Components and methods for electrochemical reduction of gaseous CO2

Abstract

Provided is a multi-layer gas diffusion electrode for sustaining the electrochemical reduction of gaseous CO2 and / or CO to multi-carbon products, the multi-layer gas diffusion electrode including a gas diffusion layer including a support layer, a microporous layer having pores sized to maintain gaseous CO2 and / or CO, or a combination thereof, available for electrochemical reduction, and a catalyst layer including a catalyst favoring the reduction of CO2 and / or CO. Also provided are the gas diffusion electrodes described herein, a spacer positionable between an ion exchange membrane and an anode of a membrane electrode assembly, a reactor including a membrane electrode assembly and a support structure, a method for producing a stack reactor that can include a gas diffusion electrode and a spacer, a method for diagnosing and isolating at least one failed repeating cell unit in an electrolyzer stack reactor, and a rinsing method for enhancing operation of an electrochemical reduction system.

Description

[Technical field]

[0001] The technical field relates generally to electrochemical reduction systems for the electrochemical conversion of gaseous CO, CO, or combinations thereof to carbon products, and more particularly to specific components and assemblies of electrochemical reduction systems designed to facilitate the electrochemical conversion, as well as methods for manufacturing and operating such components and assemblies. [Background technology]

[0002] Known electrochemical reduction reactors are small-scale operation (cell area <5 cm 2 (Examples include membrane electrode assemblies (MEAs) designed for 1000-milliliter (1000-milliliter) fuel cells.) As the size of reactors using this technology increases, various challenges arise or remain to be overcome.

[0003] For example, porous polytetrafluoroethylene (PTFE) filters can be used as a porous support substrate in the cathode of an MEA due to their hydrophobic properties, as described by Dinh et al. "CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface" Science. 2018 May 18;360(6390):783-787. However, PTFE is not electrically conductive, which can cause a lack of current conduction and lead to large in-plane resistance (i.e., along the plane of the electrode) and cell voltage drop, especially in high current cells (>80A / cell).

[0004] In another example, the stability of the ion exchange membrane in the MEA is important and the membrane may fail due to mechanical instability caused by mechanical perforation, localized heating, drying, chemical decomposition, etc. The current state of the art solution in this field is to use reinforced membranes, however, these reinforced membranes result in increased cell voltage, reduced membrane-electrode contact, and degradation over time.

[0005] In another example, as the size of the reactor using the MEA increases (>5 cm 2 ), serpentine channels may be used to better control the flow of reactants and products along the surface of the MEA. In this approach, unsupported channel regions may suffer from reduced electrical contact with the flow field / current collectors or current distributors and mechanical instabilities in the MEA. In addition, the cathode / anode areas directly above the land areas of the flow field may experience reduced mass transport as species must diffuse far from the channel to reach these areas and vice versa. This reduction in mass transport results in limited access to the CO2 / CO reactant gases, compromising reaction efficiency. Furthermore, a reduced convection effect may be observed, leading to the creation of hot zones and resulting in uneven heat distribution. Due to the heat released from the reaction, these regions are more likely to reach higher temperatures that may damage the MEA and / or electrolyzer components.

[0006] In another example, during operation of known MEAs, cations migrating through the ion exchange membrane during CO2 electroreduction can form solid salts with bicarbonate or carbonate anions on the cathode side (cathode compartment) of the CO2 electrochemical reactor. When the cathode compartment and the cathode porous structure are filled with solid salts, CO2 cannot reach the catalyst, the CO2 reduction reaction stops, and no new CO2 reduction products are produced.

[0007] As another example, commercially available CO electrolyser reactors are typically small in area (5 cm 2) and are limited to single cell designs. Such reactors are useful for testing catalysts and reaction conditions on a laboratory scale, but if industrially meaningful conversion rates are to be realized, both cell size and volume must be increased. Once combined, any defects in the single cell will affect the overall performance.

[0008] Therefore, various improvements in the field of electrolytic reduction of CO2 or CO on an industrial scale are still needed. Summary of the Invention

[0009] In one aspect, a multi-layer gas diffusion electrode (GDE) for sustaining the electrochemical reduction of gaseous CO, CO, or a combination thereof to a multi-carbon product is provided, the multi-layer gas diffusion electrode comprising: A gas diffusion layer (GDL), support layer, a gas diffusion layer including a microporous layer (MPL) having pores sized to maintain gaseous CO, CO, or a combination thereof available for electrolytic reduction; a catalyst layer comprising a catalyst favorable for the reduction of CO2, CO, or a combination thereof; Each one of the support layer and the MPL is hydrophobic and conductive, and the GDE is conductive from one layer to the other.

