Electrolyzer cell assemblies with bump-seal face-seal elements

Abstract

Electrolyzer cell assemblies using face-seal elements in the form of bump seals for sealing against membrane assemblies are disclosed. Some implementations also feature perimeter seal elements that may seal against flow fields that are housed within the electrolyzer cell assemblies. The disclosed electrolyzer cell assemblies may offer superior sealing performance as compared with O-ring-based assemblies.

Description

Docket No. OPUSP048WOELECTROLYZER CELL ASSEMBLIES WITH BUMP-SEAL FACESEAL ELEMENTSINCORPORATION BY REFERENCE

[0001] A PCT Request Form 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 PCT Request Form is incorporated by reference herein in its entirety and for all purposes.BACKGROUND

[0002] Fuel cell and electrolyzer stacks both typically include a plurality of cells that each utilize a component referred to as a “membrane electrode assembly” (MEA). An MEA typically includes a polymer electrolyte membrane (PEM) that has one or more layers of catalyst material applied to one or both sides. The MEA is typically sandwiched between two flow fields that are configured to distribute fluids across the MEA during use. The present disclosure is directed at improvements to structures that are used to position and retain such flow fields in place relative to an MEA.

[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] In some implementations, an apparatus may be provided that includes an electrolyzer cell assembly including one or more frames. Each frame may include a seal region and one or more recessed regions and may be made of a rigid material. The one or more frames may include a first frame, and the one or more recessed regions of the first frame may include a first recessed region. The first frame may have an opening, a first side, a first surface that is within the seal region of the first frame and also part of the first side of the first frame, a second sideDocket No. OPUSP048WO opposite the first side of the first frame, and a second surface that is within the seal region of the first frame and also part of the second side of the first frame. The opening of the first frame may be bounded by the seal region of the first frame. The electrolyzer cell assembly may also include one or more face-seal elements, each face-seal element located within one of the one or more recessed regions of one of the one or more frames and having at least a portion with a transverse cross-sectional profile comprising a first sub-profile proximate the recessed region in which that face-seal element is located and a second sub-profile on an opposite side of that face-seal element from the first sub-profile of that face-seal element. The one or more faceseal elements may include a first face-seal element located in the first recessed region of the first frame. The second sub-profile of the first face-seal element may include at least a recessed portion located between two raised portions, the first recessed region of the first frame may be within the seal region of the first frame and on the first side of the first frame, the first faceseal element may extend along a first path extending around the opening of the first frame, and the second side of the first frame may be closer to a portion of the first recessed region of the first frame than to the first surface of the first frame. The two raised portions of the first faceseal element, when the first face-seal element is in an uncompressed state, may extend out of the first recessed region of the first frame and past a first reference plane that is co-planar with the first surface of the first frame, and the recessed portion of the first face-seal element may not extend out of the first recessed region of the first frame past the first reference plane.

[0006] In some implementations, the one or more recessed regions of the first frame may further include a second recessed region and the one or more face-seal elements may include a second face-seal element located in the second recessed region of the first frame. The second recessed region of the first frame may be within the seal region of the first frame and on the second side of the first frame, the second face- seal element may extend along a second path extending around the opening of the first frame, and the first side of the first frame may be closer to a portion of the second recessed region of the first frame than to the second surface of the first frame.

[0007] In some such implementations, the second sub-profile of the second face- seal element may include at least a recessed portion located between two raised portions, the two raised portions of the second face-seal element, when the second face-seal element is in an uncompressed state, may extend out of the second recessed region of the first frame and past a second reference plane that is co-planar with the second surface of the first frame, and the recessed portion of the second face-seal element may not extend out of the second recessed region of the first frame past the second reference plane.Docket No. OPUSP048WO

[0008] In some alternate implementations, the second sub-profile of the second face-seal element may define a planar surface that extends around the opening of the first frame and faces in the same direction as the second side of the first frame.

[0009] In some implementations, the one or more frames may further include a second frame, the one or more recessed regions of the second frame may include a first recessed region, and the second frame may have an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame. The opening of the second frame may be bounded by the seal region of the second frame, the one or more face-seal elements may include a third face-seal element located in the first recessed region of the second frame, the second sub-profile of the third face-seal element may include at least a recessed portion located between two raised portions, and the first recessed region of the second frame may be within the seal region of the second frame and on the first side of the second frame. The third face-seal element may extend along a third path extending around the opening of the second frame, the second side of the second frame may be closer to a portion of the first recessed region of the second frame than to the first surface of the second frame, the two raised portions of the third face-seal element, when the third face-seal element is in an uncompressed state, may extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, and the recessed portion of the third face-seal element may not extend out of the first recessed region of the second frame past the third reference plane.

[0010] In some such implementations, the one or more recessed regions of the second frame may include a second recessed region, the one or more face-seal elements may include a fourth face-seal element located in the second recessed region of the second frame, the second subprofile of the fourth face-seal element may include at least a recessed portion located between two raised portions, and the second recessed region of the second frame may be within the seal region of the second frame and on the second side of the second frame. The fourth face-seal element may extend along a fourth path extending around the opening of the second frame, the first side of the second frame may be closer to a portion of the second recessed region of the second frame than to the second surface of the second frame, the two raised portions of the fourth face- seal element, when the fourth face- seal element is in an uncompressed state, may extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, and the recessed portion of theDocket No. OPUSP048WO fourth face-seal element may not extend out of the second recessed region of the second frame past the fourth reference plane.

[0011] In some implementations, the apparatus may further include one or more perimeter seal elements, the one or more perimeter seal elements including a first perimeter seal element, wherein the first perimeter seal element may extend from the first side of the first frame to the second side of the first frame, and the first perimeter seal element may be in contact with a perimeter wall of the first frame that spans between the first side of the first frame to the second side of the first frame and that bounds the opening of the first frame.

[0012] In some such implementations, the first perimeter seal element may be contiguous with the first face- seal element.

[0013] In some implementations, the first perimeter seal element may be contiguous with the second face- seal element.

[0014] In some implementations, the first perimeter seal element may also be contiguous with the first face- seal element.

[0015] In some implementations, the one or more perimeter seal elements may further include a second perimeter seal element, the second perimeter seal element may extend from the first side of the second frame to the second side of the second frame, and the second perimeter seal element may be proximate a perimeter wall of the second frame that spans between the first side of the second frame to the second side of the second frame and that bounds the opening of the second frame.

[0016] In some implementations, the second perimeter seal element may be contiguous with the third face- seal element.

[0017] In some implementations, the second perimeter seal element may be contiguous with the fourth face-seal element.

[0018] In some implementations, the second perimeter seal element is also contiguous with the third face-seal element.

[0019] In some implementations, the first sub-profile may be linear for each of one or more of the one or more face-seal elements in which the second sub-profile includes at least the recessed portion located between the two raised portions, and each recessed region where the first subprofile of the face- seal element located therein is linear may have a planar surface proximate the first sub-profile of the face-seal element located therein.

[0020] In some implementations, each of one or more of the one or more recessed regions in which the face- seal element located therein may have a second sub-profile that includes at least the recessed portion located between the two raised portions itself has a transverse cross-sectionDocket No. OPUSP048WO having convex portions, each convex portion corresponding in location to one of the raised portions.

[0021] In some implementations, each face-seal element may be located in a recessed region having the cross-section with the convex portions has a nominally constant thickness in the raised portions thereof.

[0022] In some implementations, the planar surface of the second face-seal element may overlap the raised portions of the fourth face- seal element when viewed along an axis perpendicular to the planar surface of the second face- seal element.

[0023] In some implementations, the planar surface of the second face-seal element may also overlap the raised portions of both the first face-seal element and the third face-seal element when viewed along an axis perpendicular to the planar surface of the second face-seal element.

[0024] In some implementations, the raised portions of the first face- seal element and the raised portions of the third face- seal element may be aligned with one another when viewed along a direction perpendicular to the first surface of the first frame.

[0025] In some implementations, each face-seal element may include an elastomeric material.

[0026] In some implementations, each perimeter seal element may include an elastomeric material.

[0027] In some implementations, at least one of the one or more face-seal elements may be affixed by an adhesive within the recessed region in which it is located.

[0028] In some implementations, at least one of the one or more face-seal elements may be comolded with the frame having the recessed region in which that face-seal element is located.

[0029] In some implementations, the electrolyzer cell assembly may further include a membrane assembly. The membrane assembly may include a catalyst-containing membrane and may have a first side and a second side, the membrane assembly may be positioned between the second side of the first frame and the second side of the second frame, at least a portion of the first side of the membrane assembly may be in contact with the raised portions of the fourth face-seal element, and at least a portion of the second side of the membrane assembly may be in contact with the second face-seal element.

[0030] In some implementations, the membrane assembly may further include a first porous transport layer and a second porous transport layer, and the catalyst-containing membrane may be interposed between the first porous transport layer and the second porous transport layer.

[0031] In some implementations, the catalyst-containing membrane may extend beyond the first porous transport layer and the second porous transport layer and the second face-sealDocket No. OPUSP048WO element and the fourth face-seal element may contact opposite sides of the catalyst-containing membrane.

[0032] In some implementations, the electrolyzer cell assembly may further include a separator plate. The separator plate may be coextensive with the first side of the first frame and the opening of the first frame, the separator plate may be in contact with the first face-seal element, and the separator plate may cap the opening of the first frame.

[0033] In some implementations, there may be multiple instances of the electrolyzer cell assembly arranged in a stack, and each separator plate that is adjacent the second frame of an adjacent electrolyzer cell assembly may be in contact with the third face- seal element of that adjacent electrolyzer cell assembly.

[0034] In some implementations, the electrolyzer cell assembly may further include a first flow field and a second flow field, the first flow field may be positioned within the opening of the first frame, the second flow field may be positioned within the opening of the second frame, and the membrane assembly may be interposed between the first flow field and the second flow field.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] FIG. 1 depicts an exploded view of an example multi-cell COx electrolyzer stack.

[0037] FIG. 2 depicts a perspective view of the example multi-cell COx electrolyzer of FIG. 1.

[0038] FIG. 3 depicts an exploded view of an example cell for a multi-cell COx electrolyzer.

[0039] FIG. 4 depicts an exploded view of the example cell for a multi-cell COx electrolyzer of FIG. 3 from a different perspective.

[0040] FIG. 5 depicts a cutaway view of the example cell for a multi-cell COx electrolyzer of FIG. 3.

[0041] FIG. 6 depicts a cross-sectional view of a portion of an electrolyzer cell assembly such as is shown in FIG. 3.

[0042] FIG. 7 depicts a cross-sectional view of a portion of another variant of an electrolyzer cell assembly such as is shown in FIG. 3.

[0043] FIG. 8 depicts a cross-sectional view of a portion of an example face-seal element.Docket No. OPUSP048WO

[0044] FIG. 9 depicts a cross-sectional view of a portion of an alternate version of an example face-seal element.

[0045] FIG. 10 depicts isometric and cutaway detail views of an example face-seal element.

[0046] FIG. 11 depicts isometric and cutaway detail views of another example face-seal element.

