axial direction and in a distributed manner with respect to at least the second direction.

[0011] In some embodiments, the cathode frame may include the first opening arranged in a central portion of the cathode frame, at least one first fluidic inlet passage fluidically connected to the anodic parts of the cells, at least one first fluidic outlet passage fluidically connected to the anodic parts of the cells, at least one second fluidic inlet passage fluidically connected to the first opening, and at least one second fluidic outlet passage fluidically connected to the first opening.

[0012] In some embodiments, the anode frame may include the second opening arranged in a central portion of the anode frame, at least one third fluidic inlet passage fluidically connected to the second opening, at least one third fluidic outlet passage fluidically connected to the second opening, at least one fourth fluidic inlet passage fluidically connected to the cathodic parts of the cells, and at least one second fluidic outlet passage fluidically connected to the cathodic parts of the cells.

[0013] In some embodiments, each of the separator plates may include a plurality of fastener orifices through which the frame fasteners respectively extend, at least one first hole through which an inlet anolyte flow path extends, at least one second hole through which an outlet anolyte flow path extends, at least one third hole through which an inlet gaseous COx flow path extends, and at least one fourth hole through which an outlet COx reduction byproduct flow path extends.

[0014] In some embodiments, the cathode frame may include a first surface facing the MEA and a second surface facing away from the first surface. The second surface of the cathode frame may include at least one first protrusion through which the at least one first fluidic inlet passage extends, at least one second protrusion through which the at least one first fluidic outlet passage extends, at least one third protrusion through which the at least one second fluidic inlet passage extends, and at least one fourth protrusion through which the at least one second fluidic outlet passage extends.

[0015] In some embodiments, the at least one first protrusion of the cathode frame may be arranged and may be configured to extend through the at least one first hole in a first separator plate among the separator plates and may abut against the anode frame of a first adjacent cell among the cells such that the at least one first fluidic inlet passage of the cathode frame is substantially aligned in the axial direction with the at least one third fluidic inlet passage of the anode frame of the first adjacent cell. The at least one second protrusion of the cathode frame may be arranged and may be configured to extend through the at least one second hole in the first separator plate and may abut against the anode frame of the first adjacent cell such that the at least one first fluidic outlet passage of the cathode frame is substantially aligned in the axial direction with the at least one third fluidic outlet passage of the anode frame of the first adjacent cell. The at least one third protrusion of the cathode frame may be arranged and may be configured to extend through the at least one third hole in the first separator plate and may abut against the anode frame of the first adjacent cell such that the at least one second fluidic inlet passage of the cathode frame is substantially aligned in the axial direction with the at least one fourth fluidic inlet passage of the anode frame of the first adjacent cell. The at least one fourth protrusion of the cathode frame may be arranged and may be configured to extend through the at least one fourth hole in the first separator plate and may abut against the anode frame of the first adjacent cell such that the at least one second fluidic outlet passage of the cathode frame is substantially aligned in the axial direction with the at least one fourth fluidic outlet passage of the anode frame of the first adjacent cell.

[0016] In some embodiments, at least one of the first to fourth protrusions may be sized to form a clearance fit with a corresponding one of the first to fourth holes.

[0017] In some embodiments, the cathode frame may further include a plurality of first cathode fastener orifices arranged about a peripheral area of the cathode frame. The peripheral area may encircle the first opening of the cathode frame. The anode frame may further include a plurality of first anode fastener orifices and a plurality of first swage nuts. The plurality of first anode fastener orifices may be arranged about a peripheral area of the anode frame. The peripheral area of the anode frame may encircle the second opening of the anode frame. The first cathode fastener orifices may be substantially aligned with the first anode fastener orifices in the axial direction. Each first swage nut among the first swage nuts may be disposed in one or the other of a corresponding one of the first anode fastener orifices and a corresponding one of the first cathode fastener orifices. The first swage nuts may be configured to interface with corresponding frame fasteners among the frame fasteners.

[0018] In some embodiments, each of the cathode fastener orifices and anode fastener orifices may be counterbored. The counterbored portions of those cathode fastener orifices and / or anode fastener orifices not including a first swage nut among the first swage nuts may be configured to form a clearance fit with a respective frame fastener among the frame fasteners.

[0019] In some embodiments, the frame fasteners may be shoulder screws.

[0020] In some embodiments, the first components may further include a first support frame and a second support frame. The first support frame may be interposed between the cathode GDL and the cathode frame. The first support frame may include a first frame opening exposing a portion of the cathode GDL to the cathode flow field. The portion of the cathode GDL may abut against the cathode flow field. The second support frame may be interposed between the MEA and the anode PTL. The second support frame may include a second frame opening exposing a portion of the MEA to the anode PTL. The portion of the MEA may abut against the anode PTL. The first support frame, the cathode GDL, the MEA, and the second support frame may form a unitized MEA assembly.

[0021] In some embodiments, the first components may further include a first cathode gasket interposed between the first support frame and the cathode frame. The first cathode gasket may encircle the first opening in the cathode frame to form a first fluidic seal around the cathode flow field. The second components may further include a first anode gasket set. The first anode gasket set may include a first anode gasket, at least one second anode gasket, at least one third anode gasket, at least one fourth anode gasket, and at least one fifth anode gasket. The first anode gasket may be interposed between the second support frame and the anode frame. The first anode gasket may encircle the second opening in the anode frame to form a first fluidic seal around the anode flow field. The at least one second anode gasket may be interposed between the cathode frame and the anode frame. The at least one second anode gasket may encircle the at least one first fluidic inlet passage of the cathode frame and the at least one third fluidic inlet passage of the anode to form at least one fluidic seal. The at least one third anode gasket interposed between the cathode frame and the anode frame, the at least one third anode gasket encircling the at least one first fluidic outlet passage in the cathode frame and the at least one third fluidic outlet passages in the anode frame to form at least one fluidic seal. The at least one fourth anode gasket may be interposed between the cathode frame and the anode frame. The at least one third anode gasket may encircle the at least one second fluidic inlet passage in the cathode frame and the at least one fourth fluidic inlet passage in the anode frame to form at least one fluidic seal. The at least one fifth anode gasket may be interposed between the cathode frame and the anode frame. The at least one fifth anode gasket may encircle the at least one second fluidic outlet passage and the at least one fourth fluidic outlet passage in the anode frame to form at least one fluidic seal.

[0022] In some embodiments, the first components may further include a second cathode gasket interposed between a first separator plate among the separator plates and the cathode frame. The second cathode gasket may encircle the first opening in the cathode frame to form a second fluidic seal around the cathode flow field. The second components may further include a second anode gasket set. The second anode gasket set may include a sixth anode gasket, at least one seventh anode gasket, at least one eighth anode gasket, at least one ninth anode gasket, and at least one tenth anode gasket. The sixth anode gasket may be interposed between the anode frame and a second separator plate among the separator plates. The sixth anode gasket may encircle the second opening in the anode frame to form a second fluidic seal around the anode flow field. The at least one seventh anode gasket may be interposed between the anode frame and the second separator plate. The at least one seventh anode gasket may encircle the at least one first hole in the second separator plate and the at least one third fluidic inlet passage in the anode frame to form at least one fluidic seal. The at least one eighth anode gasket may be interposed between the anode frame and the second separator plate. The at least one eighth anode gasket may encircle the at least one second hole in the second separator plate and the at least one third fluidic outlet passage in the anode frame to form at least one fluidic seal. The at least one ninth anode gasket may be interposed between the anode frame and the second separator plate. The at least one ninth anode gasket may encircle the at least one third hole in the second separator plate and the at least one fourth fluidic inlet passage in the anode frame to form at least one fluidic seal. The at least one tenth anode gasket may be interposed between the anode frame and the second separator plate. The at least one ninth anode gasket may encircle the at least one fourth hole in the second separator plate and the at least one fourth fluidic outlet passage in the anode frame to form at least one fluidic seal.

[0023] In some embodiments, the cells may be formed of a plurality of repeat units. Each repeat unit among the repeat units may include an instance of the first components, an instance of the second components, and the separator plate that may be interposed between the cathode frame of that instance of the first components and the anode frame of that instance of the second components, that separator plate may be interposed between that instance of the first components and that instance of the second components.

[0024] In some embodiments, the first end assembly may include a first end plate and a cathode interface assembly. The cathode interface assembly may include an instance of the first components and a cathode interface separator plate interposed between the first end plate and a first repeat unit among the repeat units. A first end cell may be formed between the cathode interface assembly and the instance of the second components of the first repeat unit. The first end cell may be interposed between the first end plate and the plurality of cells.

[0025] In some embodiments, the first end assembly may further include a first insulation plate, a manifold, and a first bus plate between the first end plate and the cathode interface assembly. The manifold may include at least one first inlet fluidically connected to the anodic parts of the cells via the inlet anolyte flow path, at least one first outlet fluidically connected to the anodic parts of the cells via the outlet anolyte flow path, at least one second inlet fluidically connected to the cathodic parts of the cells via the inlet gaseous COx flow path, and at least one second outlet fluidically connected to the cathodic parts of the cells via the outlet COx reduction byproduct flow path. The first bus plate may be configured to receive a first electric potential. The first insulation plate may be configured to electrically insulate the first end plate from the first bus plate.

[0026] In some embodiments, the first bus plate, the manifold, and the first insulation plate may be sequentially stacked on the cathode interface assembly.

[0027] In some embodiments, the inlet anolyte flow path, the outlet anolyte flow path, the inlet gaseous COx flow path, and the outlet COx reduction byproduct flow path may not extend into the bus plate and the first insulation plate.

[0028] In some embodiments, the first bus plate, the insulation plate, and the manifold may be sequentially stacked on the cathode interface assembly.

[0029] In some embodiments, the first end assembly may further include a capping plate, an inlet runner, and an outlet runner. The inlet and outlet runners may be coupled to the manifold such that the inlet and outlet runners are stacked in the axial direction between the capping plate and the manifold.

[0030] In some embodiments, the inlet anolyte flow path, the outlet anolyte flow path, the inlet gaseous COx flow path, and the outlet COx reduction byproduct flow path may extend through the first insulation plate.

[0031] In some embodiments, the first bus plate may be coupled to the manifold via a plurality of first fasteners different from the tensioning members and the frame fasteners. The first insulation plate may be coupled to the first end plate via a plurality of second fasteners different from the tensioning members, the frame fasteners, and the first fasteners.

[0032] In some embodiments, the first bus plate may be coupled to the first insulation plate via a plurality of first fasteners different from the tensioning members and the frame fasteners. In some embodiments, the first insulation plate may be coupled to the manifold via the first fasteners.

[0033] In some embodiments, the second end assembly may include a second end plate and an anode interface assembly. The anode interface assembly may include an instance of the second components and an anode interface separator plate interposed between a second repeat unit among the repeat units and the second end plate. A second end cell may be formed between the instance of the first components of the second repeat unit and the anode interface assembly. The second end cell may be interposed between the plurality of cells and the second end plate.

[0034] In some embodiments, the second end assembly may further include a second bus plate and a second insulation plate sequentially stacked in the axial direction between the anode interface assembly and the second end plate. The second bus plate may be configured to receive a second electric potential. The second insulation plate may be configured to electrically insulate the second end plate from the second bus plate.

[0035] In some embodiments, the second insulation plate may be coupled to the second end plate via a plurality of third fasteners different from the tensioning members and the frame fasteners.

[0036] In some embodiments, the second end assembly may further include a bladder gasket. The second insulation plate may include a first recess, a second recess, and an orifice. The first recess may be formed in a central portion of the second insulation plate. The second recess may encircle a central region of the central portion. The second recess may support the bladder gasket therein. The orifice may be configured to receive one or more control fluids. The bus plate may be slidably disposed in the first recess and may be configured to abut against the bladder gasket and / or a surface of the first recess facing the bus plate in the axial direction. A distance in the axial direction between the bus plate and the surface of the first recess facing the bus plate in the axial direction may be configured to increase in response to accumulation of the one or more control fluids in an area between the bus plate and the insulation plate that may be fluidically sealed via at least the bladder gasket.

[0037] In some embodiments, the second end plate may include a first main body, a second end plate protrusion extending from the first main body in the axial direction, and a second end plate opening extending into a central portion of the second end plate protrusion in a direction opposite the axial direction and terminating at a recessed surface facing the cells. The second end assembly may further include a piston interposed between the second insulation plate and the second end plate. The piston may include a second main body and a piston protrusion extending from the second main body in the direction opposite the axial direction and terminating at a protruded surface facing the recessed surface. At least a portion of the piston protrusion may be slidably disposed in at least a portion of the second end plate opening.

[0038] In some embodiments, the second end assembly may further include a plurality of biasing members. The piston protrusion may include a plurality of piston protrusion openings extending into the protruded surface in the axial direction. The second end plate may further include a plurality of support protrusions extending in the axial direction from the recessed surface and may be arranged in correspondence with the piston protrusion openings. The biasing members may be respectively supported in the second end plate opening via corresponding support protrusions among the support protrusions such that, in a first compressed state of the second end assembly, the biasing members are compressed between the protruded surface and the recessed surface and respective portions of the support protrusions may at least partially extend into corresponding piston protrusion openings among the piston protrusion openings.

[0039] In some embodiments, the second end plate may further include one or more orifices fluidically connected to the second end plate opening. The one or more orifices may be configured to receive one or more control fluids. The piston protrusion may include a plurality of piston gaskets encircling the piston protrusion and offset from one another in the axial direction. The piston gaskets may interface with one or more inner sidewalls of the second end plate opening such that the second end plate opening, the piston protrusion, and the piston gaskets form a cavity within the second end assembly. A distance in the axial direction between the protruded surface and recessed surface may be configured to increase in response to accumulation of the one or more control fluids in the cavity.

[0040] In some embodiments, the cells may be configured to reduce input gaseous COx into one or more byproducts, and the one or more control fluids and the input gaseous COx may be equivalent.

[0041] In some embodiments, the apparatus may further include a source of gaseous COx. The source may be configured to input the gaseous COx to the cells and the second end assembly at substantially equivalent pressures.

[0042] In some embodiments, the apparatus may further include a source of gaseous COx. The source may be configured to input the gaseous COx to the cells at a first pressure and to the second end assembly at a second pressure. The first and second pressures may, at steady state, be in equilibrium.

[0043] In some embodiments, the apparatus may further include a plurality of datum rods extending in the axial direction along peripheral surfaces of the cells. The second insulation plate may include a plurality of openings configured to respectively support corresponding datum rods among the datums rods therein.

[0044] In some embodiments, the cathode and anode frames may be formed of one or more polymers.

[0045] In some embodiments, the cathode and anode frames may include at least one of polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyamide (PA), poly(methylmethacrylate) (PMMA), polyethylene naphthalate (PEN), polyetherketone (PEK), polyetheretherketone (PEEK), polystyrene (PS), polyetherimide (PEI), polyphenylene sulfide (PPS), polyarylate (PAR), polyether sulfone (PES), cyclic olefin copolymer (COC), polyvinyl alcohol (PVA), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), polychlorotrifluoroethylene (PCTFE), and polyethylene terephthalate glycol (PETG).

[0046] In some embodiments, the separator plates may be formed of one or more metals.

[0047] In some embodiments, the separator plates may include at least one of aluminum, aluminum alloy, copper, copper alloy, tin, tin alloy, titanium, titanium alloy, tungsten, tungsten alloy, zinc, zinc alloy, steel, and stainless steel.

[0048] In some embodiments, when viewed in the axial direction, the tensioning members may encircle the cells such that the cells are spaced apart from the tensioning members.

[0049] According to some embodiments, a COx electrolyzer frame (“frame”) may include a main body portion, an opening, a first fluidic passage, a first recess, a second recess, and a first connecting riser. The main body portion may have a first surface opposing a second surface in an axial direction. The opening may extend through a central region of the main body portion in the axial direction. The first fluidic passage extending through the main body portion in the axial direction. The first recess may be in the first surface. The first recess may be fluidically connected to the opening and may extend in a second direction transverse to the axial direction. The second recess may in the second surface. The second recess may be fluidically connected to the first fluidic passage and may extend in a third direction transverse to the axial direction. The first connecting riser may extend in the axial direction and may be fluidically interposed between the first recess and the second recess such that the opening is fluidically connected to the first fluidic passage.

[0050] In some embodiments, the frame may further include a third recess in the first surface. The third recess may encircle the opening and the first recess.

[0051] In some embodiments, when viewed in the axial direction, the second recess may cross underneath the third recess.

[0052] In some embodiments, the frame may further include a fourth recess in the first surface. The fourth recess may encircle the first fluidic passage.

[0053] In some embodiments, when viewed in the axial direction, the second recess may cross underneath the fourth recess.

[0054] In some embodiments, the frame may further include a fifth recess in the second surface and encircling the opening. When viewed in the axial direction, the first recess may cross above the fifth recess.

[0055] In some embodiments, the first recess may include a proximal end, a distal end, and a plurality of sidewalls connecting the proximal end and the distal end to one another. A first sidewall among the sidewalls may extend in a first oblique direction with respect to the second direction. A second sidewall among the sidewalls may extend in a second oblique direction with respect to the second direction. The second oblique direction may be different from the first oblique direction.

[0056] In some embodiments, the first connecting riser may extend into the proximal end of the first recess, and the distal end of the first recess may extend into the opening.

[0057] In some embodiments, the frame may further include a plurality of protrusions extending in the axial direction from a surface of the first recess. The surface may be recessed from the first surface.

[0058] In some embodiments, at least one of the protrusions may have a different cross-sectional area than at least another one of the protrusions.

[0059] In some embodiments, the protrusions may include one or more first protrusions, one or more second protrusions, and at least one third protrusion. The one or more first protrusions may have respective first cross-sectional areas in a plane perpendicular to the axial direction. The one or more second protrusions may have respective second cross-sectional areas in the plane perpendicular to the axial direction. The second cross-sectional areas may be respectively smaller than the first cross-sectional areas. The at least one third protrusion may have a third cross-sectional area in the plane perpendicular to the axial direction. The third cross-sectional area may be smaller than each of the second cross-sectional areas. The one or more second protrusions may be disposed closer to the proximal end of the first recess than each of the one or more first protrusions and the at least one third protrusion. A majority of the one or more first protrusions may be disposed closer to the opening than each of the one or more second protrusions and the at least one third protrusion. The at least one third protrusion may be disposed between the one or more second protrusions and the majority of the one or more first protrusions.

[0060] In some embodiments, the third recess may include first sides extending generally in the second direction, and second sides extending between the first sides. Each of the second sides may include a first portion extending in a fourth direction transverse to the axial and second directions, a second portion extending from a first side of the first portion in a third oblique direction forming a first angle with the fourth direction, a third portion arcuately extending between and connecting the second portion to one of the first sides, a fourth portion extending from a second side of the first portion in a fourth oblique direction forming a second angle with the fourth direction, and a fifth portion arcuately extending between and connecting the fourth portion to another one of the first sides.

[0061] In some embodiments, the frame may further include a second fluidic passage extending through the main body portion in the axial direction, and a third fluidic passage extending through the main body portion in the axial direction. Within the frame, the second and third fluidic passages may be fluidically isolated from the first fluidic passage and the opening.

[0062] In some embodiments, the frame may further include a first protrusion extending from the second surface in the axial direction. The first fluidic passage, the second recess, and the first connecting riser may be formed in the first protrusion.

[0063] In some embodiments, the frame may further include a second protrusion extending from the second surface in the axial direction, and a third protrusion extending from the second surface in the axial direction. The second fluidic passage may extend through the second protrusion, and the third fluidic passage may extend through the third protrusion.

[0064] In some embodiments, the second fluidic passage may be arranged adjacent to a first side of the first fluidic passage. The third fluidic passage may be arranged adjacent to a second side of the first fluidic passage. The second side of the first fluidic passage may oppose the first side of the first fluidic passage in a fourth direction transverse to the axial direction and the second direction.

[0065] In some embodiments, the frame may further include a sixth recess in the first surface. The sixth recess may be fluidically connected to the first connecting riser and a proximal end of the first recess. The sixth recess may extend in a fourth direction transverse to the axial direction and the second direction.

[0066] In some embodiments, the frame may further include a second fluidic passage, a seventh recess, and a second connecting riser. The second fluidic passage may extend through the main body portion in the axial direction. The seventh recess may be in the second surface. The seventh recess may be fluidically connected to the second fluidic passage and may extend in a fifth direction transverse to the axial direction. The second connecting riser may extend in the axial direction and may be fluidically interposed between the seventh recess and the first recess such that the opening is fluidically connected to the second fluidic passage. The first connecting riser may be fluidically connected to a first side of the sixth recess. The second connecting riser may be fluidically connected to a second side of the sixth recess opposing the first side of the sixth recess in the fourth direction.

[0067] In some embodiments, the first recess may be one of a plurality of first recesses in the first surface that extend parallel to one another in the second direction.

[0068] In some embodiments, the first recesses may include a first group of the first recesses, a second group of the first recesses, and a third group of the first recesses. The first recesses of the first group may be spaced apart from one another according to a first pitch. The second group of the first recesses may be arranged adjacent to a first side of the first group of the first recesses. The first recesses of the second group may be spaced apart from one another according to a second pitch different from the first pitch. The third group of the first recesses may be arranged adjacent to a second side of the first group of the first recesses. The first recesses of the third group may be spaced apart from one another according to a third pitch different from the first and second pitches.

[0069] In some embodiments, the first pitch may be a constant pitch, the second pitch may be a first variable pitch, and the third pitch may be a second variable pitch.

[0070] In some embodiments, the first and second variable pitches may increase in size with increasing distance from the first group of the first recesses.

[0071] In some embodiments, the second recess may be one of a plurality of second recesses in the second surface extending parallel to one another in the third direction.

[0072] In some embodiments, the seventh recess may be one of a plurality of seventh recesses in the second surface extending parallel to one another in the fifth direction, and the third and fifth directions may extend obliquely with respect to the second direction.

[0073] In some embodiments, the frame may further include a third fluidic passage, a fourth fluidic passage, eighth recesses, and ninth recesses. The third fluidic passage may extend through the main body portion in the axial direction and may being separated from the first fluidic passaged by a first septal wall. The fourth fluidic passage may extend through the main body portion in the axial direction and may be separated from the second fluidic passaged by a second septal wall. The eighth recesses may be in the second surface and may extend parallel to one another in a sixth direction. The eighth recesses may be fluidically interposed between the third fluidic passage and the first connecting riser such that the third fluidic passage is fluidically connected to the opening. The ninth recesses may be in the second surface and may extending parallel to one another in a seventh direction. The ninth recesses may be fluidically interposed between the fourth fluidic passage and the second connecting riser such that the fourth fluidic passage is fluidically connected to the opening.

[0074] In some embodiments, the third direction may form a first oblique angle with respect to the second direction, the fifth direction may form a second oblique angle with respect to the second direction, the second oblique angle may be different from the first oblique angle, the sixth direction may form a third oblique direction with respect to the second direction, the third oblique angle may be different from the first and second oblique angles, the ninth direction may forms a fourth oblique direction with respect to the second direction, and the fourth oblique angle may be different from the first to third oblique angles.

[0075] In some embodiments, the first oblique angle may be greater than the third oblique angle, the second oblique angle may be greater than the fourth oblique angle, an absolute value of the first and second oblique angles may be substantially equivalent, and an absolute value of the third and fourth oblique angles may be substantially equivalent.

[0076] In some embodiments, the frame may further include a tenth recess in the second surface, an eleventh recess in the second surface, and a twelfth recess in the first surface. The fourth recess may encircle the first fluidic passage and the third fluidic passage. The tenth recess may encircle the first fluidic passage, the third fluidic passage, the second recesses, the eighth recesses, and the first connecting riser. The eleventh recess may encircle the second fluidic passage, the fourth fluidic passage, the seventh recesses, the ninth recesses, and the second connecting riser. The twelfth recess may encircle the second fluidic passage and the fourth fluidic passage. When viewed in the axial direction, the second recesses and the eighth recesses may cross underneath the fourth recess, and the seventh recesses and the ninth recesses may cross underneath the twelfth recess.

[0077] In some embodiments, the frame may further include a fifth fluidic passage extending through the main body portion in the axial direction. Within the frame, the fifth fluidic passage may be fluidically isolated from the first fluidic passage, the second fluidic passage, and the opening.

[0078] In some embodiments, the first fluidic passage may be arranged adjacent to a first side of the fifth fluidic passage. The second fluidic passage may be arranged adjacent to a second side of the fifth fluidic passage. The second side of the fifth fluidic passage may oppose the first side of the fifth fluidic passage in the fourth direction.

[0079] In some embodiments, the frame may further include a plurality of first fastener orifices arranged in a peripheral area of the main body portion and encircling the opening.

[0080] In some embodiments, the frame may further include a plurality of second fastener orifices arranged in an intermediate area interposed between the first opening and the peripheral area. A pitch between adjacent second fastener orifices among the second fastener orifices may be smaller than a pitch between adjacent first fastener orifices among the first fastener orifices.

[0081] In some embodiments, the first and second fastener orifices may be counterbored.

[0082] In some embodiments, the frame may be formed of one or more polymers.

[0083] In some embodiments, the frame may include at least one of polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyamide (PA), poly(methylmethacrylate) (PMMA), polyethylene naphthalate (PEN), polyetherketone (PEK), polyetheretherketone (PEEK), polystyrene (PS), polyetherimide (PEI), polyphenylene sulfide (PPS), polyarylate (PAR), polyether sulfone (PES), cyclic olefin copolymer (COC), polyvinyl alcohol (PVA), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), polychlorotrifluoroethylene (PCTFE), and polyethylene terephthalate glycol (PETG).

[0084] According to some embodiments, a COx electrolyzer apparatus (“apparatus”) includes a first end assembly, a second end assembly, and a plurality of COx electrolyzer cells (“cells”). The second end assembly is coupled to the first end assembly. The plurality of COx electrolyzer cells (“cells”) are interposed between the first end assembly and the second end assembly and arranged in a stack along an axial direction. Each cell among the cells is configured to reduce input gaseous COx into one or more byproducts. In an operational state of the COx electrolyzer apparatus in which the cells reduce the input gaseous COx into the one or more byproducts, the second end assembly is configured to expand in the axial direction in response to accumulation of one or more control fluids in an internal cavity of the second end assembly. The expansion of the second end assembly is configured to constrain expansion of the cells in the axial direction. A flow path of the one or more control fluids is fluidically connected to a flow path of the input gaseous COx.

[0085] In some embodiments, each cell among the cells may include a membrane electrode assembly (“MEA”), a cathode frame, a cathode flow field, a cathode gas diffusion layer (GDL), an anode frame, an anode flow field, and an anode porous transport layer (PTL). The MEA may have a cathodic part, an anodic part, and a separator between the cathodic part and the anodic part. The cathode frame may be adjacent to the cathodic part. The cathode flow field may be at least partially disposed in a first opening in the cathode frame. The cathode GDL may be adjacent to the cathode frame and may cover the cathode flow field. The anode frame may be adjacent to the anodic part of the MEA. The anode flow field may be at least partially disposed in a second opening in the anode frame. The anode PTL may be adjacent to the anode frame and may cover the anode flow field.

[0086] In some embodiments, the second end assembly may include a first plate, a first gasket, and a second plate. The first plate may include a recess in a central portion of the first plate, a second recess encircling a central region of the central portion, and a first orifice configured to receive one or more control fluids. The first gasket may be at least partially disposed in the second recess. The second plate may be slidably disposed in the first recess and may be configured to abut against the first gasket and / or a recessed surface of the first recess facing the second plate in the axial direction such that the first recess, the first gasket, and the second plate define a cavity internal to the second end assembly. A distance in the axial direction between the second plate and the recessed surface of the first recess may be configured to increase in response to the accumulation of the one or more control fluids in the cavity.

[0087] In some embodiments, the second plate may be a first bus plate configured to receive a first electric potential, and the first plate may be an insulation plate configured to electrically insulate the first bus plate from at least one other component of the first and / or second end assemblies.

[0088] In some embodiments, the second end assembly may further include a second end plate. The first plate may be interposed between the second plate and the second end plate.

[0089] In some embodiments, the first insulation plate may be coupled to the second end plate via a plurality of first fasteners.

[0090] In some embodiments, the first orifice may be formed in the recessed surface and may extend through the first plate in the axial direction.

[0091] In some embodiments, the second end plate may include a second orifice having a proximal end fluidically connected to the first orifice in the first plate and a distal end fluidically connected to a fluidic inlet coupling.

[0092] In some embodiments, the first and second orifices may be substantially aligned in the axial direction.

[0093] In some embodiments, the apparatus may further include a gasket interposed between the first plate and the second end plate. The gasket may encircle the first and second orifices to form a fluidic seal.

[0094] In some embodiments, the second end assembly may include a first plate, a piston, and one or more gaskets. The first plate may include a first main body, a first protrusion extending from the first main body in the axial direction, a first blind opening extending into a central portion of the first protrusion in a second direction opposite the axial direction, and at least one first orifice fluidically connected to the first blind opening and configured to receive one or more control fluids. The piston may include a second main body and a second protrusion extending from the second main body in the second direction, at least a portion of the second protrusion may be slidably received in at least a portion of the first blind opening in the first protrusion. The one or more gaskets may encircle the second protrusion and may be configured to interface with one or more outer sidewalls of the second protrusion and one or more inner sidewalls of the first blind opening such that the first opening, the second protrusion, and the at least one gasket define a cavity internal to the second end assembly. The first blind opening may terminate at a first recessed surface. The second protrusion may terminate at a first protruded surface facing the first recessed surface in the second direction. A distance in the axial direction between the first protruded surface and the first recessed surface may be configured to increase in response to the accumulation of the one or more control fluids in the cavity.

[0095] In some embodiments, the one or more gaskets may be a plurality of gaskets, and the gaskets may be offset from one another in the axial direction.

[0096] In some embodiments, the second protrusion may include one or more recesses extending into the one or more outer sidewalls of the second protrusion in one or more directions transverse to the axial direction. The one or more gaskets may be respectively supported in corresponding recesses among the one or more recesses.

[0097] In some embodiments, the second end assembly may further include a plurality of biasing members, the second protrusion may further include a plurality of second blind openings extending into the first protruded surface in the axial direction, and the first plate may further include a plurality of third protrusions extending from the first recessed surface in the axial direction. The biasing members may be respectively supported in the first blind opening via corresponding third protrusions among the third protrusions such that, in a first compressed state of the second end assembly, the biasing members may be compressed between the first protruded surface and the first recessed surface and respective portions of the third protrusions may at least partially extend into corresponding second blind openings among the second blind openings.

[0098] In some embodiments, respective widths of the second blind openings in a direction perpendicular to the axial direction may be greater than respective widths of the third protrusions in the direction perpendicular to the axial direction.

[0099] In some embodiments, respective heights of the third protrusions from the first recessed surface in the axial direction may be greater than respective depths of the second blind openings from the first protruded surface in the axial direction.

[0100] In some embodiments, the first plate may be a second end plate of the apparatus configured to be coupled to the first end plate via a plurality of tensioning members extending in the axial direction.

[0101] In some embodiments, the second end assembly may further include an insulation plate and a first bus plate sequentially stacked in the axial direction from the piston such that the first bus plate and the insulation plate are interposed between the cells and the piston. The first bus plate may be configured to receive a first electric potential. The insulation plate may be configured to electrically insulate the first bus plate from at least one other component of the second end assembly and / or the first end plate.

[0102] In some embodiments, the first bus plate and the insulation plate may be coupled to the piston via a plurality of fasteners.

[0103] In some embodiments, the at least one first orifice may be a plurality of first orifices configured to receive one or more control fluids.