[0010] In some embodiments, the support layer includes a first conductive material and a first hydrophobic polymer. For example, the first conductive material can be carbon paper, carbon felt, carbon cloth, or metal mesh. For example, the first hydrophobic polymer can be PTFE. The support layer can have a first hydrophobic polymer content of 5% to 60% by weight. Optionally, the first hydrophobic polymer content can be 30% to 50% by weight.

[0011] In some embodiments, the support layer can have a thickness of from 50 μm to 1000 μm. Optionally, the thickness of the support layer can be from 100 μm to 300 μm.

[0012] In some embodiments, the MPL can include a second conductive material and a second hydrophobic polymer. For example, the second hydrophobic polymer can be PTFE. For example, the second conductive material can include porous particles. Optionally, the second conductive material can consist of or include carbon nanoparticles. Further optionally, the second conductive material can include acetylene black, ketjen black, carbon black, carbon nanotubes, graphite, graphene, or any combination thereof. The MPL can have a second hydrophobic polymer content of 60% to 99% by weight, and optionally, the second hydrophobic polymer content is 80% to 95% by weight.

[0013] In some embodiments, the MPL has an MPL thickness of 0.5-500 μm. Optionally, the MPL thickness can be 10-80 μm.

[0014] In some embodiments, the catalyst can be provided as particles, and the catalyst layer further comprises a binder that binds the catalyst particles and promotes ionic conductivity and CO2 availability to the catalyst particles. For example, the binder can be an ionomer or PTFE. For example, the ionomer can be Nation®, Fumion®, or the like.

[0015] In some embodiments, the catalyst particles are metals, metal oxides, or mixed metals. For example, the catalyst particles can be nanoparticles. The catalyst particles can have a size of 1 nm to 10,000 nm. Optionally, the size of the catalyst nanoparticles can be 10 nm to 100 nm. In addition, the catalyst layer can have a thickness of up to 10 μm.

[0016] In some embodiments, the multi-layer GDE can further include a stabilization layer comprising solid particles having surfaces modified with functional groups to prevent the catalyst layer from rebuilding during operation of the multi-layer gas diffusion electrode. For example, the solid particles of the stabilization layer can be particles of carbon, graphite, graphene, TiO2, SiO2, ceria, or any combination thereof. The solid particles can have a particle size of 1 nm to 1 μm. The solid particles can have a particle size of 10 nm to 100 nm. For example, the functionalization group can be an ionized unit of an ion-conducting ionomer, imidazolium, sulfonic acid, poly(arylpiperidinium). Optionally, the ion-conducting ionomer can be Nation®, Fumion®, or analogs thereof. In addition, the stabilization layer can have a thickness of up to 10 μm.

[0017] In another aspect, a method is provided for producing a gas diffusion electrode (GDE) comprising a gas diffusion layer (GDL) and a catalyst layer, the method comprising: providing a hydrophobic and conductive support layer; blade coating a microporous layer ink onto a support layer, the microporous layer ink comprising conductive particles and a hydrophobic polymer to form a microporous layer (MPL); heat treating the MPL to sinter the hydrophobic polymer within the network of conductive particles to form the GDL; spraying a catalyst ink comprising catalyst particles and a binder onto the GDL to form a catalyst layer.

[0018] In some embodiments, the method can include forming a catalyst ink by mixing catalyst particles, a binder, and a solvent.

[0019] In some embodiments, the catalyst particles can be copper nanoparticles and the binder is an ionomer.

[0020] In some embodiments, blade coating can include producing an MPL having a thickness between 0.5 μm and 500 μm.

[0021] In some embodiments, heat treating the MPL can include heating the GDL at a temperature between 300-400°C.

[0022] In some implementations, the GDE can further include a stabilizing layer comprising solid particles having a surface modified with functional groups, and the method can further include spraying a stabilizing ink comprising the solid particles and a binder onto the catalyst layer. Optionally, the method can include forming the stabilizing ink by mixing the solid particles, the binder, and a solvent. For example, the solid particles can be carbon nanoparticles and the binder can be an ion-conducting polymer.

[0023] In another aspect, a spacer positionable between an ion exchange membrane and an anode of a membrane electrode assembly is provided, the spacer including a hydrophilic, porous and non-conductive layer.

[0024] In some embodiments, the hydrophilic, porous and non-conductive layer may be made from polyester, rayon, silk, cotton, cheesecloth, PES, nylon, hydrophilic PTFE, cellulose, polypropylene, polyethylene, or any combination thereof.

[0025] In some embodiments, the hydrophilic, porous and non-conductive layer may be made from woven fibers. For example, the woven fibers may be synthetic textile fibers.