[0047] FIG. 12 depicts a cross-sectional view of a portion of another variant of an electrolyzer cell assembly such as is shown in FIG. 3.

[0048] FIG. 13 depicts a cross-sectional view of a portion of another variant of an electrolyzer cell assembly such as is shown in FIG. 3.

[0049] FIG. 13’ depicts a variant of a face-seal element.

[0050] FIG. 14 depicts a cross-sectional view of a portion of another variant of an electrolyzer cell assembly such as is shown in FIG. 3.

[0051] FIG. 15 depicts a cross-sectional view of a portion of another variant of an electrolyzer cell assembly such as is shown in FIG. 3.DETAILED DESCRIPTION

[0052] While the concepts herein may be applied to any electrolyzer, they are particularly well suits for implementation in the context of a carbon oxide (COx) reduction electrolyzer due to the higher operating pressures typically used in carbon oxide electrolyzer cell assemblies.

[0053] FIG. 1 depicts an exploded view of an example multi-cell COXelectrolyzer stack. FIG. 2 depicts a perspective view of the example multi-cell COXelectrolyzer of FIG. 1. As seen in FIGS. 1 and 2, multi-cell COXelectrolyzer stack (or stack) 100 includes a plurality of COXelectrolyzer cells (or cells), such as cell 101, formed by stacking a plurality of repeat units 103 between cathode interface assembly 105 of cathode side assembly 107 and anode interface assembly 109 of anode side assembly 111.

[0054] The cathode side assembly 107 may include the cathode interface assembly 105, bus (or terminal) plate 113, manifold assembly 115, isolation plate 117, and end plate 119 sequentially stacked from a first side of the plurality of repeat units 103 in a first direction, e.g., an axial direction, which may extend parallel to the z-axis direction. Among other functions, the cathode side assembly 107 may at least be configured to provide one or more reactants to the cells to feed the COXreduction process and output one or more products from the cells in association therewith. The anode side assembly 111 may include the anode interface assembly 109, bus (or terminal) plate 121, isolation plate 123, and end plate 125 sequentially stacked from a second side of the plurality of repeat units 103 in a second direction opposite the firstDocket No. OPUSP048WO direction. Among other functions, the anode side assembly 111 may be at least configured to constrain axial expansion of the cells during the COXreduction process in a manner that prevents or reduces the likelihood of the plurality of cells from being overly compressed but which maintains corresponding fluidic seals and electrical conductivity between associated components of the stack 100.

[0055] The respective end plates 119 and 125 of the cathode side assembly 107 and the anode side assembly 111 may be coupled to one another via a plurality of biasing members 127 (e.g., anchors, bolts, studs, tie rods, etc.) extending in the axial direction and passing through corresponding holes in the end plates 119 and 125 and retained by nuts or other threaded fasteners. It is also noted that the end plates 119 and 125 may be formed of any suitable material, such as aluminum alloys, steel, magnesium alloys, titanium alloys, and / or the like. The biasing members 127 may be at least partially threaded to respectively engage with, for instance, threaded fasteners (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 the end plates 119 and 125, the biasing members 127, and the threaded fasteners. Thus, the end plates 119 and 125 may generally serve to act as load- spreading members that act to distribute a clamping load relatively evenly over the other elements of stack 100. While the biasing members 127 are described as passing through the holes that may be defined in the end plates 119 and 125 and engaging with, for example, threaded fasteners to effect a clamping force, alternative arrangements are contemplated. For example, alternative arrangements of the biasing members 127 may include providing protrusions (e.g., pins) that extend outward from peripheral surfaces of the end plates 119 and 125 (e.g., in the X-Y plane), with the biasing members 127 engaging with one or more of these protrusions on each of the end plates 119 and 125. In such an example, one or more tensioning devices, e.g., turnbuckles, may be associated with each of the biasing members 127 such that the clamping force may be applied to the plurality of cells.

[0056] The bus plates 113 and 121 are respectively provided with terminal portions 113t and 12 It protruding outwardly from corresponding peripheral surfaces and may be respectively connected to a power supply. In some cases, the terminal portions 113t and 121t may have, for example, lugs, terminal blocks, or other electrical connection mechanisms to facilitate electrical connections between the bus plates 113 and 121 and a corresponding positive or negative voltage or current source. For example, the terminal portion 113t on a cathode side of stack 100 may be connected to a negative electrode of the power supply, and the terminal portion 12 It on an anode side of the stack 100 may be connected to a positive electrode of theDocket No. OPUSP048WO power supply. In this manner, the bus plates 113 and 121 may provide common electrical connections for the plurality of cells of stack 100, such as the cell 101 and thereby enable an electrical potential or current to be generated across the plurality of cells of the stack 100 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 the stack 100 through application of a voltage or current across the bus plates 113 and 121, 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 COXinto carbon monoxide, a hydrocarbon, and / or other catalyst-specific products. As will become more apparent below, the bus plate 113 may be sized so as not to interfere with various fluidic passages through the stack 100.

[0057] According to various embodiments, bus plates 113 and 121 may be formed of a first electrically conductive material, e.g., aluminum alloys, iron, steel alloys, nickel alloys, lead, steel, zinc, and / or the like, that is coated (or plated) with a second, more electrically conductive coating, e.g., silver plating, gold plating, copper plating, or other material with relatively higher electrical conductivity, to provide a high level of electrical conductivity between the bus plates 113 and 121 and the corresponding flow fields (discussed later herein) of the cells of the stack 100.

[0058] The bus plate 113 may, for example, be electrically insulated from the end plate 119 by the isolation plate 117 and / or at least one other layer of electrically insulating material. As shown, the isolation plate 117 is disposed between the electrically conductive portion of the bus plate 113 and the end plate 119, and may include a plurality of fastener orifices through which the biasing members 127 may pass.

[0059] Similar to the bus plate 113, the bus plate 121 may be electrically insulated from the end plate 125 by the isolation plate 123 and / or at least one other layer of electrically insulating material that may act in a similar manner as the isolation plate 117 with respect to the bus plate 113 and the end plate 119, but with respect to the end plate 125 and the bus plate 121. Similar to isolation plate 117, isolation plate 123 may include a plurality of fastener orifices through which biasing members 127 may pass.

[0060] The manifold assembly 115 may include manifold block (or main body) 141, first fluidic inlet connectors (or couplings) 143, first fluidic outlet connectors 145, second fluidic inlet connector 147, and second fluidic outlet connector 149. The first fluidic inlet connectors 143, for example, may supply fluid to the anode sides of the cells 101, while the first fluidic outlet connectors 145 may receive fluid from the anode sides of the cells 101. Similarly, theDocket No. OPUSP048WO second fluidic inlet connector 147 may supply fluid to the cathode side of the cells 101 while the second fluidic outlet connector 149 may receive fluid from the cathode side of the cells 101.

[0061] The cells 101 of FIGS. 1 and 2 may generally each include a membrane electrode assembly (MEA) sandwiched between two or more gas-permeable layers which are, in turn sandwiched between an anode flow field and a cathode flow field. The anode flow field and the cathode flow fields may, for example, be housed within corresponding frames that may provide fluid feed-through passages that allow fluid supplied from the first fluidic inlet connectors 143 and the second fluidic inlet connector 147 to pass between the cells 101 and flow into the anode flow fields and cathode flow fields, respectively of the cells 101. The frames may also have additional feed-through passages that allow the fluid that flows out of the anode flow fields and the cathode flow fields to, for example, be routed to the first outlet connectors 145 and the second outlet connectors 149, respectively. Such fluid flow may occur while a voltage or current is applied across the terminal portions 113t and 121t, for example, such that an electrochemical reaction, e.g., a reduction reaction, involving the catalystcontaining layer occurs within each cell 101.

[0062] FIGS. 3 and 4, for example, depict exploded views of an example electrolyzer cell assembly 302 (which is conceptually similar to the cells 101, although with a somewhat different form factor). In the example electrolyzer cell assembly 302, which may also be referred to as an electrolyzer cell assembly, a membrane assembly 312 is provided that has a catalyst-containing membrane 314 that may be made of, for example, a polytetrafluoroethylene-based copolymer or a similar, suitable material that is then coated with catalyst(s). The catalyst-containing membrane may, for example, have a region (such as the region 314a) that is coated on one or both sides with one or more catalysts that may be selected so as to result in a desired COx reduction reaction taking place when COx gas is provided to the first fluidic inlet connectors 143 and water is provided to the second fluidic inlet connector 147 (referring back to FIGS. 1 and 2). Catalyst-containing membranes are typically relatively expensive materials — a square meter of Nafion™, which is produced by The Chemours Company and which is a commonly used membrane material for catalyst-containing membranes, can cost approximately $2000 US.

[0063] The catalysts may take the form of metal catalyst particles (e.g., nanoparticles) that are unsupported or supported on a conductive substrate such as carbon particles. In certain embodiments, the cathode catalyst layer may include gold (Au) particles and the anode catalystDocket No. OPUSP048WO layer may include metal oxide catalyst particles such as iridium oxide, nickel oxide, nickel iron oxide, iridium ruthenium oxide, platinum oxide, or the like.

[0064] The membrane assembly 312 may also include one or more porous layers 316, such as the porous layer 316a and the porous layer 316b. Each porous layer 316 may, in some cases, be, for example, a gas diffusion layer (GDL) or a porous transport layer (PTL). The porous layers may serve to permit fluids to be transported between the MEA and the flow fields, e.g., from the flow fields to the MEA or from the MEA to the flow fields. The fluids transported by the porous layers may, for example, include liquids and / or gases that may be delivered into the electrolyzer or generated within the MEA. The porous layers 316 may also provide additional structural support to the membrane assembly 312 and help retain the catalyst(s) applied to one or both sides of the catalyst-containing membrane 314 in place.

[0065] The primary focus of this disclosure is on sealing systems for sealing various aspects of the electrolyzer cell assemblies 302, but a brief discussion of the overall structure of the electrolyzer cell assemblies 302 is provided first for context. In many electrolyzer cell discussions it is common to designate the elements that are located on the “anode side” or the “cathode side” of the membrane assembly 312. However, as the present discussion relates to sealing features that may be used on either “side” of the membrane assembly 312, the various elements of the electrolyzer cell assembly exploded views of an example cell 302 discussed with respect to FIGS. 3 and 4 are not assigned designations indicating whether they are anodeside or cathode-side and are instead referred to more generically. It will be understood that the sealing features and structures discussed herein may be used in either the anode- side or the cathode-side context.

[0066] As can be seen in FIGS. 3 and 4, the electrolyzer cell assembly 302 includes, in addition to the membrane assembly 312, various elements, including a separator plate 310 (a separator plate 310a and a separator plate 310b are shown, although one of these two separator plates 310a and 310b would actually be “part” of an adjacent electrolyzer cell assembly 302), two frames 304a and 304b, a first flow field 306, and a second flow field 308. The separator plates 310 may be made of an electrically conductive, high-strength material, such as a steel alloy, a titanium alloy, or other such materials, and may serve to act as part of the electrically conductive path that extends through the flow fields 306 and 308 and the membrane assemblies 312 of the electrolyzer cell assemblies 302 when such electrolyzer cell assemblies 302 are assembled into a stack, e.g., as shown in the example of FIGS. 1 and 2. The separator plates 310 may also serve a structural function, as they may act as a structural web that may connect with the frames 304 and reinforce the frames 304 against potentially displacing outward, e.g.,Docket No. OPUSP048WO when the fluids introduced into one or both of the flow fields 306 and 308 are introduced at relatively high fluidic pressures, e.g., hundreds of pounds per square inch. Such pressures may exert a significant outward load on the frames 304, causing them to bulge outward unless restrained, e.g., through being coupled to the separator plates 310.