[0104] In some embodiments, in the operational state of the apparatus, the cavity may be dead-headed.

[0105] In some embodiments, the first plate may further include at least one second orifice fluidically connected to the first blind opening. The at least one second orifice may be configured to bleed off excess accumulation of the one or more control fluids in the cavity in response to the accumulation of the one or more control fluids exceeding a predefined threshold.

[0106] In some embodiments, the one or more control fluids and the input gaseous COx may be substantially equivalent.

[0107] In some embodiments, the apparatus may further include at least one source configured to input the gaseous COx to the cells at a first pressure and the one or more control fluids to the second end assembly at a second pressure. The first and second pressures may be substantially equivalent.

[0108] In some embodiments, the apparatus may further include at least one source configured to input the gaseous COx to the cells at a first pressure and the one or more control fluids to the second end assembly at a second pressure. At steady state, the first and second pressures may be in equilibrium.

[0109] In some embodiments, the at least one source may be configured to input the gaseous COx to the cells and the one or more control fluids to the second end assembly substantially simultaneously.

[0110] In some embodiments, the at least one source may be configured to delay the input of the one or more control fluids with respect to the input of the gaseous COx.

[0111] In some embodiments, the at least one source may be configured to delay the input of the one or more control fluids until the expansion of the cells reaches a defined threshold.

[0112] In some embodiments, the flow path of the one or more control fluids may not be routed through the cells.

[0113] The foregoing general description and the following detailed description are illustrative and explanatory and are intended to provide further explanation of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Various embodiments disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements.

[0115] FIG. 1 depicts a diagram of an example MEA for use in COx reduction.

[0116] FIG. 2 depicts a CO2 electrolyzer configured to receive water and CO2 as a reactant at a cathode and expel CO as a byproduct.

[0117] FIG. 3 depicts an example construction of a CO2 reduction MEA having a cathode catalyst layer, an anode catalyst layer, and an anion-conducting PEM.

[0118] FIG. 4 depicts an example construction of a CO reduction MEA having a cathode catalyst layer, an anode catalyst layer, and an anion-conducting PEM.

[0119] FIG. 5 depicts an exploded view of an example multi-cell COx electrolyzer stack.

[0120] FIG. 6 depicts a perspective view of the example multi-cell COx electrolyzer of FIG. 5.

[0121] FIGS. 7 and 8 depict side views of the example multi-cell COx electrolyzer of FIG. 6.

[0122] FIG. 9 depicts a cross-sectional view of the example multi-cell COx electrolyzer of FIG. 7 taken along sectional line 9-9.

[0123] FIG. 10 depicts a cross-sectional view of the example multi-cell COx electrolyzer of FIG. 8 taken along sectional line 10-10.

[0124] FIG. 11A depicts an exploded view of an example repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6.

[0125] FIG. 11B depicts an exploded view of some cathode components of another example repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6.

[0126] FIG. 11C depicts a cross-sectional view of the cathode components of the example repeat unit of FIG. 11B.

[0127] FIG. 11D depicts an exploded view of anode components of the example repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6.

[0128] FIG. 11E depicts a cross-sectional view of the anode components of the example repeat unit of FIG. 11D.

[0129] FIG. 12 depicts a plan view of an example manifold block of the example multi-cell COx electrolyzer of FIG. 6.

[0130] FIGS. 13, 14, 15, and 16 depict side views of the example manifold block of FIG. 12.

[0131] FIG. 17 depicts an exploded view of an example cathode interface assembly of the example multi-cell COx electrolyzer stack of FIG. 6.

[0132] FIG. 18 depicts the example cathode interface assembly of FIG. 17 in a non-exploded state.

[0133] FIG. 19 depicts an exploded view of an illustrative COx electrolyzer cell of the example multi-cell COx electrolyzer stack of FIG. 6.

[0134] FIG. 20 depicts a bottom view of a representative repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6.

[0135] FIG. 21 depicts a cross-sectional view of the representative repeat unit of FIG. 20 taken along sectional line 21-21.

[0136] FIG. 22 depicts a cross-sectional view of the representative repeat unit of FIG. 20 taken along sectional line 22-22.

[0137] FIGS. 23 and 24 depict enlarged portions of the cross-sectional view of FIG. 22.

[0138] FIG. 25 depicts a perspective view of the example unitized MEA assembly of the example multi-cell COx electrolyzer stack of FIG. 6.

[0139] FIG. 26 depicts a top view of the example unitized MEA assembly of FIG. 25.

[0140] FIG. 27 depicts a cross-sectional view of the example unitized MEA assembly of FIG. 26 taken along sectional line 27-27.

[0141] FIG. 28 depicts a first perspective view of an example cathode frame.

[0142] FIG. 29 depicts a bottom view of the example cathode frame of FIG. 28.

[0143] FIGS. 30 and 31 depict enlarged portions of the example cathode frame of FIG. 28.

[0144] FIG. 32 depicts a second perspective view of the example cathode frame of FIG. 28.

[0145] FIG. 33 depicts a top view of the example cathode frame of FIG. 32.

[0146] FIG. 34 depicts a cross-sectional view of the example cathode frame of FIG. 33 taken along sectional line 34-34.

[0147] FIG. 35 depicts an enlarged portion of the example cathode frame of FIG. 33.

[0148] FIG. 36 depicts a cross-sectional view of the example cathode frame of FIG. 35 taken along sectional line 36-36.

[0149] FIG. 37 depicts a first perspective view of an example anode frame.

[0150] FIG. 38 depicts a top view of the example cathode frame of FIG. 37.

[0151] FIG. 39 depicts a second perspective view of the example anode frame of FIG. 37.

[0152] FIG. 40 depicts a bottom view of the example anode frame of FIG. 39.

[0153] FIG. 41 depicts an enlarged portion of the example anode frame of FIG. 38.

[0154] FIG. 42 depicts an enlarged portion of the example anode frame of FIG. 40

[0155] FIG. 43 depicts a plan view of an example separator plate of the representative repeat unit of FIG. 11A.

[0156] FIG. 44 depicts an example anode interface separator of FIG. 47.

[0157] FIGS. 45 and 46 depict top and bottom plan views of an example cathode interface separator of the example cathode interface assembly of FIG. 18.

[0158] FIG. 47 depicts an exploded view of an example anode interface assembly of the example multi-cell COx electrolyzer stack of FIG. 6.

[0159] FIG. 48 depicts the example anode interface assembly of FIG. 47 in an assembled state.

[0160] FIG. 49 depicts an example of a cathode flow field with a single serpentine channel.

[0161] FIG. 50 depicts a diagram of an example multiple serpentine channel arrangement.

[0162] FIG. 51 depicts a diagram of another example multiple serpentine channel arrangement.

[0163] FIG. 52 depicts an example of a cathode flow field that includes a two-channel multiple serpentine channel arrangement.

[0164] FIGS. 53, 54, and 55 depict an example cathode flow field that may be used in some implementations.

[0165] FIGS. 56, 57, and 58 depict an example cathode flow field that may be used in some implementations.

[0166] FIG. 59 depicts an example of a cathode flow field that has four cathode serpentine channels arranged in a multiple serpentine channel arrangement

[0167] FIG. 60 depicts a cross-sectional view of a cathode flow field with square- or rectangular-cross-section serpentine channels.

[0168] FIG. 61 shows a cross-sectional view of a cathode flow field with a plurality of square- or rectangular-cross-section serpentine channels with rounded interior bottom edges.

[0169] FIG. 62 shows a cross-sectional view of a cathode flow field with a plurality of U-shaped cross-section serpentine channels.

[0170] FIG. 63 depicts an example of a cathode flow field with peninsular walls having variable wall thickness.

[0171] FIG. 64 depicts a plan view of a simplified representation of an example cathode flow field.

[0172] FIG. 65 depicts a cathode flow field with two zones and a boundary.

[0173] FIG. 66 depicts a cathode flow field with serpentine channels arranged in a bilaterally symmetric manner.

[0174] FIG. 67 depicts the same cathode flow field as in FIG. 66 in a scaled-up, broken view manner to allow various features to be more easily labeled and seen.

[0175] FIG. 68 depicts another cathode flow field with serpentine channels arranged in a bilaterally symmetric manner.

[0176] FIG. 69 depicts the same cathode flow field as in FIG. 68 in a scaled-up, broken view manner to allow various features to be more easily labeled and seen.

[0177] FIG. 70 depicts an example of a cathode flow field with a parallel channel arrangement.

[0178] FIG. 71 depicts a schematic of an example parallel channel flow field.

[0179] FIG. 72 depicts an example of a branching parallel channel flow field.

[0180] FIG. 73 depicts the same branching channel flow field as in FIG. 72 but in enlarged form and with the middles of the parallel channels omitted by way of a break section.

[0181] FIG. 74 depicts a schematic of another example of a branching parallel channel flow field.

[0182] FIG. 75 depicts a schematic of yet another example of a branching parallel channel flow field.

[0183] FIG. 76 depicts an example of a cathode flow field that features branching parallel channels.

[0184] FIG. 77 depicts a detail view of the left and right sides of the upper half of the cathode flow field of FIG. 76, with the remainder of the flow field omitted from view.

[0185] FIG. 78 depicts an example of a cathode flow field with an interdigitated channel arrangement.

[0186] FIG. 79 depicts a side view of a gas diffusion layer.

[0187] FIG. 80 depicts a flowchart of an example process to form a pre-compressed stack of gas diffusion layers.

[0188] FIG. 81 depicts a partial cross-sectional view of an example apparatus to form a pre-compressed stack of gas diffusion layers.

[0189] FIG. 82 depicts a partial cross-sectional view of an example roll-to-roll system to form a pre-compressed stack of gas diffusion layers.

[0190] FIG. 83 depicts a plan view of a portion of an illustrative anode flow field of the example multi-cell COx electrolyzer of FIG. 6.

[0191] FIGS. 84A and 84B depict respective cross-sectional views of the illustrative anode flow field of FIG. 83 taken along sectional lines 84A-84A and 84B-84B according to some embodiments.

[0192] FIG. 85A depicts a plan view of a portion of an illustrative anode flow field of the example multi-cell COx electrolyzer of FIG. 6.

[0193] FIGS. 85B and 85C depict respective cross-sectional views of the illustrative anode flow field of FIG. 85A taken along sectional lines 85B-85B and 85C-85C according to some embodiments.

[0194] FIG. 86 depicts a plan view of an illustrative insulation plate of the example multi-cell COx electrolyzer of FIG. 6.

[0195] FIG. 87 depicts a cross-sectional view of the illustrative insulation plate of FIG. 86 taken along sectional line 87-87.

[0196] FIG. 88 depicts a plan view of an illustrative end plate of the example multi-cell COx electrolyzer of FIG. 6.

[0197] FIG. 89 depicts a cross-sectional view of the illustrative end plate of FIG. 88 taken along sectional line 89-89.

[0198] FIG. 90 depicts an enlarged portion of the cross-sectional view of FIG. 9

[0199] FIG. 91 depicts a perspective view of an example multi-cell COx electrolyzer stack.

[0200] FIGS. 92 and 93 depict respective side views of the example multi-cell COx electrolyzer stack of FIG. 91.

[0201] FIGS. 94 and 95 depict respective cross-sectional views the example multi-cell COx electrolyzer stack of FIG. 91 respectively taken along sectional lines 94-94 and 95-95.

[0202] FIG. 96 depicts a perspective view of an example port side assembly of the example multi-cell COx electrolyzer stack of FIG. 91.

[0203] FIGS. 97 and 98 depict top and bottom plan views of an example manifold block of the example port side assembly of FIG. 96.

[0204] FIGS. 99 and 100 depict bottom and top plan views of an example insulation plate of the example port side assembly of FIG. 96.

[0205] FIG. 101 depicts a perspective view of an example piston side assembly of the example multi-cell COx electrolyzer stack of FIG. 91 in an exploded state.

[0206] FIG. 102 depicts a top plan view of the example piston side assembly of FIG. 101 in an assembled state.

[0207] FIG. 103 depicts a cross-sectional view of the example piston side assembly of FIG. 102 taken along sectional line 103-103.

[0208] FIG. 104 depicts a perspective view of an example end plate of the example piston side assembly of FIG. 101.

[0209] FIGS. 105 and 106 depict a top and bottom plan views of the example end plate of FIG. 104.

[0210] FIG. 107 depicts a perspective view of an example piston of the piston side assembly of FIG. 101.

[0211] FIGS. 108 and 109 depict top and bottom plan views of the example piston of FIG. 107.DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0212] COx electrolyzers, e.g., CO2 electrolyzers, using membrane electrode assemblies may share some structural similarities with existing polymer electrolyte membrane (PEM) water electrolyzers, although there are several respects in which COx electrolyzers may differ significantly from such PEM water electrolyzer systems.

[0213] In a typical COx electrolyzer, a membrane electrode assembly (MEA) may be one of multiple elements that are stacked together in what may be referred to as a “cell”; in the discussion below, the term “cell” is used to refer to this multi-element assembly.

[0214] An example MEA 100 for use in COx reduction is shown in FIG. 1. The MEA 100 has a cathode layer 120 and an anode layer 140 separated by an ion-conducting polymer layer 160 that provides a path for ions to travel between the cathode layer 120 and the anode layer 140. In certain embodiments, the cathode layer 120 includes an anion-conducting polymer and / or the anode layer 140 includes a cation-conducting polymer. In certain embodiments, the cathode layer 120 and / or the anode layer 140 of the MEA 100 are porous. The pores may facilitate gas and / or fluid transport and may increase the amount of catalyst surface area that is available for reaction.

[0215] The ion-conducting layer 160 may, for example, include two or three sublayers: a polymer electrolyte membrane (PEM) 165, an optional cathode buffer layer 125, and / or an optional anode buffer layer 145. One or more layers in the ion-conducting layer 160 may be porous. In certain embodiments, at least one layer is nonporous so that reactants and products of the cathode cannot pass via gas and / or liquid transport to the anode and vice versa. In certain embodiments, the PEM layer 165 is nonporous. Example characteristics of anode buffer layers and cathode buffer layers are provided elsewhere herein. In some cases, the ion-conducting layer 160 includes only a single layer or two sublayers.

[0216] FIG. 2 shows CO2 electrolyzer 203 configured to receive water (H2O) and CO2 (e.g., humidified or dry gaseous CO2) as a reactant at a cathode 205 and expel CO as a product. Electrolyzer 203 is also configured to receive water as a reactant at an anode 207 and expel gaseous oxygen (O2). Electrolyzer 203 includes bipolar layers having an anion-conducting polymer 209 adjacent to cathode 205 and a cation-conducting polymer 211 (illustrated as a proton-exchange membrane) adjacent to anode 207.

[0217] As illustrated in the magnification inset of a bipolar interface 213 in electrolyzer 203, the cathode 205 includes an anion exchange polymer (which, in this example, is the same anion-conducting polymer 209 that is in the bipolar layers), electronically conducting carbon support particles 217, and metal nanoparticles 219 supported on the support particles. CO2 and water are transported via pores (such as pore 221) and reach metal nanoparticles 219 where they react, in this case with hydroxide (OH) ions, to produce bicarbonate (HCO3) ions and reduction reaction products (not shown). CO2 may also reach metal nanoparticles 219 by transport within anion exchange polymer 209.

[0218] Hydrogen ions are transported from anode 207, and through the cation-conducting polymer 211, until they reach bipolar interface 213, where they are hindered from further transport toward the cathode 205 by anion exchange polymer 209. At interface 213, the hydrogen ions may react with bicarbonate or carbonate ions to produce carbonic acid (H2CO3), which may decompose to produce CO2 and water. As explained herein, the resulting CO2 may be provided in gas phase and may be provided with a route in the MEA back to the cathode 205 where it can be reduced. The cation-conducting polymer 211 hinders transport of anions, such as bicarbonate ions, to the anode 207 where they could react with protons and release CO2, which would be unavailable to participate in a reduction reaction at the cathode 205.

[0219] As illustrated, a cathode buffer layer having an anion-conducting polymer may work in concert with the cathode 205 and its anion-conductive polymer to block transport of protons to the cathode 205. While MEAs employing ion conducting polymers of appropriate conductivity types in the cathode 205 and cathode buffer layer may hinder transport of cations to the cathode 205 and, if present, an anode buffer layer may similarly hinder transport of the anions to the anode 207, cations and anions may still come in contact in the MEA's interior regions, such as in the membrane layer.

[0220] As illustrated in FIG. 2, bicarbonate and / or carbonate ions combine with hydrogen ions between the cathode layer and the anode layer to form carbonic acid, which may decompose to form gaseous CO2. It has been observed that MEAs sometimes delaminate, possibly due to this production of gaseous CO2, which does not have an easy egress path.

[0221] The delamination issue can be addressed by employing a cathode buffer layer having inert filler and associated pores. One possible explanation of its effectiveness is that the pores create paths for the gaseous carbon dioxide to escape back to the cathode 205 where it can be reduced. In some embodiments, the cathode buffer layer is porous, but at least one layer between the cathode layer and the anode layer is nonporous. This can prevent the passage of gases and / or bulk liquid between the cathode and anode layers while preventing delamination. For example, the nonporous layer can prevent the direct passage of water from the anode 207 to the cathode 205. The porosity of various layers in an MEA is described further at other locations herein.Examples of Bipolar MEAs

[0222] As an example, an MEA includes a cathode layer including a reduction catalyst and a first anion-conducting polymer (e.g., Sustainion, FumaSep FAA-3, or Tokuyama anion exchange polymer), an anode layer including an oxidation catalyst and a first cation-conducting polymer (e.g., PFSA polymer), a membrane layer including a second cation-conducting polymer and arranged between the cathode layer and the anode layer to conductively connect the cathode layer and the anode layer, and a cathode buffer layer including a second anion-conducting polymer (e.g., Sustainion, FumaSep FAA-3, or Tokuyama anion exchange polymer) and arranged between the cathode layer and the membrane layer to conductively connect the cathode layer and the membrane layer. In this example, the cathode buffer layer can have a porosity between about 1 and 90 percent by volume but can additionally or alternatively have any suitable porosity (including, e.g., no porosity). In other examples the cathode buffer layer can have any suitable porosity (e.g., between 0.01-95%, 0.1-95%, 0.01-75%, 1-95%, 1-90%, etc.).

[0223] Too much porosity can lower the ionic conductivity of the buffer layer. In some embodiments, the porosity is 20% or below, and in particular embodiments, between 0.1-20%, 1-10%, or 5-10%. Porosity in these ranges can be sufficient to allow movement of water and / or CO2 without losing ionic conductivity. Porosity may be measured as described further below.

[0224] In a related example, the membrane electrode assembly can include an anode buffer layer that includes a third cation-conducting polymer, and is arranged between the membrane layer and the anode layer to conductively connect the membrane layer and the anode layer. The anode buffer layer preferably has a porosity between about 1 and 90 percent by volume, but can additionally or alternatively have any suitable porosity (including, e.g., no porosity). However, in other arrangements and examples, the anode buffer layer can have any suitable porosity (e.g., between 0.01-95%, 0.1-95%, 0.01-75%, 1-95%, 1-90%). As with the cathode buffer layer, in some embodiments, the porosity is 20% or below, e.g. 0.1-20%, 1-10%, or 5-10%.

[0225] In an example, an anode buffer layer may be used in an MEA having a cathode catalyst layer with anion exchange polymer, a cathode buffer layer with anion-exchange polymer, a membrane with cation-exchange polymer, and an anode buffer layer with anion-exchange polymer. In such a structure, the anode buffer layer may be porous to facilitate water transport to the membrane / anode buffer layer interface. Water will be split at this interface to make protons that travel through the membrane and hydroxide that travels to the anode catalyst layer. In some cases, at least one catalyst (e.g., a carbon catalyst, a metal catalyst, etc.) may be utilized to promote the splitting of the water at this interface. For instance, the at least one catalyst may include a cobalt-based catalyst, an iron-nickel-based catalyst, a palladium-based catalyst, platinum-based catalyst, ruthenium (IV) dioxide (RuO2), nickel-stabilized, ruthenium dioxide (Ni—RuO2), iridium (IV) dioxide (IrO2), graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphitic carbon nitride (g-C3N4), graphene quantum dots (GQDs), graphene quantum sheets (GQSs), and / or the like. One advantage of this structure is the potential use of low-cost water oxidation catalysts (e.g., NiFeOx) that are only stable in basic conditions.

[0226] In another specific example, the membrane electrode assembly includes a cathode layer including a reduction catalyst and a first anion-conducting polymer (e.g., Sustainion, FumaSep FAA-3, Tokuyama anion exchange polymer), an anode layer including an oxidation catalyst and a first cation-conducting polymer, a membrane layer including a second anion-conducting polymer (e.g., Sustainion, FumaSep FAA-3, Tokuyama anion exchange polymer) and arranged between the cathode layer and the anode layer to conductively connect the cathode layer and the anode layer, and an anode buffer layer including a second cation-conducting polymer and arranged between the anode layer and the membrane layer to conductively connect the anode layer and the membrane layer.

[0227] An MEA containing an anion-exchange polymer membrane and an anode buffer layer containing cation-exchange polymer may be used for CO reduction. In this case, water would form at the membrane / anode buffer layer interface. Pores in the anode buffer layer could facilitate water removal. One advantage of this structure would be the use of an acid-stable (e.g., IrOx) water oxidation catalyst.

[0228] In a related example, the membrane electrode assembly can include a cathode buffer layer that includes a third anion-conducting polymer and is arranged between the cathode layer and the membrane layer to conductively connect the cathode layer and the membrane layer. The third anion-conducting polymer can be the same or different from the first and / or second anion-conducting polymer. The cathode buffer layer preferably has a porosity between about 1 and 90 percent by volume but can additionally or alternatively have any suitable porosity (including, e.g., no porosity). However, in other arrangements and examples, the cathode buffer layer can have any suitable porosity (e.g., between 0.01-95%, 0.1-95%, 0.01-75%, 1-95%, 1-90%). In some embodiments, the porosity is 20% or below, and in particular embodiments, between 0.1-20%, 1-10%, or 5-10%.

[0229] In an example, a cathode catalyst layer composed of Au nanoparticles 4 nm in diameter supported on Vulcan XC72 or XC72R carbon and mixed with TM1 (mTPN-1) anion exchange polymer electrolyte may be used. The cathode catalyst layer may be about 15 μm thick, have a gold to gold+carbon ratio by weight (Au / (Au+C)) of 20%, have a TM1 to catalyst mass ratio of 0.32, have mass loading of 1.4-1.6 mg / cm2 (total Au+C), and have estimated porosity of 0.56. In another example, an anion-exchange polymer layer composed of TM1 and PTFE particles may be provided. The PTFE particles may be approximately 200 nm in diameter and the TM1 molecular weight may be approximately 30 k-45 k. The thickness of such an example anion-exchange polymer layer may be about 15 μm, and the PTFE particles may introduce a porosity of about 8%. A proton-exchange membrane layer composed of perfluorosulfonic acid polymer (e.g., Nafion 115 or Nafion 117) may also be provided, with a thickness of approximately 100 μm to approximately 200 μm. The proton-exchange membrane may form a continuous layer that prevents significant movement of gas (CO2, CO, H2) through the layer. An anode catalyst layer composed of Ir or IrOx nanoparticles (100-200 nm aggregates) that is 10 μm thick may also be provided.COx Anion Exchange Membrane-Only MEA for COx Reduction

[0230] In some embodiments, an MEA does not contain a cation-conducting polymer layer. In such embodiments, the electrolyte is not a cation-conducting polymer and the anode, if it includes an ion-conducting polymer, does not contain a cation-conducting polymer. Various examples thereof are provided below.

[0231] An AEM-only MEA allows conduction of anions across the MEA. In embodiments in which none of the MEA layers has significant conductivity for cations, hydrogen ions have limited mobility in the MEA. In some implementations, an AEM-only membrane provides a neutral or an alkaline pH environment (e.g., at least about pH 7) and may facilitate CO2 and / or CO reduction by suppressing the hydrogen evolution parasitic reaction at the cathode. As with other MEA designs, the AEM-only MEA allows ions, notably anions such as hydroxide, bicarbonate, or carbonate ions, to move through polymer-electrolyte. The pH may be lower in some embodiments; a pH of 4 or greater may be sufficient to suppress hydrogen evolution. The AEM-only MEA also permits electrons to move to, and through, metal and carbon in catalyst layers. In embodiments, the AEM-only MEA may include pores in the anode layer, pores in the cathode layer, and / or pores in the PEM, thereby permitting liquids and gas to move through such pores.

[0232] In certain embodiments, the AEM-only MEA comprises an anion-exchange polymer electrolyte membrane positioned between a cathode and an anode. The cathode and the anode are each electrocatalyst layers. In some embodiments, one or both electrocatalyst layers also contain anion-exchange polymer-electrolyte.

[0233] In certain embodiments, an AEM-only MEA is formed by depositing cathode and anode electrocatalyst layers onto porous conductive supports, such as gas diffusion layers, porous transport layers, and / or the like, to form gas diffusion electrodes (GDEs). An anion-exchange membrane is then sandwiched between the gas diffusion electrodes.

[0234] In certain embodiments, an AEM-only MEA is used for CO2 reduction. The use of an anion-exchange polymer electrolyte avoids a low pH environment that disfavors CO2 reduction. Further, water is transported away from the cathode catalyst layer when an AEM is used, thereby preventing water build up (flooding) which can block reactant gas transport in the cathode of the cell.

[0235] Water transport in the MEA occurs through a variety of mechanisms, including diffusion and electro-osmotic drag. In some embodiments, at current densities of the CO2 electrolyzers described herein, electro-osmotic drag is the dominant mechanism. Water is dragged along with ions as they move through the polymer electrolyte. For a cation-exchange membrane such as Nafion membrane, the amount of water transport is well characterized and understood to rely on the pre-treatment / hydration of the membrane. Protons move from positive to negative potential (anode to cathode) with each carrying 2-4 water molecules with it, depending on pretreatment.

[0236] In certain embodiments, an AEM-only MEA may be employed in CO reduction reactions. Unlike the CO2 reduction reaction, CO reduction does not produce carbonate or bicarbonate anions that could transport to the anode and release valuable reactant.

[0237] FIG. 3 illustrates an example construction of a CO2 reduction MEA 301 having a cathode catalyst layer 303, an anode catalyst layer 305, and an anion-conducting PEM 307. In certain embodiments, cathode catalyst layer 303 may include metal catalyst particles (e.g., nanoparticles) that are unsupported or supported on a conductive substrate such as carbon particles. In some implementations, cathode catalyst layer 303 additionally includes an anion-conducting polymer. The metal catalyst particles may catalyze CO2 reduction, particularly at or within a non-acidic environment. In certain embodiments, anode catalyst layer 305 includes metal oxide catalyst particles (e.g., nanoparticles) that are unsupported or supported on a conductive substrate such as metal oxides, carbides, etc. In some implementations, the anode catalyst layer 305 may additionally include an anion-conducting polymer. Examples of metal oxide catalyst particles for anode catalyst layer 305 may include iridium oxide, nickel oxide, nickel iron oxide, iridium ruthenium oxide, platinum oxide, and the like. The anion-conducting PEM 307 may include any of various anion-conducting polymers such as, for example, HNN5 / HNN8 by Ionomr, FumaSep by Fumatech, TM1 by Orion, PAP-TP by W7energy, Sustainion by Dioxide Materials, and the like. These and other anion-conducting polymers that have an ion exchange capacity (IEC) ranging from 1.1 to 2.6, working pH ranges from 0-14, limited solubility in some organic solvents, reasonable thermal stability and mechanical stability, good ionic conductivity / ASR, and acceptable water uptake / swelling ratio may be used. The polymers may be chemically exchanged to certain anions, such as bicarbonate, carbonate, etc., instead of halogen anions prior to use.

[0238] As illustrated in FIG. 3, CO2, such as CO2 gas, may be provided to cathode catalyst layer 303. In certain embodiments, the CO2 may be provided via a gas diffusion electrode. At the cathode catalyst layer 303, the CO2 reacts to produce a reduction product indicated generically as CxOyHz. Anions produced at the cathode catalyst layer 303 may include hydroxide, carbonate, and / or bicarbonate. These may diffuse, migrate, or otherwise move to the anode catalyst layer 305. At the anode catalyst layer 305, an oxidation reaction may occur such as oxidation of water or hydroxide ion to produce diatomic oxygen and hydrogen ions or water. In some applications, the hydrogen ions may react with hydroxide, carbonate, and / or bicarbonate to produce water, carbonic acid, and / or CO2. In some cases, fewer interfaces may provide lower resistance for the reaction(s) to occur. In some embodiments, a relatively highly basic environment (e.g., at least a pH above 7) is maintained for C2 and C3 hydrocarbon synthesis.

[0239] FIG. 4 illustrates an example construction of a CO reduction MEA 401 having a cathode catalyst layer 403, an anode catalyst layer 405, and an anion-conducting PEM 407. Overall, the constructions of MEA 401 may be similar to that of MEA 301 in FIG. 3. However, the cathode catalyst may be chosen to promote a CO reduction reaction, which means that different reduction catalysts would be used in CO and CO2 reduction embodiments.

[0240] In some embodiments, an AEM-only MEA may be advantageous for CO reduction. The water uptake number of the AEM material can be selected to help regulate moisture at the catalyst interface, thereby improving CO availability to the catalyst. AEM-only membranes can be favorable for CO reduction due to this reason. Bipolar membranes can be more favorable for CO2 reduction due to better resistance to CO2 dissolving and crossover in basic anolyte media.

[0241] In various embodiments, cathode catalyst layer 403 may include metal catalyst particles (e.g., nanoparticles) that are unsupported or supported on a conductive substrate such as carbon particles. In some implementations, cathode catalyst layer 403 may additionally include an anion-conducting polymer. In certain embodiments, anode catalyst layer 405 includes metal oxide catalyst particles (e.g., nanoparticles) that are unsupported or supported on a conductive substrate such as metal oxides, carbides, etc. In some implementations, the anode catalyst layer 405 may additionally include an anion-conducting polymer. Examples of metal oxide catalyst particles for anode catalyst layer 405 may include those identified for the anode catalyst layer 305 of FIG. 3. Anion-conducting PEM 407 may include any of various anion-conducting polymers such as, for example, those identified for the PEM 307 of FIG. 3.

[0242] As illustrated in FIG. 4, CO gas may be provided to cathode catalyst layer 403. In certain embodiments, the CO may be provided via a gas diffusion electrode. At the cathode catalyst layer 403, the CO may react to produce a reduction product indicated generically as CxOyHz.

[0243] Anions produced at the cathode catalyst layer 403 may include hydroxide ions. These may diffuse, migrate, or otherwise move to the anode catalyst layer 405. At the anode catalyst layer 405, an oxidation reaction may occur such as oxidation of water or hydroxide ion to produce diatomic oxygen and hydrogen ions or water. In some applications, the hydrogen ions may react with hydroxide ions to produce water.

[0244] While the general configuration of the MEA 401 is similar to that of MEA 301, there are certain differences in the MEAs. For CO2 reduction, a significant amount of CO2 may be dissolved and then transferred to the anode for an AEM-only MEA such as shown in FIG. 3. For CO reduction, there is less likely to be significant CO gas crossover. In this case, the reaction environment for CO reduction could be more basic than the reaction environment for CO2 reduction. MEA materials, including the catalyst, may be selected to have good stability in high pH environments.Example of AEM-Only MEA

[0245] 1. Copper metal (40 nm thick Cu, about 0.05 mg / cm2) was deposited onto a porous carbon sheet (Sigracet 39BC gas diffusion layer) via electron beam deposition. Ir metal nanoparticles were deposited onto a porous titanium sheet at a loading of 3 mg / cm2 via drop casting or ultrasonic spray deposition. An anion-exchange membrane from Ionomr (25-50 μm, 80 mS / cm2 OH— conductivity, 2-3 mS / cm2 HCO3− conductivity, 33-37% water uptake) was sandwiched between the porous carbon and titanium sheets with the electrocatalyst layers facing the membrane.