[0026] In some embodiments, the spacer may include a coating of an ionomer on a hydrophilic, porous, and non-conductive layer.

[0027] In some embodiments, the spacer can have a thickness between 0.001 mm and 3 mm. Optionally, the spacer can have a thickness between 100 μm and 400 μm.

[0028] In some embodiments, the hydrophilic, porous and non-conductive layer can have a porosity of 10% to 90%. For example, the hydrophilic, porous and non-conductive layer can have pores with a pore size of 0.0001 mm to 1 mm. Optionally, the pore size can be 10 to 100 μm.

[0029] In another aspect, a membrane electrode assembly is provided for the electrolytic reduction of CO, CO, or a mixture thereof to a carbon product. The membrane electrode assembly comprises: A cathode; An anode; an ion exchange membrane positioned between the cathode and the anode, the ion exchange membrane being in contact with the cathode; a spacer positioned between the ion exchange membrane and the anode, the spacer including a hydrophilic, porous and non-conductive layer, the spacer having one side in contact with the ion exchange membrane and another side in contact with the anode.

[0030] In some embodiments, the spacer may be adhered, fixed, hot pressed, placed against, or pressed against the anode and / or ion exchange membrane (electrodes).

[0031] In some embodiments, the membrane electrode assembly can have an improvement in life of at least 100%, at least 1000%, or at least 2000% compared to a membrane electrode assembly in which the spacer is omitted.

[0032] In some embodiments, the spacer can further include at least one feature described herein.

[0033] In some embodiments, the cathode of the membrane electrode assembly can be a gas diffusion electrode as described herein.

[0034] In another aspect, a reactor is provided for the electrolytic reduction of CO, CO, or a mixture thereof to carbon products. The reactor comprises: a membrane electrode assembly including a cathode, an anode, and an ion exchange membrane; a support structure including a pair of opposing support substructures, each support substructure contacting one side of the membrane electrode assembly to uniformly maintain the membrane electrode assembly intermediate the pair of opposing support substructures; Each supporting substructure includes at least one layer of porous and conductive material to ensure the flow of reactants, products, electrolyte, and electrons to and from the anode and cathode of the membrane electrode assembly.

[0035] In some embodiments, each supporting substructure may be welded, glued, fastened, hot pressed, or pressed against the cathode or anode of the membrane electrode assembly.

[0036] In some embodiments, the porous and conductive material may include titanium, copper, aluminum, stainless steel, bronze, brass, galvanized steel, platinum, nickel, carbon, carbon steel, iron, lead, or any combination thereof.

[0037] In some embodiments, the porous and conductive material can be a metal that avoids catalyzing the hydrogen evolution reaction (HER).

[0038] In some embodiments, the porous and conductive material can be a metal that is corrosion resistant.

[0039] In some embodiments, the porous and conductive material can be a metal that is resistant to hydrogen embrittlement.

[0040] In some embodiments, the membrane electrode assembly has a thickness of at least 100 cm 2 The particle size may be 100 nm to 100 nm.

[0041] In some embodiments, the supporting substructure in contact with the cathode of the membrane electrode assembly is a cathode supporting substructure, and the cathode supporting substructure can be made of a single layer of porous and conductive material. For example, the cathode supporting substructure can have a thickness of 200 to 1300 micrometers. Optionally, the cathode supporting substructure has a thickness of 600 to 900 micrometers. For example, the cathode supporting substructure single layer can have pores with a pore size ranging from 1 mm to 10 mm, optionally from 5 to 7 mm. For example, the cathode supporting substructure single layer can be made of titanium, copper, aluminum, stainless steel, or a combination thereof.

[0042] In some embodiments, the support substructure in contact with the anode of the membrane electrode assembly is an anode support substructure, and the anode support substructure can be made of multiple layers of porous, conductive and corrosion-resistant material. For example, the anode support substructure can include at least two layers. Optionally, the anode support substructure can include at least four layers. For example, each one of the multiple layers of the anode support substructure can be made of titanium. For example, the anode support substructure can have a thickness of 500 to 3000 micrometers. Optionally, the thickness of the anode support substructure can be 1000 to 2000 micrometers. For example, each layer of the anode support substructure can have pores with a pore size in the range of 1 to 10 mm, optionally 3 to 7 mm.

[0043] In some embodiments, the support structure may further include a turbulence enhancer added to at least one of the support substructures.

[0044] In some embodiments, the reactor may further include a cathode flow field provided in contact with one of the pair of opposing support substructures, and an anode flow field provided in contact with the other of the pair of opposing support substructures.