[0067] The first flow field 306 and the second flow field 308 may each provide one or more flow paths that are recessed into the sides of the first flow field 306 and the second flow field 308 that face towards the membrane assembly 312. The flow paths, which take the form of serpentine channels 309 in this example, may serve to distribute fluids delivered via the first inlet feed-through passages 305a and second inlet feed-through passages 305b across opposing sides of the membrane assembly 312 as those fluids flow along the flow paths, thereby “wetting” both sides of the membrane assembly 312 (although it will be understood that “wetted,” in this context, refers to whether a surface is in contact with a fluid being flowed, as opposed to actually being in contact with a liquid). Fluid that flows out of the flow paths in the first flow field 306 and the second flow field 308 may respectively flow into first outlet feed-through passages 307a and second outlet feed-through passages 307b.

[0068] FIG. 5 depicts a cutaway view of the example cell for a multi-cell COXelectrolyzer of FIG. 3; the cutaway profile is shown in the plan view of the electrolyzer cell assembly 302 shown at bottom right, and detail views of the circled regions are shown at top right and within the bounds of the electrolyzer cell assembly 302. As can be seen, the frames 304a and 304b may each have flow paths 311 that link the inlet feed-through passages 305a and 305b with surfaces of the flow fields 306 and 308, as appropriate, that provide entrance points for the channels 309 (or that otherwise allow fluids to be introduced into the flow fields 306 and / or 308).

[0069] The electrolyzer cell assembly 302 may also include face-seal elements 334 that are each positioned as to form a seal between one of the frames 304 and one of the elements adjacent the frame 304, e.g., the membrane assembly 312 or the separator plate 310. The electrolyzer cell assembly 302 may also include additional seal elements (not shown here) to seal between the various layers thereof and around the inlet feed-through passages 305 and the outlet feed-through passages 307.

[0070] Various example implementations of such face- seal elements and configurations that may be used in the context of the electrolyzer cell assembly 302 are discussed below with reference to FIGS. 6, 7, and 12 through 15. Figures 8 through 11 depict other aspects of such face-seal elements and configurations. Each of FIGS. 6, 7, and 12 through 15 depicts a cross- sectional view of a portion of the electrolyzer cell assembly 302, namely a portion of theDocket No. OPUSP048WO electrolyzer cell assembly 302 that includes inner edges or portions of the frames 304, an outer edge or portion of the first flow field 306, an outer edge or portion of the second flow field 308, a portion of the membrane assembly 312 that includes outer edges or portions of the porous layers 316 and a region of the catalyst-containing membrane 314 in between those outer edges or portions of the porous layers 316. Four of the face-seal elements 334 are also depicted.

[0071] It will be observed that the frames 304 may each have a first side 326 that faces towards the separator plate 310 that is adjacent thereto, e.g., the frame 304a has a first side 326a that faces towards the separator plate 310a, while the frame 304b has a first side 326b that faces towards the separator plate 310b. The frames 304 may also each have a second side 328 that faces towards the membrane assembly 312, e.g., the frame 304a has a second side 328a that faces towards the membrane assembly 312 while the frame 304b has a second side 328b that faces towards the membrane assembly 312. At least a portion of the membrane assembly 312 is thus positioned between the second sides 328a and 328b of the frames 304a and 304b, respectively.

[0072] The frames 304 may each define an opening 324, e.g., an inner perimeter wall 322a of the frame 304a may define an opening 324a, while an inner perimeter wall 322b of the frame 304b may define an opening 324b. The openings 324 may each be sized so as to receive and contain one of the flow fields, e.g., the opening 324a may be sized such that the first flow field 306 (not shown) fits within the frame 304a with little or no assembly gaps, while the opening 324b may similarly be sized such that the second flow field 308 (not shown) fits within the frame 304b with little or no assembly gaps.

[0073] The face-seal elements 334 may all be located within recessed regions 320 located within a seal region 318 of the electrolyzer cell assembly 302. For example, a face-seal element 334a may be located within a recessed region 320aa of the frame 304a and another face-seal element 334b may be located within a recessed region 320ab of the frame 304a. Similarly, a face-seal element 334c may be located within a recessed region 320ba of the frame 304b and another face-seal element 334d may be located within a recessed region 320bb of the frame 304b. The second side 328a of the frame 304a may be closer to a portion of the recessed region 320aa than to the first surface 330a, and the first side 326a of the frame 304a may be closer to a portion of the recessed region 320ab than to the second surface 332a. Similarly, the second side 328b of the frame 304b may be closer to a portion of the recessed region 320ba than to the first surface 330b, and the first side 326b of the frame 304b may be closer to a portion of the recessed region 320bb than to the second surface 332b. The seal region 318 may, for example, extend entirely around, and bound, the openings 324 and is wide enough (relative to the widthDocket No. OPUSP048WO shown in FIG. 6) to contain the face-seal elements 334 and the recessed regions 320 that house the face-seal elements 334.

[0074] As can be seen in FIG. 6, the first side 326a of the frame 304a includes the recessed region 320aa as well as a first surface 330a that is adjacent the recessed region 320aa and that defines a first reference plane 350a. Similarly, the second side 328a of the frame 304a includes the recessed region 320ab as well as a second surface 332a that is adjacent the recessed region 320ab and that defines a second reference plane 350b.

[0075] The first side 326a of the frame 304b includes the recessed region 320ba and similarly a first surface 330b that is adjacent the recessed region 320ba and that defines a third reference plane 350c. Similarly, the second side 328a of the frame 304b includes the recessed region 320bb as well as a second surface 332b that is adjacent the recessed region 320bb and that defines a fourth reference plane 350d.

[0076] Put another way, each reference plane 350 may be co-planar with the respective first surface 330 or second surface 332 that defines it. It will be noted that in FIG. 6, the various reference planes 350, the first surfaces 330, and the second surfaces 332 are all shown as slightly offset (upward or downward) from the actual surfaces of the frames 304 that define them; this is simply a convention to allow the viewer to more easily perceive them without the various lines that represent such features overlapping one another and being indistinguishable from one another. In actual practice, for example, the first surface 330a and the first reference plane 350a would both be co-planar with the uppermost surface of the frame 304a that is within the seal region 318.

[0077] As can also be seen in FIG. 6, the membrane assembly 312 includes the catalystcontaining membrane 314 and the porous layers 316a and 316b. The porous layers 316a and 316b do not, in this example, extend into or past the corresponding recessed regions 320 that are located in the second sides 328 of the frames 304. However, in other implementations, one or both porous layers 316a and 316b may extend into or passed the corresponding recessed region 320 that is located in the second side 328 of the frame 304 adjacent thereto.

[0078] FIG. 7 depicts the same portion of the electrolyzer cell assembly 302 of FIG. 6 but with the various elements assembled together, e.g., into a stack of adjoining layers. FIG. 7 also depicts two adjoining electrolyzer cell assemblies 302 in dashed outline so that the repeating nature of the depicted electrolyzer cell assembly 302 within a stack of electrolyzer cell assemblies 302 can be seen (it will be noted that the separator plate 310b would, for example, be rendered in dashed lines as well since it would generally be part of the lower dashed electrolyzer cell assembly 302). As can be seen, the face-seal element 334b is in contact withDocket No. OPUSP048WO one side of the catalyst-containing membrane while the face-seal element 334d is in contact with an opposite side of the catalyst-containing membrane 314, thereby forming a seal between the catalyst-containing membrane 314 and the frames 304. FIG. 7 also depicts the first flow field 306 and the second flow field 308, which have been placed within the openings 324a and 324b, respectively. As can be seen, the channels 309a and 309b of the first flow field 306 and the second flow field 308, respectively, are capped off with respect to the first flow field 306 and the second flow field 308 by the membrane assembly 312.

[0079] One of the face-seal elements 334 (334a) that is shown in FIG. 6 is shown in more detail in FIG. 8. As can be seen in FIG. 8, portions of the opening 324a and the frame 304a are visible, as is the recessed region 320a and the face-seal element 334a that is housed within the recessed region 320a.

[0080] As can be seen from the depicted transverse cross-sectional profile of the face-seal element 334a, the transverse cross-sectional profile of the face-seal element 334a includes a first sub-profile 342 that is in contact with the recessed region 320 that the face-seal element 334a is located within, i.e., the recessed region 320aa. In this example, the surface of the recessed region 320aa that the first sub-profile 342 of the face-seal element 334a is in contact with is a planar surface 354, resulting in the first sub-profile 342 being linear in nature. The transverse cross-sectional profile of the face-seal element 334a also includes a second subprofile 344 that is on the opposite side of the face-seal element 334a from the first sub-profile 342 and that defines a surface of the face-seal element 334a that faces towards the component that will be placed directly adjacent the frame 304a, e.g., the separator plate 310a in this example. It will be understood that the face-seal element 334a may generally have the shape provided when the transverse cross-sectional profile of the face-seal element 334 is swept along an enclosed path, e.g., a rectangular path with rounded comers. For example, the path may, in some instances, be a path that is co-linear with the outermost or innermost edge of the depicted face-seal element 334a of FIGS. 3 or 4. Such a path may extend around the opening 324a of the frame 304a. The other face-seal elements 334 may similarly follow respective paths that are similarly configured.

[0081] The second sub-profile 344 in the depicted face-seal element 334a defines a “bump seal” surface of the face-seal element 334a, e.g., having at least a recessed portion 348 that is located between two raised portions 346. In additional implementations, there may be additional recessed portions 348 and additional raised portions 346, with each recessed portion 348 positioned in between two of the raised portions 346. The various raised portions 346 andDocket No. OPUSP048WO recessed portion(s) 348 of a given face-seal element 334 may be contiguous and made of an elastomeric material, such as neoprene, nitrile, silicone, etc.

[0082] Such bump seals may offer multiple advantages over traditional seals, e.g., O-rings. For example, bump seals may be considerably thinner than O-rings while providing equivalent sealing performance. For example, in the context of an electrolyzer cell assembly for a COx electrolyzer, the operating pressures experienced within the electrolyzer cell assembly, which may exceed 150 psi, may require the use of an O-ring that has a cross-sectional profile diameter of approximately 3 mm. In contrast, a bump seal that is able to withstand similar pressures may have a cross-sectional profile with a height of 1 mm (in the direction perpendicular to the surface against which such a bump seal is sealing). This allows the frames within which such bump seals are mounted to be reduced in thickness and / or allows for additional clearance within the frame structure for routing flow paths that communicate fluid between the flow fields 306 and 308 and the feed-through passages 305 and 307. The reduced depth of the recessed regions that retain bump seals, as compared with the deeper depth required for grooves for equivalent O-ring seals, may also avoid scenarios in which the frames have localized regions where the thickness of the frame is significantly decreased as compared with its nominal or maximum thickness. For example, a typical frame might be 5 mm or 6 mm thick, and if O-rings are used, the thickness of the frame in the region of the O-ring grooves might drop to 50% or less of the nominal frame thickness. In contrast, using equivalent bump seals might cause the thickness of the frame in the recessed region to drop to only 80% or 90% of the nominal thickness, thereby resulting in a much stronger frame component that is more resilient and able to withstand higher electrolyzer cell working pressures than an equivalent thickness frame that uses O-ring seals might.