[0246] 2. Sigma Aldrich 80 nm spherical Cu nanoparticles, mixed with FAA-3 anion exchange solid polymer electrolyte from Fumatech, FAA-3 to catalyst mass ratio of 0.10, setup as described above.

[0247] U.S. Patent Application Publication No. US 2017 / 0321334, published Nov. 9, 2017, and U.S. Patent Application Publication No. 20190226103, published Jul. 25, 2019, which describe various features and examples of MEAs, are incorporated herein by reference in their entireties. All publications referred to herein are incorporated by reference in their entireties as if fully set forth herein.Multi-Cell COx Electrolyzer Stacks

[0248] While the above discussion has provided a general overview of various aspects of COx MEA construction and characteristics, the following discussion is intended to address aspects of multi-cell COx electrolyzer stacks.

[0249] FIG. 5 depicts an exploded view of an example multi-cell COx electrolyzer stack. FIG. 6 depicts a perspective view of the example multi-cell COx electrolyzer of FIG. 5. FIGS. 7 and 8 depict side views of the example multi-cell COx electrolyzer of FIG. 6. FIG. 9 depicts a cross-sectional view of the example multi-cell COx electrolyzer of FIG. 7 taken along sectional line 9-9. FIG. 10 depicts a cross-sectional view of the example multi-cell COx electrolyzer of FIG. 8 taken along sectional line 10-10. FIG. 11A depicts an exploded view of an illustrative repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6. FIG. 17 depicts an exploded view of a cathode interface assembly of the example multi-cell COx electrolyzer stack of FIG. 6. FIG. 19 depicts an exploded view of an illustrative COx electrolyzer cell of the example multi-cell COx electrolyzer stack of FIG. 6.

[0250] As seen in FIGS. 5-11A, 17, and 19, multi-cell COx electrolyzer stack (or stack) 500 includes a plurality of COx electrolyzer cells (or cells), such as cell 501, formed by stacking a plurality of repeat units 503 (individually referenced as repeat units 503_1 to 503_n, where “n” is an integer greater than or equal to one) between cathode interface assembly 505 of port side assembly 507 and anode interface assembly 509 of bladder side assembly 511. In this manner, any given cell among the plurality of COx electrolyzer cells may be formed by the conjunction of 1) cathode interface assembly 505 (which includes MEA 1105) and anode components 1101 of repeat unit 503_1; 2) cathode components 1103 (which include MEA 1105) of a first repeat unit (e.g., repeat unit 503_1) and anode components 1101 of a second repeat unit (e.g., repeat unit 503_2) adjacent to the first repeat unit; or 3) cathode components 1103 of repeat unit 503_n and anode interface assembly 509. Accordingly, the MEA of any given cell among the plurality of COx electrolyzer cells may be configured to facilitate a COx reduction process, such as described in association with one or more of FIGS. 1 to 4.

[0251] Port side assembly 507 may include cathode interface assembly 505, bus (or terminal) plate 513, manifold assembly 515, insulation plate 517, and end plate 519 sequentially stacked from a first side of the plurality of repeat units 503 in a first direction, e.g., an axial direction, which may extend parallel to the z-axis direction. Among other functions, port side assembly 507 may at least be configured to provide one or more reactants to the cells to feed the COx reduction process and output one or more byproducts from the cells in association therewith. Bladder side assembly 511 may include anode interface assembly 509, bus (or terminal) plate 521, insulation plate 523, and end plate 525 sequentially stacked from a second side of the plurality of repeat units 503 in a second direction opposite the first direction. Among other functions, bladder side assembly 511 may be at least configured to constrain axial expansion of the cells during the COx reduction process in a manner that prevents or reduces the likelihood of the plurality of cells from being overly compressed, but maintains corresponding fluidic seals and electrical conductivity between associated components of stack 500.

[0252] Respective end plates 519 and 525 of port side assembly 507 and bladder side assembly 511 may be coupled to one another via a plurality of tensioning members 527 (e.g., anchors, bolts, studs, tie rods, etc.) extending in the axial direction. As such, end plates 519 and 525 may include respectively pluralities of fastener orifices 519h and 525h through which tensioning members 527 may pass. In some embodiments, fastener orifices 519h and 525h may be respectively arranged about corresponding peripheral regions of end plates 519 and 525. It is also noted that end plates 519 and 525 may be formed of any suitable material, such as aluminum, magnesium, titanium, and / or the like. Tensioning members 527 may be at least partially threaded to respectively engage with, for instance, threaded fasteners 529 (e.g., nuts, rivets, etc.). In this manner, a clamping force extending in the axial direction may be applied to the plurality of cells via the conjunction of end plates 519 and 525, tensioning members 527, and threaded fasteners 529. As such, end plates 519 and 525 may generally serve to act as load-spreading members that distribute a clamping load relatively evenly over the other elements of stack 500. In some instances, first washers 531 may be respectively disposed between the heads of tensioning members 527 and upper surface 519a of end plate 519, and second washers 533 may be respectively disposed between lower surface 525b of end plate 525 and threaded fasteners 529. It is contemplated that one or more of first washers 531 may be formed as lock washers and / or respectively integrated with the heads of tensioning members 527 such as in the case of flanged bolts. Similarly, one or more of second washers 533 may be formed as lock washers and / or respectively integrated with threaded fasteners 529 such as in the case of flanged nuts.

[0253] Bus plates 513 and 521 are respectively provided with terminal portions 513t and 521t protruding outwardly from corresponding peripheral surfaces and may be respectively connected to a power supply. In some cases, terminal portions 513t and 521t may have, for example, lugs, terminal blocks, and / or other electrical connection mechanisms to facilitate electrical connections between bus plates 513 and 521 and a corresponding positive or negative voltage or current source. For example, terminal portion 513t on a cathode side of stack 500 may be connected to a negative electrode of the power supply, and terminal portion 521t on an anode side of the stack 500 may be connected to a positive electrode of the power supply. In this manner, bus plates 513 and 521 may provide common electrical connections for the plurality of cells of stack 500, such as cell 501, and, thereby, enable an electrical potential or current to be generated across the plurality of cells of stack 500 that may drive the reduction and oxidation reactions within the plurality of cells. For instance, when an electrical potential difference is imposed on the plurality of cells of stack 500 through application of a voltage or current across bus plates 513 and 521, the resulting electrical potential difference may cause an oxidation reaction at the anode sides of the cells (e.g., oxidation of water to molecular oxygen) and a reduction reaction at the cathode sides of the cells, e.g., that converts the COx into carbon monoxide, a hydrocarbon, and / or other catalyst-specific byproducts. As will become more apparent below, bus plate 513 may be sized so as not to interfere with various fluidic passages through stack 500.

[0254] According to various embodiments, bus plates 513 and 521 may be formed of a first electrically conductive material, e.g., aluminum, iron, nickel, lead, steel, zinc, and / or the like, and may be coated (or plated) with a second, more electrically conductive coating material, e.g., silver plating, gold plating, copper plating, or other material with relatively higher electrical conductivity, to provide a higher level of electrical conductivity between bus plates 513 and 521 and the corresponding flow fields (e.g., anode and cathode flow fields 1111 and 1127) of the respective cells of stack 500.

[0255] Bus plate 513 may, for example, be electrically insulated from end plate 519 by insulation plate 517 and / or at least one other layer of electrically insulating material. As shown, insulation plate 517 is disposed between the electrically conductive portion of bus plate 513 and end plate 519, and may include a plurality of fastener orifices 517h through which tensioning members 527 may pass. In some cases, electrical insulation between bus plate 513 and end plate 519 may be additionally or alternatively provided by manifold assembly 515 when, for instance, manifold assembly 515 is formed of an electrically non-conductive material. Further, electrical insulation may be additionally or alternatively provided by forming (or bonding) electrically insulating material on (or to) a surface of bus plate 513 facing end plate 519, a surface of end plate 519 facing bus plate 513, or at least one surface of manifold assembly 515 facing end plate 519 or end plate 525. Regardless of how such electrical insulation is provided, bus plate 513 may be electrically insulated from end plate 519. When, however, end plate 519 is made of an electrically non-conductive material, or in which end plate 519 is otherwise electrically isolated from, for example, bus plate 521 and / or end plate 525, insulation plate 517 (or other electrically insulating material) may be omitted.

[0256] Similar to bus plate 513, bus plate 521 may be electrically insulated from end plate 525 by insulation plate 523 and / or at least one other layer of electrically insulating material that may act in a similar manner as insulation plate 517 with respect to bus plate 513 and end plate 519, but with respect to end plate 525 and bus plate 521. Similar to insulation plate 517, insulation plate 523 may include a plurality of fastener orifices 523h through which tensioning members 527 may pass. In some embodiments, electrical insulation may be additionally or alternatively provided by forming (or bonding) electrically insulating material on (or to) a surface of bus plate 521 facing end plate 525 and / or a surface of end plate 525 facing bus plate 521. In some implementations, insulation plate 523 (or other electrically insulating material) may be omitted if end plate 525 is otherwise electrically isolated from bus plate 521. It is also contemplated that bus plate 521 may be allowed to come into electrically conductive contact with end plate 525 in those instances when the various components of the cells of stack 500 are otherwise configured to maintain electrical insulation between bus plates 513 and 521 other than a conductive path through the various MEAs of the plurality of cells. However, as will become more apparent below, insulation plate 523 may be utilized in association with bus plate 521 to constrain (e.g., actively constrain) axial expansion of the plurality of cells of stack 500. It is noted that an example configuration of insulation plate 523 will be described in more detail in association with FIGS. 86 and 87.

[0257] According to some embodiments, insulation plate 523 may be coupled to end plate 525 via a plurality of first fasteners 535. Similarly, insulation plate 517 may be coupled to end plate 519 via a plurality of second fasteners 537. Further, bus plate 513 may be coupled to manifold assembly 515 via a plurality of third fasteners 539. First, second, and third fasteners 535, 537, and 539 may be any suitable fastening mechanism, such as flathead machine screws, rivets, etc., but embodiments are not limited thereto.Manifold Assembly

[0258] FIG. 12 depicts a bottom plan view of an example manifold block of the example multi-cell COx electrolyzer of FIG. 6. FIGS. 13-16 depict side views of the example manifold block of FIG. 12. It is noted that hidden internal features of the manifold block (or main body) 541 that would otherwise not be visible in the view of FIG. 12 are shown in dashed-line format.

[0259] In general (and with continued reference to FIGS. 5-10), manifold assembly 515 may be configured to provide one or more reactants to the plurality of cells to feed the COx reduction process. For instance, in a COx electrolyzer, an anolyte (e.g., liquid water) may be provided to the anode sides of the plurality of cells of stack 500 during operation, while a catholyte (e.g., gaseous COx, such as CO and / or CO2), may be provided to the cathode sides of the cells. In some implementations, an aqueous solution may be provided in place of water, and references to water herein may be understood to also be inclusive of the use of an aqueous solution as well. The liquid water may, through an electrolysis reaction on the anode sides of the cells, undergo oxidation to create oxygen (O2) gas, H+ protons, and electrons. The H+ protons may be drawn through the MEAs (such as MEA 1105 in FIG. 11A) of the plurality of cells due to an electromagnetic field that is present within the cells due to the electrical potential that is applied across the cells via bus plates 513 and 521 and may react with the bicarbonate and / or hydroxide and / or formate that is produced at the cathode sides of the cells. Manifold assembly 515 may also be configured to allow one or more byproducts of a COx reduction process to be expelled from the cells. Thus, as will become more apparent below, manifold assembly 515 may include (or define), for example, at least a portion of one or more fluidic inlet passages and at least a portion of one or more fluidic outlet passages that may be used to convey fluid to and from the anode and cathode sides of the plurality of cells of stack 500.

[0260] Referring to FIGS. 5-10 and 12-16, manifold assembly 515 may include main body 541, first fluidic inlet connectors (or couplings) 543, first fluidic outlet connectors 545, second fluidic inlet connector 547, and second fluidic outlet connector 549. Main body 541 may be a generally rectangular plate-shaped body having first surface 1201 opposing second surface 1203 in the axial direction. Although main body 541 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. When assembled as part of stack 500, first surface 1201 may face end plate 525 and interface with bus plate 513 and cathode interface assembly 505, whereas second surface 1203 may face end plate 519 and interface with insulation plate 517. First and second surfaces 1201 and 1203 may be bounded by third, fourth, fifth, and sixth surfaces 1205, 1207, 1209, and 1211. It is noted, however, that embodiments are not limited to the aforementioned configuration, and main body 541 may be formed having any other suitable geometric configuration with corresponding bounding surfaces.

[0261] In some embodiments, main body 541 includes first fluidic inlet ports 1213 and 1215 in third and fourth surfaces 1205 and 1207, respectively, that are configured to interface with first fluidic inlet connectors (or inlet connectors) 543, first fluidic outlet ports (or outlet ports) 1217 and 1219 in third and fourth surfaces 1205 and 1207, respectively, that are configured to interface with first fluidic outlet connectors (or outlet connectors) 545, second fluidic inlet port (or inlet port) 1221 in fifth surface 1209 that is configured to interface with second fluidic inlet connector (or inlet connector) 547, and second fluidic outlet port (or outlet port) 1223 in sixth surface 1211 that is configured to interface with second fluidic outlet connector (or outlet connector) 549. As such, first and second inlet and outlet ports 1213-1223 may include corresponding threaded regions, such as threaded region 1215t of first fluidic inlet port 1215 and threaded region 1221t of second fluidic inlet port 1221, to engage with respective threaded regions of first and second fluidic inlet and outlet connectors 543-549. Alternatively, first and second fluidic inlet and outlet connectors 543-549 may be respectively welded, e.g., sweat welded, to first and second inlet and outlet ports 1213-1223 or otherwise coupled to first and second inlet and outlet ports 1213-1223.

[0262] First fluidic inlet ports 1213 and 1215 may be fluidically connected to corresponding third fluidic outlet ports in first surface 1201 via respective connecting passages. For instance, first fluidic inlet port 1215 may be fluidically connected to third fluidic outlet port 1225 via connecting passage 1227. Similarly, first fluidic outlet ports 1217 and 1219 may be fluidically connected to corresponding third fluidic inlet ports in first surface 1201 via respective connecting passages. For instance, first fluidic outlet port 1217 may be fluidically connected to third fluidic inlet port 1229 via connecting passage 1231. Third fluidic outlet and inlet ports 1225 and 1229 respectively include a plurality of orifices fluidically connected to one another via corresponding connecting passages. For example, third fluidic outlet port 1225 may include first and second outlet orifices 1225a and 1225b fluidically connected to one another via connecting passage 1233, whereas third fluidic inlet port 1229 may include first and second inlet orifices 1229a and 1229b fluidically connected to one another via connecting passage 1235. Likewise, second fluidic inlet and outlet ports 1221 and 1223 may be fluidically connected to corresponding fourth fluidic outlet and inlet ports 1237 and 1239 in first surface 1201 via respective connecting passages 1241 and 1243. Accordingly, the conjunction of first fluidic inlet ports 1213 and 1215, respective connecting passages (e.g., connecting passage 1227), and corresponding third fluidic outlet ports (e.g., third fluidic outlet port 1225) may be configured to provide water to inlet passages 1001 and 1003 of stack 500. The conjunction of first fluidic outlet ports 1217 and 1219, respective connecting passages (e.g., connecting passage 1235), and corresponding third fluidic inlet ports (e.g., third fluidic inlet port 1229) may be configured to allow water to be expelled from outlet passages of stack 500. It is noted that the outlet passages of stack 500 may be similar to inlet passages 1001 and 1003, but may terminate at first fluidic outlet connectors 545 versus initiate at first fluidic inlet connectors 543. Further, the conjunction of second fluidic inlet port 1221, connecting passage 1241, and fourth fluidic outlet port 1237 may be configured to provide gaseous COx to inlet passage 901 of stack 500, whereas the conjunction of second fluidic outlet port 1223, connecting passage 1243, and fourth fluidic inlet port 1239 may be configured to expel one or more byproducts of the COx reduction process from outlet passage 903 of stack 500.

[0263] In some embodiments, first surface 1201 of main body 541 may include recessed region 1245 configured to receive at least a portion of bus plate 513 therein when manifold assembly 515 is incorporated as part of stack 500. Recessed region 1245 may include one or more portions (e.g., portions 1245a and 1245b) either of which may receive terminal portion 513t of bus plate 513 therein. Additionally, recessed region 1245 may include one or more threaded openings 1247 extending into main body 541 that are configured to threadedly engage with third fasteners (e.g., flatheaded machine screws) 539, which may be utilized to couple bus plate 513 to manifold assembly 515. In some embodiments, threaded openings 1247 may be provided as blind openings including, for instance, swage nuts pressed and / or clinched into main body 541 in a manner that third fasteners 539 engage with the swage nuts. Further, when manifold assembly 515 is incorporated as part of stack 500 and at least a portion of bus plate 513 is received in recessed region 1245, respective fluidic seals may be formed between third fluidic outlet and inlet ports 1225 and 1229 and corresponding ports (or openings) in cathode interface assembly 505 via gaskets 553. Similarly, respective fluidic seals may be formed between fourth fluidic outlet and inlet ports 1237 and 1239 and corresponding ports of cathode interface assembly 505 via gaskets 555.

[0264] Main body 541 may further include recesses 1249 and 1251 in third surface 1205 and recess 1253 in fifth surface 1209 to allow datum rods 557 of stack 500 to extend from, for instance, insulation plate 523 in the axial direction and at least partially into corresponding recesses 1249-1253. During assembly of stack 500, datum rods 557 may be utilized to maintain alignment between components of stack 500. In some cases, external surfaces of datum rods 557 may optionally abut against outer surfaces of the plurality of repeat units 503, cathode interface assembly 505, anode interface assembly 509, and / or recesses 1249-1253 of manifold assembly 515.Repeat Unit

[0265] FIG. 20 depicts a bottom view of a representative repeat unit of the example multi-cell COx electrolyzer stack of FIG. 6. FIG. 21 depicts a cross-sectional view of the representative repeat unit of FIG. 20 taken along sectional line 21-21. FIG. 22 depicts a cross-sectional view of the representative repeat unit of FIG. 20 taken along sectional line 22-22. FIGS. 23 and 24 depict enlarged portions of the cross-sectional view of FIG. 22.

[0266] Referring to FIGS. 11A and 20-24, representative repeat unit (or repeat unit) 1100 may include separator plate 1107 at least partially stacked between anode components 1101 and cathode components 1103. Anode components 1101 may include anode PTL 1109, anode flow field 1111, first anode gasket set 1113, anode frame 1115, and second anode gasket set 1117. In some embodiments, anode components 1101 may further include anode annular insert 1118 (see FIGS. 11B and 11C). It is noted that various anode components, such as first and second anode gasket sets 1113 and 1117 are not shown in FIGS. 11B and 11C for illustrative convenience. Cathode components 1103 may not only include MEA unit 1119 having MEA 1105 and cathode GDL 1121 stacked between first and second support frames 1123 and 1125, but may also include cathode flow field 1127, first cathode gasket 1129, cathode frame 1131, and second cathode gasket 1133. In some embodiments, cathode components 1103 may further include cathode annular insert 1134 (see FIGS. 11D and 11E). It is noted that various cathode components, such as MEA 1105, first and second support frames 1123 and 1125, and first and second cathode gasket sets 1129 and 1133 are not shown in FIGS. 11B and 11C for illustrative convenience.

[0267] According to various embodiments, anode frame 1115 may be coupled to cathode frame 1131 via any suitable fastening mechanism(s), e.g., anchors, bolts, nuts, rivets, screws, and / or the like. For instance, anode frame 1115 may be coupled to cathode frame 1131 via swage (or press) nuts 1135 pressed and / or clinched into anode frame 1115 and fasteners 1137 (e.g., shoulder screws), which interface with cathode frame 1131 and extend through separator plate 1107 to engage with swage nuts 1135. In some embodiments, swage nuts 1135 may be pressed and / or clinched into cathode frame 1131 versus anode frame 1115 such that fasteners 1137 interface with anode frame 1115 and extend through separator plate 1107 to engage swage nuts 1135 of cathode frame 1131. It is also contemplated that a first some of swage nuts 1135 may be pressed and / or clinched into anode frame 1115 and a second some of swage nuts 1135 may be pressed and / or clinched into cathode frame 1131 such that a corresponding first some of fasteners 1137 interface with cathode frame 1131 and extend through separator plate 1107 to engage with the first some of swage nuts 1135 and a corresponding second some of fasteners 1137 interface with anode frame 1115 and extend through separator plate 1107 to engage the second some of swage nuts 1135 of cathode frame 1131. Hereinafter, it will be assumed that swage nuts 1135 are incorporated as part of anode frame 1115 and fasteners 1137 interface with cathode frame 1131 and extend through separator plate 1107 to engage swage nuts 1135 of anode frame 1115. In this manner, second anode gasket set 1117 may be interposed between anode frame 1115 and separator plate 1107, whereas second cathode gasket 1133 may be interposed between separator plate 1107 and cathode frame 1131.

[0268] As can be seen in FIGS. 20-24, at least a portion of anode PTL 1109 and anode flow field 1111 may be supported in one or more openings in anode frame 1115, whereas cathode flow field 1127 and at least a portion of unitized MEA assembly 1119 may be supported in one or more openings in cathode frame 1131. In this manner, first cathode gasket 1129 may be interposed between cathode frame 1131 and unitized MEA assembly 1119 to encircle, encompass, circumscribe, surround, and / or the like (hereinafter “encircle”) cathode flow field 1127 and bulged portion 1123c (see FIGS. 25-27) of support frame 1123. First anode gasket 1113a of first anode gasket set 1113 may not only be interposed between anode frame 1115 and anode PTL 1109, but may also encircle anode flow field 1111. Second and third anode gaskets 1113b and 1113c of first anode gasket set 1113 may interface with anode frame 1115 to form fluidic seals with an adjacent repeat unit or cathode interface assembly 505, as will become more apparent below.

[0269] According to various embodiments, when repeat unit 1100 is assembled, anode flow field 1111 may be supported in at least one opening in anode frame 1115 such that a first surface of anode flow field 1111 abuts against a corresponding surface of anode PTL 1109 and a second surface of anode flow field 1111 abuts against a corresponding surface of separator plate 1107. In those instances when repeat unit 1100 includes anode annular insert 1118, anode annular insert 1118 may be at least partially supported in at least one opening in anode frame 1115 and may encircle anode flow field 1111. To this end, at least a portion of first surface 1118a (e.g., a top surface) of anode annular insert 1118 may abut against one or more corresponding surfaces of a unitized MEA assembly stacked between two adjacent repeat units or a unitized MEA assembly of cathode interface assembly 505. At least a portion of second surface 1118b (e.g., a bottom surface) of anode annular insert 1118 opposing first surface 1118a may abut against a corresponding surface of anode frame 1115. Additional features and effects of anode annular insert 1118 will be described later in association with anode frame 1115. Similarly, when repeat unit 1100 is assembled, cathode flow field 1127 may be supported in at least one opening in cathode frame 1131 such that a first surface of cathode flow field 1127 abuts against a corresponding surface of separator plate 1107 and a second surface of cathode flow field 1127 at least abuts against a corresponding surface of cathode GDL 1121, which may be exposed by an opening 1123a (see FIGS. 25-27) in support frame 1123 of unitized MEA assembly 1119. In those instances when repeat unit 1100 includes cathode annular insert 1134, cathode annular insert 1134 may be at least partially supported in at least one opening in cathode frame 1131 and may encircle cathode flow field 1127. To this end, at least a portion of first surface 1134a (e.g., a top surface) of cathode annular insert 1134 may abut against a corresponding surface of cathode frame 1131, and at least a portion of second surface 1134b (e.g., a bottom surface) of cathode annular insert 1134 opposing first surface 1134a may abut against one or more corresponding surfaces of a unitized MEA assembly of an associated repeat unit, e.g., repeat unit 1100. Other features and effects of cathode annular insert 1134 will be described later in connection with cathode frame 1131.

[0270] Aspects of the various components of repeat unit 1100 will be now described in more detail not only in association with the description of cell 501, but also the text associated with FIGS. 25-43, 49-79, 83, 84A, 84B, and 85A-85C.

[0271] COx Electrolyzer Cell

[0272] Referring to FIG. 19, an exploded view of cell 501 is shown. Cell 501 is formed between cathode components 1103_1 of repeat unit 503_1 and anode components 1103_2 of repeat unit 503_2. Separator plates 1107_1 and 1107_2 of repeat units 503_1 and 503_2 separate cell 501 from adjacent cells of stack 500. With this in mind, anode components 1101_1 of repeat unit 503_1 and cathode components 1103_2 of repeat unit 503_2 are shown in partially assembled states and form portions of such cells adjacent to cell 501. Hereinafter, components of cell 501 will be referenced followed by an underscore and identifier to indicate the repeat unit to which the components are a part without specifying the repeat unit itself.

[0273] Cell 501 may include MEA 1105_1 interposed between anode porous transport layer (PTL) 1109_2 and cathode GDL 1121_1. In some cases, MEA 1105_1 and cathode GDL 1121_1 may be part of a unitized MEA assembly, such as unitized MEA assembly 1119_1, which includes MEA 1105_1 and cathode GDL 1121_1 sandwiched between support frames 1123_1 and 1125_1 (see also FIGS. 25-27). Support frames 1123_1 and 1125_1 may not only include respective openings 1123a_1 and 1125a_1 exposing corresponding surfaces of MEA 1105_1 and cathode GDL 1121_1 to adjacent components, but may also respectively include protruded tab portions 1123b_1 and 1125b_1 that may facilitate handling of unitized MEA assembly 1119_1 during manufacture and testing. In some embodiments, protruded tab portions 1123b_1 and 1125b_1 may be silkscreened, inscribed, embossed, or otherwise marked with identifying information, such as identifying information indicating a cell to which unitized MEA assembly 1119_1 belongs. Support frame 1123_1 may also include bulged portion 1123c_1 (see also bulged portion 1123c in FIG. 27) to accommodate MEA 1105_1 and cathode GDL 1121_1 in a cavity (e.g., cavity 2701 in FIG. 27) formed between support frames 1123_1 and 1125_1. Accordingly, the design of unitized MEA assembly 1119_1 may allow its components to be preassembled and tested before incorporation into, for example, cell 501, which may increase assembly efficiencies and reduce both cell-level and stack-level defects.

[0274] With continued reference to FIG. 19, anode PTL 1109_2 may be interposed between MEA 1105_1 and anode flow field 1111_2, whereas cathode GDL 1121_1 may be interposed between MEA 1105_1 and cathode flow field 1127_1. As such, opening 1125a_1 in support frame 1125_1 may allow MEA 1105_1 and anode flow field 1111_2 to be fluidically connected via anode PTL 1111_2, and opening 1123a_1 in support frame 1123_1 may allow MEA 1105_1 and cathode flow field 1127_1 to be fluidically connected via cathode GDL 1127_1. As will become more apparent below, anode PTL 1109_2 and anode flow field 1111_2 may, for example, be supported in one or more openings in anode frame 1115_2 and encircled by first anode gasket 1113a_2 of first anode gasket set 1113_2 at a first side of anode frame 1115_2. Similarly, cathode flow field 1127_1 and at least a portion of unitized MEA assembly 1119_1 (and, thereby, at least cathode GDL 1121_1) may be supported in one or more openings of cathode frame 1131_1 and encircled by first cathode gasket 1129_1 at a first side of cathode frame 1131_1. In turn, anode frame 1115_2 may be stacked between unitized MEA assembly 1119_1 and separator plate 1107_2, and cathode frame 1131_1 may be stacked between separator plate 1107_1 and unitized MEA assembly 1119_1. Second anode gasket set 1117_2 may be disposed between anode frame 1115_2 and separator plate 1107_2, whereas second cathode gasket 1133_1 may be disposed between cathode frame 1131_1 and separator plate 1107_1. In this manner, first anode gasket 1117a_2 of second anode gasket set 1117_2 may encircle anode flow field 1111_2 at a second side of anode frame 1111_2, and second cathode gasket 1133_1 may encircle cathode flow field 1127_1 at a second side of cathode frame 1131_1.

[0275] Gaskets 1113a_2 and 1129_1 may not only provide fluidic seals between unitized MEA assembly 1119_1 and the corresponding flow fields 1111_2 and 1127_1, but may also provide structural support to avoid over-compression of anode PTL 1109_2 and cathode GDL 1121_1. It is also noted that gaskets 1113a_2 and 1129_1 may be formed thin enough so that anode PTL 1109_2 and cathode GDL 1121_1 are not under-compressed when assembled as part of stack 500. For example, gaskets 1113a_2 and 1129_1 may be sized such that anode PTL 1109_2 and cathode GDL 1121_1 are compressed and sealed against corresponding surfaces of flow fields 1111_2 and 1127_1 to maintain electrical contact while preventing or discouraging fluids from pooling during operation. In a similar manner, gaskets 1117a_2 and 1133_1 may provide fluidic seals between separator plates 1107_2 and 1107_1 and corresponding surfaces of flow fields 1111_2 and 1127_1.

[0276] Each element within cell 501 may provide particular functionality to cell 501, and various components of stack 500 may provide shared functionality with each of the plurality of cells including cell 501. For instance, end plates 519 and 525 may generally serve to act as load-spreading members that distribute a clamping load relatively evenly over the plurality of cells of stack 500 including cell 501. Manifold assembly 515 may include, for example, main body 541 forming at least a portion of one or more fluidic inlet ports, which may begin at inlet connectors 543, and at least a portion of one or more fluidic outlet ports, which may terminate at outlet connectors 545, that may be used to convey fluid to and from the anode sides of the plurality of cells of stack 500 including cell 501. As will become more apparent below, the fluidic inlet port(s) and fluidic outlet port(s) of manifold assembly 515 may be fluidically connected to corresponding inlet and outlet fluidic passages in not only anode frame 1115_2 and cathode frame 1131_1 of cell 501, but also inlet and outlet fluidic passages of the anode and cathode frames of the other cells of stack 500. In a similar fashion, main body 541 of manifold assembly 515 may form at least a portion of one or more fluidic inlet ports, which may begin at inlet connector 547, and at least a portion of one or more fluidic outlet ports, which may terminate at outlet connector 549, that may be used to convey fluid to and from the cathode sides of the plurality of cells of stack 500 including cell 501. Thus, and as will become more apparent below, the fluidic inlet port(s) and fluidic outlet port(s) of manifold assembly 515 may be fluidically connected to corresponding inlet and outlet fluidic passages in not only anode frame 1115_2 and cathode frame 1131_1 of cell 501, but also inlet and outlet fluidic passages of the anode and cathode frames of the other cells of stack 500.