[0045] In some embodiments, the cathode of the membrane electrode assembly can be a gas diffusion electrode as described herein.

[0046] In some embodiments, the membrane electrode assembly can further include at least one feature described herein.

[0047] In another aspect, a method is provided for facilitating operation of an electrolytic reduction system for converting CO, CO, or a mixture thereof into carbon products, the method comprising: injecting CO, CO or a mixture thereof into an inlet of a cathode compartment of an electroreduction system to perform electroreduction of the CO, CO or a mixture thereof to carbon products, the electroreduction comprising forming carbonate salts within the cathode compartment along a flow path; injecting a rinsing fluid into the inlet of the cathode compartment to dissolve and remove at least a portion of the carbonate salt along the flow path to form a salt-enriched fluid; and recovering at least one of the carbon product and the salt-enriched fluid from an outlet of the cathode compartment.

[0048] In some embodiments, the injection of the rinsing fluid can be alternated with the injection of CO, CO, or a mixture thereof. Alternatively, the injection of CO, CO, or a mixture thereof can be maintained during the injection of the rinsing fluid.

[0049] In some implementations, the rinsing fluid can be water, deionized water, a mixture of water and surface tension reducing molecules, or waste electrolyte.

[0050] In some embodiments, injection of the rinsing fluid is performed periodically during the rinsing period. For example, the rinsing period can have a duration of 20 seconds to 30 minutes. Optionally, the duration of the rinsing period can be 1 to 3 minutes.

[0051] In some embodiments, the ratio of the volumetric flow rate of the rinsing fluid to the volumetric flow rate of the CO2, CO, or mixtures thereof may be between 0.05 and 0.5.

[0052] In some embodiments, the injection of the rinsing fluid can be performed at a ratio of volumetric flow rate of the rinsing fluid to the volume of the cathode compartment of 20 to 200 per minute. Optionally, the ratio of volumetric flow rate to the volume of the cathode compartment can be 50 to 80 per minute.

[0053] In some embodiments, the injection of the rinsing fluid may be performed at a rinse frequency of 30 minutes to 12 hours. Optionally, the rinse frequency may be from 1 hour to 3 hours.

[0054] In some embodiments, the method can include providing a membrane electrode assembly as described herein or a reactor as described herein as part of an electroreduction system, wherein the cathode compartment is contained within the membrane electrode assembly.

[0055] In another aspect, an electrolytic reduction system is provided for converting CO, CO, or a mixture thereof into carbon products. The system comprises: a cathodic compartment including a gas diffusion electrode that sustains the electrolytic reduction of CO, CO, or a mixture thereof, and an inlet in fluid communication with the gas diffusion electrode; A distribution assembly comprising: a first supply line in fluid communication with a source of CO, CO, or mixtures thereof, and for supplying the CO, CO, or mixtures thereof to an inlet of the cathode compartment to effect electrolytic reduction of the CO, CO, or mixtures thereof to carbon products, the electrolytic reduction including forming carbonate salts along a flow path within the cathode compartment; a second supply line in fluid communication with a source of rinsing fluid; a valve operable to fluidly connect the cathode compartment inlet to a second supply piping for injecting a rinsing fluid into the cathode compartment inlet, thereby dissolving and removing at least a portion of the carbonate salts along the flow path to form a salt-enriched fluid; and a pump operable to control a volumetric flow rate of the rinsing fluid to the cathode compartment.

[0056] In some embodiments, the system may further comprise a controller operably connected to the valves and pumps for automatic actuation of the valves and pumps to periodically trigger injection of rinsing fluid at a rinse frequency and for a rinse period. For example, the rinse period may have a duration of 20 seconds to 30 minutes. Optionally, the duration of the rinse period may be 1 to 3 minutes. For example, the rinse frequency may be 30 minutes to 12 hours. Optionally, the rinse frequency may be 1 to 3 hours.

[0057] In some embodiments of the system, the ratio of the volumetric flow rate of the rinsing fluid through the second supply line to the volumetric flow rate of CO2, CO or a mixture thereof through the first supply line may be between 0.05 and 0.5.

[0058] In some embodiments, the system may further include a rinsing fluid reservoir that is a source of rinsing fluid, and a waste collection tank that receives the recovered salt-enriched fluid.

[0059] In some implementations of the system, the rinse fluid can be water, deionized water, a mixture of water and surface tension reducing molecules, or waste electrolyte.

[0060] In some implementations of the system, the cathode compartment may further include a porous mesh support substructure in contact with the cathode flow field and the catalytic gas diffusion electrode, and in fluid communication with each other to define a flow path.