[0083] Bump seals may also generally allow for higher contact pressures to be developed between the seal and the surface- sealed against than may be achieved with O-ring seals. For example, an O-ring seal such as discussed above (e.g., approximately 3 mm in cross-sectional diameter) may generate between 0.7 to 1.6 MPa of seal pressure under a given compression load applied to an electrolyzer cell assembly, whereas a bump seal such as discussed above may generate between 3 and 5 MPa of seal pressure under similar conditions, thereby providing a seal interface with a much higher leak resistance and much higher pressure limit than may be obtained with O-rings. This, in turn, may allow for higher pressures to be used within the electrolyzer cell assembly, e.g., in the cathode side of the cell, which may boost throughput and yield of the cell assembly.Docket No. OPUSP048WO

[0084] O-ring seals may also generally be more difficult to manage during the assembly process of the electrolyzer cell assembly. For example, O-ring seals may become dislodged from the grooves that receive them or, in some cases, fall out of the grooves entirely. Bump seals, in contrast, may be bonded or adhered into place, and thereby be prevented from falling out of the frames into which they are received. O-ring seals also tend to move within the grooves that contain them once subjected to pressure. For example, when an O-ring seal is pressurized, the pressure may push the O-ring seal outward until it collides with the outer wall of the O-ring groove. This has the effect of slightly stretching the O-ring (thereby causing its cross-sectional diameter to decrease slightly) and reducing the clamping pressure generated by the O-ring. For example, as the surfaces of the O-ring that contact the opposing surfaces to be sealed increase in area due to the stretching of the O-ring, the clamping pressure provided by the O-ring to such surfaces for a given amount of O-ring compression will decrease. Bump seals, in contrast, may have a shallower depth than O-ring seals that provide equivalent sealing performance for a given pressure, resulting in a correspondingly lower-profile cross-section that similarly generates a proportionately lower amount of outward force on the bump seal than would be experienced by an O-ring seal. Moreover, as discussed later, bump seals may be adhered, bonded, or co-molded in place, which may provide additional restraint against outward movement of the bump seal.

[0085] In FIG. 8, the face-seal element 334a is shown in an uncompressed state. It will be observed that the raised portions 346 of the face-seal element 334a, when the face-seal element 334a is in the uncompressed state, extend out of the recessed region 320aa of the frame 304a and past the first reference plane 350a. In the depicted example, the recessed portion 348 of the face-seal element 334a, in contrast, does not extend past the first reference plane 350a.

[0086] In some implementations, the raised portions 346 of the face-seal element 334a, when the face-seal element 334a is in the uncompressed state, may extend out of the recessed region 320aa of the frame 304a and past the first reference plane 350a by between 100 pm and 250 pm, and may have an overall thickness of 1 mm in the direction of compression, with the raised portions 346 having a height relative to the recessed portions 348 of approximately 0.75 mm and a width of approximately 2 mm each. In other implementations, the raised portions may extend out of the recessed regions of the frames and past the corresponding reference planes by between about 50 pm and about 500 pm, between about 50 pm and about 280 pm, between about 280 pm and about 500 pm, between about 50 pm and about 160 pm, between about 160 pm and about 280 pm, between about 280 pm and about 390 pm, between about 390 pm and about 500 pm, between about 50 pm and about 110 pm, between about 110 pm and about 160Docket No. OPUSP048WO pm, between about 160 pm and about 220 pm, between about 220 pm and about 280 pm, between about 280 pm and about 330 pm, between about 330 pm and about 390 pm, between about 390 pm and about 440 pm, or between about 440 (am and about 500 (am. The overall thickness of the face-seal elements may, in some implementations, be between about 800 pm and about 1600 pm, between about 800 pm and about 1200 pm, between about 1200 pm and about 1600 pm, between about 800 pm and about 1000 pm, between about 1000 pm and about 1200 pm, between about 1200 pm and about 1400 pm, between about 1400 pm and about 1600 pm, between about 800 pm and about 900 pm, between about 900 pm and about 1000 pm, between about 1000 pm and about 1100 pm, between about 1100 pm and about 1200 pm, between about 1200 pm and about 1300 pm, between about 1300 pm and about 1400 pm, between about 1400 pm and about 1500 pm, or between about 1500 pm and about 1600 pm. In some such implementations, the raised portions may have a height relative to the recessed portions of between about 50 pm and about 500 pm, between about 50 pm and about 280 pm, between about 280 pm and about 500 pm, between about 50 pm and about 160 pm, between about 160 pm and about 280 pm, between about 280 pm and about 390 pm, between about 390 pm and about 500 pm, between about 50 pm and about 110 pm, between about 110 pm and about 160 pm, between about 160 pm and about 220 pm, between about 220 pm and about 280 pm, between about 280 pm and about 330 pm, between about 330 pm and about 390 pm, between about 390 pm and about 440 pm, or between about 440 pm and about 500 pm. In some implementations, the width of each raised portion may be between about 1.2 mm and about 3 mm, between about 1.2 mm and about 2.1 mm, between about 2.1 mm and about 3 mm, between about 1.2 mm and about 1.6 mm, between about 1.6 mm and about 2.1 mm, between about 2.1 mm and about 2.6 mm, between about 2.6 mm and about 3 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 1.9 mm, between about 1.9 mm and about 2.1 mm, between about 2.1 mm and about 2.3 mm, between about 2.3 mm and about 2.6 mm, between about 2.6 mm and about 2.8 mm, or between about 2.8 mm and about 3 mm. Face-seal elements with dimensions such as those discussed above, including the specific example discussed above as well as the various permutations of dimensional ranges discussed above, may be particularly well-suited for use in COx electrolyzer systems due to their relatively small cross-sectional size and good sealing performance under the operating pressures typically seen in such electrolyzers.

[0087] FIG. 9 depicts an alternative design for the face-seal element 334, e.g., such as is discussed later with respect to FIG. 12, in which the surface of the recessed region 320aa that contacts the first sub-profile 342 of the face-seal element 334a is not a planar surface, but isDocket No. OPUSP048WO itself similar in profile to the second sub-profile 344 of the face-seal element 334a. For example, the surface of the recessed region 320aa that contacts the first sub-profile 342 of the face-seal element 334a has convex portions 356 that are each positioned so as to be under one of the raised portions 346 of the second sub-profile 344 of the face-seal element 334a. Correspondingly, the first sub-profile 342 has concave portions that conform to the convex portions 356 of the facing surface of the recessed region 320aa. In some such implementations, the thickness of the face-seal element 334a may be constant or nominally constant, e.g., within ±10% of a nominal value, within the raised portions 346 and in a direction normal or perpendicular to the convex portions 356 of the surface of the recessed region 320a. Such faceseal elements may have similar dimensions to those discussed above with respect to FIG. 8.

[0088] It will be understood that the face-seal element geometries discussed above with respect to FIGS. 8 and 9 may be generally applicable to any of the face-seal elements discussed herein that are discussed as having or shown to have raised portions and recessed portions.

[0089] Additionally, in some implementations, the face-seal elements may include regions in which the recessed portions do not exist and are instead replaced with raised portions that extend between adjacent raised portions of the transverse cross-sectional profile. FIGS. 10 and 11 illustrate such implementations. FIG. 10 depicts an example face-seal element that does not have such additional raised portions, while FIG. 11 depicts an example face- seal element that has such additional raised portions. In both FIGS. 10 and 11, a comer portion of the depicted face-seal elements 1034 within the circled region has been cut away and removed, thereby revealing the cross-sectional shapes, generally represented by transverse cross-sections 1037, of the face-seal elements 1034 at the cut locations. Additionally, the paths 1038 that the transverse cross-sections 1037 are swept along are also shown in the cut-out regions. In both FIGS. 10 and 11, the circled region is also reproduced in magnified detail in the lower right of the Figures.

[0090] As can be seen in FIG. 10, the face-seal element 1034 of FIG. 10 is constant in transverse cross-section about the entire circumference or perimeter of the face-seal element 1034. In contrast, the face-seal element 1034 of FIG. 11 has a plurality of additional raised portions 1035 that are distributed at locations along the circumference or perimeter of the faceseal element 1034. As can be seen from the detail view in FIG. 11, the transverse cross-section of the face-seal elements at the locations of these additional raised portions 1035 do not have the recessed portion that is present in the remaining regions of the face-seal element 1034. As a result, a ridge is formed between the two raised portions of the cross-sectional profile 1037 by the additional raised portion 1035 such that when the face-seal element is pressed against aDocket No. OPUSP048WO mating surface, the raised portions of the cross-sectional profile 1037, as well as the additional raised portions 1035, press against the mating surface. By positioning multiple such additional raised portions 1035 along the length of the face-seal element 1034, it is possible to, in effect, fluidically seal portions of the recessed portions between the raised portions off from one another. This, for example, may reduce the potential for leakage. For example, if the inner raised portion of the face- seal element 1034 in FIG. 10 were to leak in one location, the fluid that leaks in at that location would flow along the entire length of the recessed portion, which might allow the fluid to then encounter another potential leak point through the outer raised portion of the face-seal element 1034 located, for example, on the opposite side of the faceseal element 1034. In the example of FIG. 11, however, fluid that leaked past the inner raised portion of the face-seal element 1034 would fill the recessed portion in that immediate area, but would be prevented from flowing past the additional raised portions 1035 that bracket that segment of the recessed portion. While the fluid could certainly leak past the outer raised portion in that same segment of the face-seal element 1034 if it found a potential leak point in that segment, it would not be able to freely travel to any of the other segments of the recessed portion and would thus not be able to easily leak out of the face- seal element 1034 at potential leak points in those other regions. It will be understood that any of the face-seal elements with raised and recessed portions discussed herein may implement such additional raised portions.

[0091] Returning to FIGS. 6 and 7, it can be seen that the face-seal elements 334 of the implementation of FIGS. 6 and 7 are positioned such that the face-seal elements 334 of adjoining electrolyzer cell assemblies 302 that are in contact with each separator plate 310 contact the intervening separator plate 310 in generally the same location with respect to the distances from the perimeter walls 322.