[0277] According to various embodiments, bus plate 521 may be electrically connected to anode flow field 1111_2 (and, in some instances, anode frame 1115_2) via anode interface separator 4703, anode flow field 1111, and anode PTL 1109 of anode interface assembly 509 (see FIGS. 5-10 and 47), as well as the corresponding separator plates 1107, anode flow fields 1111, anode PTLs 1109, MEAs 1105, cathode GDLs 1121, and cathode flow fields 1127 between anode interface assembly 509 and cell 501 (see also FIGS. 5-11); similarly, bus plate 513 may be electrically connected to cathode flow field 1127_1 (and, in some instances, cathode frame 1131_1) via cathode interface separator 1701, cathode flow field 1127, cathode GDL 1121, and MEA 1105 of cathode interface assembly 505 (see FIGS. 5-10 and 17). Anode and cathode flow fields 1111_2 and 1127_1 may be made of any suitable material(s) that is electrically conductive and otherwise capable of withstanding relatively long-term exposure to the fluids flowed within stack 500 during normal operating conditions. For example, flow fields 1111_2 and 1127_1 may be made from titanium or titanium alloy, stainless steel (although stainless steel may have a higher susceptibility to corrosion than other materials), porous graphite, a carbon-fiber reinforced thermoset polymer, etc.

[0278] In general, anode and cathode frames 1115_2 and 1131_1 may have inlets that correspond in location to the fluidic inlet passageways that begin at inlet connectors 543 and 547, and outlets that corresponding in location to the fluidic outlet passageways that terminate at outlet connectors 545 and 549. To this end, anode and cathode flow fields 1111_2 and 1127_1 may each have one or more channels that are formed in surfaces of the corresponding flow fields that are in contact with anode PTL 1109_2 and cathode GDL 1121_1, respectively, that are routed so as to allow the fluid that is conducted through the channels to come into contact with the adjacent PTL or GDL in a generally distributed manner.

[0279] For example, anode flow field 1111_2 may feature one or more inlet openings (or channels) and one or more outlet openings (or channels) that may, respectively, fluidically connect with corresponding openings in anode frame 1115_2. One or more anode channels, e.g., serpentine channels, may be provided in a surface of anode flow field 1111_2 that is in contact with anode PTL 1109_2. The anode channels may serve to distribute the fluid introduced to the anode side of cell 501 across anode PTL 1109_2 such that the anolyte is able to come into contact with anode PTL 1109_2 in a spatially distributed manner such that the anolyte may be allowed to flow through anode PTL 1109_2 in a relatively uniform manner across the entire area, or most of the entire area, of anode PTL 1109_2. An illustrative anode frame 1115 and some example anode flow fields 1111 will be described in more detail in association with FIGS. 37-42 and 83-85.

[0280] Similarly, cathode flow field 1127_1 may feature one or more inlet openings (or channels) and one or more outlet openings (or channels) that may, respectively, fluidically connect with corresponding openings in cathode frame 1131_1. One or more cathode channels may be provided in a surface of cathode flow field 1127_1 that is in contact with cathode GDL 1121_1. The cathode channels may serve to distribute the fluid introduced to the cathode side of cell 501 across cathode GDL 1121_1 such that the cathode fluid is able to come into contact with cathode GDL 1121_1 in a spatially distributed manner such that the cathode fluid may be allowed to flow through cathode GDL 1121_1 in a relatively uniform manner across the entire area, or most of the entire area, of cathode GDL 1121_1.

[0281] An illustrative cathode frame 1131 and example cathode flow fields 1127 will be described in more detail in association with FIGS. 28-36 and 49-78.

[0282] Anode PTL 1109_2 and cathode GDL 514 may both serve to help gases that are generated within or provided via anode flow field 1111_2 and cathode flow field 1127_1, respectively, to diffuse across the active area of MEA 1105_1. A typical GDL suitable for use in a COx electrolyzer may include, for example, a fibrous substrate that provides structural support, e.g., to the catalyst layer in MEA 1105_1, and may allow gas to flow from the adjacent flow field towards the MEA (including in directions parallel to the plane of MEA 1105_1, thereby allowing the gas to flow laterally underneath portions of the adjacent flow field that may be in contact with the GDL). Such a GDL may also permit water that is present in MEA 1105_1 or that is trapped within the GDL and / or trapped between that GDL and MEA 1105_1 to escape into the channel(s) of a flow field that is adjacent to the GDL, thereby potentially allowing that water to be expelled from that flow field as a result of fluid flow through that flow field. The GDL may also serve as an electrical conductor that serves to conduct electrical charge through MEA 1105_1. Similarly, a typical PTL suitable for use in a COx electrolyzer may include, for example, a porous, metallic matrix that provides structural support, e.g., to the catalyst layer in MEA 1105_1, and may allow water to flow from the adjacent flow field towards the MEA (including in directions parallel to the plane of MEA 1105_1, thereby allowing the water to flow laterally above portions of the adjacent flow field that may be in contact with the PTL). Such a PTL may also permit gas that is present in MEA 1105_1 or that is trapped within the PTL and / or trapped between that PTL and MEA 1105_1 to escape into the channel(s) of a flow field that is adjacent to the PTL, thereby potentially allowing that water to be expelled from that flow field as a result of fluid flow through that flow field. The PTL may also serve as an electrical conductor that serves to conduct electrical charge through MEA 1105_1.

[0283] According to some embodiments, MEA 1105_1 for a COx electrolyzer may feature a metal nanoparticle catalyst layer that is pressed into contact with cathode GDL 1121_1. In some implementations, the metal nanoparticle catalyst layer may alternatively be formed on cathode GDL 1121_1 and pressed into contact with MEA 1105_1. In yet further cases, there may be metal nanoparticle catalyst layers that may be formed on both MEA 1105_1 and cathode GDL 1121_1 and then pressed into contact with each other. One example of such a catalyst layer is a layer of carbon material supporting a layer of, or incorporating, gold nanoparticles. Various types of MEAs and appropriate catalysts for use in a COx electrolyzer are discussed in U.S. patent application Ser. Nos. 15 / 586,173 and 15 / 586,182, both filed May 3, 2017, and both titled “REACTOR WITH ADVANCED ARCHITECTURE FOR THE ELECTROCHEMICAL REACTION OF CO2, CO, AND OTHER CHEMICAL COMPOUNDS,” and U.S. Patent Application No. 62 / 939,960, filed Nov. 25, 2019, and titled “MEMBRANE ELECTRODE ASSEMBLY FOR COx REDUCTION,” each of which is hereby incorporated herein by reference in their entireties. It is noted, however, that these are merely examples and other configurations are contemplated.

[0284] Within the context of a multi-cell architecture, such as in the case of stack 500, multiple cells (including cell 501) may be served by common fluidic inlet ports / outlet ports and / or a common electrical potential source. It is noted that the overall multi-cell stack performance may be partially defined by the uniformity of electrical efficiency and product selectivity across the plurality of cells of stack 500, and this uniformity may be driven by the uniformity of gas flow delivery to / across each of the plurality of cells. To this point, the selection of flow field geometry, in that it relates to flow field pressure drop, may have a noticeable effect on overall stack flow uniformity. This may be because the flow uniformity is improved when the pressure drop across / through the plurality of cells is about an order of magnitude more than a pressure difference between discrete locations along a plenum where collective flow is distributed into individual cells within stack 500. Thus, establishing appropriate dimensions may be significant when working with a fixed plenum geometry toward the overall performance of stack 500.

[0285] As mentioned earlier, in a COx electrolyzer, liquid water may be provided to the anode side of cell 501 during operation, while gaseous COx may be provided to the cathode side of cell 501. In some implementations, an aqueous solution may be provided in place of water, and references to water herein may be understood to also be inclusive of the use of an aqueous solution as well. The liquid water may, through an electrolysis reaction on the anode side of cell 501, undergo oxidation to create oxygen (O2) gas, H+ protons, and electrons. The H+ protons may be drawn through MEA 1105_1 due to the electromagnetic field that is present within cell 501 due to the electrical potential that is applied across cell 501 and may react with the bicarbonate and / or hydroxide and / or formate that is produced at the cathode side.

[0286] For a variety of other reasons, water may enter the cathode of MEA 1105_1. In some implementations, liquid water is transported by one or more phenomena to the cathode. Thus, water molecules from the anode side of cell 501 may be transported to the cathode side of cell 501, e.g., through electroosmotic drag caused by the movement of the H+ protons from the anode side of cell 501 to the cathode side of cell 501. The rate of water delivery to and / or generation within the cathode side of cell 501 may be relatively high, e.g., for every molecule of CO gas that is produced through reduction of COx gas, there may be, for example, between five (5) and nine (9) molecules of water generated in and / or drawn to the cathode side of cell 501. This imbalance presents a significant challenge—for every molecule of COx gas that is reduced on the cathode side of cell 501, between five (5) and nine (9) molecules of water may need to be removed from the cathode side of cell 501. In some COx gas electrolyzers, such as those that may use a copper catalyst and may be used to generate CH4, for every molecule of COx gas that is reduced on the cathode side of cell 501, between five (5) and 36 molecules of water may need to be removed from the cathode side of cell 501, presenting an even greater water management challenge.

[0287] This imbalance between the rate of COx gas reduction and rate of water accumulation on the cathode side of cell 501 is further complicated by the relatively low gas flow rate of COx gas as compared with the typical gas flow rate on the cathode side in fuel cells, as well as the relatively lower temperatures and higher pressures used in COx electrolyzers as compared with fuel cells. For example, fuel cells may dilute the flow of O2 in the cathode of a fuel cell using nitrogen (N2), thereby allowing a higher volumetric flow rate to be used in a fuel cell than may be used in a COx electrolyzer. Such higher volumetric flow rates may allow for a faster rate of water molecule evacuation to be provided for in a fuel cell as compared with a COx electrolyzer. In contrast, the COx gas that is provided to a COx electrolyzer may generally be high-purity COx gas, which, in combination with the higher working pressures that may be common in COx electrolyzers, may allow for much lower volumetric flow rates to be used to provide a similar level of desired reactant gas flow within a COx electrolyzer as compared to a comparably sized fuel cell. The generally slower flow rate that is present in a COx electrolyzer as opposed to in a fuel cell may, in combination with the higher rate of water creation in and / or migration to the cathode side of cell 501, cause significant issues in a COx electrolyzer if not adequately handled that are not as significant a concern in fuel cells.

[0288] For example, approximately 90% of the water that is generated in / delivered to the cathode side of the cell during operation of a fuel cell may be in vapor phase, and thus, easily flowed out of the cathode flow field as compared with the water that is generated in / delivered to the cathode side of cell 501 during operation of a COx electrolyzer. In a typical COx electrolyzer, less than 2% of the gas phase that is generated in / delivered to the cathode side of cell 501 may be water in the vapor phase; the rest is in liquid phase. As a result of this significant liquid / vapor phase imbalance, as well as the significantly higher rate of water condensation in COx electrolyzers, COx electrolyzers are confronted with unique challenges with liquid water management that are not encountered in fuel cells. Such issues are, of course, also not present in water electrolyzers since the reactant that is delivered to the cathode side of water electrolyzers in the first place is liquid water that migrates from the anode, and the presence of liquid water in the cathode is, thus, not only expected, but desired and by design.

[0289] In COx electrolyzers, the presence of high concentrations of liquid water on the cathode side of cell 501 presents particular challenges that must be overcome in order for COx electrolyzers to be able to operate efficiently. In particular, the presence of liquid water in the cathode side of COx electrolyzers may interfere with the flow of gaseous COx through cathode GDL 1121_1 to MEA 1105_1 in cell 501. For example, excess liquid water that collects in the cathode channels of cathode flow field 1127_1 and / or cathode GDL 1121_1 may form a physical barrier that occludes portions of the cathode channels of cathode flow field 1127_1 and / or cathode GDL 1121_1 and prevents the gaseous COx from coming into contact with some or all of MEA 1105_1. This limits the reduction efficiency of cell 501 and may even, in some cases, cause permanent damage to cell 501 that may decrease the reduction efficiency of cell 501 going forward even if the liquid water is later removed. An additional issue that may occur if there is excess liquid water present in a COx electrolyzer is that the water may be reduced instead of the COx gas, resulting in the production of hydrogen instead of the desired reaction product.

[0290] COx electrolyzers may not only experience significantly higher rates of liquid water generation as compared with similarly sized fuel cell reactors, but may also tend to operate under conditions that tend to inhibit, at least in comparison to fuel cells, the ability of COx electrolyzers to compensate for such increased liquid water generation in some respects. For example, the input gas, e.g., air, that is provided to the cathode side of fuel cells tends to be provided at a higher flow rate as compared with the input gas that is provided to the cathode side of COx electrolyzers. As air is abundantly available, there is little concern with respect to a fuel cell with providing more air than can be utilized in the reduction reaction of a fuel cell. As a result, air may be provided to the cathode flow field in a fuel cell at a much higher flow rate than may be needed in order to support the reduction reaction taking place within the fuel cell, thereby allowing more kinetic energy to be available in fuel cell cathode input gas flows that may be used to assist with forcibly expelling water that has accumulated within the fuel cell cathode flow field. Further, in fuel cells, the oxidant gas may commonly be diluted with other gases, e.g., nitrogen in air, and higher flow rates may, thus, be used to ensure a sufficient rate of delivery of the oxidant gas to the cathode side of the fuel cell. The increased flow velocity in fuel cells may serve to forcibly push any potential droplets of liquid water that are present in the cathode flow field channel(s) through the flow field and to the fluidic outlet port of the cathode flow field, thereby rapidly evacuating what little liquid water is present in the flow field channels from the flow field.

[0291] In contrast, the input gas in a COx electrolyzer is the COx gas, and one of the main reasons for using COx electrolyzers is to reduce COx emissions that may be harmful to the environment by converting COx gas to other, more desirable gases or liquids (e.g., commercially valuable gases or liquids or gases or liquids that are less harmful to the environment, e.g., water and / or oxygen). It may, thus, be desirable to reduce the flow rate of the COx gas to a level that still achieves high, and preferably maximal, COx reduction for a given electrical current density used with a COx electrolyzer, but also reduces or minimizes the amount of extra COx gas that is flowed through the COx electrolyzer and is not reduced.

[0292] Due to such factors, COx electrolyzers may operate using a high-purity, undiluted input gas stream or streams, e.g., pure COx gas or relatively pure COx gas, that is flowed into the cathode side of cell 501 at relatively low speeds, at least as compared with equivalently sized fuel cells having similar construction. For example, some COx electrolyzers may be capable of operating at flow speeds comparable to or lower than those found in a typical fuel cell. In some implementations, COx electrolyzers are configured to operate at an average COx gas flow velocity in the flow field channels of between about 0.02 m / s and about 30 m / s, between about 0.02 m / s and about 15 m / s, between about 15 m / s and about 30 m / s, between about 0.02 m / s and about 7.5 m / s, between about 7.5 m / s and about 15 m / s, between about 15 m / s and about 23 m / s, between about 23 m / s and about 30 m / s, between about 0.02 m / s and about 3.8 m / s, between about 3.8 m / s and about 7.5 m / s, between about 7.5 m / s and about 11 m / s, between about 11 m / s and about 15 m / s, between about 15 m / s and about 19 m / s, between about 19 m / s and about 23 m / s, between about 23 m / s and about 26 m / s, or between about 26 m / s and about 30 m / s. In some implementations, COx electrolyzers are configured to operate at a COx gas flow velocity of about 2 m / s to 10 m / s, or about 5 m / s to 10 m / s, or about 7.5 m / s to about 10 m / s.

[0293] As indicated, in some implementations, relatively low flow rates provide advantages in COx electrolyzers, such as relatively high COx utilizations (not to be confused with conversion efficiency) due to low molar flow rates, which are often associated with low volumetric or linear flow rates. Another benefit is in maintaining the MEA (e.g., MEA 1105_1 of cell 501) at an acceptable hydration level. High gas flow rates tend to dry out the MEA, which leads to degradation. Further, for a fixed utilization, flow field designs having shorter channels, and hence more channels per cell, allow for lower gas speeds. In some embodiments, COx electrolyzers are configured to operate at a COx flow speed in flow channels of between about 0.02 m / s and about 5 m / s, between about 0.02 m / s and about 2.5 m / s, between about 2.5 m / s and about 5 m / s, between about 0.02 m / s and about 1.3 m / s, between about 1.3 m / s and about 2.5 m / s, between about 2.5 m / s and about 3.8 m / s, between about 3.8 m / s and about 5 m / s, between about 0.02 m / s and about 0.64 m / s, between about 0.64 m / s and about 1.3 m / s, between about 1.3 m / s and about 1.9 m / s, between about 1.9 m / s and about 2.5 m / s, between about 2.5 m / s and about 3.1 m / s, between about 3.1 m / s and about 3.8 m / s, between about 3.8 m / s and about 4.4 m / s, or between about 4.4 m / s and about 5 m / s.

[0294] In contrast, the typically lower flow rates seen in COx electrolyzers, coupled with the significantly higher rates of liquid water introduction into the cathode side of cell 501, make water evacuation in COx electrolyzers much more challenging as compared with other electrochemical devices, e.g., fuel cells or water electrolyzers.

[0295] Accordingly, various features and technologies may be used to help mitigate the detrimental effects of liquid water accumulation in COx electrolyzer cathodes, as well as liquid water supply in COx electrolyzer anodes. For example, anode frame 1115_2, cathode frame 1131_1, anode flow field 1111_2, and cathode flow field 1127_1 may be constructed so as to have one or more structural features that may allow for more effective liquid water management in cell 501. For example, anode frame 1115_2, cathode frame 1131_1, anode flow field 1111_2, and cathode flow field 1127_1 may have corresponding channels, risers, protrusions, distributors, collectors, etc., that may, for example, be designed to have certain characteristics that may contribute to 1) more effective water and gaseous COx delivery to the anode and cathode sides of cell 501, 2) more effective water evacuation in the context of a COx electrolyzer, 3) more effective mitigation of the potential performance degradation that may occur in such a COx electrolyzer in the event that liquid water collects within, for instance, the cathode side of cell 501, and 4) more effective expulsion from cell 501 of the byproducts of the COx reduction process. Accordingly, cathode frame 1131_1, anode frame 1115_2, cathode flow field 1127_1, and anode flow field 1111_2 will now be discussed in more detail in association with FIGS. 28-78, 83, 84A, 84B, and 85A-85C.Cathode Frame

[0296] As previously discussed in association with FIGS. 5-11A, cathode flow field 1127 may be supported in an opening of cathode frame 1131 between separator plate 1107 and unitized MEA assembly 1119, as well as include a plurality of fluidic passages to facilitate fluid flow (or communication) through stack 500, and, in particular, through a cell of stack 500, such as cell 501. Various details of an illustrative cathode frame 1131 will now be discussed in more detail in association with FIGS. 28-36.

[0297] FIG. 28 depicts a first perspective view of an example cathode frame. FIG. 29 depicts a bottom view of the example cathode frame of FIG. 28. FIGS. 30 and 31 depict enlarged portions of the example cathode frame of FIG. 28. FIG. 32 depicts a second perspective view of the example cathode frame of FIG. 28. FIG. 33 depicts a top view of the example cathode frame of FIG. 32. FIG. 34 depicts a cross-sectional view of the example cathode frame of FIG. 33 taken along sectional line 34-34. FIG. 35 depicts an enlarged portion of the example cathode frame of FIG. 33. FIG. 36 depicts a cross-sectional view of the example cathode frame of FIG. 35 taken along sectional line 36-36.

[0298] Cathode frame (or frame) 1131 may be a generally rectangular plate-shaped body having first surface 2801 (e.g., a top surface) opposing second surface 2803 (e.g., a bottom surface) in axial direction 2901 (see FIG. 29). Although frame 1131 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. For convenience, frame 1131 will be described in association with a generally rectangular configuration. First and second surfaces 2801 and 2803 may be bounded by one or more peripheral surfaces, such as peripheral surfaces (or surfaces) 2805, 2807, 2809, and 2811 that may be connected to one another via one or more other peripheral surfaces, such as peripheral surface (or surface) 2813. In some embodiments, frame 1131 may have a symmetrical configuration about one or more reference planes perpendicular to axial direction 2901 shown in FIG. 29. For instance, a configuration of frame 1131 may be symmetrical about either or both of reference planes 2903 and 2905 (see FIG. 29), but embodiments are not limited thereto.

[0299] According to various embodiments, first fluidic inlet passages 2815 and 2817 may be adjacent to peripheral edge 2805, and first fluidic outlet passages 2819 and 2821 may be adjacent to peripheral edge 2809. First fluidic inlet passages 2815 and 2817 may form portions of inlet passages 1001 and 1003 (see FIG. 10) of stack 500 in association with inlet connectors 543 of manifold assembly 515 (see FIGS. 5-10) that provide input water to the various anode frames (e.g., anode frame 1115 in FIG. 11A) of stack 500, and, thereby, to the corresponding anode flow fields (such as anode flow field 1111 in FIG. 11A) of the plurality of cells, such as cell 501. First fluidic outlet passages 2819 and 2821 may form portions of outlet passages (that are similar to inlet passages 1001 and 1003 (see FIG. 10), but associated with outlet connectors 545 of manifold assembly 515 versus inlet connectors 543 (see FIG. 5)) of stack 500 that output water from the various anode frames of stack 500, such as anode frame 1115 in FIG. 11A, and, thereby, from corresponding anode flow fields (e.g., anode flow field 1111 in FIG. 11) of the plurality of cells. In some cases, first fluidic inlet and outlet passages 2815-2821 may be defined by respective pluralities of orifices separated from one another via corresponding septal walls. For instance, first fluidic inlet passage 2815 may include first and second inlet orifices 2815a and 2815b separated from one another via septal wall 2803s1, whereas first fluidic outlet passage 2819 may include first and second outlet orifices 2819a and 2819b separated from one another via septal wall 2803s2. Illustrative septal walls are also depicted in the cross-sectional views of FIGS. 23 and 34. For example, septal wall 2803s3 is shown separating first and second outlet orifices 2821a and 2821b forming first fluidic outlet passage 2821 in FIG. 34, and septal wall 2803s4 is shown separating first and second inlet orifices 2817a and 2817b forming first fluidic inlet passage 2817 in FIG. 23. The presence of these septal walls, such as septal walls 2803s1-2803s4, may increase the structural rigidity and, thereby, reliability of frame 1131 in the vicinity of first fluidic inlet and outlet passages 2815-2821.

[0300] According to various implementations, frame 1131 includes through opening (or opening) 2823 formed completely through a first central portion of frame 1131 and may be configured to receive at least a portion of cathode flow field 1127 (see, e.g., FIGS. 11A, 23, and 24) therein. In this manner, opening 2823 may be shaped and sized to correspond with the shape and size of cathode flow field 1127. For example, opening 2823 may have a generally rectangular shape with rounded corners, but embodiments are not limited thereto. Frame 1131 may also include blind opening (or opening) 2825 formed in a second central portion of frame 1131 encircling the first central portion of frame 1131. In some cases, opening 2825 may be omitted or may be at least partially filled by cathode annular insert 1134, as will become more apparent below. When included as part of cathode frame 1131, opening 2825 may terminate at surface 2803r, which may be recessed from second surface 2803, and may be configured to receive at least a portion of unitized MEA assembly 1119 (see, e.g., FIGS. 11A, 23, and 24) and / or at least a portion of cathode annular insert 1134 therein. As such, opening 2825 may be shaped and sized to correspond with the shape and size of the portion of unitized MEA assembly 1119 and / or cathode annular insert 1134, but embodiments are not limited thereto. For instance, opening 2825 may have a generally rectangular shape with rounded corners, but embodiments are not limited thereto. In some implementations, the sides of opening 2825 extending respectively adjacent to surfaces 2805 and 2809 of frame 1131 may bulge towards surfaces 2805 and 2809, and, thereby, away from opening 2823. For example, as seen in FIGS. 29 and 31, the side of opening 2825 extending adjacent to surface 2809 of frame 1131 may not only have central portion 2825a extending in a first direction parallel (or substantially parallel) to surface 2809, but may also have second portions 2825b extending from central portion 2825a that are angled inwards from first portion 2825a towards opening 2823 by, for instance, angle 3101. Central portion 2825a may have width 3103 in the first direction, whereas second portions 2825b may have corresponding widths 3105, which may be greater than width 3103. Curved (or arcuate) corners 2825c of opening 2825 may respectively extend from second portions 2825b to connect the side of opening 2825 extending adjacent to surface 2809 to corresponding sides of opening 2825 extending in a second direction transverse to the first direction, e.g., extending parallel (or substantially parallel) to surfaces 2807 and 2811 of frame 1131. Embodiments, however, are not limited thereto.

[0301] In those implementations including cathode annular insert 1134, cathode annular insert 1134 may be at least partially supported in opening 2825 such that first surface 1134a of cathode annular insert 1134 abuts against surface 2803r of frame 1131 and inner peripheral surface 1134c of cathode annular insert 1134 encircles an outer peripheral boundary of cathode flow field 1127, and thereby, an inner peripheral boundary of opening 2825 (see also FIGS. 11D and 11E). To this end, outer peripheral surface 1134d of cathode annular insert 1134 may be shaped and sized to correspond with the shape and size of an inner peripheral boundary of opening 2825. In some cases, thickness 1134t of cathode annular insert 1134 may be equivalent (or substantially equivalent) to the depth of opening 2825, but implementations are not limited thereto. When thickness 1134t of cathode annular insert 1134 corresponds to the depth of opening 2825, cathode annular insert 1134 may fill the void in cathode frame 1131 corresponding to opening 2825. It is also contemplated that cathode annular insert 1134 may include one or more notched portions 1134n1 and 1134n2 such that cathode annular insert 1134 does not completely fill the void corresponding to opening 2825. Whatever the case, cathode annular insert 1134 may have a generally ring-like configuration, and as such, may not be truly annular. For instance, cathode annular insert 1134 may have a generally rectangular cross-section when viewed along the z-axis direction shown in FIGS. 11D and 11E, thus giving rise to a cathode annular insert having two-fold symmetry instead of axial symmetry. As such, cathode annular insert 1134 may have, for instance, a circular, an oval, a polygonal, or any other suitable cross-sectional geometry when viewed along the z-axis direction shown in FIGS. 11D and 11E.

[0302] As seen in FIG. 29, openings 2823 and 2825 may be arranged between second fluidic inlet and outlet passages 2827 and 2829, which form respective portions of inlet and outlet passages 901 and 903 of stack 500 in association with input and outlet connectors 547 and 549 of manifold assembly 515 (see FIGS. 5 and 9). Referring momentarily to FIGS. 7, 9, 11A, 23, 24, and 29, inlet passage 901 may supply one or more reactants (e.g., gaseous COx) to frame 1131, and, thereby, to cathode flow field 1127 at least partially supported in opening 2823 when frame 1131 is incorporated as part of a cell, such as cell 501. Outlet passage 903, however, may enable one or more byproducts of the COx reduction process to be routed from frame 1131, and, thereby, from the corresponding cathode flow field 1127 at least partially supported in one or more of openings 2823 and 2825. Adverting back to FIGS. 28-36, to enable such exchange of fluids to and from cathode flow field 1127 (see FIG. 11A), second fluidic inlet passage 2827 may be fluidically connected to opening 2823 via channel 3501, connecting riser 3001, and buffering passage 2831, and second fluidic outlet passage 2829 may be fluidically connected to opening 2823 via channel 3301, connecting riser 3109, and buffering passage 2833.

[0303] Buffering passages 2831 and 2833 may be corresponding recesses formed in surface 2803r that respectively terminate at surfaces 2831a and 2833a. To facilitate reactant supply to, and byproduct expulsion from, the corresponding cathode flow field 1127 (see, e.g., FIGS. 23 and 24) at least partially supported in opening 2823, buffering passages 2831 and 2833 may have corresponding outer sidewalls 2831b and 2833b that respectively expand from connecting risers 3001 and 3109 towards opening 2823. For instance, buffering passages 2831 and 2833 may have a generally triangular shape, but embodiments are not limited thereto. In some instances, respective widths 3111 of buffering passages 2831 and 2833 may be smaller than width 3103 of central portion 2825a of opening 2825. Buffering passages 2831 and 2833 may also include corresponding pluralities of protrusions 3003 arranged at one or more intervals to accelerate reactant / byproduct flow between adjacent protrusions among the protrusions 3003 and between protrusions 3003 and correspondingly adjacent sidewalls 2831b and 2833b. In association with buffering passage 2831, protrusions 3003 may not only promote a draw of reactant from connecting riser 3001, but may also facilitate a distributed flow of reactant to an input portion of cathode flow field 1127 (see, e.g., FIGS. 23 and 24) at least partially supported in opening 2823. Protrusions 3003, in association with buffering passage 2833, may promote a draw of byproduct from an output portion of cathode flow field 1127 (see, e.g., FIGS. 23 and 24) at least partially supported in opening 2823 to connecting riser 3109. Although protrusions 3003 are shown as generally cylindrically shaped bosses, embodiments are not limited thereto. For instance, one or more of protrusions 3003 may be generally elliptical bosses, generally rectangular bosses, generally pentagonal bosses, generally hexagonal bosses, etc. When incorporated as part of a cell, such as cell 501, cathode annular insert 1134 may be at least partially supported in opening 2825 to at least partially fill the void corresponding to opening 2825. By filling the void corresponding to opening 2825 (which is formed between opening 2823 in frame 1131 and recess 2835) the likelihood that input reactant(s) (e.g., gaseous COx) that are to be supplied to cathode flow field 1127 from buffering passage 2831 instead flow around cathode flow field 1127 via opening 2825 (illustrated in FIG. 11D as reactant bypass flow 1136) and become expelled via buffering passage 2833 is reduced or eliminated. It is noted that reactant bypass flow 1136 decreases the amount of input reactant flowing through cathode flow field 1134, and as such, has the potential to decrease the efficiency of the cell. In some cases, both opening 2825 and cathode annular insert 1134 may be omitted, thereby further reducing the possibility of reactant bypass flow 1136. In those instances when opening 2825 is formed in frame 1131 and cathode annular insert 1134 is not utilized, the compression of at least a portion of unitized MEA assembly 1119 therein may also serve to reduce or prevent reactant bypass flow 1136.

[0304] According to some embodiments, the inclusion of cathode annular insert 1134 may also aid in providing additional compression of GDL 1121 in the region occupied by cathode annular insert 1134 when the cell (e.g., cell 501) and / or stack 500 is assembled and compressed, whether as part of the assembly process or during use of stack 500. This additional compression may decrease in-plane permeability of GDL 1121 in the region corresponding to cathode annular insert 1134 and may further mitigate the potential for reactant bypass flow 1136. Given, however, that the presence of cathode annular insert 1134 between GDL 1121 and frame 1131 is likely to compress cathode annular insert 1134 in the axial direction, notched portions 1134n1 and 1134n2 may be formed in cathode annular insert 1134 in areas corresponding to buffering passages 2831 and 2833 to prevent or reduce the likelihood that cathode annular insert 1134 compresses into respective portions of buffering passages 2831 and 2833 that interface with opening 2823 in frame 1131. As such, notched portions 1134n1 and 1134n2 may be formed such that their leading edges corresponding to portions of inner peripheral surface 1134c of cathode annular insert 1134 overlap with corresponding protrusions 3003 respectively formed in buffering passages 2831 and 2833 to support cathode annular insert 1134 in the areas corresponding to buffering passages 2831 and 2833. For example, the leading edges of notched portions 1134n1 and 1134n2 may be supported by one or more of protrusions 3003. In some examples, the leading edges of notched portions 1134n1 and 1134n2 may be supported by one or more of protrusions 3003 positioned nearest to connecting riser 3001. Notched portions 1134n1 and 1134n2, however, may be omitted. In some cases, additional protrusions 3003 may be provided in buffering passages 2831 and 2833 to support cathode annular insert 1134 thereon, and thereby, to similarly prevent or reduce the likelihood that cathode annular insert 1134 compresses into the respective portions of buffering passages 2831 and 2833 that interface with opening 2823 in frame 1131.