[0061] In some embodiments of the system, the cathode compartment may be part of a membrane electrode assembly as described herein, or may be part of a reactor (stacked or non-stacked) as described herein.

[0062] In another aspect, an electrolyzer stack reactor is provided for reducing CO, CO, or a mixture thereof to a carbon product. The electrolyzer stack reactor comprises: a pair of endplates, the pair including a proximal endplate and a distal endplate; A plurality of repeating cell units positioned between a proximal endplate and a distal endplate, each repeating cell unit comprising: a cathode flow field having a cathode inlet and a cathode outlet; an anode flow field having an anode inlet and an anode outlet; a membrane electrode assembly positioned between a cathode flow field and an anode flow field; and a manifold assembly for distributing CO, CO or mixtures thereof, and carbon products to and from each repeating cell unit in parallel, said manifold assembly comprising: a cathode inlet manifold branched to the cathode inlet of each repeating cell unit for distributing CO, CO or a mixture thereof to the membrane electrode assembly via the cathode flow field; an anode inlet manifold branched to the anode inlets of each repeating cell unit for distributing the anolyte through the anode flow field to the membrane electrode assembly; a cathode outlet manifold branched to the cathode outlet of each repeating cell unit for discharging the carbon product from the membrane electrode assembly through the cathode flow field; an anode outlet manifold branched to an anode outlet of each repeating cell unit for discharging spent anolyte from the membrane electrode assembly via the anode flow field; A pair of bus bars extending across a plurality of repeating cell units, an anode bus bar electrically connecting the anode flow fields of each one of the plurality of repeating cell units in parallel; a cathode bus bar electrically connecting the cathode flow fields of each one of the plurality of repeating cell units in parallel; and a pair of bus bars comprising:

[0063] In some embodiments, the cathode inlet can be located at the top of at least one repeating cell unit and the anode inlet can be located at the bottom of at least one repeating cell unit.

[0064] In some embodiments, the anolyte and the CO, CO, or mixtures thereof can flow co-currently through the anode inlet manifold and the cathode inlet manifold, respectively. Alternatively, the anolyte can flow through the anode inlet manifold counter-currently to the CO, CO, or mixtures thereof flowing through the cathode inlet manifold.

[0065] In some implementations, the anode inlet manifold and the cathode inlet manifold can each include inlet ports defined in both the proximal and distal endplates.

[0066] In some embodiments, the anode outlet manifold and the cathode outlet manifold can each include outlet ports defined in both the proximal and distal endplates.

[0067] In some embodiments, the cathode inlet and outlet manifolds and the anode inlet and outlet manifolds branch off to the respective cathode inlets and outlets and anode inlets and outlets through tubing or headers extending externally from the multiple repeating cell units. Alternatively, the cathode inlet and outlet manifolds and the anode inlet and outlet manifolds can branch off to the respective cathode inlets and outlets and anode inlets and outlets through internal inlet and outlet ports defined internally within the housing of each anode flow field and cathode flow field of the multiple repeating cell units. Still alternatively, the cathode inlet and outlet manifolds can branch off to the respective cathode inlets and outlets internally, while the anode inlet and outlet manifolds can branch off to the respective anode inlets and outlets externally, or vice versa.

[0068] In some embodiments, the plurality of repeating cell units can comprise between 2 and 10,000 repeating cell units.

[0069] In some embodiments, the electrolyzer stack reactor may include a plurality of fuses, each fuse connecting at least one of the anode busbar and the cathode busbar to a corresponding repeating cell unit in series.

[0070] In some embodiments, at least one repeating cell unit can include at least one porous support substructure having one side in contact with the membrane electrode assembly and the other side in contact with the anode flow field or the cathode flow field. For example, the at least one porous support substructure can be made from at least one metal mesh layer.

[0071] In some embodiments, at least one repeat unit has a length of 100 cm 2 ~1000cm 2 The cell area may be 0.01 to 0.1 mm.

[0072] In some embodiments, the membrane electrode assembly of each repeating cell unit further comprises at least one feature as described herein.

[0073] In some embodiments, the cathode of each repeating cell unit is a gas diffusion electrode as described herein.

[0074] In some embodiments, each repeating cell unit is an electrolyzer reactor as described herein.