[0092] In contrast, the two face-seal elements 334 within each electrolyzer cell assembly 302 that are in contact with the membrane assembly 312 of that electrolyzer cell assembly 302 may be positionally offset from one another relative to the edge of the openings 324a and 324b. As a result of such positioning, the regions where the face-seal element 334b and the face-seal element 334d both contact the membrane assembly 312 and, in this instance, the catalystcontaining membrane 314, are offset laterally from one another, i.e., such contact regions do not overlap with one another when viewed along an axis perpendicular to the major planes of the separator plates 310. Such an arrangement may serve a dual purpose — in such a configuration, the face-seal elements 334b and 334d may provide twice as many sealing locations as they might if the face-seal elements 334b and 334d were instead positioned so as to contact overlapping regions of the membrane assembly 312 (e.g., similar to how the face-Docket No. OPUSP048WO seal elements 334a and 334c contact overlapping regions of the separator plates 310). For example, since the membrane assembly 312 may be quite thin, e.g., on the order of less than 1000 pm, e.g., less than 900 pm thick, and made of thin membranes or porous layers, the membrane assembly 312 may be prone to flexing. As a result, if the membrane assembly 312 is pinched between two elastomeric face-seal elements 334, such as the face-seal elements 334b and 334d, there is a potential that the pressures that are exerted on the membrane assembly 312 and the face-seal elements 334b and 334d may cause the membrane assembly 312 pinched therebetween and one of the face-seal elements 334b and 334d to deform, thereby reducing the clamping force exerted by the other of the face-seal elements 334b and 334d on the membrane assembly 312. This can potentially increase the risks of a leak past one or the other of the faceseal elements 334b and 334d. By staggering the face-seal elements 334b and 334d with respect to their respective distances from the inner edge of the frames such that the membrane assembly 312 is pinched between the face-seal element 334b and a surface of the rigid frame 304b in one location and between the face-seal element 334d and a surface of the rigid frame 304a in another location, each of the seals provided by the face-seal elements 334b and 334d is immune from being compromised by potential deflection in the other of the face- seal elements 334b and 334d. The other benefit that may accrue from the implementation shown in FIG. 7 is that the membrane assembly 312 is protected from potential out-of-plane deformation. In other words, the depicted confirmation maintains the membrane assembly 312 in a planar state, with no potential for significant dimpling of the membrane assembly 312. Such issues are not a concern for the face-seal elements 334a and 334c, as those face-seal elements 334 are in contact with the significantly stronger and more rigid separator plates 310. Such a benefit increases the robustness of the electrolyzer cell assembly 302, as it protects the relatively fragile membrane assembly 312 from deformation that can compromise the effectiveness of the electrolyzer cell assembly 302.

[0093] FIG. 12 depicts an implementation that is similar to that of FIG. 7, but which has faceseal elements 334 that are configured as shown in FIG. 9. It will be understood that elements of the implementation of FIG. 12 (as well as in the implementations depicted in other Figures herein) that are similar to elements of FIG. 7 that were discussed earlier may not, for the sake of brevity, be described again below. In such instances, the reader is directed to refer to the earlier discussion of such elements and it is to be understood that such earlier discussion of such elements is, unless indicated to the contrary or otherwise apparent from the context, applicable to such later-discussed implementations as well.Docket No. OPUSP048WO

[0094] As can be seen in FIG. 12, the face-seal elements 334 may, by virtue of having thinner thicknesses in their raised portions than the face-seal elements 334 of the implementation of FIG. 7, undergo more strain than the counterpart face-seal elements 334 in FIG. 7 under otherwise identical compression scenarios (e.g., the face-seal elements in both FIG. 7 and FIG. 12 being compressed the same total amount). As a result of this greater strain, the face- seal elements of FIG. 12 may exert a greater amount of sealing pressure on the separator plate 310 and the membrane assembly 312 in the implementation of FIG. 12 as compared with the faceseal elements 334 of the implementation of FIG. 7.

[0095] FIG. 13 depicts an implementation that is similar to that of FIG. 7, but with face- seal elements 334a and 334c connected with perimeter seal elements. As can be seen, the transverse cross-sectional profiles of the face-seal elements 334a and 334c each connect with a thin layer of material that extends along, and contacts, the perimeter wall 322a or 322b, respectively, before then extending along the second sides 328a or 328b, respectively, and towards the outer edge of the membrane assembly 312. The thin layers of material that extend along the perimeter walls 322a and 322b, e.g., from the respective first sides 326 of the frames 304 to the respective second sides 328 of the frames 304, act as perimeter seal elements 336a and 336b, respectively, that bound the openings 324a and 324b, respectively, and may be sized so as to cause the openings 324a and 324b, respectively, to be slightly smaller in size than the flow fields 306 and 308, respectively. Such a configuration provides for an interference or light press fit between the flow fields 306 and 308 and the respective openings 324a and 324b in frames 304a and 304b, respectively. In other implementations, the perimeter seal elements 336a and / or 336b may be sized such that the openings 324a and 324b are sized the same as, or slightly larger than, the flow fields 306 and 308, e.g., providing a 0.1 mm gap between the perimeter seal elements 336 and the flow fields 306 or 308. In some such implementations, the portions of the thin layer that connect the perimeter seal elements 336 with their respective face-seal elements 334 may be sized to have a portion that extends above the reference planes 350 that are proximate thereto. For example, FIG. 13’ depicts the face-seal element 334a and connected perimeter seal element 336 with a portion 336’ that extends above the reference plane 350a; this portion 336’, being of relatively small cross-section, is compressed downward and potentially inward when the various layers of the cell are compressed during assembly (the left image shows the face-seal element and connected perimeter seal element 336 when uncompressed; the right image shows the same elements in a compressed state). In such configurations, the portion of the connecting portion that extends above the corresponding reference plane 350 may be compressed by the separator plate 310 when the electrolyzer cellDocket No. OPUSP048WO assembly 302 is assembled and the layers thereof compressed together, thereby causing the compressed material of that portion to expand laterally and press against the flow field 306 or 308 that is adjacent that perimeter seal element 336 and provide a seal around the perimeter of the corresponding flow field 306 or 308. Such an arrangement can provide more clearance for assembly as the flow field 306 or 308 is placed within the corresponding opening 324, while also providing a resulting “taking up” of at least a portion of such clearance when the electrolyzer cell is assembled. The portions of the thin layers that extend outward along the second sides 328a and 328b may, in some implementations, be configured to be at the same elevations as the surfaces of the second sides that contact the porous layers 316a and 316b. In other implementations, the portions of the thin layers that extend outward along the second sides 328a and 328b may be configured to be at elevations that are, when the portions of the thin layers are uncompressed, closer to the catalyst-containing membrane than the surfaces of the second sides that contact the porous layers 316a and 316b — in such configurations, these portions of the thin layers may be compressed slightly when the frames 304a and 304b are compressed against the membrane assembly 312, thereby providing an additional level of sealing between the frames 304a and 304b and the membrane assembly 312. The perimeter seal elements 336 may also act to fill the potential gaps between the frames 304 and the flow fields 306 and / or 308. For example, fluid that is supposed to flow through the channels 309 may, in some instances, flow within the gap between a frame 304 and a flow field 306 or 308 — such a gap may offer a more direct route for fluid flow (and have lower flow resistance) than the channels 309 may provide, and fluid may therefore preferentially flow through the gap instead of the channels 309, thereby bypassing or circumventing the channels 309. The fluid that bypasses the channels 309 would thus not be distributed across the membrane assembly 312 and cannot participate in the COx reduction reaction. The use of perimeter seal elements may prevent or mitigate such bypass fluid flow in an electrolyzer cell assembly.

[0096] FIG. 14 depicts an implementation of the electrolyzer cell assembly that is similar to that of FIG. 13 except that the face-seal elements 334 of FIG. 14 are of the type shown in FIG. 9 and the face-seal element 334d in FIG. 14 is a face-seal that has a second sub-profile that is planar as opposed to having a recessed portion 348 in between two adjacent raised portions 346. The face-seal element 334d thus generally has a planar surface facing the second side 328a of the frame 304a (i.e., facing in the same direction as the second side 328b of the frame 304b) and extending around the opening 324b of the frame 304b. The implementation of FIG. 14 also differs from that of FIG. 7 in that the face-seal element 334d and the face-seal element 334b are positioned so as to overlap each other when viewed along axes perpendicular to theDocket No. OPUSP048WO separator plates 310. The face-seal element 334d of FIG. 14 may be designed to be relatively thin, e.g., 500 pm+100 pm, such that the amount of deformation that the face-seal element 334d of FIG. 14 may undergo may be much less than would be experienced if the face-seal element 334d were to have a recessed portion between two raised portions, e.g., such as is present in the face-seal element 334b of FIG. 14. Such a configuration may allow for a more compact seal arrangement as the face-seal elements 334 of FIG. 14 are located at two different distances from the openings 324 as opposed to the three different distances that the face-seal elements 334 of FIGS. 7, 12, and 13 are positioned at. This allows the membrane assembly 312 to still be effectively sealed against by the face-seal elements 334 while allowing the overall size of the membrane assembly 312, or at least the catalyst-containing membrane 314 contained therein, to be reduced as compared with the implementations of FIGS. 7, 12, and 13. As the catalyst-containing membrane (or, perhaps more accurately, the membrane used in the catalystcontaining membrane) can be quite expensive (e.g., approximately $2000 / square meter) and is used in each and every electrolyzer cell assembly 302, any reduction in the amount of the catalyst-containing membrane that extends beyond the edges of the flow fields and in between the second sides 328 of the frames 304 may reduce the overall costs of an electrolyzer cell assembly 302. It will be understood that while the catalyst-containing membrane 314 is shown as extending past the outermost face-seal elements 334 in each implementation depicted herein, in actual practice, the catalyst-containing membrane 314 may instead be sized smaller, e.g., such that it only extends a few millimeters past the outermost face-seal element 334 of a particular implementation.

[0097] It will be understood that while the implementation of FIG. 14 includes perimeter seal elements 336, such perimeter seals 336 may also be omitted in the example of FIG. 14, if desired.

[0098] FIG. 15 depicts another implementation that is similar to that of FIG. 14, except that all of the face-seal elements have been placed proximate the edges of the openings 324a and 324b, as appropriate. As a result, all four face-seal elements 334 of FIG. 15 overlap each other when viewed along a direction perpendicular to the separator plates 310. This provides the most compact face-seal arrangement that can be provided, thereby effectively minimizing the potential size of the catalyst-containing membrane 314 relative to the openings 324 while still providing for effective sealing between the frames 304 and the membrane assembly 312.

[0099] As can be seen in FIG. 15, the face-seal element 334d of FIG. 15 is similar to the faceseal element 334d of FIG. 14, and provides a similar degree of sealing without potentially compromising the sealing effectiveness of either of the face-seal elements 334b or 334d andDocket No. OPUSP048WO avoiding potentially subjecting the membrane assembly 312 to undesired localized deformation in the seal region.