[0305] In some embodiments, protrusions 3003 may be sized similar (or substantially similar) to one another or at least one protrusion among protrusions 3003 may be sized differently than at least one other protrusion among protrusions 3003. This may be with respect to the lengths, widths, and / or heights of protrusions 3003. For example, protrusions 3003 may include first, second, and third protrusions 3003a, 3003b, and 3003c. With respect to a reference plane perpendicular to the axial direction, a cross-sectional area of first protrusions 3003a may be larger than a cross-sectional area of second protrusions 3003b, and a cross-sectional area of second protrusions 3003b may be larger than a cross-sectional area of third protrusions 3003c. In some cases, second protrusions 3003b of buffering passages 2831 and 2833 may be disposed respectively closer to connecting risers 3001 and 3109 than first and third protrusions 3003a and 3003c. Third protrusions 3003c may be arranged amongst first protrusions 3003a and positioned such that third protrusions 3003c are disposed between second protrusions 3003b and a majority of first protrusions 3003a. Embodiments, however, are not limited to such a configuration and / or arrangement of protrusions 3003.

[0306] Frame 1131 may also include recess 2835 in surface 2803 and recess 3303 in surface 2801 that are configured to respectively receive corresponding portions of first and second cathode gaskets 1129 and 1133 (see, e.g., FIGS. 11A, 23, and 24) therein when, for example, frame 1131 is assembled as part of a repeat unit (e.g., repeat unit 503_1 in FIG. 5) or cathode interface assembly 505 (see FIG. 5). Recess 2835 may be formed to encircle the periphery of opening 2825 and recess 3303 may be formed to encircle the periphery of opening 2823. It is noted that the conjunction of second fluidic inlet passage 2827, channel 3501, connecting riser 3001, and buffering passage 2831 enables reactant supply to flow from an area outside of first cathode gasket 1129 (see, e.g., FIGS. 11A, 23, and 24) to an area inside of first cathode gasket 1129 without disturbing the integrity of or seal provided by first cathode gasket 1129. Similarly, the conjunction of buffering passage 2833, connecting riser 3109, channel 3301, and second fluidic outlet passage 2829 enables byproduct flow from an area inside of first cathode gasket 1129 (see, e.g., FIGS. 11A, 23, and 24) to an area outside of first cathode gasket 1129 without disturbing the integrity of or seal provided by first cathode gasket 1129.

[0307] According to some embodiments, frame 1131 may include first protruded portions 3305 extending from surface 2801 and encircling corresponding first fluidic inlet and outlet passages 2815, 2817, 2819, and 2821. Second protruded portions 3307 may also extend from surface 2801, but encircle respective second fluidic inlet and outlet passages 2827 and 2829. In some implementations, the second protruded portion 3307 encircling second fluidic inlet passage 2827 may also encircle channel 3501 and connecting riser 3001, and the second protruded portion 3307 encircling second fluidic outlet passage 2829 may also encircle channel 3301 and connecting riser 3109. In some embodiments, first and second protruded portions 3305 and 3307 may protrude from surface 2801 by height 3401, but embodiments are not limited thereto. For instance, one or more of first and second protruded portions 3305 and 3307 may have a different height than at least another one or more of first and second protruded portions 3305 and 3307. When assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), first and second protruded portions 3305 and 3307 of frame 1131 may be received in and through corresponding openings in a separator plate (such as separator plate 1107 in FIG. 11A; see also FIGS. 23 and 24) or corresponding recesses 4607-4617 (see FIG. 46) in cathode interface separator 1701 (see FIG. 17) of cathode interface assembly 505 (see, e.g., FIGS. 5-10 and 17). As such, one or more of first and second protruded portions 3305 and 3307 may be sized to form respective clearance or interference fits with the corresponding openings in the separator plate (such as separator plate 1107 in FIG. 11A) or corresponding recesses 4607-4617 (see FIG. 46) in cathode interface separator 1701 (see FIGS. 17 and 46) when frame 1131 is assembled as part of a repeat unit (e.g., repeat unit 503_1 in FIG. 5 or as part of cathode interface assembly 505, see, e.g., FIGS. 5-10, 17, and 18).

[0308] In some embodiments, one or more of first and second protruded portions 3305 and 3307 may be sized to form respective clearance fits with corresponding features in (or of) the separator plate to which frame 1131 interfaces when incorporated as part of stack 500 (such as separator plate 1107 in FIG. 11A) or cathode interface separator 1701 (see, e.g., FIG. 17) depending on the location of frame 1131 within stack 500). In addition, one or more of first and second protruded portions 3305 and 3307 may be sized to form respective interference fits with the corresponding features in the separator plate to which frame 1131 interfaces when incorporated as part of stack 500 (such as separator plate 1107 in FIG. 11A) or cathode interface separator 1701 (see, e.g., FIG. 17) depending on the location of frame 1131 within stack 500). For example, respective outer boundaries of first and second protruded portions 3305 and 3307 may be about 0.01% to about 5% larger (in the case of an interference fit) or about 0.01% to about 10% smaller (in the case of a clearance fit) than corresponding boundaries of the corresponding features in the separator plate (such as separator plate 1107 in FIG. 11A) or cathode interface separator 1701 (see, e.g., FIG. 17) depending on the location of frame 1131 within stack 500). The clearance and / or interference fits may be utilized to constrain in-plane expansion (e.g., expansion in, for instance, a plane parallel to an x-y plane (see FIG. 11A)) of frame 1131 (and, in some embodiments, anode frame 1115) during operation of stack 500 without unduly stressing frame 1131 and / or anode frame 1115. In some embodiments, first and second protruded portions 3305 and 3307 may be sized to form respective clearance fits with corresponding features in (or of) the separator plate (such as separator plate 1107 in FIG. 11A) or cathode interface separator 1701 (see, e.g., FIG. 17) depending on the location of frame 1131 within stack 500) in a cooled, non-operational state of stack 500 (see FIGS. 5 and 6), but expand to form corresponding interference fits in a steady-state operational condition of stack 500. This may prevent (or at least reduce the likelihood of) misalignments, bunching, etc., of cathode GDLs 1121 and anode PTLs 1109 of the various cells of stack 500, as well as prevent (or reduce the likelihood of) misalignments between adjacent frames of adjacent cells of stack 500. Such a configuration may also allow frame 1131 and / or anode frame 1115 (see FIG. 11A) to be formed of more compliant materials that, in some cases, may be less expensive and / or easier to manufacture (and, in some cases, not electrically conductive). It is noted, however, that the separator plate (e.g., separator plate 1107 in FIG. 11A) or cathode interface separator 1701 (see, e.g., FIG. 17) depending on the location of frame 1131 within stack 500) may be formed of a stronger and / or more rigid material(s) to increase the strength and / or rigidity of the various repeat units (e.g., repeat unit 1100 of FIG. 11A; see also repeat units 503 in FIGS. 5-10) and / or cathode interface assembly 505 (see, e.g., FIGS. 5-10, 17, and 18).

[0309] According to various embodiments, first protruded portions 3305 may be sized and shaped to interface with second anode gaskets 1117b of second anode gasket set 1117 and second protruded portions 3307 may be sized and shaped to interface with third anode gaskets 1117c of second anode gasket set 1117. As such, cross-flow between first and second fluidic inlet and outlet passages 2815, 2817, 2819, 2821, 2827, and 2829 may be prevented.

[0310] Frame 1131 may also include first fastener orifices 2837 arranged about a peripheral area of frame 1131 at one or more intervals. In some embodiments, a pitch between adjacent first fastener orifices 2837 may be constant (or substantially constant), but embodiments are not limited thereto. Second and third fastener orifices 2839 and 2841 may be inset from first fastener orifices 2837 in central portions of frame 1131 respectively near second fluidic inlet and outlet passages 2827 and 2829. A pitch between adjacent second fastener orifices 2839 and a pitch between adjacent third fastener orifices 2841 may be smaller than the pitch(es) between adjacent first fastener orifices 2837. In various embodiments, first, second, and third fastener orifices 2837, 2839, and 2841 may extend completely through frame 1131 and may be counterbored with respect to, for example, surface 2803. When assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), first, second, and third fastener orifices 2837, 2839, and 2841 may be configured to respectively receive corresponding fasteners 1137 (see FIG. 11A), which may engage with, for instance, swage nuts 1135 (see FIG. 11A) incorporated into (or as part of) anode frame 1115 (see, e.g., FIGS. 11A and 21), as will become more apparent below. In those instances when frame 1131 is incorporated as part of cathode interface assembly 505 (see, e.g., FIGS. 5-10, 17, and 18)), first, second, and third fastener orifices 2837, 2839, and 2841 may be configured to respectively receive corresponding fasteners 1137 (see FIG. 17), which may engage with, for instance, first, second, and third threaded fastener orifices 4539, 4541, and 4543 of cathode interface separator 1701 (see, e.g., FIGS. 17, 18, and 45), as will become more apparent below.

[0311] According to various embodiments, one or more of the counterbored portions of first, second, and third fastener orifices 2837, 2839, and 2841 may be sized to form respective clearance or interference fits with corresponding fasteners 1137 (see FIG. 11A) or corresponding portions (e.g., head or shoulder portions) of fasteners 1137 (see, e.g., FIG. 21) when frame 1131 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A) or as part of cathode interface assembly 505 in, for instance, FIGS. 5-10, 17, and 18. In some embodiments, one or more of the counterbored portions of first, second, and third fastener orifices 2837, 2839, and 2841 may be sized to form respective clearance fits with corresponding fasteners 1137 (see, e.g., FIGS. 11A, 17, and 21) and one or more of the counterbored portions of first, second, and third fastener orifices 2837, 2839, and 2841 may be sized to form respective interference fits with corresponding fasteners 1137. For example, respective widths (e.g., diameters) of the counterbored portions of first, second, and third fastener orifices 2837, 2839, and 2841 may be about 0.01% to about 10% larger (in the case of a clearance fit) or about 0.01% to about 5% smaller (in the case of an interference fit) than corresponding widths (e.g., diameters) of respective portions (e.g., head or shoulder portions) of fasteners 1137 (see, e.g., FIGS. 11A, 17, and 21). In some embodiments, one or more of the counterbored portions of first, second, and third fastener orifices 2837, 2839, and 2841 may be sized to form respective clearance fits with corresponding fasteners 1137 (see, e.g., FIGS. 11A, 17, and 21) or corresponding portions (e.g., head or shoulder portions) of fasteners 1137 (see, e.g., FIG. 21) when frame 1131 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A) or as part of cathode interface assembly 505 in, for instance, FIGS. 5-10, 17, and 18, and stack 500 (see, e.g., FIG. 5) is in a cooled, non-operational state, but expand to form corresponding interference fits in a steady-state operational condition of stack 500. These clearance and / or interference fits may be utilized to constrain in-plane expansion (e.g., expansion in, for instance, a plane parallel to an x-y plane (see FIG. 11A)) of frame 1131 (and, in some embodiments, anode frame 1115 in FIG. 11A) during operation of stack 500 without unduly stressing frame 1131 and / or anode frame 1115. This may prevent (or at least reduce the likelihood of) misalignments, bunching, etc., of anode PTLs 1109 and cathode GDLs 1121 of the various cells / repeat units of stack 500 (see, e.g., FIGS. 5-10), as well as prevent (or reduce the likelihood of) misalignments between adjacent frames of adjacent cells / repeat units of stack 500. Such a configuration may also allow frame 1131 and / or anode frame 1115 to be formed of more compliant materials that, in some cases, may be less expensive and / or easier to manufacture (and, in some cases, not electrically conductive).

[0312] According to some embodiments, frame 1131 and / or cathode annular insert 1134 may be formed of any suitable thermoplastic and / or thermosetting material, such as, for instance, polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyamide (PA), poly(methylmethacrylate) (PMMA), polyethylene naphthalate (PEN), polyetherketone (PEK), polyetheretherketone (PEEK), polystyrene (PS), polyetherimide (PEI), polyphenylene sulfide (PPS), polyarylate (PAR), polyether sulfone (PES), cyclic olefin copolymer (COC), polyvinyl alcohol (PVA), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), polychlorotrifluoroethylene (PCTFE), polyethylene terephthalate glycol (PETG), and / or the like. In some cases, frame 1131 and / or cathode annular insert 1134 may be formed of one or more metals or metal alloys, such as aluminum, aluminum alloy, copper, copper alloy, tin, tin alloy, titanium, titanium alloy, tungsten, tungsten alloy, zinc, zinc alloy, steel, stainless steel, etc. It is noted, however, that when formed of a metal or metal alloy, frame 1131 may, in some embodiments, include a coating or other feature to, for instance, electrically insulate frame 1131 from a corresponding cathode GDL (e.g., cathode GDL 1121 in FIG. 11A) and / or cathode flow field (e.g., cathode flow field 1127 in FIG. 11A) associated therewith. It is also contemplated that a base material of frame 1131 may be coated with, for example, one or more other materials, e.g., one or more corrosion-resistant materials. Whatever the case, frame 1131 and / or cathode annular insert 1134 may be formed in any suitable manner, such as additively manufactured, stamped, injection molded, compression molded, casted, machined, and / or the like.Anode Frame

[0313] Similar to cathode flow field 1127 (see, e.g., FIGS. 11A, 23, and 24), anode flow field 1111 may be at least partially supported in an opening of anode frame 1115 (see, e.g., FIGS. 11A, 23, and 24), which also includes a plurality of fluidic passages to facilitate fluid communication (or flow) through stack 500 (see, e.g., FIGS. 5-10), and, in particular, through a COx electrolyzer cell of stack 500, such as cell 501. Various details of an illustrative anode frame 1115 will now be discussed in more detail in association with FIGS. 37-42.

[0314] FIG. 37 depicts a first perspective view of an example anode frame. FIG. 38 depicts a top view of the example anode frame of FIG. 37. FIG. 39 depicts a second perspective view of the example anode frame of FIG. 37. FIG. 40 depicts a bottom view of the example anode frame of FIG. 39. FIG. 41 depicts an enlarged portion of the example anode frame of FIG. 38. FIG. 42 depicts an enlarged portion of the example anode frame of FIG. 40.

[0315] Anode frame (or frame) 1115 may be a generally rectangular plate-shaped body having first surface 3701 (e.g., a top surface) opposing second surface 3703 (e.g., a bottom surface) in axial direction 3801. Although frame 1115 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. For convenience, frame 1115 will be described in association with a generally rectangular configuration. First and second surfaces 3701 and 3703 may be bounded by one or more peripheral surfaces, such as peripheral surfaces (or surfaces) 3705, 3707, 3709, and 3711 that may be connected to one another via one or more other peripheral surfaces, such as peripheral surface (or surface) 3713. In some embodiments, frame 1115 may have a symmetrical configuration about one or more reference planes perpendicular to axial direction 3801 (see FIGS. 38 and 40). For instance, a configuration of frame 1115 may be symmetrical about either or both of reference planes 3803 and 3805 depicted in FIGS. 38 and 40, but embodiments are not limited thereto.

[0316] According to various embodiments, first fluidic inlet passages 3715 and 3717 may be adjacent to peripheral edge 3705, and first fluidic outlet passages 3719 and 3721 may be adjacent to peripheral edge 3709. First fluidic inlet passages 3715 and 3717 may form portions of inlet passages 1001 and 1003 (see FIG. 10) of stack 500 in association with inlet connectors 543 of manifold assembly 515 (see FIGS. 5-10) that provide input water to frame 1115, and, thereby, to a corresponding anode flow field 1111 (see, e.g., FIGS. 11A, 23, and 24) associated with frame 1115. First fluidic outlet passages 3719 and 3721 may form portions of outlet passages (that are similar to inlet passages 1001 and 1003 (see FIG. 10), but associated with outlet connectors 545 of manifold assembly 515 versus inlet connectors 543 (see, e.g., FIGS. 5-10)) of stack 500 that output water from frame 1115, and, thereby, from the corresponding anode flow field 1111 (see, e.g., FIGS. 11A, 23, and 24) associated with frame 1115. In some implementations, first fluidic inlet and outlet passages 3715-3721 may be defined by respective pluralities of orifices separated from one another via corresponding septal walls. For instance, first fluidic inlet passage 3715 may include first and second inlet orifices 3715a and 3715b separated from one another via septal wall 3701s1, whereas first fluidic outlet passage 3719 may include first and second outlet orifices 3719a and 3719b separated from one another via septal wall 3701s2. An illustrative septal wall is also depicted in the enlarged view of FIG. 42 and the cross-sectional view of FIG. 23. That is, septal wall 3701s3 is shown separating first and second outlet orifices 3721a and 3721b forming first fluidic outlet passage 3721 in FIG. 42, and septal wall 3701s4 is shown separating first and second inlet orifices 3717a and 3717b forming first fluidic inlet passage 3717 in FIG. 23. As with cathode frame 1131 (see, e.g., FIG. 11A), the presence of the septal walls in frame 1115, such as septal walls 3701s1-3701s3, may increase the structural rigidity and, thereby, reliability of frame 1115 in the vicinity of first fluidic inlet and outlet passages 3715-3721.

[0317] According to various embodiments, frame 1115 also includes through opening (or opening) 3723 formed completely through a first central portion of frame 1115 and may be configured to receive at least a portion of anode flow field 1111 therein (see, e.g., FIGS. 11A, 23, and 24). As such, opening 3723 may be sized and shaped to correspond with the size and shape of anode flow field 1111. For example, opening 3723 may have a generally rectangular shape with rounded corners, but embodiments are not limited thereto. Frame 1115 may also include blind opening (or opening) 3725 formed in a second central portion of frame 1115 encircling the first central portion of frame 1115. In some cases, opening 3725 may be omitted or may be at least partially filled by anode annular insert 1118, as will become more apparent below. When included as part of frame 1115, opening 3725 may terminate at surface 3701r, which may be recessed from first surface 3701, and may be configured to receive at least a portion of anode PTL 1109 (see, e.g., FIGS. 11A, 23, and 24) and / or at least a portion of anode frame insert 1118 therein. As such, opening 3725 may be sized and shaped to correspond with the size and shape of anode PTL 1109 (see, e.g., FIGS. 11A, 23, and 24) and / or anode frame insert 1118. For instance, opening 3725 may have a generally rectangular shape with rounded corners, but embodiments are not limited thereto. To enable fluid flow to and from anode flow field 1111 (see, e.g., FIGS. 11A, 23, and 24) at least partially supported in opening 3723, first fluidic inlet passages 3715 and 3717 may be fluidically connected to opening 3723 via corresponding channels 4001, 4003, 4005, and 4007, respective connecting risers 3727 and 3729, distribution channel 3731, and supply (or inlet) channels 3733. First fluidic outlet passages 3719 and 3721 may be fluidically connected to opening 3723 via outlet channels 3735, collection channel 3737, respective connecting risers 3739 and 3741, and corresponding channels 4009, 4011, 4013, and 4015.

[0318] In those implementations including anode annular insert 1118, anode annular insert 1118 may be at least partially supported in opening 3725 such that second surface 1118b of anode annular insert 1118 abuts against surface 3701r of frame 1115 and inner peripheral surface 1118c of anode annular insert 1118 encircles an outer peripheral boundary of anode flow field 1111, and thereby, an inner peripheral boundary of opening 3723 (see also FIGS. 11B and 11C). To this end, outer peripheral surface 1118d of anode annular insert 1118 may be shaped and sized to correspond with the shape and size of an inner peripheral boundary of opening 3725. In some cases, thickness 1118t of anode annular insert 1118 may be equivalent (or substantially equivalent) to the depth of opening 3725, but implementations are not limited thereto. When thickness 1118t of anode annular insert 1118 corresponds to the depth of opening 3725, anode annular insert 1118 may fill the void in frame 1115 corresponding to opening 3725. It is also contemplated that anode annular insert 1118 may not completely fill the void corresponding to opening 3725, such as can be appreciated in FIGS. 11B and 11C. In such instances, inner peripheral surface 1118c of anode annular insert 1118 may be offset from the inner peripheral boundary of opening 3723 and PTL 1109 may fill a remaining amount of space not filled by anode annular insert 1118. Whatever the case, anode annular insert 1118 may have a generally ring-like configuration, and as such, may not be truly annular. For instance, anode annular insert 1118 may have a generally rectangular cross-section when viewed along the z-axis direction shown in FIGS. 11B and 11C, thus giving rise to an anode annular insert having two-fold symmetry instead of axial symmetry. As such, anode annular insert 1118 may have, for instance, a circular, an oval, a polygonal, or any other suitable cross-sectional geometry when viewed along the z-axis direction shown in FIGS. 11B and 11C.

[0319] Inlet and outlet channels 3733 and 3735 may be blind recesses formed in surface 3701r that extend from opening 3723 and terminate at distribution channel 3731 and connecting risers 3727 and 3729 in the case of inlet channels 3733 and distribution channel 3737 and connecting risers 3739 and 3741 in the case of outlet channels 3735, such as illustrated in FIGS. 37, 38, and 41. In some cases, inlet and outlet channels 3733 and 3735 may not only extend parallel (or substantially parallel) to one another, but may also extend parallel (or substantially parallel) to reference plane 3803. When incorporated as part of a cell, such as cell 501, anode annular insert 1118 may be at least partially supported in opening 3725 to at least partially fill the void corresponding to opening 3725. As previously noted, a remaining area of the void may be filled by PTL 1109, and as such, anode annular insert 1118 may serve to extend the outer boundary of PTL 1109 further outwards towards recess 3747 in frame 1115. By filling the void corresponding to opening 3725 (which is formed between opening 3723 and recess 3747) the likelihood that input water that is to be supplied to anode flow field 1111 from inlet channels 3733 instead flows around anode flow field 1111 via opening 3725 (illustrated in FIG. 11B as bypass flow 1120) and becomes expelled via outlet channels 3735 is reduced or eliminated. It is noted that bypass flow 1120 decreases the amount of input water flowing through anode flow field 1111, and as such, has the potential to decrease the efficiency of the cell. In some cases, both opening 3725 and anode annular insert 1118 may be omitted, thereby further reducing the possibility of bypass flow 1120. In those instances when opening 3725 is formed in frame 1115 and anode annular insert 1118 is not utilized, PTL 1109 may be formed to completely (or substantially completely) fill opening 3725 to reduce or prevent the likelihood of bypass flow 1120.

[0320] According to some embodiments, the presence of anode annular insert 1118 may not only prevent or reduce the likelihood of bypass flow 1120 during operation of stack 500, but may also prevent or reduce the likelihood that bypass flow 1120 or compression forces within the system (e.g., stack 500) cause the anode side of MEA 1105 to push against the outer periphery of PTL 1109 and become mechanically deteriorated via abrasion, cutting, etc. Anode annular insert 1118 may also prevent or reduce the likelihood that, for instance, first anode gasket 1113a intrudes into one or more of inlet and / or outlet channels 3733 and 3735.

[0321] To facilitate distributed supply and collection of water to and from anode flow field 1111 (see, e.g., FIGS. 11A, 23, and 24), inlet and outlet channels may have respective outer channels flanking corresponding central channels. For example, as seen in FIG. 41, outlet channels 3735 may be divided into first outer outlet channels 3735a arranged in first outer portion 4101, second outer outlet channels 3735b arranged in second outer portion 4103, and central outlet channels 3735c arranged in central portion 4105. Central outlet channels 3735c may be spaced apart from one another at constant interval 4107, whereas first and second outer outlet channels 3735a and 3735b may be spaced apart from one another with variable intervals that may increase in size with increasing distance from central portion 4105. For instance, adjacent first outer outlet channels 3735a near central portion 4105 may be spaced apart from one another by interval 4109 and adjacent first outer outlet channels 4135a further away from central portion 4105 may be spaced apart from one another by interval 4111, which may be greater than interval 4109. Inlet channels 3733 may be similarly arranged and configured as outlet channels 3735, but with respect to an inlet side of opening 3723 versus the outlet side of opening 3723 associated with outlet channels 3735.

[0322] The central inlet and outlet channels (e.g., central outlet channels 3735c) of inlet and outlet channels 3733 and 3735 may respectively terminate at and be fluidically connected to distribution channels 3731 and 3737. Some of the first outer inlet and outlet channels of inlet and outlet channels 3733 and 3735 may respectively terminate at and be fluidically connected to distribution channels 3731 and 3737, whereas other ones of the first outer inlet and outlet channels (e.g., the identified first outer outlet channels 3735a in FIG. 41) of inlet and outlet channels 3733 and 3735 may respectively terminate at and be fluidically connected to connecting risers 3727 and 3741. Similarly, some of the second outer inlet and outlet channels of inlet and outlet channels 3733 and 3735 may respectively terminate at and be fluidically connected to distribution channels 3731 and 3737, whereas other ones of the second outer inlet and outlet channels (e.g., the identified second outer outlet channels 3735b in FIG. 41) of inlet and outlet channels 3733 and 3735 may respectively terminate at and be fluidically connected to connecting risers 3729 and 3739.

[0323] Distribution channels 3731 and 3737 may be formed as blind recesses in surface 3701r and may extend in a direction transverse to the direction of extension of inlet and outlet channels 3735, such as depicted in FIGS. 37, 38, and 41. In some embodiments, distribution channels 3731 and 3737 may extend parallel (or substantially parallel) to reference plane 3805. Distribution channel 3731 may be flanked on either side by and fluidically connected to connecting risers 3727 and 3729, which may be formed as orifices extending through frame 1115 from surface 3701r to surface 3703 in axial direction 3801, such as can be appreciated from FIGS. 37-42. Similarly, distribution channel 3737 may be flanked on either side by and fluidically connected to connecting risers 3739 and 3741, which may be formed as orifices extending through frame 1115 from surface 3701r to surface 3703 in axial direction 3801.

[0324] As seen in FIGS. 39 and 40, connecting risers 3727, 3729, 3739, and 3749 may be fluidically connected to first fluidic inlet and outlet passages 3715-3721, respectively, via corresponding groups of channels 4001-4015. For instance, connecting riser 3727 may be fluidically connected to first fluidic inlet passages 3715 via channels 4001 and 4003, whereas connecting riser 3729 may be fluidically connected to first fluidic inlet passages 3717 via channels 4005 and 4007. Further, connecting riser 3739 may be fluidically connected to first fluidic outlet passages 3719 via channels 4009 and 4011, whereas connecting riser 3741 may be fluidically connected to first fluidic outlet passages 3721 via channels 4013 and 4015.

[0325] Channels 4001-4015 may be formed as blind recesses in surface 3703 and may extend in oblique directions with respect to, for instance, a direction of extension of reference plane 3803, as can be appreciated in FIGS. 39, 40, and 42. For instance, as seen in FIG. 42, channels 4015 may not only extend parallel (or substantially parallel) to one another, but may extend from first outlet orifice 3721a of first fluidic outlet passage 3721 to connecting riser 3741 at oblique angle 4201. Similarly, channels 4013 may not only extend parallel (or substantially parallel) to one another, but may extend from second outlet orifice 3721b of first fluidic outlet passage 3721 to connecting riser 3741 at oblique angle 4203, which may be smaller than oblique angle 4201. In some embodiments, channels 4013 and 4015 may be formed as respective groups of six channels, but embodiments are not limited thereto. For example, any number of channels may be utilized, such as less or more than six. Additionally, channels 4013 and 4015 may have the same number of individual channels or a different number of individual channels. To this end, the individual channels among channels 4013 and 4015 may have equivalent (or substantially equivalent) cross-sectional areas in a plane perpendicular to their respective directions of longitudinal extension. In some embodiments, some of the individual channels may have equivalent (or substantially equivalent) cross-sectional areas (such as channels 4013a and 4013b) and at least one of the individual channels may have a different cross-sectional area (such as channel 4013c). In the case of individual channel 4013c, its cross-sectional area may vary in size, such as increase in cross-sectional area with increasing distance from second outlet orifice 3721b of first fluidic outlet passage 3721. Channels 4001-4011 may be similarly configured as described in association with channels 4013 and 4015, but with respect to the corresponding connecting risers and first fluidic inlet and outlet passages associated therewith.

[0326] According to various embodiments, openings 3723 and 3725 may be arranged between second fluidic inlet and outlet passages 3743 and 3745, which form respective portions of inlet and outlet passages 901 and 903 (see FIG. 9) of stack 500 in association with input and outlet connectors 547 and 549 of manifold assembly 515 (see, e.g., FIGS. 5-10). Inlet passage 901 (see FIG. 9) may supply one or more reactants (e.g., gaseous COx) to the various cathode frames 1131 of stack 500 (see, e.g., FIG. 5), and, as such, to the corresponding cathode flow fields 1127 (see, e.g., FIGS. 5-11A) supported in association therewith when frame 1115 is incorporated as part of a cell, such as cell 501. Outlet passage 903 (see FIG. 9), however, may enable one or more byproducts of the COx reduction process to be expelled from the various cathode frames 1131 of stack 500 (see, e.g., FIGS. 5-11A), and, thereby, from the corresponding cathode flow fields 1127 supported in association therewith.

[0327] Frame 1115 may also include recesses 3747-3759 in surface 3701 that may be configured to respectively receive corresponding portions of gaskets among first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24) therein when, for example, frame 1115 is assembled as part of a repeat unit (e.g., repeat unit 503_1 in FIG. 5) or anode interface assembly 509 (see, e.g., FIGS. 5-10, 47, and 48). For instance, and with momentary reference to FIGS. 11A, 23, and 24 in addition to FIGS. 37-42, recess 3747 may be formed to encircle the periphery of opening 3725 and interface with first anode gasket 1113a of first anode gasket set 1113, whereas recesses 3749-3755 may be formed to respectively encircle the peripheries of first fluidic inlet and outlet passages 3715-3721 and respectively interface with second anode gaskets 1113b of first anode gasket set 1113. It is noted that the conjunction of first fluidic inlet passages 3715 and 3717, channels 4001, 4003, 4005, and 4007, connecting risers 3727 and 3729, distribution channel 3731, and supply channels 3733 enables, for example, water to flow from an area outside of first anode gasket 1113a of first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24) to an area inside of first anode gasket 1113a of first anode gasket set 1113 without disturbing the integrity of or seal provided by first anode gasket 1113a of first anode gasket set 1113. The same is true with respect to the integrity of and seals provided by those second anode gaskets 1113b of first anode gasket set 1113 that interface with recesses 3749 and 3751, see, e.g., FIGS. 11A, 23, and 24). In a similar fashion, the conjunction of first fluidic outlet passages 3719 and 3721, outlet channels 3735, collection channel 3737, connecting risers 3739 and 3741, and channels 4009, 4011, 4013, and 4015 enables, for example, water to flow from an area inside of first anode gasket 1113a of first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24) to an area outside of first anode gasket 1113a of first anode gasket set 1113 without disturbing the integrity of or seal provided by first anode gasket 1113a of first anode gasket set 1113. The same is true with respect to the integrity of and seals provided by those second anode gaskets 1113b of first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24) that interface with recesses 3753 and 3755. In addition, recesses 3757 and 3759 may be formed to encircle the respective peripheries of second fluidic inlet and outlet passages 3743 and 3745 and interface with third anode gaskets 1113c of first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24).