[0075] In another aspect, a method for diagnosing and isolating at least one faulty repeat cell unit in an electrolyzer stack reactor comprising a proximal end plate and a distal end plate and a plurality of repeat cell units positioned between the proximal end plate and the distal end plate, the method comprising: electrically connecting each cathode of the plurality of repeating cell units in parallel to a cathode bus bar; electrically connecting each anode of the plurality of repeating cell units in parallel to an anode bus bar; fluidly connecting in parallel each cathode of the plurality of repeating cell units to a cathode manifold assembly for distributing CO, CO, or a mixture thereof and recovering carbon products; fluidly connecting in parallel each anode of the plurality of repeating cell units to an anode manifold assembly for distributing anolyte and recovering spent anolyte; monitoring a current of each repeat cell unit to detect a potential malfunction of at least one repeat cell unit; When at least one defective repeat cell unit is detected, a method is provided that includes bypassing the defective repeat cell unit by fluidly and / or electrically disconnecting the at least one defective repeat cell unit from adjacent repeat cell units.

[0076] In some embodiments, the method may include monitoring a voltage of the electrolyzer stack reactor and detecting a short circuit when the monitored voltage decreases.

[0077] In some embodiments, the method can include providing an electrolyzer stack reactor further comprising at least one feature described herein.

[0078] For example, electrically disconnecting at least one defective repeating cell unit can be performed by disconnecting a fuse connected in series with the defective repeating cell unit.

[0079] It will be understood that the present technology and components will be described in conjunction with exemplary embodiments, but are not intended to limit their scope to such embodiments. On the contrary, all alternatives, modifications, and equivalents that may be included as defined by this description are intended to be encompassed. The objects, advantages, and other features of the present technology and components will become more apparent and be better understood upon reading the following non-limiting description of the invention, which is given with reference to the accompanying drawings. [Brief description of the drawings]