[0100] While the implementation of FIG. 15 may, as with the implementation of FIG. 14, be implemented without perimeter seal elements, the depicted implementation includes perimeter seal elements 336a and 336b, which are similar to the perimeter seal elements 336a and 336b of the implementation of FIG. 14. In the implementation of FIG. 15, however, the perimeter seal element 336a is connected with both of the face-seal elements 334a and 334b, forming one contiguous elastomeric seal structure that extends from the recessed region 320aa on the first side 326a of the frame 304a to the recessed region 320ab on the second side 328a of the frame 304a. Similarly, the perimeter seal element 336b in FIG. 15 is connected with both of the faceseal elements 334c and 334d, forming one contiguous elastomeric seal structure that extends from the recessed region 320ba on the first side 326b of the frame 304b to the recessed region 320bb on the second side 328b of the frame 304b. It will also be noted that the face-seal elements 334 in the implementation of FIG. 15 are also positioned directly adjacent, e.g., within a millimeter or a few millimeters of, the openings 324 / interior edges of the frames 304. This allows the face-seal elements 334b and 334d to still fully clamp / seal to the membrane assembly 312 — and in particular, the catalyst-containing membrane 314 — while generally minimizing the amount of material needed for the catalyst-containing membrane.

[0101] It will be understood that if the perimeter seal elements 336 are used in a particular implementation, there may be perforations therethrough in the locations where the channels 309 (or other features for routing fluid flow through a flow field) for the flow fields 306 and / or 308 through the perimeter seal elements 336 in such locations in order to allow for fluid to flow from the inlet feed-through passages 305 to the flow fields 306 and / or 308 via fluid flow passages located in the frames 304 into the channels 309 of the flow fields 306 and / or 308, and to correspondingly allow fluid to flow from the flow fields 306 and / or 308 to the outlet feed- through passages 307 via similar fluid flow passages located in the frames 304.

[0102] It will be further understood that in implementations in which a perimeter seal element is used, the material providing the perimeter seal element may be contiguous with one or both of the face- seal elements that the perimeter seal element shares a frame with and as depicted in the various examples discussed above. In other implementations, however, a perimeter seal element may be discontiguous with one or both of the face- seal elements that the perimeter seal element shares a frame with.

[0103] The frames discussed herein may, in some instances, be formed so as to be contiguous with the flow fields that are housed within their respective openings, such that the frame andDocket No. OPUSP048WO flow field housed within the frame are a single component. In such implementations, the region of the combined part that corresponds to the flow field may be made of an electrically conductive material (to allow electrical current passing between the terminals, such as via the terminal portions 113t and 121t), such as an electrically conductive plastic or polymeric material, while the region of the combined part that corresponds with the frame may be made of either the same material or, optionally, an electrically insulating material. For example, such a combined part may be made using a co-molding process in which two different polymers — one electrically conductive and the other electrically insulating — are used to injection mold different regions of the combined frame / flow field part. Regardless of whether the frames are formed as separate pieces or as parts that combine the flow fields with the frames, the frames may be made of a rigid material, such as a metal or rigid plastic material. For the purposes of this disclosure, a rigid material is understood to be a material having a modulus of elasticity in the gigapascal range.

[0104] In some implementations, one or more, or all, of the face-seal elements 334 may be provided using any of a number of manufacturing techniques. For example, in some implementations, a face-seal element may be co-molded in place with the frame having the recessed region that the face-seal element is located within. In such an implementation, the frame may first be molded from a rigid material using an injection molding process. The molded frame may then be subjected to a second injection molding process in which an elastomeric material is injected into regions of a mold cavity that contains the molded frame and has additional, face- seal-element- shaped cavities proximate the recessed regions of the molded frame. During this second injection molding process of the co-molding process, the interface between the recessed region and the molten elastomeric material of the face-seal element may partially melt, resulting in a chemical and / or mechanical bond between the faceseal element and the recessed region of the molded frame. In such instances, it will be understood that the transition between the rigid material of the frame and the elastomeric material of the face-seal element may be a gradient, e.g., without a clear dividing boundary, such as would be the case if the face-seal element were made as a discrete part and installed into the recessed region when in a solid state. In such implementations, it will be understood that the first sub-profile of such a face- seal element (and the profile of the portion of the recessed region that is adjacent thereto) may be viewed, for the purposes of this disclosure and for interpreting the language of the claims accompanying this disclosure, as having the contours of the recessed region of the molded frame that existed prior to the injection of the molten elastomeric material for the face- seal element.Docket No. OPUSP048WO

[0105] In other implementations, as suggested above, one or more face- seal elements may be manufactured as separate components from the frames and then installed into the frames after manufacture. In some such implementations, the face-seal elements may simply be retained in place through virtue of being lightly press-fit into the recessed regions, while in other implementations, the face-seal elements may be adhered or bonded in place within the recessed regions. Such bonding or adhesion may, for example, be provided through the use of a pres sure- sensitive adhesive, a liquid or gel adhesive, or other bonding mechanisms. It will be understood that the adhesive or bonding agent may be considered to be part of the face-seal element, such that the face-seal element may be considered to be “in contact with” the recessed region when there is, for example, an adhesive layer (which may be elastomeric or non- elastomeric) in between the elastomeric portion of the face-seal element and the rigid material of the frame / recessed region.

[0106] It will be understood that while the face-seal elements 334 having second sub-profiles 344 that have raised portions 346 that are shown in various Figures herein are generally all of the same type, e.g., the type depicted in FIG. 8 or the type depicted in FIG. 9, within a given implementation, some implementations may utilize a mix of the two different types of such face-seal elements 334, e.g., the type depicted in FIG. 6 for contact with the separator plates 310 and the type depicted in FIG. 7 for contact with the membrane assembly 312, or vice versa. Alternatively, the type depicted in FIG. 6 may be used with one frame of a given electrolyzer cell assembly and the type depicted in FIG. 7 may be used in the other frame of a given electrolyzer cell assembly.

[0107] It will be understood that in the implementations discussed above, some or all of the various elements that may be repeated within each implementation, e.g., face-seal elements, frames, recessed regions, etc., may be referred to individually within each implementation using ordinal indicators, e.g., first, second, third, etc., despite being referred to above using identical element names but different callouts, e.g., callouts ending in a, b, c, etc. In such instances, the order of such ordinal indicators may not necessarily align with the order of the callouts, e.g., callouts ending in a, b, and c may not necessarily correspond with the first, second, and third instances of an element, but may potentially map to the second, third, and first such elements, or the first, third, and second such elements, respectively.

[0108] It is to be understood that the phrases “for each <item> of the one or more <items>,” “each <item> of the one or more <items>,” or the like, if used herein, are inclusive of both a single-item group and multiple-item groups, i.e., the phrase “for ... each” is used in the sense that it is used in programming languages to refer to each item of whatever population of itemsDocket No. OPUSP048WO is referenced. For example, if the population of items referenced is a single item, then “each” would refer to only that single item (despite the fact that dictionary definitions of “each” frequently define the term to refer to “every one of two or more things”) and would not imply that there must be at least two of those items. Similarly, the term “set” or “subset” should not be viewed, in itself, as necessarily encompassing a plurality of items — it will be understood that a set or a subset can encompass only one member or multiple members (unless the context indicates otherwise).

[0109] The use, if any, of ordinal indicators, e.g., (a), (b), (c)... or the like, in this disclosure and claims is to be understood as not conveying any particular order or sequence, except to the extent that such an order or sequence is explicitly indicated. For example, if there are three steps labeled (i), (ii), and (iii), it is to be understood that these steps may be performed in any order (or even concurrently, if not otherwise contraindicated) unless indicated otherwise. For example, if step (ii) involves the handling of an element that is created in step (i), then step (ii) may be viewed as happening at some point after step (i). Similarly, if step (i) involves the handling of an element that is created in step (ii), the reverse is to be understood. It is also to be understood that use of the ordinal indicator “first” herein, e.g., “a first item,” should not be read as suggesting, implicitly or inherently, that there is necessarily a “second” instance, e.g., “a second item.”

[0110] For the purposes of this disclosure, the term “fluidically connected” is used with respect to volumes, plenums, holes, etc., that may be connected with one another, either directly or via one or more intervening components or volumes, 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. The term "fluidically adjacent," if used, refers to placement of a fluidic element relative to another fluidic element such that there are no potential structures fluidically interposed between the two elements that might potentially interrupt fluid flow between the two fluidic elements. For example, in a flow path having a first valve, a second valve, and a third valve placedDocket No. OPUSP048WO sequentially therealong, the first valve would be fluidically adjacent to the second valve, the second valve fluidically adjacent to both the first and third valves, and the third valve fluidically adjacent to the second valve. The term “fluidically” will be understood to generally mean “with respect to fluidic flow.”

[0111] It should be appreciated that all combinations of the foregoing concepts (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0112] It is to be further understood that the above disclosure, while focusing on a particular example implementation or implementations, is not limited to only the discussed example, but may also apply to similar variants and mechanisms as well, and such similar variants and mechanisms are also considered to be within the scope of this disclosure. For example, this disclosure includes at least the following numbered implementations.

[0113] Implementation 1: An apparatus comprising: an electrolyzer cell assembly comprising: one or more frames, wherein: each frame includes a seal region and one or more recessed regions, each frame is made of a rigid material, the one or more frames include a first frame, the one or more recessed regions of the first frame include a first recessed region, the first frame has an opening, a first side, a first surface that is within the seal region of the first frame and also part of the first side of the first frame, a second side opposite the first side of the first frame, and a second surface that is within the seal region of the first frame and also part of the second side of the first frame, and the opening of the first frame is bounded by the seal region of the first frame; and one or more face- seal elements, each face- seal element located within one of the one or more recessed regions of one of the one or more frames and having at least a portion with a transverse cross-sectional profile comprising a first sub-profileDocket No. OPUSP048WO proximate the recessed region in which that face- seal element is located and a second sub-profile on an opposite side of that face-seal element from the first sub-profile of that face-seal element, wherein: the one or more face-seal elements include a first face-seal element located in the first recessed region of the first frame, the second sub-profile of the first face- seal element includes at least a recessed portion located between two raised portions, the first recessed region of the first frame is within the seal region of the first frame and on the first side of the first frame, the first face-seal element extends along a first path extending around the opening of the first frame, the second side of the first frame is closer to a portion of the first recessed region of the first frame than to the first surface of the first frame, the two raised portions of the first face- seal element, when the first faceseal element is in an uncompressed state, extend out of the first recessed region of the first frame and past a first reference plane that is co-planar with the first surface of the first frame, and the recessed portion of the first face- seal element does not extend out of the first recessed region of the first frame past the first reference plane.

[0114] Implementation 2: The apparatus of implementation 1, wherein: the one or more recessed regions of the first frame further include a second recessed region, the one or more face-seal elements include a second face-seal element located in the second recessed region of the first frame, the second recessed region of the first frame is within the seal region of the first frame and on the second side of the first frame, the second face- seal element extends along a second path extending around the opening of the first frame, and the first side of the first frame is closer to a portion of the second recessed region of the first frame than to the second surface of the first frame.

[0115] Implementation 3: The apparatus of implementation 2, wherein: the second sub-profile of the second face-seal element includes at least a recessed portion located between two raised portions,Docket No. OPUSP048WO the two raised portions of the second face-seal element, when the second face-seal element is in an uncompressed state, extend out of the second recessed region of the first frame and past a second reference plane that is co-planar with the second surface of the first frame, and the recessed portion of the second face-seal element does not extend out of the second recessed region of the first frame past the second reference plane.