[0328] Similar to recesses 3747-3759 formed in surface 3701, frame 1115 may include recesses 4017-4029 in surface 3703 that may be configured to respectively receive corresponding portions of gaskets among second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24) therein when, for example, frame 1115 is assembled as part of a repeat unit (e.g., repeat unit 503_1 in FIG. 5) or anode interface assembly 509 (see, e.g., FIGS. 5-10, 47, and 48). For instance, recess 3717 may be formed to encircle the periphery of opening 3723 and interface with first anode gasket 1117a of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). Recesses 4019-4025 may be formed to respectively encircle combined peripheries of associated first fluidic inlet and outlet passages 3715-3721, corresponding channels 4001-4015, and respective connecting risers 3727, 3729, 3739, and 3741 and respectively interface with second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). For example, recess 4019 may be formed to encircle a combined periphery of first fluidic inlet passages 3717, channels 4005 and 4007, and connecting riser 3729 and to interface with one of second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24), whereas recess 4021 may be formed to encircle a combined periphery of first fluidic inlet passages 3715, channels 4001 and 4003, and connecting riser 3727 to interface with another one of second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). Similarly, recess 4023 may be formed to encircle a combined periphery of first fluidic outlet passages 3721, channels 4013 and 4015, and connecting riser 3741 to interface with still another one of second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24), whereas recess 4025 may be formed to encircle a combined periphery of first fluidic outlet passages 3719, channels 4009 and 4011, and connecting riser 3739 to interface with yet another one of second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). It is noted that the conjunction of first fluidic inlet passages 3715 and 3717, channels 4001, 4003, 4005, and 4007, connecting risers 3727 and 3729, distribution channel 3731, and supply channels 3733 enables, for example, water to flow from an area outside of first anode gasket 1113a of first anode gasket set 1113 (see, e.g., FIGS. 11A, 23, and 24) to an area inside of first anode gasket 1113a of first anode gasket set 1113 without also disturbing the integrity of or seal provided by second anode gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). In addition, recesses 4027 and 4029 may be formed to at least encircle the respective peripheries of second fluidic inlet and outlet passages 3743 and 3745 and interface with third anode gaskets 1117c of second anode gasket set 1117 (see, e.g., FIGS. 11A, 23, and 24). It is noted that the size, shape, and location of recesses 4019-4029 may correspond with the size, shape, and location of protrusions 3305 and 3307 (see FIGS. 32-36) of cathode frame 1131 to enable second and third anode gaskets 1117b and 1117c (see, e.g., FIGS. 11A, 23, and 24) to form corresponding seals between anode and cathode frames 1115 and 1131 when anode and cathode frames 1115 and 1131 are stacked in relation with other anode and cathode frames 1115 and 1131 of stack 500 (see, e.g., FIGS. 5-11A, 23, and 24). Accordingly, cross-flow between first and second fluidic inlet and outlet passages 3715-3721, 3743, and 3745 may be prevented.

[0329] Frame 1115 may also include first fastener orifices 3761 arranged about a peripheral area of frame 1115 at one or more intervals. In some embodiments, a pitch between adjacent first fastener orifices 3761 may be constant (or substantially constant), but embodiments are not limited thereto. Second and third fastener orifices 3763 and 3765 may be inset from first fastener orifices 3761 in central portions of frame 1115 near second fluidic inlet and outlet passages 3743 and 3745. A pitch between adjacent second fastener orifices 3763 and a pitch between adjacent third fastener orifices 3765 may be smaller than the pitch(es) between adjacent first fastener orifices 3761. In various embodiments, first, second, and third fastener orifices 3761, 3763, and 3765 may extend completely through frame 1115 and may be counterbored with respect to surface 3701. According to various embodiments, swage nuts 1135 (see, e.g., FIGS. 11A and 21) may be pressed into, for example, the counterbored portions of first, second, and third fastener orifices 3761, 3763, and 3765 such that, when frame 1115 is assembled as part of a repeat unit (e.g., repeat unit 503_1 in FIG. 5) or as part of anode interface assembly 509 (see, e.g., FIGS. 5-10, 47, and 48), first, second, and third fastener orifices 3761, 3763, and 3765 may be configured to respectively engage with corresponding fasteners 1137 (see, e.g., FIGS. 11A and 21), which may be received in corresponding first, second, and third fastener orifices 2837, 2839, and 2841 of cathode frame 1131 (see, e.g., FIGS. 11A, 21, 28, 29, 32, 33, and 35).

[0330] According to some embodiments, frame 1115 and / or anode annular insert 1118 may be formed of any suitable thermoplastic and / or thermosetting material, such as, for instance, PET, PC, PI, PA, PMMA, PEN, PEK, PEEK, PEI, PPS, PAR, PES, COC, PVA, PS, ECTFE, PTFE, PBT, PCTFE, PETG, and / or the like. In some cases, frame 1115 and / or anode annular insert 1118 may be formed of one or more metals or metal alloys, such as, for example, aluminum, aluminum alloy, copper, copper alloy, tin, tin alloy, titanium, titanium alloy, tungsten, tungsten alloy, zinc, zinc alloy, steel, stainless steel, etc. It is noted, however, that when formed of a metal or metal alloy, frame 1115 and / or anode annular insert 1118 may, in some embodiments, include a coating or other feature to, for instance, electrically insulate frame 1115 or anode annular insert 1118 from a corresponding anode PTL (e.g., anode PTL 1109 in FIG. 11A) and / or anode flow field (e.g., anode flow field 1111 in FIG. 11A) associated therewith. It is also contemplated that a base material of frame 1131 and / or anode annular insert 1118 may be coated with, for instance, one or more other materials, e.g., one or more corrosion-resistant materials. That being said, in some cases, anode annular insert 1118 may be formed of one or more materials with equivalent, substantially equivalent, or at least similar chemical inertness as PTL 1109. To this end, anode annular insert 1118 may have a porous or non-porous configuration. Whatever the case, frame 1115 and / or anode annular insert 1118 may be formed in any suitable manner, such as additively manufactured, injection molded, compression molded, stamped, casted, machined, and / or the like.Separator Plate

[0331] FIG. 43 depicts a plan view of an example separator plate of the representative repeat unit of FIG. 11A. Separator plate 1107 may be a generally rectangular plate-shaped body having first surface 4301 (e.g., a top surface) opposing a second surface in axial direction 4303. Although separator plate 1107 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. For convenience, separator plate 11070 will be described in association with a generally rectangular configuration. First surface 4301 and the second surface may be bounded by one or more peripheral surfaces, such as peripheral surfaces (or surfaces) 4305, 4307, 4309, and 4311 that may be connected to one another via one or more other peripheral surfaces, such as peripheral surface (or surface) 4313. Separator plate 1107 may also have terminal 4307t protruding from peripheral surface 4307. It is noted that when corresponding separator plates (such as separator plate 1107) are interposed between adjacent cells among stack 500 (see FIGS. 5-10), corresponding voltage drops between adjacent separator plates (and, thereby, associated with respective cells correspondingly between the adjacent separator plates) may be probed via respective terminals (such as terminal 4307t) of the corresponding separator plates, such as separator plate 1107 (see also FIG. 7). In some embodiments, separator plate 1107 may have a symmetrical configuration about one or more reference planes perpendicular to axial direction 4303. For instance, a configuration of separator plate 1107 may be symmetrical about either or both of reference planes 4315 and 4317 (apart from the presence of terminal 4307t), but embodiments are not limited thereto.

[0332] According to various implementations, separator plate 1107 includes first openings 4319 and 4321 adjacent to peripheral surface 4305, second openings 4323 and 4325 adjacent to peripheral surface 4309, third opening 4327 adjacent to peripheral surface 4305, and fourth opening 4329 adjacent to peripheral surface 4309. Openings 4319 and 4321 may be sized, shaped, and located in correspondence with the size, shape, and location of protrusions 3305 (see, e.g., FIGS. 32 and 33) adjacent to peripheral surface 2805 of cathode frame 1131 such that, when separator plate 1107 is incorporated as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), protrusions 3305 adjacent to peripheral surface 2805 of cathode frame 1131 may be received in openings 4319 and 4321 (see also FIG. 23). Similarly, openings 4323 and 4325 may be sized, shaped, and located in correspondence with the size, shape, and location of protrusions 3305 adjacent to peripheral surface 2809 of cathode frame 1131 (see, e.g., FIGS. 32 and 33) such that, when separator plate 1107 is incorporated as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), protrusions 3305 adjacent to peripheral surface 2809 of cathode frame 1131 may be received in openings 4323 and 4325. Further, openings 4327 and 4329 may be sized, shaped, and located in correspondence with the size, shape, and location of protrusions 3307 adjacent to peripheral surfaces 2805 and 2809 of cathode frame 1131 (see, e.g., FIGS. 24, 32, and 33) such that, when separator plate 1107 is incorporated as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), protrusions 3307 adjacent to peripheral surfaces 2805 and 2809 of cathode frame 1131 may be respectively received in openings 4327 and 4329 (see also FIG. 24). Relative dimensioning between openings 4319-4329 and first and second protrusions 3305 and 3307 has already been described in association with cathode frame 1131, and, therefore, duplicative descriptions will be omitted to avoid obscuring embodiments described herein. In this manner, first surface 4301 of separator plate 1107 may abut against surface 3701 of anode frame 1115 (see, e.g., FIGS. 23, 24, 37, and 38) and the second surface of separator plate 1107 may abut against surface 2801 of cathode frame 1131 (see, e.g., FIGS. 23, 24, 32, and 33) when the repeat unit (e.g., repeat unit 1100 in FIG. 11A) is assembled, such as assembled in a compressed state (see also FIGS. 20-24). Separator plate 1107 may also include first fastener orifices 4331 arranged about a peripheral area of separator plate 1107 at one or more intervals. In some embodiments, a pitch between adjacent first fastener orifices 4331 may be constant (or substantially constant), but embodiments are not limited thereto. Second and third fastener orifices 4333 and 4335 may be inset from first fastener orifices 4331 in central portions of separator plate 1107 near third and fourth openings 4327 and 4329. A pitch between adjacent second fastener orifices 4333 and a pitch between adjacent third fastener orifices 4335 may be smaller than the pitch(es) between adjacent first fastener orifices 4331. In various embodiments, first, second, and third fastener orifices 4331, 4333, and 4335 may extend completely through separator plate 1107 such that, when separator plate 1107 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A), fasteners 1137 extending from cathode frame 1131 may extend through separator plate 1107 and may be threadedly engaged with corresponding swage nuts 1135 pressed and / or clinched into first, second, and third fastener orifices 3761, 3763, and 3765 of anode frame 1115 (see also FIGS. 11A and 21).

[0333] According to various embodiments, one or more of first, second, and third fastener orifices 4331, 4333, and 4335 may be sized to form respective clearance or interference fits with corresponding fasteners 1137 (see FIG. 11A) or corresponding portions (e.g., shoulder portions) of fasteners 1137 (see, e.g., FIG. 21) when separator plate 1107 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A). In some cases, one or more of first, second, and third fastener orifices 4331, 4333, and 4335 may be sized to form respective clearance fits with corresponding fasteners 1137 (see FIG. 11A) or corresponding portions (e.g., shoulder portions) of fasteners 1137 (see, e.g., FIG. 21) and one or more of first, second, and third fastener orifices 4331, 4333, and 4335 may be sized to form respective interference fits with corresponding fasteners 1137 (see FIG. 11A) or corresponding portions (e.g., shoulder portions) of fasteners 1137 (see, e.g., FIG. 21). For example, respective sizes (e.g., diameters) of first, second, and third fastener orifices 4331, 4333, and 4335 may be about 0.01% to about 10% larger (in the case of a clearance fit) or about 0.01% to about 5% smaller (in the case of an interference fit) than corresponding widths (e.g., diameters) of respective portions (e.g., shoulder portions) of fasteners 1137 (see, e.g., FIGS. 11A, 17, and 21). In some embodiments, one or more of first, second, and third fastener orifices 4331, 4333, and 4335 may be sized to form respective clearance fits with corresponding fasteners 1137 (see, e.g., FIGS. 11A, 17, and 21) or corresponding portions (e.g., shoulder portions) of fasteners 1137 (see, e.g., FIG. 21) when separator plate 1107 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A) and stack 500 (see, e.g., FIG. 5) is in a cooled, non-operational state, but when stack 500 is in a steady-state operational condition, fasteners 1137 may expand to form corresponding interference fits with the one or more of first, second, and third fastener orifices 4331, 4333, and 4335. These clearance and / or interference fits may be utilized to constrain in-plane expansion (e.g., expansion in, for instance, a plane parallel to an x-y plane (see FIG. 11A)) of anode and cathode frames 1115 and 1131 during operation of stack 500 (see, e.g., FIG. 5) without unduly stressing anode and cathode frames 1115 and 1131.

[0334] It is also noted that, when separator plate 1107 is assembled as part of a repeat unit (e.g., repeat unit 1100 in FIG. 11A) with cathode frame 1131 coupled to anode frame 1115 via fasteners 1137 and swage nuts 1135 (see also FIGS. 11A and 21-24), some of the various gaskets of second anode gasket set 1117 may not only be interposed between surface 4301 of separator plate 1107 and some of the various recesses in surface 3703 of anode frame 1115 (see, e.g., FIGS. 39 and 40), but may also encircle the various protrusions extending from surface 2801 of cathode frame 1131 (see, e.g., FIGS. 32 and 33). For example, second gaskets 1117b of second anode gasket set 1117 (see, e.g., FIGS. 11A and 23) may not only be interposed between surface 4301 of separator plate 1107 and corresponding recesses 4019-4025 in surface 3703 of anode frame 1115 (see also FIGS. 39 and 40), but may also encircle protrusions 3305 extending from surface 2801 of cathode frame 1131 (see also FIGS. 32 and 33) to fluidically seal corresponding first fluidic inlet and outlet passageways between cathode frame 1131 and anode frame 1115 (see, e.g., second anode gasket 1117b fluidically sealing first fluidic inlet passageway 2301 that is outlined in FIG. 23 in a dash-dot-dot line format). In a similar fashion, third gaskets 1117c of second anode gasket set 1117 (see, e.g., FIGS. 11A and 24) may not only be interposed between surface 4301 of separator plate 1107 and corresponding recesses 4027-4029 in surface 3703 of anode frame 1115 (see also FIGS. 39 and 40), but may also encircle protrusions 3307 extending from surface 2801 of cathode frame 1131 (see also FIGS. 32 and 33) to fluidically seal corresponding second fluidic inlet and outlet passageways between cathode frame 1131 and anode frame 1115 (see, e.g., third anode gasket 1117c fluidically sealing second fluidic outlet passageway 2401 that is outlined in FIG. 24 in a dash-dot-dot line format).

[0335] According to various embodiments, separator plate 1107 may be formed of any suitable thermoplastic and / or thermosetting material, such as, for instance, PET, PC, PI, PA, PMMA, PEN, PEK, PEEK, PEI, PPS, PAR, PES, COC, PVA, PS, ECTFE, PTFE, PBT, PCTFE, PETG, and / or the like. In some cases, separator plate 1107 may be formed of one or more metals or metal alloys, such as, for example, aluminum, aluminum alloy, copper, copper alloy, tin, tin alloy, titanium, titanium alloy, tungsten, tungsten alloy, zinc, zinc alloy, steel, stainless steel, etc. For instance, in one embodiment, separator plate 1107 may be formed of titanium, which may increase the strength and rigidity of a repeat unit, such as repeat unit 1100 in FIG. 11A, as well as enable electrical conductivity between adjacent cells of stack 500 (see, e.g., FIGS. 5 and 7). In some embodiments, a material(s) and / or configuration of separator plate 1107 may be stronger and / or more rigid than a material(s) and / or configuration of anode and cathode frames 1115 and 1131 (see also FIG. 11A). In some instances, an electrical conductivity of separator plate 1107 may be greater than corresponding electrical conductivities of anode and cathode frames 1115 and 1131 (see also FIG. 11A). It is also contemplated that a base material of separator plate 1107 may be coated with, for instance, one or more other materials, e.g., one or more corrosion-resistant materials. Whatever the case, separator plate 1107 may be formed in any suitable manner, such as additively manufactured, injection molded, compression molded, stamped, casted, machined, and / or the like.Cathode Interface Assembly

[0336] FIG. 17 depicts an exploded view of an example cathode interface assembly of the example multi-cell COx electrolyzer stack of FIG. 6. FIG. 18 depicts the example cathode interface assembly of FIG. 17 in a non-exploded state. FIGS. 45 and 46 depict top and bottom plan views of an example cathode interface separator of the example cathode interface assembly of FIG. 18.

[0337] As seen in FIGS. 5-10, 17, and 18, cathode interface assembly 505 may include equivalent components as cathode components 1103 of repeat unit 1100 described in association with FIG. 11A, except cathode interface assembly 505 may also include cathode interface separator 1701, third cathode gaskets 1703, and fourth cathode gaskets 1705. As such, duplicative descriptions of equivalent components will be omitted to avoid obscuring embodiments disclosed herein. It is noted, however, that instead of cathode frame 1131 being coupled to anode frame 1115 as in repeat unit 1100 (see FIG. 11A), cathode frame 1131 may be coupled to cathode interface separator 1701, which will now be described in more detail in association with FIGS. 45 and 46.

[0338] Referring to FIGS. 45 and 46, cathode interface separator 1701 may be a generally rectangular plate-shaped body having first surface 4501 (e.g., a top surface) opposing second surface 4503 (e.g., a bottom surface) in axial direction 4601. Although cathode interface separator 1701 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. For convenience, cathode interface separator 1701 will be described in association with a generally rectangular configuration. First and second surfaces 4501 and 4503 may be bounded by one or more peripheral surfaces, such as peripheral surfaces (or surfaces) 4505, 4507, 4509, and 4511 that may be connected to one another via one or more other peripheral surfaces, such as peripheral surface (or surface) 4513. In some embodiments, cathode interface separator 1701 may have a symmetrical configuration about one or more reference planes perpendicular to axial direction 4601. For instance, a configuration of cathode interface separator 1701 may be symmetrical about either or both of reference planes 4603 and 4605, but embodiments are not limited thereto.

[0339] According to various embodiments, cathode interface separator 1701 may include first fluidic inlet passages 4515 and 4517 adjacent to peripheral edge 4505, and first fluidic outlet passages 4519 and 4521 adjacent to peripheral edge 4509. With additional reference to FIGS. 5-11A, first fluidic inlet passages 4515 and 4517 may form portions of inlet passages 1001 and 1003 of stack 500 in association with inlet connectors 543 of manifold assembly 515 that provide, for example, input water to anode frames 1115 of stack 500, and, thereby, to the corresponding anode flow fields 1111 of the plurality of cells, such as cell 501. First fluidic outlet passages 4519 and 4521 may form portions of outlet passages (that are similar to inlet passages 1001 and 1003, but associated with outlet connectors 545 of manifold assembly 515 versus inlet connectors 543) of stack 500 that output water from anode frames 1115, and, thereby, from corresponding anode flow fields 1111 of the plurality of cells, such as cell 501 (see also FIGS. 5-11A). In some implementations, first fluidic inlet and outlet passages 4515-4521 may be defined by respective pluralities of orifices separated from one another via corresponding septal walls. For instance, first fluidic inlet passage 4515 may include first and second inlet orifices 4515a and 4515b separated from one another via septal wall 4501s1, whereas first fluidic outlet passage 4519 may include first and second outlet orifices 4519a and 4519b separated from one another via septal wall 4501s2. As with anode and cathode frames 1115 and 1131 (see, e.g., FIG. 11A), the presence of these septal walls, such as septal walls 4501s1 and 4501s2, may increase the structural rigidity and, thereby, reliability of cathode interface separator 1701 in the vicinity of first fluidic inlet and outlet passages 4515-4521.

[0340] Cathode interface separator 1701 may further include second inlet and outlet passages 4523 and 4525, which form respective portions of inlet and outlet passages 901 and 903 of stack 500 (see FIG. 9) in association with input and outlet connectors 547 and 549 of manifold assembly 515 (see, e.g., FIGS. 5 and 9). Inlet passage 901 (see FIG. 9) may supply one or more reactants (e.g., gaseous COx) to the various cathode frames 1131 of stack 500 (see, e.g., FIGS. 5 and 9), and, as such, to the corresponding cathode flow fields 1127 supported in association therewith when cathode interface separator 1701 is incorporated as part of a cell, such as a cell formed between cathode interface assembly 505 and repeat unit 503_1 (see, e.g., FIGS. 5-11A and 19). Outlet passage 903, however, may enable one or more byproducts of the COx reduction process to be expelled from the various cathode frames 1131 of stack 500, and, thereby, from the corresponding cathode flow fields 1127 supported in association therewith (see, e.g., FIGS. 5-11A and 19).

[0341] Similar to anode frame 1115 (see, e.g., FIGS. 11A, 37, and 38), cathode interface separator 1701 may also include recesses 4527-4537 in surface 4501 that may be configured to respectively receive corresponding portions of gaskets 553 and 555 when, for example, cathode interface assembly 505 is assembled as part of stack 500, e.g., when cathode interface assembly 505 is stacked in relation to manifold assembly 515 with bus plate 513 interposed therebetween (see, e.g., FIGS. 5-10, 17, and 18). For instance, recesses 4527-4533 may be formed to respectively encircle the peripheries of first fluidic inlet and outlet passages 4515-4521 and respectively interface with corresponding gaskets 553 (which may respectively encircle third fluidic outlet and inlet ports 1225 and 1229 of manifold assembly 515 (see, e.g., FIG. 12)), whereas recesses 4535 and 4537 may be formed to respectively encircle the peripheries of second fluidic inlet and outlet passages 4535 and 4537 and respectively interface with corresponding gaskets 555 (which may respectively encircle fourth fluidic outlet and inlet ports 1239 and 1237 of manifold assembly 515 (see, e.g., FIG. 12)). As such, corresponding fluidic seals may be formed with respective outlet and inlet ports of manifold assembly 515 when cathode interface assembly 505 is assembled as part of stack 500 (see, e.g., FIGS. 5-10).

[0342] Referring to FIG. 46, second surface 4503 may include first recesses 4607-4613 respectively encircling first fluidic inlet and outlet passages 4515-4521, as well as second recesses 4615 and 4617 respectively encircling second fluidic inlet and outlet passages 4535 and 4537. In some embodiments, first and second recesses 4607-4617 may be recessed into surface 4503 by a depth equivalent (or substantially equivalent) to height 3401 (see FIG. 34) of first and second protrusions 3305 and 3307 of cathode frame 1131, but embodiments are not limited thereto. For instance, the depth at which first and second recessed 4607-4617 extend into surface 4503 may be greater than or smaller than height 3401 (see FIG. 34) provided sufficient fluidic seals may be formed between cathode interface separator 1701 and cathode frame 1131 when a cell is formed between cathode interface assembly 505 and repeat unit 503_1 (see also FIGS. 5-10 and 17). In other words, the depth of first and second recesses 4607-4617 may at least permit a portion of first and second protrusions 3305 and 3307 of cathode frame 1131 to be received therein when a cell is formed between cathode interface assembly 505 and repeat unit 503_1 (see also FIGS. 5-10). With this in mind, first and second recesses 4607-4613 may be sized and shaped to interface with corresponding protrusions among first and second protrusions 3305 and 3307 of cathode frame 1131 (see FIGS. 32-33).

[0343] Cathode interface separator 1701 may further include third recesses 4619-4625 in surface 4503 respectively encircling first fluidic inlet and outlet passages 4515-4521 and associated recesses 4607-4613, as well as include fourth recesses 4627 and 4629 respectively encircling second fluidic inlet and outlet passages 4523 and 4525 and associated recesses 4615-4617. It is also noted that third and fourth recesses 4619-4629 may be respectively sized, shaped, and located to further correspond with the size, shape, and location of protrusions 3305 and 3307 of cathode frame 1131 (see FIGS. 32-33) to enable third and fourth cathode gaskets 1703 and 1705 to form corresponding seals between cathode interface separator 1701 and first and second protrusions 3305 and 3307 of cathode frame 1131 when a cell is formed between cathode interface assembly 505 and repeat unit 503_1 (see also FIGS. 5-10, 32, and 33). Accordingly, the conjunction of first and second recesses 4607-4617 of cathode interface separator 1701, third and fourth recesses 4619-4629 of cathode interface separator 1701, first and second protrusions 3305 and 3307 of cathode frame 1131 (see FIGS. 32-33), and third and fourth cathode gaskets 1703 and 1705 may prevent cross-flow between first and second fluidic inlet and outlet passages 4515-4525. It is also noted that, when a cell is formed between cathode interface assembly 505 and repeat unit 503_1 (see, e.g., FIGS. 5-10), second cathode gasket 1133 may be interposed between a central portion of surface 4503 and recess 3303 in cathode frame 1131 (see FIGS. 17, 32, and 33) to form a fluidic seal around cathode flow field 1127 at least partially supported in an opening of cathode frame 1131. In this manner, corresponding surfaces of cathode flow field 1127 may abut against surface 4503 of cathode interface separator 1701 and a surface of cathode GDL 1121 facing cathode flow field 1127 similar to how corresponding surfaces of cathode flow field 1127 may abut against a surface of cathode GDL 1121 of unitized MEA assembly 1119 and a surface of separator plate 1107 described in association with, for instance, FIGS. 5-11A, 23, and 24.

[0344] Cathode interface separator 1701 may also include first threaded fastener orifices 4539 arranged about a peripheral area of cathode interface separator 1701 at one or more intervals. In some embodiments, a pitch between adjacent first threaded fastener orifices 4539 may be constant (or substantially constant), but embodiments are not limited thereto. Cathode interface separator 1701 may optionally include second and third threaded fastener orifices 4541 and 4543 inset from first threaded fastener orifices 4539 in central portions of cathode interface separator 1701 near second fluidic inlet and outlet passages 4523 and 4525. A pitch between adjacent second threaded fastener orifices 4541 and a pitch between adjacent third threaded fastener orifices 4543 may be smaller than the pitch(es) between adjacent first threaded fastener orifices 4539. In some embodiments, one or more of first, second, and third threaded fastener orifices 4539-4543 may be formed similar to first, second, and third fastener orifices 3761-3765 of anode frame 1115 (see, e.g., FIGS. 11A and 37-42), and, thereby, include swage nuts 1135 versus being threaded. Regardless, when cathode interface separator 1701 is assembled as part of cathode interface assembly 505 (see also FIGS. 5-10), first, second, and third threaded fastener orifices 4539, 4541, and 4543 may be configured to respectively engage with corresponding fasteners 1137 respectively received in and extending from corresponding first, second, and third fastener orifices 2837, 2839, and 2841 of cathode frame 1131 (see FIGS. 28, 29, 32, 33, and 35). Further, as can be appreciated from at least FIG. 17, cathode frame 1131 of cathode interface assembly 505 may be coupled to cathode interface separator 1701 with second, third, and fourth cathode gaskets 1133, 1703, and 1705 interposed therebetween.

[0345] According to various embodiments, cathode interface separator 1701 may be formed of any suitable thermoplastic and / or thermosetting material, such as, for instance, PET, PC, PI, PA, PMMA, PEN, PEK, PEEK, PEI, PPS, PAR, PES, COC, PVA, PS, ECTFE, PTFE, PBT, PCTFE, PETG, and / or the like. In some cases, cathode interface separator 1701 may be formed of one or more metals or metal alloys, such as, for example, aluminum, aluminum alloy, copper, copper alloy, tin, tin alloy, titanium, titanium alloy, tungsten, tungsten alloy, zinc, zinc alloy, steel, stainless steel, etc. For instance, in one embodiment, cathode interface separator 1701 may be formed of titanium, which may increase the strength and rigidity of cathode interface assembly 505 (see, e.g., FIGS. 5-10, 17, and 18). In some cases, a material(s) and / or configuration of cathode interface separator 1701 may be stronger and / or more rigid than a material(s) and / or configuration of anode and cathode frames 1115 and 1131 (see also FIG. 11A). Also, an electrical conductivity of cathode interface separator 1701 may, in some embodiments, be greater than corresponding electrical conductivities of anode and cathode frames 1115 and 1131 (see also FIG. 11A). It is also contemplated that a base material of cathode interface separator 1701 may be coated with, for instance, one or more other materials, e.g., one or more corrosion-resistant materials. Whatever the case, cathode interface separator 1701 may be formed in any suitable manner, such as additively manufactured, injection molded, compression molded, stamped, casted, machined, and / or the like.Anode Interface Assembly

[0346] FIG. 47 depicts an exploded view of an example anode interface assembly of the example multi-cell COx electrolyzer stack of FIG. 6. FIG. 48 depicts the example anode interface assembly of FIG. 47 in an assembled state. FIG. 44 depicts an example anode interface separator of FIG. 47.

[0347] As seen in at least FIGS. 5, 6, 11A, 44, 47, and 48, anode interface assembly 509 may include equivalent components as anode components 1101 of repeat unit 1100, except anode interface assembly 509 may omit third anode gaskets 1117c of second anode gasket set 1117 and include anode frame 4701 instead of anode frame 1115. As such, duplicative descriptions of equivalent components will be omitted to avoid obscuring embodiments disclosed herein. In addition, anode interface assembly 509 may include anode interface separator 4703, which may be configured substantially equivalent to separator plate 1107 of repeat unit 1100, except anode interface separator 4703 may exclude openings / orifices 4319-4335 (see FIG. 43). It is also noted that anode frame 4701 may be substantially equivalent to anode frame 1115 (see also FIGS. 37-42), except that anode frame 4701 may omit second fluidic inlet and outlet passages 3743 and 3745, recesses 4027 and 4029 in surface 3703, and first, second, and third fastener orifices 3761, 3763, and 3765, as well as swage nuts 1135. Thus, instead of anode frame 4701 being coupled to an adjacent cathode frame, such as cathode frame 1115, as in repeat unit 1100 described at least in association with FIG. 11A, anode frame 4701 may simply be interposed between unitized MEA assembly 1119_n of repeat unit 503_n and anode interface separator 4703 when anode interface assembly 509 is incorporated as part of stack 500 (see also FIGS. 5-10). As such, second and third anode gaskets 1113b and 1113c of first anode gasket set 1113 may interface with recesses in surface 4701a of anode frame 4701 similar to recesses 3749-3759 in surface 3701 of anode frame 1115 and abut against surface 2803 of cathode frame 1131 of repeat unit 503_n around first and second fluidic inlet and outlet passages 2815-2821 (see also FIGS. 28-36). Further, first anode gasket 1113a of first anode gasket set 1113 may interface with a recess in surface 4701a of anode frame 4701 similar to recess 3747 in surface 3701 of anode frame 1115, abut against a corresponding surface of support frame 1125 of unitized MEA assembly 1119 (see also FIGS. 25-27), and encircle opening 1125a in support frame 1125 (see also FIGS. 25-27). In a similar fashion, first and second anode gaskets 1117a and 1117b of second anode gasket set 1117 may simply interface with recesses in surface 4701b of anode frame 4701 similar to recesses 4017-4025 in surface 3703 of anode frame 1115 (see also FIGS. 39, 40, and 42) and may abut against first surface 4703a of anode interface separator 4703.Bladder

[0348] As previously discussed, bladder side assembly 511 (see, e.g., FIG. 5) may be at least configured to constrain axial expansion of the plurality of cells, such as cell 501, of stack 500 during the COx reduction process(es) in a manner that prevents or reduces the likelihood of the plurality of cells from being overly or insufficiently compressed, but maintain corresponding fluidic seals and electrical conductivity between associated components of stack 500. These features may be provided by the conjunction of bladder bus plate 521, insulation plate 523, end plate 525, gaskets 559 and 561, and fluidic inlet connector 563 (see, e.g., FIGS. 5-10).