[0080] [Figure 1] 1 is a schematic cross-sectional view of an electrolytic reduction reactor encompassed herein, comprising a cathode flow field and an anode flow field, a membrane electrode assembly positioned between the cathode flow field and the anode flow field, and two support plates, each support plate sandwiched between an MEA and a flow field. [Diagram 2] FIG. 2 is a schematic diagram of a layer of a gas diffusion layer. [Diagram 3] FIG. 1 is a schematic diagram of a blade coating method for a gas diffusion layer. [Figure 4]2 is a graph showing the selectivity (Faraday efficiency (%)) for H2 of a 5 cm2 cathode containing four commercially available gas diffusion layers (GDL240 refers to CeTech GDL240™, H23C8 refers to Freudenberg H23C8™, GDS2230 refers to AvCarb GDS2230™, and 25BC refers to Sigracet 25BC™) and a custom cathode encompassed herein at a current density of 200 mA / cm2. [Diagram 5] FIG. 2 is a graph showing the selectivity (Faraday efficiency (%)) for H 2 , CO, and C 2 H 4 of a 5-cm 2 cathode including a gas diffusion layer as proposed herein at a current density of 200 mA / cm 2 . [Figure 6] FIG. 1 is a graph showing the selectivity (Faraday efficiency (%)) for H, CO, and C2H4 of a 5-cm2 cathode containing different gas diffusion layers (GDLs) at 200 mA / cm2, with the best results for ethylene being obtained using a GDL as proposed herein that contains a support layer and a hydrophobic / microporous layer containing carbon nanoparticles and PTFE. [Figure 7] 7A-7C are graphs showing the selectivity (faradaic efficiency (%)) for H, CO, and C2H4 of a 5-cm2 cathode containing microporous layers with three different thicknesses at applied current densities of 200 mA / cm2 (FIG. 7), 300 mA / cm2 (FIG. 8), and 400 mA / cm2 (FIG. 9). [Figure 8] 7A-7C are graphs showing the selectivity (faradaic efficiency (%)) for H, CO, and C2H4 of a 5-cm2 cathode containing microporous layers with three different thicknesses at applied current densities of 200 mA / cm2 (FIG. 7), 300 mA / cm2 (FIG. 8), and 400 mA / cm2 (FIG. 9). [Figure 9] 7A-7C are graphs showing the selectivity (faradaic efficiency (%)) for H, CO, and C2H4 of a 5-cm2 cathode containing microporous layers with three different thicknesses at applied current densities of 200 mA / cm2 (FIG. 7), 300 mA / cm2 (FIG. 8), and 400 mA / cm2 (FIG. 9). [Figure 10]FIG. 1 is a graph showing the faradaic efficiency (in %) for H, CO and C2H4, and the cell voltage (in V) for selected materials as the hydrophobic, porous and non-conductive layer of the spacer in the membrane electrode assembly, when the membrane electrode assembly does not include any spacer. [Figure 11A] 1 is a graph showing the faradaic efficiency (in %) for H 2 , CO, and C 2 H 4 , and the cell voltage (in V) versus time (in hours) for a membrane electrode assembly that does not contain a spacer. [Figure 11B] 1 is a graph showing the faradaic efficiency (in %) for H 2 , CO, and C 2 H 4 , and the cell voltage (in V) versus time (in hours) for a membrane electrode assembly including a spacer. [Figure 12] FIG. 1 is a graph showing the faradaic efficiency (in %) and cell voltage (V) for H2, CO and C2H4 versus the material selected as the hydrophobic, porous and non-conductive layer of the spacer in the membrane electrode assembly, with no spacer present or with an ionomer coated spacer present. [Figure 13] FIG. 1 is a schematic cross-sectional view of a portion of an electrolytic reduction reactor as encompassed herein, including a cathode flow field and an anode flow field, a membrane electrode assembly positioned between the cathode flow field and the anode flow field, and two layered metal mesh supporting substructures, each supporting substructure sandwiched between an MEA and a flow field. [Figure 14] 13 is a graph showing voltage distribution in the cathode flow field without the mesh support substructure. [Figure 15] 13 is a graph showing voltage distribution in the cathode flow field in the presence of a one-layer mesh support substructure. [Figure 16]Two graphs are included showing CO2 / CO mass transfer in the cathode flow field in the absence of a mesh support substructure: the graph on the left shows the CO2 concentration (in mol / m3) in two adjacent flow field channels and their surrounding land areas. The graph on the right shows the normalized CO concentration (normalized by the total concentration of the flow, 41.6 mol / m3) when looking at a cross-sectional view of the cathode. (The ion exchange membrane is at the bottom surface of the cathode, and the flow field channels are at the top surface of the cathode.) [Figure 17] 1 is a graph showing normalized CO concentration when looking at a cross-section of the cathode (with the ion exchange membrane on the bottom surface of the cathode and the flow field channels on the top surface of the cathode in the presence of a four-layer mesh support substructure). [Figure 18] FIG. 13 is a graph showing the selectivity (Faraday efficiency (%)) of an 800-cm2 cathode for H2, CO, and C2H4 at an applied current density of 100 mA / cm2 with and without a mesh support substructure between the cathode and the cathode flow field. [Figure 19] FIG. 1 is a graph showing the selectivity (Faraday efficiency (%)) for H, CO, and C2H4 versus applied current density in mA / cm2 for an 800-cm2 cathode without the presence of a mesh supporting substructure. [Figure 20] FIG. 1 is a graph showing the selectivity (Faraday efficiency (%)) for H, CO, and C2H4 versus applied current density in mA / cm2 for an 800-cm2 cathode with one layer titanium mesh supporting substructure. [Figure 21] FIG. 1 is a graph showing selectivity (Faraday efficiency (%)) for H, CO, and C2H4 versus time (in days) for an 800-cm2 cathode supported by three layers of diamond-shaped titanium mesh having pore sizes in the range of 0.050 to 0.150 inches. [Figure 22]FIG. 1 is a graph showing selectivity (Faraday efficiency (%)) for H, CO, and C2H4 versus time (in days) for an 800-cm2 cathode supported by one layer of large diamond-shaped titanium mesh having pore sizes in the range of 0.100 to 0.300 inches. [Diagram 23] FIG. 1 is a graph showing selectivity (Faraday efficiency (%)) for H, CO, and C2H4 versus time (in days) for an 800-cm2 cathode supported by one layer of copper mesh. [Figure 24] FIG. 2 is a top perspective view of an electrolyzer stack reactor as encompassed herein. [Diagram 25] FIG. 1 is a top perspective exploded view of the components of the anode flow field (and current collector) assembly, including the internal anode inlet and outlet manifolds and the housing with the anode flow field (and current collector) inserts. [Figure 26] FIG. 13 is a top perspective view of the anode flow field (and current collector) assembly, including ports for connection to the external manifold assembly and anode flow field (and current collector) insert, combined into a single piece. [Figure 27] FIG. 2 is a front view of the cathode flow field assembly. [Figure 28] FIG. 1 is a front view of the anode flow field (and current collector) assembly. [Figure 29] FIG. 25 is a top view of the electrolyzer stack reactor of FIG. [Diagram 30] FIG. 2 is a top perspective exploded view of the components of an electrolyzer stack reactor as encompassed herein, including a plurality of repeating cell units that can be configured as the electrolytic reduction reactor diagrammed in FIG. 1. [Diagram 31] FIG. 1 is a simplified process flow diagram of a rinse run of an electrolyzer reactor that includes at least one membrane electrode assembly that sustains the electrolytic reduction of CO, CO2, or a mixture thereof. [Diagram 32]FIG. 1 is a schematic diagram of the inlet and outlet flows to and from an electrolyzer reactor containing at least one membrane electrode assembly that sustains the electrolytic reduction of CO, CO2, or a mixture thereof. [Diagram 33] Included are two graphs showing current (in Amps), voltage (in Volts), and CO2 flow rate (in kg / hr) versus time while the rinse system valve is switched from a closed to an open position. [Diagram 34] Graph showing selectivity (Faraday efficiency (%)) for H2, CO and C2H4 before and after rinsing (stripes). [Diagram 35] 1 is a graph showing selectivity (Faraday efficiency (%)) for H2, CO, and C2H4 versus time (in hours) when no rinse run is performed on the electrolyzer reactor. [Diagram 36] 1 is a graph showing selectivity (Faraday efficiency (%)) for H2, CO, and C2H4 versus time (in hours) when a rinse run is performed on the electrolyzer reactor. [Figure 37] FIG. 1 is a graph showing the selectivity (Faraday efficiency (%)) for H, CO, and C2H4, and the cell voltage (in V) versus time (in hours) when a rinse run is performed on an electrolyzer reactor with a rinse frequency of 118 min. [Figure 38] FIG. 1 is a graph showing the selectivity (Faraday efficiency (%)) for H, CO and C2H4, and cell voltage (in V) versus time (in hours) when a rinse run is performed on an electrolyzer reactor with a rinse frequency of 68 minutes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0081] The present technology relates to the design of components of an electrolytic reduction system that promotes the electrochemical conversion of gaseous CO2, CO, or a combination thereof to carbon products. A multi-layer gas diffusion electrode is provided that can be used as a cathode to support the electrochemical reduction of gaseous CO2, CO, or a combination thereof to carbon products. Each layer of the multi-layer gas diffusion electrode can be designed to be hydrophobic and conductive, as described in more detail below. More specifically, the multi-layer gas diffusion electrode can be part of a membrane electrode assembly (MEA) that further includes an anode and an ion exchange membrane (IEM) that separates the cathode from the anode. For example, the ion exchange membrane can be an anionic exchange membrane (AEM), a cationic exchange membrane (CEM), or a bipolar membrane (BPM). A hydrophilic spacer is further provided that can be part of the MEA and can be positioned between the IEM and the anode, as described in more detail below. Additionally, the MEA may be part of an electrolytic reduction reactor (also referred to as an electrochemical flow cell reactor, MEA electrolyzer, or electrolyzer reactor) further comprising a cathode flow field for supplying gaseous CO2, CO, or a combination thereof to the cathode side of the MEA, and an anode flow field for supplying anolyte to the anode side of the MEA. An electrolytic reduction reactor is further provided that further comprises a support structure including a pair of opposing porous and conductive support plates, each support plate being provided between the MEA and a flow field (anode or cathode) to uniformly maintain the MEA between the pair of opposing support plates, as described in more detail below. An electrolytic reduction system is further provided that includes an electrolytic reduction reactor and additional components such as a distribution assembly including supply piping, and at least one valve for distributing required fluids (gaseous CO2 / CO, anolyte, or rinse fluid) to the electrolytic reduction reactor, as described in more detail below.The electrolytic reduction reactor may further be used as at least one repeating cell unit from a plurality of repeating cell units stacked between a proximal end plate and a distal end plate to form an electrolytic cell stack reactor, as described in more detail below.