[0116] Implementation 4: The apparatus of implementation 2, wherein: the second sub-profile of the second face- seal element defines a planar surface that extends around the opening of the first frame and faces in the same direction as the second side of the first frame.

[0117] Implementation 5: The apparatus of any of implementations 1 through 4, wherein: the one or more frames further include a second frame, the one or more recessed regions of the second frame include a first recessed region, the second frame has an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame, the opening of the second frame is bounded by the seal region of the second frame, the one or more face- seal elements include a third face- seal element located in the first recessed region of the second frame, the second sub-profile of the third face-seal element includes at least a recessed portion located between two raised portions, the first recessed region of the second frame is within the seal region of the second frame and on the first side of the second frame, the third face- seal element extends along a third path extending around the opening of the second frame, the second side of the second frame is closer to a portion of the first recessed region of the second frame than to the first surface of the second frame, the two raised portions of the third face- seal element, when the third face- seal element is in an uncompressed state, extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, and the recessed portion of the third face-seal element does not extend out of the first recessed region of the second frame past the third reference plane.

[0118] Implementation 6: The apparatus of implementation 5, wherein:Docket No. OPUSP048WO the one or more recessed regions of the second frame include a second recessed region, the one or more face-seal elements include a fourth face-seal element located in the second recessed region of the second frame, the second sub-profile of the fourth face-seal element includes at least a recessed portion located between two raised portions, the second recessed region of the second frame is within the seal region of the second frame and on the second side of the second frame, the fourth face- seal element extends along a fourth path extending around the opening of the second frame, the first side of the second frame is closer to a portion of the second recessed region of the second frame than to the second surface of the second frame, the two raised portions of the fourth face-seal element, when the fourth face-seal element is in an uncompressed state, extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, and the recessed portion of the fourth face-seal element does not extend out of the second recessed region of the second frame past the fourth reference plane.

[0119] Implementation 7: The apparatus of any of implementations 1 through 6, further comprising one or more perimeter seal elements, the one or more perimeter seal elements including a first perimeter seal element, wherein: the first perimeter seal element extends from the first side of the first frame to the second side of the first frame, and the first perimeter seal element is in contact with a perimeter wall of the first frame that spans between the first side of the first frame to the second side of the first frame and that bounds the opening of the first frame.

[0120] Implementation 8: The apparatus of implementation 7, wherein the first perimeter seal element is contiguous with the first face- seal element.

[0121] Implementation 9: The apparatus of implementation 7, including at least the elements of implementation 2, wherein the first perimeter seal element is contiguous with the second face-seal element.

[0122] Implementation 10: The apparatus of implementation 9, wherein the first perimeter seal element is also contiguous with the first face-seal element.

[0123] Implementation 11: The apparatus of any of implementations 7 through 10, including at least the elements of implementation 5Docket No. OPUSP048WO the one or more perimeter seal elements further includes a second perimeter seal element, the second perimeter seal element extends from the first side of the second frame to the second side of the second frame, and the second perimeter seal element is proximate a perimeter wall of the second frame that spans between the first side of the second frame to the second side of the second frame and that bounds the opening of the second frame.

[0124] Implementation 12: The apparatus of implementation 11, wherein the second perimeter seal element is contiguous with the third face-seal element.

[0125] Implementation 13: The apparatus of implementation 11, including at least the elements of implementation 2, wherein the second perimeter seal element is contiguous with the fourth face-seal element.

[0126] Implementation 14: The apparatus of implementation 13, wherein the second perimeter seal element is also contiguous with the third face-seal element.

[0127] Implementation 15: The apparatus of any of implementations 1 through 14, wherein: the first sub-profile is linear for each of one or more of the one or more face-seal elements in which the second sub-profile includes at least the recessed portion located between the two raised portions, and each recessed region where the first sub-profile of the face-seal element located therein is linear has a planar surface proximate the first sub-profile of the face- seal element located therein.

[0128] Implementation 16: The apparatus of any of implementations 1 through 14, wherein: each of one or more of the one or more recessed regions in which the face-seal element located therein has a second sub-profile that includes at least the recessed portion located between the two raised portions itself has a transverse cross-section having convex portions, each convex portion corresponding in location to one of the raised portions.

[0129] Implementation 17: The apparatus of implementation 16, wherein each face-seal element located in a recessed region having the cross-section with the convex portions has a nominally constant thickness in the raised portions thereof.

[0130] Implementation 18: The apparatus of any of implementations 1 through 17, including at least the elements of implementations 4 and 6, wherein the planar surface of the second face-seal element overlaps the raised portions of the fourth face-seal element when viewed along an axis perpendicular to the planar surface of the second face-seal element.Docket No. OPUSP048WO

[0131] Implementation 19: The apparatus of implementation 18, wherein the planar surface of the second face-seal element also overlaps the raised portions of both the first face-seal element and the third face-seal element when viewed along an axis perpendicular to the planar surface of the second face-seal element.

[0132] Implementation 20: The apparatus of any one of implementations 1 through 18, including at least the elements of implementation 5, wherein the raised portions of the first face-seal element and the raised portions of the third face-seal element are aligned with one another when viewed along a direction perpendicular to the first surface of the first frame.

[0133] Implementation 21: The apparatus of any of implementations 1 through 20, wherein each face-seal element comprises an elastomeric material.

[0134] Implementation 22: The apparatus of implementation 21, including at least the elements of implementation 7, wherein each perimeter seal element comprises an elastomeric material.

[0135] Implementation 23: The apparatus of any of implementations 1 through 22, wherein at least one of the one or more face-seal elements is affixed by an adhesive within the recessed region in which it is located.

[0136] Implementation 24: The apparatus of any of implementations 1 through 22, wherein at least one of the one or more face-seal elements is co-molded with the frame having the recessed region in which that face-seal element is located.

[0137] Implementation 25: The apparatus of any of implementations 5 through 24, including at least the elements of implementation 5, wherein the electrolyzer cell assembly further comprises a membrane assembly, wherein: the membrane assembly includes a catalyst-containing membrane and has a first side and a second side, the membrane assembly is positioned between the second side of the first frame and the second side of the second frame, at least a portion of the first side of the membrane assembly is in contact with the raised portions of the fourth face-seal element, and at least a portion of the second side of the membrane assembly is in contact with the second face-seal element.

[0138] Implementation 26: The apparatus of implementation 25, wherein: the membrane assembly further includes a first porous transport layer and a second porous transport layer, andDocket No. OPUSP048WO the catalyst-containing membrane is interposed between the first porous transport layer and the second porous transport layer.

[0139] Implementation 27: The apparatus of implementation 26, wherein the catalystcontaining membrane extends beyond the first porous transport layer and the second porous transport layer and the second face-seal element and the fourth face-seal element contact opposite sides of the catalyst-containing membrane.

[0140] Implementation 28: The apparatus of any of implementations 1 through 27, wherein the electrolyzer cell assembly further comprises a separator plate, wherein: the separator plate is coextensive with the first side of the first frame and the opening of the first frame, the separator plate is in contact with the first face- seal element, and the separator plate caps the opening of the first frame.

[0141] Implementation 29: The apparatus of implementation 25, including at least the elements of implementation 5 and comprising multiple instances of the electrolyzer cell assembly arranged in a stack, wherein each separator plate that is adjacent the second frame of an adjacent electrolyzer cell assembly is in contact with the third face-seal element of that adjacent electrolyzer cell assembly.

[0142] Implementation 30: The apparatus of any of implementations 25 through 29, including at least the elements of implementation 25, wherein: the electrolyzer cell assembly further comprises a first flow field and a second flow field, the first flow field is positioned within the opening of the first frame, the second flow field is positioned within the opening of the second frame, and the membrane assembly is interposed between the first flow field and the second flow field.

Claims

Docket No. OPUSP048WOCLAIMSWhat is claimed is:

1. An apparatus comprising: an electrolyzer cell assembly comprising: one or more frames, wherein: each frame includes a seal region and one or more recessed regions, each frame is made of a rigid material, the one or more frames include a first frame, the one or more recessed regions of the first frame include a first recessed region, the first frame has an opening, a first side, a first surface that is within the seal region of the first frame and also part of the first side of the first frame, a second side opposite the first side of the first frame, and a second surface that is within the seal region of the first frame and also part of the second side of the first frame, and the opening of the first frame is bounded by the seal region of the first frame; and one or more face- seal elements, each face- seal element located within one of the one or more recessed regions of one of the one or more frames and having at least a portion with a transverse cross-sectional profile comprising a first sub-profile proximate the recessed region in which that face-seal element is located and a second sub-profile on an opposite side of that face-seal element from the first sub-profile of that face-seal element, wherein: the one or more face-seal elements include a first face-seal element located in the first recessed region of the first frame, the second sub-profile of the first face- seal element includes at least a recessed portion located between two raised portions, the first recessed region of the first frame is within the seal region of the first frame and on the first side of the first frame, the first face-seal element extends along a first path extending around the opening of the first frame, the second side of the first frame is closer to a portion of the first recessed region of the first frame than to the first surface of the first frame,Docket No. OPUSP048WO the two raised portions of the first face- seal element, when the first faceseal element is in an uncompressed state, extend out of the first recessed region of the first frame and past a first reference plane that is co-planar with the first surface of the first frame, and the recessed portion of the first face-seal element does not extend out of the first recessed region of the first frame past the first reference plane.

2. The apparatus of claim 1, wherein: the one or more recessed regions of the first frame further include a second recessed region, the one or more face-seal elements include a second face-seal element located in the second recessed region of the first frame, the second recessed region of the first frame is within the seal region of the first frame and on the second side of the first frame, the second face- seal element extends along a second path extending around the opening of the first frame, and the first side of the first frame is closer to a portion of the second recessed region of the first frame than to the second surface of the first frame.

3. The apparatus of claim 2, wherein: the second sub-profile of the second face-seal element includes at least a recessed portion located between two raised portions, the two raised portions of the second face-seal element, when the second face-seal element is in an uncompressed state, extend out of the second recessed region of the first frame and past a second reference plane that is co-planar with the second surface of the first frame, and the recessed portion of the second face-seal element does not extend out of the second recessed region of the first frame past the second reference plane.

4. The apparatus of claim 2, wherein: the second sub-profile of the second face-seal element defines a planar surface that extends around the opening of the first frame and faces in the same direction as the second side of the first frame.Docket No. OPUSP048WO5. The apparatus of any of claims 1 through 4, wherein: the one or more frames further include a second frame, the one or more recessed regions of the second frame include a first recessed region, the second frame has an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame, the opening of the second frame is bounded by the seal region of the second frame, the one or more face-seal elements include a third face-seal element located in the first recessed region of the second frame, the second sub-profile of the third face- seal element includes at least a recessed portion located between two raised portions, the first recessed region of the second frame is within the seal region of the second frame and on the first side of the second frame, the third face- seal element extends along a third path extending around the opening of the second frame, the second side of the second frame is closer to a portion of the first recessed region of the second frame than to the first surface of the second frame, the two raised portions of the third face- seal element, when the third face- seal element is in an uncompressed state, extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, and the recessed portion of the third face-seal element does not extend out of the first recessed region of the second frame past the third reference plane.