[0349] FIG. 86 depicts a plan view of an illustrative insulation plate of the example multi-cell COx electrolyzer of FIG. 6. FIG. 87 depicts a cross-sectional view of the illustrative insulation plate of FIG. 86 taken along sectional line 87-87. FIG. 88 depicts a plan view of an illustrative end plate of the example multi-cell COx electrolyzer of FIG. 6. FIG. 89 depicts a cross-sectional view of the illustrative end plate of FIG. 88 taken along sectional line 89-89. FIG. 90 depicts an enlarged portion of the cross-sectional view of FIG. 9.

[0350] Referring to FIGS. 86 and 87, insulation plate 523 may be a generally rectangular plate-shaped body having first surface 8601 (e.g., a top surface) opposing second surface 8603 (e.g., a bottom surface) in axial direction 8605. Although insulation plate 523 is described as having a generally rectangular plate-shaped configuration, embodiments are not limited thereto and any suitable geometric configuration may be utilized, such as a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. For convenience, insulation plate 523 will be described in association with a generally rectangular configuration. First and second surfaces 8601 and 8603 may be bounded by one or more peripheral surfaces, such as peripheral surfaces (or surfaces) 8607, 8609, 8611, and 8613 that may be connected to one another via one or more other peripheral surfaces, such as peripheral surface (or surface) 8615. In some embodiments, insulation plate 523 may have a symmetrical configuration about one or more reference planes perpendicular to axial direction 8605. For instance, a configuration of insulation plate 523 may be symmetrical about either or both of reference planes 8617 and 8619, but embodiments are not limited thereto.

[0351] According to various implementations, insulation plate 523 includes first recess 8621 in a central portion of surface 8601. First recess 8621 may not only terminate at surface 8623, but may also include extended portions 8625 and 8627 extending from a central area of first recess 8621 respectively towards peripheral surfaces 8609 and 8613. A size, shape, and location of first recess 8621 may be configured to enable at least a portion of bus plate 521 (see, e.g., FIGS. 5-10) to be received therein when stack 500 is assembled. As such, a corresponding portion of terminal portion 521t of bus plate 521 (see, e.g., FIGS. 5-10) may be received in one of extended portions 8625 and 8627. The central area of first recess 8621 may include second recess 8629 in a peripheral region thereof. Second recess 8629 may be configured to interface with gasket 559 (see, e.g., FIGS. 5 and 90) in a manner that, when bus plate 521 and insulation plate 523 are assembled as part of stack 500, lower surface 521b (see FIG. 90) of bus plate 521 may at least abut against gasket 559, and, depending on an extent of compression of the various components of stack 500, may either abut against surface 8623 of insulation plate 523 (such as shown in FIG. 90) or may be spaced apart from surface 8623 in an axial direction, which may extend parallel (or substantially parallel) to the z-axis direction shown in FIGS. 5 and 90 and may be the same as axial direction 8605. As will become more apparent below, a distance in axial direction 8605 between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 may be controlled to constrain axial expansion of the plurality of cells, such as cell 501, of stack 500 (see, e.g., FIGS. 5-10) during the COx reduction process(es) to maintain corresponding fluidic seals and electrical conductivity between associated components of stack 500, but in a manner that prevents or reduces the likelihood that the plurality of cells (and the associated components of the cells) are overly compressed.

[0352] For example, one or more control fluids (e.g., gaseous COx) may be introduced between bus plate 521 and insulation plate 523 to regulate a distance between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523. In some embodiments, the one or more control fluids may be provided via orifice 8631 in surface 8623 that extends through insulation plate 523 to surface 8603. A size, shape, and location of orifice 8631 may correspond with a size, shape, and location of blind orifice 8801 in surface 525a of end plate 525 (see FIGS. 88-90). Blind orifice 8801 of end plate 525 may be fluidically connected to fluidic inlet connector 563 via fluidic passageway 8803 as seen in FIGS. 88-90. As such, the one or more control fluids may be caused to flow between bus plate 521 and insulation plate 523 via the conjunction of fluidic inlet connector 563, fluidic passageway 8803, blind orifice 8801, and orifice 8631, as well as source 9001 (see FIG. 90) of the one or more control fluids. In some embodiments, source 9001 of the one or more control fluids may be the same as the source of input providing, for instance, gaseous COx, to second fluidic inlet connector 547 (see FIG. 5). Regardless of the source, the distance between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 may be controlled based on an accumulated pressure of the one or more control fluids in the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523, the area being peripherally bounded by gasket 559 (see also FIGS. 5 and 90). In this manner, regulating the distance between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 may be utilized to constrain axial expansion of the plurality of cells, such as cell 501, during operation. This may help maintain corresponding fluidic seals and electrical conductivity between associated components of stack 500 (see, e.g., FIG. 5).

[0353] According to some embodiments, when the accumulated pressure in the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 builds beyond a determined threshold, the distance between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 may increase to point at which a fluidic seal formed between gasket 559 and lower surface 521b of bus plate 521 may become compromised. If and when the fluidic seal formed between gasket 559 and lower surface 521b of bus plate 521 becomes compromised, at least some of the one or more control fluids may escape (or bleed) from the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 that may cause the accumulated pressure to decrease along with the distance between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523. In some embodiments, insulation plate 523 and / or end plate 525 may be configured with one or more fluidic passages interfacing with a relief valve configured to evacuate excess pressure built in the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 to prevent over compression of the various components of stack 500 (see, e.g., FIG. 5).

[0354] In some embodiments, surface 525a (see FIG. 88) of end plate 525 may include recess 8805 encircling blind orifice 8801. Recess 8805 may be configured to interface with gasket 561 (see, e.g., FIGS. 5 and 90) such that, when insulation plate 523, end plate 525, gasket 565, and gasket 561 are incorporated as part of stack 500 (see, e.g., FIGS. 5 and 90), gasket 561 may not only be interposed between insulation plate 523 and end plate 525, but also form a fluidic seal between orifice 8631 in insulation plate 523 and blind orifice 8801 in end plate 525. The fluidic seal between orifice 8631 in insulation plate 523 and blind orifice 8801 in end plate 525 may be enhanced through the coupling of insulation plate 523 and end plate 525. As such, insulation plate 523 may include a plurality of fastener orifices 8633 (which may be countersunk with respect to surface 8601) to enable first fasteners 535 (see FIG. 5) to extend through insulation plate 523 and engage with corresponding fastener orifices 8807 (see FIG. 88) in end plate 525. Although only one set of mating orifices configured to enable the one or more control fluids to be flowed into the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523 are shown in FIGS. 86-90, insulation plate 523 and end plate 525 may be configured with more than one set of mating orifices. In some cases, a plurality of mating orifices may be provided and arranged about the central area of recess 8621 in insulation plate 523, such as arranged at regular (or substantially regular) rotation angles about, for instance, a reference axis coincident with axial direction 8605. Such a configuration may allow for a more uniform axial force to be exerted on bus plate 521 as pressure builds in the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523.

[0355] According to various embodiments, source 9001 may be configured to supply the gaseous COx to second fluidic inlet connector 547 (see, e.g., FIGS. 5-9) at a first pressure and to supply the one or more control fluids (e.g., gaseous COx) to fluidic inlet connector 563 (see, e.g., FIGS. 5-9 and 90) at a second pressure. In some embodiments, the first and second pressures may be equivalent or substantially equivalent. In some cases, source 9001 may be configured to control (e.g., adjust) one or more of the first and second pressures based on conditions of stack 500, e.g., based on an extent of expansion of the cells of stack 500 in the axial direction, based on an accumulated pressure in the area between lower surface 521b of bus plate 521 and surface 8623 of insulation plate 523, based on the temperature of one or more components of stack 500, and / or the like (see also FIGS. 5-10). As such, the first and second pressures may reach equilibrium, such as, in response to steady state conditions, e.g., steady state operational conditions of stack 500. It is also noted that source 9001 may be configured to supply the gaseous COx to second fluidic inlet connector 547 (see, e.g., FIGS. 5-9) at a first time and to supply the one or more control fluids (e.g., gaseous COx) to fluidic inlet connector 563 (see, e.g., FIGS. 5-9 and 90) at a second time. In some embodiments, the first and second times may occur simultaneously or substantially simultaneously. In some cases, source 9001 may be configured to delay the supply of the one or more control fluids to fluidic inlet connector 563 (see, e.g., FIGS. 5-9 and 90) with respect to the provisioning of the gaseous COx to second fluidic inlet connector 547 (see, e.g., FIGS. 5-9). For example, and with reference to FIGS. 5-9 and 90, source 9001 may be configured to delay the supply of the one or more control fluids to fluidic inlet connector 563 until one or more conditions are satisfied, e.g., an extent of expansion of one or more of the cells of stack 500 in the axial direction reaches one or more defined thresholds, a temperature of one or more components of stack 500 reaches one or more defined thresholds, flow of the gaseous COx to second fluidic inlet connector 547 reaches steady state condition(s), and / or the like.

[0356] With continued reference to FIGS. 86, 88, and 90, insulation plate 523 may include a plurality of datum openings 8635 configured to receive and support respective portions of datum rods 557 therein, and end plate 525 may further include fluidic inlet port 8809 configured to interface with fluidic inlet connector 563. Fluidic inlet port 8809 may include threaded region 8809t, which may be configured to engage with a respective threaded region of fluidic inlet connector 563. Alternatively, fluidic inlet connector 563 may be welded, e.g., sweat welded, to fluidic inlet port 8809 and threaded portion 8809t may be omitted.Anode Flow Fields

[0357] FIG. 83 depicts a plan view of a portion of an illustrative anode flow field of the example multi-cell COx electrolyzer of FIG. 6. FIGS. 84A and 84B depict respective cross-sectional views of the illustrative anode flow field of FIG. 83 taken along sectional lines 84A-84A and 84B-84B according to some embodiments.

[0358] With reference to FIGS. 11A, 83, 84A, and 84B, anode flow field 1111 may be a generally rectangular plate-shaped body including a plurality of projections 8301 protruding from surface 8303 of main body portion 8305 in the axial direction, which may extend parallel to the z-axis direction. In some embodiments, projections 8301 may be rectangular prisms having length 8307 in a first direction (e.g., the x-axis direction) transverse to the axial direction, width 8309 in a second direction (e.g., the y-axis direction) transverse to the axial direction and the first direction, and height 8311 in the axial direction, but embodiments are not limited thereto. For instance, one or more of projections 8301 may be alternatively formed as cylindrical prisms, triangular prisms, pentagonal prisms, and / or the like. Projections 8301 may be spaced apart from one another by pitch 8313 in the first direction and pitch 8315 in the second direction. Although projections 8301 are shown as being arranged in a plurality of parallel rows and parallel columns, embodiments are not limited thereto. For instance, adjacent rows and / or columns of projections 8301 may be offset from one another such as shown in FIG. 85A with respect to projections 8501. In some cases, pitches 8313 and 8315 may be equivalent (or substantially equivalent) to one another, but embodiments are not limited thereto. In this manner, fluidic passages 8317 may be formed between adjacent projections among projections 8301, and, thereby, form flow paths through which water (or other anolyte) may flow in a distributed manner generally from supply channels 3733 of anode frame 1115 to collection channels 3735 of anode frame 1115 (see FIG. 37-42) to provide water to anode PTL 1109, and, thereby, to the anode side of MEA 1105 (see FIG. 11A).

[0359] Although anode flow field 1111 has been described as having a generally rectangular plate-shaped body, any suitable geometric configuration may be utilized. For instance, anode flow field 1111 may have a generally circular, generally elliptical, generally triangular, generally pentagonal, generally hexagonal, etc., configuration. Whatever configuration is utilized, anode flow field 1111 should be able to be at least partially supported in opening 3723 (see, e.g., FIGS. 23, 24, and 37-42) in anode frame 1115. Further, although anode flow field 1111 has been described in association with a pin-type implementation, embodiments are not limited thereto. For instance, any other suitable anode flow field design may be utilized, such as parallel, serpentine, interdigitated, spiral, radial, etc. An example of a rotated pin-type embodiment will be described in more detail in association with FIGS. 85A-85C.

[0360] FIG. 85A depicts a plan view of a portion of an illustrative anode flow field of the example multi-cell COx electrolyzer of FIG. 6. FIGS. 85B and 85C depict respective cross-sectional views of the illustrative anode flow field of FIG. 85A taken along sectional lines 85B-85B and 85C-85C according to some embodiments.

[0361] With reference to FIGS. 11A and 85A-85C, anode flow field 1111 may be formed in a similar manner as described in association with FIGS. 83, 84A, and 84B, but the plurality of projections 8501 in FIGS. 85A-85C may be rotated by angle 8503 with respect to a first direction (e.g., the x-axis direction) to enable leading vertices 8501a of projections 8501 to split and distribute input anolyte flow 8505. In addition, adjacent rows and columns of projections 8501 may be offset from one another. For example, adjacent rows may be offset from one another by offset amount 8507 in the first direction transverse to the axial direction (e.g., the z-axis direction), and adjacent columns may be offset from one another by offset amount 8509 in a second direction (e.g., the y-axis direction) transverse to the axial direction and the first direction. In some cases, offset amounts 8507 and 8509 may be equivalent (or substantially equivalent) to one another, but embodiments are not limited thereto.

[0362] Similar to projections 8301 described in association with FIGS. 83, 84A, and 84B, projections 8501 may protrude from surface 8511 of main body portion 8513 in the axial direction, which may extend parallel (or substantially parallel) to the z-axis direction. As shown in FIGS. 85A-85C, projections 8501 may be diamond-shaped prisms having respective lengths 8515 in the first direction, corresponding widths 8517 in the second direction, and respective heights 8519 in the axial direction, but embodiments are not limited thereto. For instance, one or more of projections 8501 may be alternatively formed as elliptical prisms, oblong prisms, lenticular prisms, sinus prisms, and / or the like. Projections 8501 may be spaced apart from one another by pitch 8521 in the first direction and pitch 8523 in the second direction. In some cases, pitches 8521 and 8523 may be equivalent (or substantially equivalent) to one another, but embodiments are not limited thereto. In this manner, fluidic passages 8525 may be formed between adjacent projections among projections 8501, and, thereby, form flow paths through which water (or other anolyte) may flow in a distributed manner generally from supply channels 3733 of anode frame 1115 (see FIGS. 37-42) to collection channels 3735 of anode frame 1115 to provide water to anode PTL 1109 (see FIG. 11A), and, thereby, to the anode side of MEA 1105.Cathode Flow Fields

[0363] Various features and technologies may be used to help mitigate the detrimental effects of liquid water accumulation in COx electrolyzer cathodes. For example, the cathode flow field 1127 may be constructed so as to have one or more structural features that may allow for more effective liquid water management within the cell 501.

[0364] For example, both the anode flow field 1111 and the cathode flow field 1127 may have a corresponding anode channel(s) and cathode channel(s), respectively. The cathode channel(s) may, for example, be designed to have certain characteristics that may contribute to more effective water evacuation in the context of a COx electrolyzer and / or that may mitigate the potential performance degradation that may occur in such a COx electrolyzer in the event that liquid water collects within the cathode side of the cell 501.Serpentine Channel Flow Fields

[0365] While various geometries of flow field channels may be used in COx electrolyzers, multiple serpentine channels generally offer superior performance in terms of providing for reliable, even distribution of COx gas to the cathode GDL 1121, and thus the MEA 1105, while also facilitating reliable removal of liquid water that may otherwise accumulate within the cathode flow field 1127 and the cathode GDL 1121 (see FIG. 11A). A serpentine channel typically has repeated longer segments that extend in generally parallel directions and are fluidically connected together by shorter segments that are fluidically interposed between them in alternating fashion, much like a switchback.

[0366] For the purposes of this disclosure, the term “fluidically connected” is used with respect to volumes, plenums, holes, etc., that may be structurally connected with one another in some way in order to form a fluidic connection, similar to how the term “electrically connected” is used with respect to components that are connected together to form an electric connection. The term “fluidically interposed,” if used, may be used to refer to a component, volume, plenum, or hole that is fluidically connected with at least two other components, volumes, plenums, or holes such that fluid flowing from one of those other components, volumes, plenums, or holes to the other or another of those components, volumes, plenums, or holes would first flow through the “fluidically interposed” component before reaching that other or another of those components, volumes, plenums, or holes. For example, if a pump is fluidically interposed between a reservoir and an outlet, fluid that flowed from the reservoir to the outlet would first flow through the pump before reaching the outlet.

[0367] Single serpentine channel arrangements may have limited water evacuation performance in the context of COx electrolyzers for larger-area cells (e.g., larger than 100 cm2). Nevertheless, their performance may be adequate for some applications. In a single serpentine channel arrangement, e.g., such as is shown in FIG. 49, a single, continuous serpentine channel 4956 switchbacks across an area 4952 of a cathode flow field 4916 bounded by shorter segments 4962 and first and last longer segments 4960. The serpentine channel 4956 is thus the only conduit for COx gas to enter a corresponding cathode GDL and MEA and is also the only conduit for liquid water that comes into the cathode flow field 4916 from the cathode GDL via that area. Thus, the rate at which liquid water is added to the serpentine channel 4956 is equal to the rate at which liquid water flows out of the area 4952 and into the cathode flow field 4916. The high rate of liquid water introduction into such a serpentine channel 4956, coupled with the long average distance that such water must travel in order to be pushed through the serpentine channel 4956 before reaching a fluidic outlet port, such as fluidic outlet port 4930, generally makes it very challenging to properly manage the liquid water levels within the cathode flow field 4916, rendering COx electrolyzers that use such single-channel serpentine cathode flow fields 4916 with significantly compromised performance compared to COx electrolyzers using, for example, multiple serpentine channel arrangements. In some implementations, a single serpentine channel has an overall channel length (distance from inlet to outlet) of about 12 m or less, or about 6 m or less, or about 2 m or less.

[0368] Multiple serpentine channels can refer to multiple separate serpentine channels that generally follow a common serpentine path, thereby resulting in an interleaved or nested arrangement of the separate serpentine channels, or can refer to multiple instances of the same serpentine channel (or nearly the same serpentine channel) that are arranged side-by-side or otherwise arranged so as to flow in parallel. FIG. 50 depicts the former arrangement, which may also be referred to herein as nested or interleaved multiple serpentine channel arrangements. In FIG. 50, four serpentine channels that generally follow the same serpentine path are shown (two are shown with interiors with white fill and two with interiors with shaded fill to make it easier to differentiate between them; a broken-line rectangle representing the combined open channel area and wall footprint area of a flow field having such an arrangement is also shown). The open channel area refers to the total area through which gas may exit the flow field and travel into the GDL; in a flow field with constant- and equal-width paths, the open channel area would generally be equal to the total path length of the channel(s) times the channel width. The wall footprint area of a flow field refers to the area of the portion of the flow field that defines walls between adjacent portions of a channel or channels of the flow field and that is pressed into contact with the GDL. Thus, both areas are evaluated within the plane of the flow field that is pressed into contact with the GDL. Fluid may be introduced into / removed from the serpentine channels through the inlet and outlet ports (the short segments terminating in small solid black circles). In FIG. 51, a similar arrangement is shown for a side-by-side arrangement of four multiple serpentine channels, which may also be referred to herein as side-by-side multiple serpentine channels. A similar convention with regard to the inlet / outlet, combined open channel area and wall footprint area, and use of shaded / unshaded fill to illustrate the different channels is used in FIG. 51 as in FIG. 50.

[0369] In such arrangements, the total length of each individual serpentine channel may generally be equal to the total lengths of the other individual serpentine channels in the multiple serpentine channels (although in the nested or interleaved multiple serpentine channel arrangements, some small variation in length may be present depending on how the channels are arranged, e.g., whether or not there is an odd or even number of longer segments in each channel), resulting in generally equal flow resistance, pressure drop, and transit time between the channels (assuming that each such channel is fluidically connected with the same fluidic environments on both ends).

[0370] FIG. 52 depicts an example of a cathode flow field 5216 that includes a two-channel multiple serpentine channel arrangement. As can be seen, the cathode flow field 5216 has a fluidic inlet port 5228 and a fluidic outlet port 5230. Two serpentine channels 5256a and 5256b are shown which follow a common serpentine path (not shown, but would generally be represented by the path followed by partition wall 5266, which separates the two serpentine channels 5256a and 5256b). The serpentine channels 5256a and 5256b switchback across an area 5252 in a generally tandem fashion. As a result, fluid that is flowed through either of the serpentine channels 5256a and 5256b, e.g., COx gas, may generally be evenly delivered to an adjoining cathode GDL within a region corresponding to the area 5252. At the same time, any liquid water that is flowed into the cathode flow field 5216 from the adjoining cathode GDL may correspondingly tend to be evenly delivered to both serpentine channels 5256a and 5256b. Thus, each serpentine channel 5256 would receive, assuming that the cathode flow field 5216 is substituted for the cathode flow field 4916 of FIG. 49, approximately half the water that was delivered to the single serpentine channel 4956 of FIG. 49. Generally speaking, the amount of water delivered to each serpentine channel in a cathode flow field having a multiple serpentine channel arrangement will be equivalent to the total amount of water received by the multiple serpentine channel arrangement divided by the number of separate channels in the multiple serpentine channel arrangement. This has the effect of reducing the amount of water that must be evacuated from each serpentine channel per unit time, which may make it more feasible to properly manage the liquid water conditions within a COx electrolyzer if the gas flow velocity is maintained or at least not proportionately decreased. For example, the lower per channel quantities of water will have less mass and require less energy in order to be pushed through the channels to the fluidic outlet port 5230 of the cathode flow field 5216. As a result, lower pressure differentials between the fluidic inlet port 5228 and fluidic outlet port 5230 of the cathode flow field 5216 may be used while still providing for efficient evacuation of liquid water from the cathode flow field 5216.

[0371] Multiple serpentine channels may also allow for relatively even distribution of the fluid that flows within them across the cathode GDL 1121 but with decreased total flow path length for each such serpentine channel as compared with multiple serpentine channel or single serpentine channel implementations having the same or similar channel depth and width and total open channel area in contact with the cathode GDL 1121 but with fewer numbers of such channels. For example, for a given multiple serpentine channel arrangement, it may be desirable to maintain the distance between adjacent portions of at least the longer portions of the serpentine channel(s) to be within a minimum distance of each other. For each additional serpentine channel that is included in a multiple serpentine channel arrangement, meeting such inter-channel spacing restrictions may be attained using serpentine channels of increasingly shorter overall lengths. For clarity, the overall length of a serpentine channel refers to the total of the average path lengths for all of the longer segments of the serpentine channel plus the total average path length of shorter segments that fluidically connect those longer segments with one another, plus the total average path length of any other segments that are fluidically interposed between the inlet and outlet of the serpentine channel.

[0372] Moreover, as serpentine channels decrease in length, the average potential distance that liquid water must travel in order to be expelled from such a serpentine channel will also decrease, as does generally the maximum amount of water that would potentially need to be removed. As a result, less energy is required to evacuate water from such serpentine channels in the event that water collects within such a serpentine channel; this is because the maximum amount of water that may need to be removed from such a channel will be less than in longer-length channels (of the same general cross-sectional area)—there is thus less mass to move. Moreover, the distance that such a water mass must be displaced by in order to push it through such a channel to the fluidic outlet port will generally be less than the distance that a similar water mass must be displaced by in order to be pushed through a longer-length channel to the fluidic outlet port. Of course, the distance that the water mass must be displaced by in order to be pushed through the channel to the fluidic outlet port is dependent on where the water mass is located within the channel. However, on average, water masses that collect in shorter-length channels will generally need to be displaced by a lesser amount than water masses that collect in longer-length channels in order to move such water masses to the fluidic outlet port of the flow field having such channels. Since less energy is needed to move such water masses (droplets) in flow fields with shorter-length passages, lower gas flow velocities, and lower pressure drops, may be used. In some embodiments, a cathode flow field has a serpentine channel with a length of about 12 m or less, or about 10 m or less, or about 6 m or less. For example, serpentine channels that have overall lengths on the order of less than about 6 meters, e.g., less than about 6 meters, less than about 5.5 meters, less than about 5 meters, less than about 4.5 meters, less than about 4 meters, less 3.5 meters, less than about 3 meters, less than about 2.5 meters, or less than about 2 meters may, in some implementations, provide a fluid flow path in the cathode flow field 1127 that allows for the flow of COx gas to be distributed across a wide area of the cathode GDL 1121 while, at the same time, avoiding being so long that evacuating liquid water from within such serpentine channels becomes too difficult. At the same time, serpentine channels that are too short may make it challenging to maintain a desired pressure drop (see later discussion below) across the cathode flow field 1127. To that end, some cathode flow field serpentine channels may be configured to also have overall lengths greater than or equal to 1.5 meters.

[0373] In some implementations, the length of an individual serpentine channel for a cathode flow field may be between about 1.5 m and about 12 m, between about 1.5 m and about 6 m, between about 1.5 m and about 3.8 m, between about 3.8 m and about 6 m, between about 1.5 m and about 2.6 m, between about 2.6 m and about 3.8 m, between about 3.8 m and about 4.9 m, between about 4.9 m and about 6 m, between about 1.5 m and about 2.1 m, between about 2.1 m and about 2.6 m, between about 2.6 m and about 3.2 m, between about 3.2 m and about 3.8 m, between about 3.8 m and about 4.3 m, between about 4.3 m and about 4.9 m, between about 4.9 m and about 5.4 m, between about 5.4 m and about 6 m, between about 1.5 m and about 1.8 m, between about 1.8 m and about 2.1 m, between about 2.1 m and about 2.3 m, between about 2.3 m and about 2.6 m, between about 2.6 m and about 2.9 m, between about 2.9 m and about 3.2 m, between about 3.2 m and about 3.5 m, between about 3.5 m and about 3.8 m, between about 3.8 m and about 4 m, between about 4 m and about 4.3 m, between about 4.3 m and about 4.6 m, between about 4.6 m and about 4.9 m, or between about 4.9 m and about 5.2 m. It will be understood that reference herein, both above and below, to a value being “between” two other values, unless the context indicates otherwise, is inclusive of the values in between the two other values as well as the values themselves.

[0374] In cathode flow fields with serpentine channels, it may be beneficial to configure the serpentine channels to have particular structural characteristics that may provide for enhanced liquid water removal while at the same time providing for effective COx delivery to the cathode GDL. For example, serpentine channels within the length ranges discussed above may be further constrained to have particular widths (the dimension of a serpentine channel in a direction parallel to the plane of the cathode GDL 1121 and transverse to the path that the channel follows (or, generally, transverse to the nominal flow direction of fluid flow through the channel)) and depths (the dimension of a serpentine channel in a direction perpendicular to the plane of the cathode GDL 1121) to further enhance their water-removal performance in the context of a COx electrolyzer. For clarity, the cathode GDL 1121 is generally in the form of a thin sheet that, when stacked with the MEA 1105 (see, e.g., FIG. 11A) and the anode PTL 1109 (see, e.g., FIG. 11A), is compressed between the cathode flow field 1127 and the anode flow field 1111 into a nominally planar geometry; reference to “the plane of the cathode GDL” is thus to be understood to refer to a plane that is generally parallel to, and coincident with, the cathode GDL 1121 in such a state. For example, such serpentine channels may have widths that are between about 0.3 mm and about 2 mm, between about 0.3 mm and about 1.2 mm, between about 1.2 mm and about 2 mm, between about 0.3 mm and about 0.72 mm, between about 0.72 mm and about 1.2 mm, between about 1.2 mm and about 1.6 mm, between about 1.6 mm and about 2 mm, between about 0.3 mm and about 0.51 mm, between about 0.51 mm and about 0.72 mm, between about 0.72 mm and about 0.94 mm, between about 0.94 mm and about 1.2 mm, between about 1.2 mm and about 1.4 mm, between about 1.4 mm and about 1.6 mm, between about 1.6 mm and about 1.8 mm, or between about 1.8 mm and about 2 mm.

[0375] Such serpentine channels may also have depths that are between about 0.3 mm and about 3 mm, between about 0.3 mm and about 1.6 mm, between about 1.6 mm and about 3 mm, between about 0.3 mm and about 0.98 mm, between about 0.98 mm and about 1.6 mm, between about 1.6 mm and about 2.3 mm, between about 2.3 mm and about 3 mm, between about 0.3 mm and about 0.64 mm, between about 0.64 mm and about 0.98 mm, between about 0.98 mm and about 1.3 mm, between about 1.3 mm and about 1.6 mm, between about 1.6 mm and about 2 mm, between about 2 mm and about 2.3 mm, between about 2.3 mm and about 2.7 mm, or between about 2.7 mm and about 3 mm.

[0376] In particular, in some cathode flow field implementations with serpentine channels, the channels may be dimensioned such that the open surface area per channel, i.e., the area that is bounded by the edges of the channel that contact the cathode GDL, is between about 750 mm2 and about 200,000 mm2, between about 750 mm2 and about 100,000 mm2, between about 100,000 mm2 and about 200,000 mm2, between about 750 mm2 and about 51,000 mm2, between about 51,000 mm2 and about 100,000 mm2, between about 100,000 mm2 and about 150,000 mm2, between about 150,000 mm2 and about 200,000 mm2, between about 750 mm2 and about 26,000 mm2, between about 26,000 mm2 and about 51,000 mm2, between about 51,000 mm2 and about 75,000 mm2, between about 75,000 mm2 and about 100,000 mm2, between about 100,000 mm2 and about 130,000 mm2, between about 130,000 mm2 and about 150,000 mm2, between about 150,000 mm2 and about 180,000 mm2, or between about 180,000 mm2 and about 200,000 mm2.

[0377] In some such implementations, such channels may be further dimensioned such that the cross-sectional area (or areas, if the channel has a varying cross-sectional area along its length) of each such channel, i.e., the area of the channel in a plane that is perpendicular to the direction of flow of fluid through the channel under normal operating conditions or to the path that the channel follows across the cathode flow field, is between about 0.15 mm2 and about 6 mm2, between about 0.15 mm2 and about 3.1 mm2, between about 3.1 mm2 and about 6 mm2, between about 0.15 mm2 and about 1.6 mm2, between about 1.6 mm2 and about 3.1 mm2, between about 3.1 mm2 and about 4.5 mm2, between about 4.5 mm2 and about 6 mm2, between about 0.15 mm2 and about 0.88 mm2, between about 0.88 mm2 and about 1.6 mm2, between about 1.6 mm2 and about 2.3 mm2, between about 2.3 mm2 and about 3.1 mm2, between about 3.1 mm2 and about 3.8 mm2, between about 3.8 mm2 and about 4.5 mm2, between about 4.5 mm2 and about 5.3 mm2, or between about 5.3 mm2 and about 6 mm2.

[0378] In yet further implementations, the total channel volume of each such channel may be between about 200 μl and about 36,000 μl, between about 200 μl and about 18,000 μl, between about 18,000 μl and about 36,000 μl, between about 200 μl and about 9,200 μl, between about 9,200 μl and about 18,000 μl, between about 18,000 μl and about 27,000 μl, between about 27,000 μl and about 36,000 μl, between about 200 μl and about 4,700 μl, between about 4,700 μl and about 9,200 μl, between about 9,200 μl and about 14,000 μl, between about 14,000 μl and about 18,000 μl, between about 18,000 μl and about 23,000 μl, between about 23,000 μl and about 27,000 μl, between about 27,000 μl and about 32,000 μl, or between about 32,000 μl and about 36,000 μl.

[0379] In some such implementations, cathode flow fields with serpentine channels may also have structural characteristics relating to the thickness of the walls that are interposed between adjacent longer segments of one or more of the serpentine channels. For example, the wall thickness in between adjacent longer segments of one or more of the serpentine channels (and thus the distance between surfaces of that channel or those channels that are closest to one another) may be selected to be between about between about 0.00005 and about 0.0013333, between about 0.00005 and about 0.00069, between about 0.00069 and about 0.0013333, between about 0.00005 and about 0.00037, between about 0.00037 and about 0.00069, between about 0.00069 and about 0.001, between about 0.001 and about 0.0013333, between about 0.00005 and about 0.00021, between about 0.00021 and about 0.00037, between about 0.00037 and about 0.00053, between about 0.00053 and about 0.00069, between about 0.00069 and about 0.00085, between about 0.00085 and about 0.001, between about 0.001 and about 0.0012, or between about 0.0012 and about 0.0013333 times the average overall length of that serpentine channel or those serpentine channels (the latter case applying if the wall separates the longer portions of two different serpentine channels from each other—for clarity, in this instance the “average” overall length is half the sum of the overall lengths of both serpentine channels). In some such serpentine channel implementations having dimensional characteristics like those discussed above, the wall thickness may be, for example, between about 0.3 mm and about 2 mm, between about 0.3 mm and about 1.2 mm, between about 1.2 mm and about 2 mm, between about 0.3 mm and about 0.72 mm, between about 0.72 mm and about 1.2 mm, between about 1.2 mm and about 1.6 mm, between about 1.6 mm and about 2 mm, between about 0.3 mm and about 0.51 mm, between about 0.51 mm and about 0.72 mm, between about 0.72 mm and about 0.94 mm, between about 0.94 mm and about 1.2 mm, between about 1.2 mm and about 1.4 mm, between about 1.4 mm and about 1.6 mm, between about 1.6 mm and about 1.8 mm, or between about 1.8 mm and about 2 mm.

[0380] Serpentine channel cathode flow fields having characteristics such as those discussed above may offer superior liquid water evacuation performance in the context of COx electrolyzers, e.g., under operating conditions typically seen in COx electrolyzers (such as are discussed earlier herein) as compared with serpentine channel cathode flow fields having other such characteristics, such as may be designed for use with fuel cells.

[0381] While including increasingly higher numbers of multiple serpentine channels in a cathode flow field would generally seem desirable, unfettered increases in the number of flow field channels of the cathode flow field 1127 may be counterproductive. Each additional parallel flow field channel that exists in the cathode flow field 1127 may represent another path that fluid flowing through the multiple serpentine channels may take if blocked from flowing through one or more other serpentine channels in the arrangement of multiple serpentine channels. When such a rerouting of fluid occurs, it may cause an increase in the pressure differential along the channel, e.g., from channel start to channel end, that may cause the fluid that is pressing against the blockage to apply greater pressure on the blockage, thereby increasing the likelihood that the blockage (liquid water) will be dislodged, propelled through the serpentine channel that is being blocked, and eventually evacuated from the cathode flow field 1127 via flow field outlet such as flow field outlet 5930. However, if there are a sufficiently high enough number of channels present, the blockage of any one of them (or a small number of them) may result in a much smaller increase in the pressure differential in any single channel that may occur when an equivalent number of channels is blocked in a flow field with a lesser number of channels. In short, the gas flow that is blocked and reroutes through the other unblocked channels may be divided among a larger number of alternate channels, thereby resulting in a smaller amount of extra gas that must flow through each unblocked channel than might be the case with a lower number of channels in a similar blockage situation. The smaller the amount of extra gas that must flow through each channel during a blockage situation, the smaller the change in pressure drop that is needed to accommodate such a change. As a result, the increase in pressure drop that may occur in unblocked channels when gas flows re-route therethrough due to a blocked channel or channels decreases as the number of channels that are present increases.

[0382] At the same time, if the total lengths of the serpentine passages are sufficiently long, e.g., 0.3 m to 6 m, the pressure drop that occurs across each such channel may be high enough that it may act to help dislodge any obstructions, e.g., water, that may exist within any individual serpentine channel regardless of the number of channels present. For example, serpentine channels for COx electrolyzers may have dimensions and operational conditions, e.g., fluidic inlet port pressures, that are selected so as to produce a 0.001 psi to 4 psi pressure drop during normal operational flows for such serpentine channels, which may be high enough to dislodge potential water blockages that may be present within the serpentine channels; while higher pressure drops may be used as well, they may be unnecessary with respect to water evacuation and simply result in wasted energy that is needed to move the fluids through the serpentine channels under such pressure drop conditions. In some implementations, serpentine channels for COx electrolyzers may have dimensions and operational conditions, e.g., fluidic inlet port pressures, that are selected so as to produce, during normal operational flow conditions for a COx electrolyzer, a pressure drop of between about 0.001 psi and about 4 psi, between about 0.001 psi and about 2 psi, between about 2 psi and about 4 psi, between about 0.001 psi and about 1 psi, between about 1 psi and about 2 psi, between about 2 psi and about 3 psi, between about 3 psi and about 4 psi, between about 0.001 psi and about 0.5 psi, between about 0.5 psi and about 1 psi, between about 1 psi and about 1.5 psi, between about 1.5 psi and about 2 psi, between about 2 psi and about 2.5 psi, between about 2.5 psi and about 3 psi, between about 3 psi and about 3.5 psi, between about 3.5 psi and about 4 psi, between about 0.001 psi and about 0.25 psi, between about 0.25 psi and about 0.5 psi, between about 0.5 psi and about 0.75 psi, between about 0.75 psi and about 1 psi, between about 1 psi and about 1.3 psi, between about 1.3 psi and about 1.5 psi, between about 1.5 psi and about 1.8 psi, between about 1.8 psi and about 2 psi, between about 2 psi and about 2.3 psi, between about 2.3 psi and about 2.5 psi, between about 2.5 psi and about 2.8 psi, between about 2.8 psi and about 3 psi, between about 3 psi and about 3.3 psi, between about 3.3 psi and about 3.5 psi, between about 3.5 psi and about 3.8 psi, between about 3.8 psi and about 4 psi, between about 0.001 psi and about 0.13 psi, between about 0.13 psi and about 0.25 psi, between about 0.25 psi and about 0.38 psi, between about 0.38 psi and about 0.5 psi, between about 0.5 psi and about 0.63 psi, between about 0.63 psi and about 0.75 psi, between about 0.75 psi and about 0.88 psi, between about 0.88 psi and about 1 psi, between about 1 psi and about 1.1 psi, between about 1.1 psi and about 1.3 psi, between about 1.3 psi and about 1.4 psi, between about 1.4 psi and about 1.5 psi, between about 1.5 psi and about 1.6 psi, between about 1.6 psi and about 1.8 psi, between about 1.8 psi and about 1.9 psi, between about 1.9 psi and about 2 psi, between about 2 psi and about 2.1 psi, between about 2.1 psi and about 2.3 psi, between about 2.3 psi and about 2.4 psi, between about 2.4 psi and about 2.5 psi, between about 2.5 psi and about 2.6 psi, between about 2.6 psi and about 2.8 psi, between about 2.8 psi and about 2.9 psi, between about 2.9 psi and about 3 psi, between about 3 psi and about 3.1 psi, between about 3.1 psi and about 3.3 psi, between about 3.3 psi and about 3.4 psi, between about 3.4 psi and about 3.5 psi, between about 3.5 psi and about 3.6 psi, between about 3.6 psi and about 3.8 psi, between about 3.8 psi and about 3.9 psi, or between about 3.9 psi and about 4 psi. In some other implementations, serpentine channels for COx electrolyzers may have dimensions and operational conditions, e.g., fluidic inlet port pressures, that are selected so as to produce, during normal operational flow conditions for a COx electrolyzer, a pressure drop of between about 4 psi and about 50 psi, between about 4 psi and about 27 psi, between about 27 psi and about 50 psi, between about 4 psi and about 16 psi, between about 16 psi and about 27 psi, between about 27 psi and about 38 psi, between about 38 psi and about 50 psi, between about 4 psi and about 9.8 psi, between about 9.8 psi and about 16 psi, between about 16 psi and about 21 psi, between about 21 psi and about 27 psi, between about 27 psi and about 33 psi, between about 33 psi and about 38 psi, between about 38 psi and about 44 psi, between about 44 psi and about 50 psi, between about 4 psi and about 6.9 psi, between about 6.9 psi and about 9.8 psi, between about 9.8 psi and about 13 psi, between about 13 psi and about 16 psi, between about 16 psi and about 18 psi, between about 18 psi and about 21 psi, between about 21 psi and about 24 psi, between about 24 psi and about 27 psi, between about 27 psi and about 30 psi, between about 30 psi and about 33 psi, between about 33 psi and about 36 psi, between about 36 psi and about 38 psi, between about 38 psi and about 41 psi, between about 41 psi and about 44 psi, between about 44 psi and about 47 psi, or between about 47 psi and about 50 psi. In some other implementations, serpentine channels for COx electrolyzers may have dimensions and operational conditions, e.g., fluidic inlet port pressures, that are selected so as to produce, during normal operational flow conditions for a COx electrolyzer, a pressure drop of between about 0.001 psi and about 50 psi, between about 0.001 psi and about 25 psi, between about 25 psi and about 50 psi, between about 0.001 psi and about 13 psi, between about 13 psi and about 25 psi, between about 25 psi and about 38 psi, between about 38 psi and about 50 psi, between about 0.001 psi and about 6.3 psi, between about 6.3 psi and about 13 psi, between about 13 psi and about 19 psi, between about 19 psi and about 25 psi, between about 25 psi and about 31 psi, between about 31 psi and about 38 psi, between about 38 psi and about 44 psi, or between about 44 psi and about 50 psi. Pressure drops in the ranges listed above may be high enough to dislodge potential water blockages that may be present within such serpentine channels, particularly in the context of the higher water generation rates that COx electrolyzers tend to exhibit.

[0383] FIGS. 53 through 55 depict an example cathode flow field 5316 that may be used in some implementations. The depicted flow field has 15 channels and 9 passes. In one implementation, the depicted flow field has a planar surface area (facing a GDL) of 700 cm2. FIG. 53 depicts an isometric view of the cathode flow field 5316. FIG. 55 depicts a detail view of the portion of FIG. 53 enclosed by a circle. FIG. 54 depicts the isometric view of FIG. 53, but with most of the channels of the flow field omitted, leaving only three channels 5358a, 5358b, and 5358c visible; this view is intended to make it easier to see the representative serpentine paths followed by the various channels. The cathode flow field 5316 actually includes 15 channels 5358. The channels in the example cathode flow field 5316 are each 0.66 mm deep by 0.81 mm wide, and each have a length of about 2,310 mm, a channel open area of about 1,880 mm2, and a volume of about 1,240 mm3. The total open channel area of the cathode flow field 5316 is, in this example, 28,200 mm2. With each of the 15 channels being separated from any adjacent channels by walls of 1.12 mm in width and the cathode flow field having dimensions of about 265 mm by 265 mm, about 40% of the cathode flow field 5316 surface area is taken up by the channels 5358. The depicted cathode flow field 5316 is designed to receive (and deliver) fluids from external manifolds that may be mounted against the external edges of the cathode flow field 5316 so as to flow fluid into or out of the channels 5358 from the side.

[0384] FIGS. 56 through 58 depict another example cathode flow field 5616 that may be used in some implementations. The depicted flow field has 34 channels and 7 passes. In one implementation, the depicted flow field has a planar surface area (facing a GDL) of 1,600 cm2. As with FIGS. 53 through 55, FIG. 56 depicts an isometric view of the cathode flow field 5616 and FIG. 58 depicts a detail view of the portion of FIG. 56 enclosed by a circle. FIG. 57 depicts the isometric view of FIG. 56, but with most of the channels of the flow field omitted, leaving only three channels 5658a, 5658b, and 5658c visible; as with FIG. 55, this view is intended to make it easier to see the representative serpentine paths followed by the various channels. The cathode flow field 5616 actually includes 34 channels 5658. The channels in the example cathode flow field 5616 are each 0.66 mm deep by 0.76 mm wide, and each have a length of about 2,440 mm, a channel open area of about 1,880 mm2, and a volume of about 1,230 mm3. The total open channel area of the cathode flow field 5616 is, in this example, 63,230 mm2. With each of the 34 channels being separated from any adjacent channels by walls of 1.14 mm in width and the cathode flow field 5616 having dimensions of about 360 mm by 450 mm, about 39% of the cathode flow field 5616 surface area is taken up by the channels 5658. As with the cathode flow field 5316, the depicted cathode flow field 5616 is designed to receive (and deliver) fluids from external manifolds that may be mounted against the external edges of the cathode flow field so as to flow fluid into or out of the channels 5658 from the side.

[0385] In certain embodiments, a serpentine flow field as in FIGS. 53-58, the channel depth is about 0.5 mm to 1.5 mm. In certain embodiments, the nominal length of each flow channel in a flow field of FIGS. 53-58 is about 300 mm to 3,000 mm. In certain embodiments, the nominal channel width in a flow field of FIGS. 53-58 is about 0.5 mm to 1 mm. In certain embodiments, the nominal channel separation distance in a flow field of FIGS. 53-58 is about 1 mm to 1.5 mm.

[0386] In some implementations, serpentine channel cathode flow fields may feature serpentine channels that have rounded or smooth transitions between the longer and shorter segments as opposed to sharp transitions between such segments. For example, FIG. 59 depicts an example of a cathode flow field 5916 that has four cathode serpentine channels 5956 arranged in a multiple serpentine channel arrangement. It will be noted that unlike the single-channel and two-channel serpentine arrangements depicted in FIGS. 49 and 52, the transitions between the longer segments are provided by arcuate shorter segments instead of straight shorter segments. In other implementations, the shorter segments may still include a straight portion but may be joined to fluidically adjacent longer segments by smaller arcuate segments. Such cathode flow fields may further enhance the water evacuation performance of a COx electrolyzer since the absence of sharp interior corners in the serpentine channels may eliminate a potential dead zone or stagnation location for fluid flow that could otherwise serve as a location where liquid water could collect and reside indefinitely during use of the cathode flow field.

[0387] Other aspects of flow field channels may be alternatively or additionally modified as well in order to promote more effective liquid water evacuation. FIG. 60, for example, depicts a cross-sectional view of a cathode flow field 6016 that is pressed against a cathode GDL 6014. A plurality of square- or rectangular-cross-section serpentine channels 6056 are formed in the face of the cathode flow field 6016 that is pressed against the cathode GDL 6014. These serpentine channels 6056 have sharp corners at their interior bottom edges 6057, which may act to create small fluid flow stagnation areas that may prevent liquid water from being readily evacuated during normal COx electrolyzer operating conditions.

[0388] FIG. 61, by contrast, shows a cross-sectional view of a similar structure with a cathode flow field 6116 that is pressed against a cathode GDL 6114. A plurality of square- or rectangular-cross-section serpentine channels 6156 are formed in the face of the cathode flow field 6116 that is pressed against the cathode GDL 6114. Unlike the serpentine channels 6056, the serpentine channels 6156 have rounded corners at their interior bottom edges 6157, which may act to reduce flow stagnation in the bottom interior edge regions of such channels, thereby promoting liquid water evacuation during normal COx electrolyzer operating conditions.

[0389] FIG. 62 is a further example of a cathode flow field that may more readily evacuate liquid water during normal COx electrolyzer operating conditions. As can be seen, a cathode flow field 6216 is pressed against a cathode GDL 6214. A plurality of U-shaped cross-section serpentine channels 6256 are formed in the face of the cathode flow field 6216 that is pressed against the cathode GDL 6214. In this case, there effectively are no interior bottom edges of the serpentine channels 6256 since the bottom surface of such serpentine channels 6256 is semicircular, which may act to further reduce flow stagnation in such channels, thereby further promoting liquid water evacuation during normal COx electrolyzer operating conditions.

[0390] In some other or additional implementations, serpentine channel cathode flow fields may have variable-width walls in between some or all of the longer segments of one or more serpentine channels. FIG. 63 depicts an example of such a cathode flow field. In FIG. 63, a cathode flow field 6316 is shown which has a four-channel serpentine arrangement with each serpentine channel 6356 having longer segments 6360 and shorter segments 6362. It will be noted that the multiple serpentine channel arrangement has “peninsular” walls 6364 that are interposed between neighboring longer segments 6360 of a common serpentine channel 6356a (or 6356b) that have opposing fluid flow directions when fluid is flowing through the serpentine channels 6356 (generally all nested or interleaved multiple serpentine channel arrangements will have peninsular walls; they are only specifically called out here due to the particulars of this example implementation).

[0391] As can be seen in FIG. 63, the peninsular walls 6364 may have a varying wall thickness. For example, the peninsular walls 6364 have a root width 6368 where the peninsular walls 6364“connect” with the outer perimeter region of the cathode flow field 6316 (which may be thought of as the “root” of the peninsular wall) and a tip width 6370 at their opposite ends. The increased width at the root as compared with the tip of the peninsular walls 6364 may reduce the chance of gas flow through the cathode GDL that might bypass some or all of the longer segments 6360 that are separated by the peninsular walls 6364 by passing under the wall, i.e., through the GDL that is sandwiched between the cathode flow field 6316 and the MEA (not shown, but see FIG. 11A) and which, in effect, caps the cathode serpentine channels 6356.

[0392] For example, in a serpentine channel of a cathode flow field that has portions thereof that are adjacent to one another, e.g., the outermost or innermost serpentine channel on a multi-channel, interleaved serpentine channel arrangement, gas that is flowed through such a channel, e.g., from point A to point B may experience a pressure drop / flow resistance if travelling from point A to point B via flow through point C that may, under some circumstances, exceed the pressure drop / flow resistance that may be experienced by that gas if it simply flowed from point A to point B more directly, e.g., by passing under the peninsular wall 6364 in between points A and B by way of the porous GDL that spans between points A and B and under the peninsular wall 6364. For example, if water accumulates in the channel between points A and C and / or between points C and B, the resulting blockage may increase the pressure drop / flow resistance for gas that flows along this path that it exceeds the pressure drop / flow resistance that the gas would experience if traveling from point A to point B more directly, e.g., under the peninsular wall 6364. As the flow path between points A and B under the peninsular wall 6364 may offer less flow resistance than the flow path between A and B via point C, the gas may then preferentially flow from point A under the peninsular wall 6364 to point B rather than via point C, thus depriving the GDL and MEA of exposure to gas that would normally flow through point C, thereby decreasing the efficiency of the COx cell in which the cathode flow field 6316 is used. To prevent this from happening, or to at least reduce the chances of this occurring, in some implementations, the peninsular walls 6364 may simply have a constant thickness along their lengths but may be thicker than partition walls 6366 that may separate other neighboring longer segments 6360 that have fluid flows in the same directions, thereby increasing the flow resistance experienced by gas that attempts to flow under the peninsular walls 6364. In other implementations, such as that shown in FIG. 63, the peninsular walls 6364 may taper towards their tips such that the tip width 6370 is less than the root width 6368, thereby causing the flow resistance under the peninsular walls 6364 to decrease from what it was near the root of a peninsular wall 6364 as the flow nears the tip of the peninsular wall 6364. This may assist with discouraging the flow of gas under the peninsular walls 6364 near the roots of those walls, but this effect may also decrease as the gas flow moves along the peninsular wall 6364 towards the tip thereof-however, the flow resistance along the desired flow path (via point C, for example) may also decrease, and there may thus not be as much of an incentive for gas to flow under the peninsular walls near the tips of the peninsular walls 6364. By tapering the thickness of the peninsular walls, the area of the cathode GDL that is compressed under the peninsular walls 6364 may be reduced as compared with non-tapering peninsular walls 6364, thereby increasing the area of the cathode GDL which has direct exposure to gas flow through the channels and increasing the opportunity for a reduction reaction to occur with such gas.Mirror Serpentine Channel Flow Fields

[0393] In the serpentine channel flow fields discussed above, the serpentine channels discussed generally do not exhibit any mirroring or bilateral symmetry. A further class of serpentine channel flow fields may, however, feature serpentine channels that are arranged in a generally bilaterally symmetric manner. In such flow fields, the flow field may generally be partitioned into two zones. The two zones may be generally equally sized and shaped, and may each contain a similar number of serpentine channels. The serpentine channel or channels in each zone may be arranged so as to generally be mirror images of one another with respect to the boundary between the two zones, e.g., the serpentine channels may exhibit bilateral symmetry about the boundary between the two zones.

[0394] FIG. 64 depicts a plan view of a simplified representation of an example mirror image cathode flow field. In FIG. 64, a cathode flow field 6416 is shown that is partitioned into two zones 6470 that are generally the same shape and size. A boundary 6472 is defined in between the two zones 6470; the zones 6470 are generally symmetrically arranged on either side of the boundary 6472. Each zone 6470 in this example includes a single cathode serpentine channel 6456, although it will be understood that each zone may include a larger number of cathode serpentine channels 6456 that follow a common path in a nested or interleaved manner, as with examples discussed earlier. The cathode serpentine channels 6456 each extend between a corresponding fluidic inlet port 6428 and a corresponding fluidic outlet port 6430 (it will be understood that these fluidic inlet ports 6428 may, for example, terminate in the same location, e.g., a common flow passage or manifold, and that the fluidic outlet ports 6430 may be similarly configured).

[0395] As is discussed further below, the symmetric arrangement of the cathode serpentine channels 6456 may provide various advantages over non-symmetric arrangements of cathode serpentine channels with respect to maintaining flow uniformity across the cathode flow field 6416. For example, the two zones 6470 may, together, generally represent an active area of the cathode flow field 6416. That active area could, for example, be traversed by a cathode serpentine channel or channels that travel back and forth between opposite sides of the active area, as shown in FIG. 65.

[0396] FIG. 65 depicts a cathode flow field 6516, two zones 6570, and a boundary 6572 that are similar to the zones 6470 and the boundary 6472 are shown as well. The cathode flow field 6516 has a serpentine channel 6556 that includes longer segments A extending in directions nominally perpendicular to a first set of opposing edges of the active area and shorter segments B extending in directions nominally parallel to a second set of opposing edges. The longer-length segments generally have lengths that are of the same order of magnitude as the distance between the first set of opposing edges of the active area (although potentially shortened somewhat to allow additional cathode serpentine channels to be routed in a nested or interleaved fashion). The longer segments A of the cathode serpentine channel 6556 can be seen to cross over the boundary 6572 and extend into both zones 6570. In such an arrangement, fluid that flows down a longer segment A, through a shorter segment B, and into another longer segment A that neighbors the original longer segment A, e.g., along the heavy dashed line 6574 shown in association with the leftmost two longer segments A in FIG. 65, will experience a pressure drop that is generally proportional to the sum of the lengths of the two longer segments A and the shorter segment B that joins them.

[0397] The gas flow through the cathode serpentine channel 6556, however, is not limited to staying within the cathode serpentine channel 6556. For example, as discussed earlier, the side of the cathode flow field 6516 in which the cathode serpentine channel 6556 is provided may be compressed against a porous or fibrous GDL (not shown) that provides an alternate flow path that allows gas to also or alternatively flow under partition walls 6566 that lie in between each pair of adjacent longer segments A, e.g., through the GDL that is sandwiched between the cathode flow field 6516 and an adjacent structure, e.g., an MEA. For example, the gas flow may also flow between the two longer segments A at the left of FIG. 65 via a flow path along dotted line 6576.

[0398] Generally speaking, the ratio of gas that flows along the flow path 6574 and the flow path 6576 may be biased towards gas flow along the channel flow path 6574 due to the fact that the cathode serpentine channel 6556 has a relatively large, open cross-section compared to the GDL flow path 6576. For example, the cathode serpentine channel 6556 may have a cross-section that is entirely open and that has relatively large dimensions (e.g., on the order of a millimeter or so in height and width), while the flow path offered by the GDL may only be on the order of a few hundred microns in height and be filled with the fibrous or porous material of the GDL. Put another way, the per-unit-length flow resistance of the GDL may be much higher than the per-unit-length flow resistance of the cathode serpentine channel 6556.

[0399] However, the overall flow resistance of the flow path 6574 will increase with increasing length of the longer segments A of the cathode serpentine channel 6556. Thus, the longer that the longer segments A of the cathode serpentine channel 6556 are, the higher the flow resistance along the flow path 6574, which causes the ratio of gas that flows through the flow path 6574 to the gas that flows through the flow path 6576 to decrease. In other words, shorter lengths of the longer segments A will result in less gas flow along the flow paths 6576 than longer lengths of the longer segments A.

[0400] Moreover, the flow resistance of the flow path 6574 may also increase during operation due to the potential of blockages, e.g., by liquid water or, for example, mineral deposits, within the cathode serpentine channel 6556. If such blockages occur, this will increase the flow resistance along the cathode serpentine channel, thereby causing the ratio of gas that flows through the flow path 6574 to the gas that flows through the flow path 6576 to decrease.

[0401] It will be understood that while only one flow path 6574 and one flow path 6576 are shown in FIG. 65, such flow paths may generally be replicated for similar geometrical features across the cathode flow field 6516 and such additional flow paths may have similar characteristics and behavior.

[0402] Returning to FIG. 64, it can be seen that by filling the same two zones 6470 with separate cathode serpentine channels 6456, the longer segments A of those serpentine channels 6456 may be decreased as compared with the longer segments A of the cathode serpentine channel 6556. In FIG. 64, the longer segments A of the cathode serpentine channels 6456 are approximately half the length of the longer segments A of the cathode serpentine channels 6556. Assuming that the cathode serpentine channels 6456 and 6556 are generally otherwise similar, e.g., similar cross-sectional areas, the flow resistance along the flow path 6474 will be significantly less, e.g., about 50% or so, of the flow resistance along the flow path 6574. This, in turn, increases the ratio of gas that flows through the cathode serpentine channels 6456 as opposed to leaking, for example, under peninsular walls 6466 (e.g., via flow path 6476). As the cathode serpentine channels 6456 traverse across the zones 6470 in a generally evenly distributed manner, this results in a more uniform distribution of gas across the zones 6470 than may occur in cathode flow fields such as the cathode flow field 6516.

[0403] Another aspect of the geometry shown in FIG. 64 is that the depicted cathode serpentine channels 6456 are arranged in a generally symmetric manner such that, at locations where the cathode serpentine channels in the two zones come into close proximity to each other, e.g., the shorter segments B that are adjacent to the boundary 6472, the total flow resistance along the serpentine channel from their respective inlets to those segments is generally equal, thereby resulting in a generally equal pressure drop from the inlet to each set of locations. This avoids a scenario in which two segments from different cathode serpentine channels are adjacent to one another but may have nominally different pressures that result in a pressure differential between them that may act to cause gas to cross from one such cathode serpentine channel to another.

[0404] For example, if one considers the flow resistance along the portions of the cathode serpentine channels 6456 that lie between the locations C in FIG. 64 and the fluidic inlet ports 6428, it can be seen that gas that flows through each cathode serpentine channel 6456 from the corresponding fluidic inlet port 6428 to the corresponding location C will flow along four longer segments A and three shorter segments B (and, arguably, a fourth shorter segment B that is not labeled but which leads from the fluidic inlet port 6428 to the leftmost longer segment A). Thus, the lengths of the portions of the cathode serpentine channels 6456 that are traversed by the gas flowing through the cathode serpentine channels 6456 may be generally the same and, accordingly (assuming that the cathode serpentine channels 6456 are otherwise the same, e.g., same cross-sectional dimensions), the total flow resistances between the fluidic inlet ports 6428 and the locations C may be the same. This results in the pressure drop experienced between the fluidic inlet ports 6428 and the locations C being generally the same, resulting in little or no pressure differential between the two locations C. As a result, there is little or no pressure differential present in the vicinity of the locations C that would act to cause gas from one cathode serpentine channel 6456 to flow from that cathode serpentine channel 6456 into the other cathode serpentine channel 6456. This avoids or reduces the risk or severity of a scenario where gas flowed into one zone 6470 migrates into the other zone 6470, resulting in a gas distribution across the cathode flow field 6416 that is skewed.

[0405] The symmetric arrangement of cathode serpentine channels depicted in FIG. 64 may thus, for example, be characterized as having, for each set of locations along the cathode serpentine channels...

Claims

1. A COx electrolyzer apparatus (“apparatus”) comprising:a first end assembly;a second end assembly coupled to the first end assembly via a plurality of tensioning members; anda plurality of COx electrolyzer cells (“cells”) interposed between the first and second end assemblies and arranged in a stack along an axial direction, wherein each of the plurality of cells comprises:a cathode frame that defines a first opening;a cathode flow field at least partially disposed in the first opening;an anode frame that defines a second opening;an anode flow field at least partially disposed in the second opening;a first support frame;a second support frame; anda membrane electrode assembly (MEA) sandwiched between the first support frame and the second support frame, wherein the MEA is positioned between the cathode flow field and the anode flow field.

2. The apparatus of claim 1, further comprising:a cathode gas diffusion layer (GDL) that is positioned between the MEA and the cathode flow field.

3. The apparatus of claim 2, wherein the cathode GDL is positioned between the first and second support frames such that one of the first and second support frames directly contacts the MEA, the other of the first and second support frames directly contacts the cathode GDL, and the MEA and the cathode GDL are both sandwiched between the first support frame and the second support frame.

4. The apparatus of claim 1, further comprising:a cathode gasket that is interposed between the cathode frame and the first support frame such that a first side of the cathode gasket abuts a face of the cathode frame and a second side of the cathode gasket abuts a face of the first support frame.

5. The apparatus of claim 4, wherein the cathode gasket encircles the cathode flow field.

6. The apparatus of claim 1, further comprising:one or more separator plates, wherein one of the one or more separator plates is positioned between adjacent cells of the plurality of cells.

7. The apparatus of claim 1, wherein the MEA comprises an anion-conducting polymer.

8. The apparatus of claim 1, wherein the cathode flow field receives gaseous carbon oxide and distributes the gaseous carbon oxide across a surface of the MEA.

9. The apparatus of claim 1, further comprising:an anode porous transport layer (PTL) positioned between the anode flow field and the MEA.

10. The apparatus of claim 1, wherein the MEA comprises:a cathode layer comprising an anion-conducting polymer;an anode layer; andan ion-conducting polymer layer positioned between the anode layer and the cathode layer.

11. The apparatus of claim 1, wherein the first support frame, the second support frame, and the MEA form a unitized MEA assembly.

12. The apparatus of claim 11, further comprising a cathode annular insert at least partially supported in at least one opening in the cathode frame and encircling the cathode flow field, wherein the cathode annular insert abuts against a corresponding surface of the cathode frame and abuts against one or more corresponding surfaces of the unitized MEA assembly.

13. The apparatus of claim 1, wherein the first support frame includes a bulged portion partially defining a cavity that is configured to receive a portion of the MEA.

14. The apparatus of claim 13, further comprising:a cathode gas diffusion layer (GDL) that is positioned between the MEA and the cathode flow field, wherein a portion of the cathode GDL is positioned in the cavity.

15. The apparatus of claim 1, wherein one or both of the first support frame and the second support frame include a protruded tab portion.

16. The apparatus of claim 1, wherein:the first end assembly further comprises a first insulation plate and a first bus plate, andan inlet anolyte flow path, an outlet anolyte flow path, an inlet gaseous COx flow path, and an outlet COx reduction byproduct flow path do not extend into the first bus plate and the first insulation plate.

17. The apparatus of claim 1, wherein:the second end assembly further comprises a second bus plate, a bladder gasket, and a first recess formed in a central portion of the second insulation plate, andthe second bus plate is slidably disposed in the first recess and configured to abut against the bladder gasket and / or a surface of the first recess facing the second bus plate in the axial direction.

18. The apparatus of claim 10, wherein the anode layer comprises an oxidation catalyst.

19. The apparatus of claim 10, wherein the anode layer comprises a cation-conducting polymer.

20. The apparatus of claim 10, wherein the cathode layer further comprises a reduction catalyst.

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