6. The apparatus of claim 5, wherein: the one or more recessed regions of the second frame include a second recessed region, the one or more face- seal elements include a fourth face- seal element located in the second recessed region of the second frame, the second sub-profile of the fourth face-seal element includes at least a recessed portion located between two raised portions, the second recessed region of the second frame is within the seal region of the second frame and on the second side of the second frame, the fourth face-seal element extends along a fourth path extending around the opening of the second frame,Docket No. OPUSP048WO the first side of the second frame is closer to a portion of the second recessed region of the second frame than to the second surface of the second frame, the two raised portions of the fourth face-seal element, when the fourth face-seal element is in an uncompressed state, extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, and the recessed portion of the fourth face- seal element does not extend out of the second recessed region of the second frame past the fourth reference plane.

7. The apparatus of claim 2, further comprising one or more perimeter seal elements, the one or more perimeter seal elements including a first perimeter seal element, wherein: the first perimeter seal element extends from the first side of the first frame to the second side of the first frame, and the first perimeter seal element is in contact with a perimeter wall of the first frame that spans between the first side of the first frame to the second side of the first frame and that bounds the opening of the first frame.

8. The apparatus of claim 7, wherein the first perimeter seal element is contiguous with the first face-seal element.

9. The apparatus of claim 7, wherein the first perimeter seal element is contiguous with the second face- seal element.

10. The apparatus of claim 9, wherein the first perimeter seal element is also contiguous with the first face- seal element.

11. The apparatus of claim 7, wherein: the one or more frames further include a second frame, the one or more recessed regions of the second frame include a first recessed region, the second frame has an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame, the opening of the second frame is bounded by the seal region of the second frame,Docket No. OPUSP048WO the one or more face-seal elements include a third face-seal element located in the first recessed region of the second frame, the second sub-profile of the third face- seal element includes at least a recessed portion located between two raised portions, the first recessed region of the second frame is within the seal region of the second frame and on the first side of the second frame, the third face- seal element extends along a third path extending around the opening of the second frame, the second side of the second frame is closer to a portion of the first recessed region of the second frame than to the first surface of the second frame, the two raised portions of the third face- seal element, when the third face- seal element is in an uncompressed state, extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, the recessed portion of the third face-seal element does not extend out of the first recessed region of the second frame past the third reference plane, the one or more perimeter seal elements further includes a second perimeter seal element, the second perimeter seal element extends from the first side of the second frame to the second side of the second frame, and the second perimeter seal element is proximate a perimeter wall of the second frame that spans between the first side of the second frame to the second side of the second frame and that bounds the opening of the second frame.

12. The apparatus of claim 11, wherein the second perimeter seal element is contiguous with the third face-seal element.

13. The apparatus of claim 11, wherein: the one or more recessed regions of the second frame include a second recessed region, the one or more face-seal elements include a fourth face-seal element located in the second recessed region of the second frame, the second sub-profile of the fourth face-seal element includes at least a recessed portion located between two raised portions, the second recessed region of the second frame is within the seal region of the second frame and on the second side of the second frame,Docket No. OPUSP048WO the fourth face- seal element extends along a fourth path extending around the opening of the second frame, the first side of the second frame is closer to a portion of the second recessed region of the second frame than to the second surface of the second frame, the two raised portions of the fourth face-seal element, when the fourth face-seal element is in an uncompressed state, extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, the recessed portion of the fourth face- seal element does not extend out of the second recessed region of the second frame past the fourth reference plane, and the second perimeter seal element is contiguous with the fourth face- seal element.

14. The apparatus of claim 13, wherein the second perimeter seal element is also contiguous with the third face- seal element.

15. The apparatus of any of claims 1 through 4 and 7 through 14, wherein: the first sub-profile is linear for each of one or more of the one or more face-seal elements in which the second sub-profile includes at least the recessed portion located between the two raised portions, and each recessed region where the first sub-profile of the face-seal element located therein is linear has a planar surface proximate the first sub-profile of the face- seal element located therein.

16. The apparatus of any of claims 1 through 4 and 7 through 14, wherein: each of one or more of the one or more recessed regions in which the face-seal element located therein has a second sub-profile that includes at least the recessed portion located between the two raised portions itself has a transverse cross-section having convex portions, each convex portion corresponding in location to one of the raised portions.

17. The apparatus of claim 16, wherein each face-seal element located in a recessed region having the cross-section with the convex portions has a nominally constant thickness in the raised portions thereof.Docket No. OPUSP048WO18. The apparatus of claim 4, wherein: the one or more frames further include a second frame, the one or more recessed regions of the second frame include a first recessed region, the second frame has an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame, the opening of the second frame is bounded by the seal region of the second frame, the one or more face- seal elements include a third face- seal element located in the first recessed region of the second frame, the second sub-profile of the third face-seal element includes at least a recessed portion located between two raised portions, the first recessed region of the second frame is within the seal region of the second frame and on the first side of the second frame, the third face- seal element extends along a third path extending around the opening of the second frame, the second side of the second frame is closer to a portion of the first recessed region of the second frame than to the first surface of the second frame, the two raised portions of the third face- seal element, when the third face- seal element is in an uncompressed state, extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, the recessed portion of the third face-seal element does not extend out of the first recessed region of the second frame past the third reference plane, the one or more recessed regions of the second frame include a second recessed region, the one or more face- seal elements include a fourth face- seal element located in the second recessed region of the second frame, the second sub-profile of the fourth face-seal element includes at least a recessed portion located between two raised portions, the second recessed region of the second frame is within the seal region of the second frame and on the second side of the second frame, the fourth face-seal element extends along a fourth path extending around the opening of the second frame, the first side of the second frame is closer to a portion of the second recessed region of the second frame than to the second surface of the second frame,Docket No. OPUSP048WO the two raised portions of the fourth face-seal element, when the fourth face-seal element is in an uncompressed state, extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, the recessed portion of the fourth face- seal element does not extend out of the second recessed region of the second frame past the fourth reference plane, and the planar surface of the second face-seal element overlaps the raised portions of the fourth face- seal element when viewed along an axis perpendicular to the planar surface of the second face- seal element.

19. The apparatus of claim 18, wherein the planar surface of the second face-seal element also overlaps the raised portions of both the first face-seal element and the third face-seal element when viewed along an axis perpendicular to the planar surface of the second face-seal element.

20. The apparatus of any one of claims 1 through 4, 7 through 14, 18, and 19, wherein: the one or more frames further include a second frame, the one or more recessed regions of the second frame include a first recessed region, the second frame has an opening, a first side, a first surface that is within the seal region of the second frame and also part of the first side of the second frame, a second side opposite the first side of the second frame, and a second surface that is within the seal region of the second frame and also part of the second side of the second frame, the opening of the second frame is bounded by the seal region of the second frame, the one or more face- seal elements include a third face- seal element located in the first recessed region of the second frame, the second sub-profile of the third face-seal element includes at least a recessed portion located between two raised portions, the first recessed region of the second frame is within the seal region of the second frame and on the first side of the second frame, the third face- seal element extends along a third path extending around the opening of the second frame, the second side of the second frame is closer to a portion of the first recessed region of the second frame than to the first surface of the second frame,Docket No. OPUSP048WO the two raised portions of the third face-seal element, when the third face-seal element is in an uncompressed state, extend out of the first recessed region of the second frame and past a third reference plane that is co-planar with the first surface of the second frame, the recessed portion of the third face-seal element does not extend out of the first recessed region of the second frame past the third reference plane, and the raised portions of the first face- seal element and the raised portions of the third faceseal element are aligned with one another when viewed along a direction perpendicular to the first surface of the first frame.

21. The apparatus of any of claims 1 through 4, 7 through 14, 18, and 19, wherein each face-seal element comprises an elastomeric material.

22. The apparatus of any of claims 2 through 4, 8 through 14, 18, and 19, further comprising one or more perimeter seal elements, the one or more perimeter seal elements including a first perimeter seal element, wherein: the first perimeter seal element extends from the first side of the first frame to the second side of the first frame, the first perimeter seal element is in contact with a perimeter wall of the first frame that spans between the first side of the first frame to the second side of the first frame and that bounds the opening of the first frame, and each perimeter seal element comprises an elastomeric material.

23. The apparatus of any of claims 1 through 4, 8 through 14, 18, and 19, wherein at least one of the one or more face-seal elements is affixed by an adhesive within the recessed region in which it is located.

24. The apparatus of any of claims 1 through 4, 8 through 14, 18, and 19, wherein at least one of the one or more face-seal elements is co-molded with the frame having the recessed region in which that face- seal element is located.

25. The apparatus of claim 5, wherein: the one or more recessed regions of the second frame include a second recessed region, the one or more face- seal elements include a fourth face- seal element located in the second recessed region of the second frame,Docket No. OPUSP048WO the second sub-profile of the fourth face-seal element includes at least a recessed portion located between two raised portions, the second recessed region of the second frame is within the seal region of the second frame and on the second side of the second frame, the fourth face- seal element extends along a fourth path extending around the opening of the second frame, the first side of the second frame is closer to a portion of the second recessed region of the second frame than to the second surface of the second frame, the two raised portions of the fourth face-seal element, when the fourth face-seal element is in an uncompressed state, extend out of the second recessed region of the second frame and past a fourth reference plane that is co-planar with the second surface of the second frame, the recessed portion of the fourth face-seal element does not extend out of the second recessed region of the second frame past the fourth reference plane, the electrolyzer cell assembly further comprises a membrane assembly, the membrane assembly includes a catalyst-containing membrane and has a first side and a second side, the membrane assembly is positioned between the second side of the first frame and the second side of the second frame, at least a portion of the first side of the membrane assembly is in contact with the raised portions of the fourth face-seal element, and at least a portion of the second side of the membrane assembly is in contact with the second face- seal element.

26. The apparatus of claim 25, wherein: the membrane assembly further includes a first porous transport layer and a second porous transport layer, and the catalyst-containing membrane is interposed between the first porous transport layer and the second porous transport layer.

27. The apparatus of claim 26, wherein the catalyst-containing membrane extends beyond the first porous transport layer and the second porous transport layer and the second face-seal element and the fourth face-seal element contact opposite sides of the catalyst-containing membrane.Docket No. OPUSP048WO28. The apparatus of any of claims 1 through 4, 8 through 14, 18, and 19, wherein the electrolyzer cell assembly further comprises a separator plate, wherein: the separator plate is coextensive with the first side of the first frame and the opening of the first frame, the separator plate is in contact with the first face- seal element, and the separator plate caps the opening of the first frame.

29. The apparatus of claim 25, comprising multiple instances of the electrolyzer cell assembly arranged in a stack, wherein each separator plate that is adjacent the second frame of an adjacent electrolyzer cell assembly is in contact with the third face-seal element of that adjacent electrolyzer cell assembly.

30. The apparatus of claim 25, wherein: the electrolyzer cell assembly further comprises a first flow field and a second flow field, the first flow field is positioned within the opening of the first frame, the second flow field is positioned within the opening of the second frame, and the membrane assembly is interposed between the first flow field and the second flow field.

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