[0082] Carbon products that can be produced through implementation of the present systems, methods, and processes include single carbon products, multi-carbon products, or combinations thereof. More specifically, the carbon products can include, for example, carbon monoxide, formate (formic acid), methane, ethylene, acetate (acetic acid), ethanol, n-propanol, acetaldehyde, and propionaldehyde.

[0083] Several methods are further encompassed herein that relate to the manufacture, use, or maintenance of components, units, and assemblies of the overall electroreduction system. For example, operation of the electroreduction reactor may be facilitated by periodically rinsing the cathode compartment of the MEA to dissolve and remove at least a portion of carbonates that may be formed during the electroreduction of gaseous CO, CO, or a combination thereof within the cathode compartment.

[0084] Gas diffusion electrode having a composite of a hydrophobic conductive porous support and a hydrophobic microporous layer for electrochemical CO2 and / or CO reduction Gas diffusion layers (GDLs) have recently been incorporated as cathode materials into electrochemical flow cell reactors for CO2 / CO reduction to significantly increase efficiency and current density. By providing gaseous CO2 / CO in close proximity to the catalyst, the CO2 / CO can diffuse to the active catalytic sites much more easily than in fully aqueous reactors (H-cells), allowing high current densities (hundreds of mA / cm2). 2 ) The hydrophobicity of the cathode in the CO2RR is necessary to avoid flooding with the liquid electrolyte and products.

[0085] At the laboratory scale, porous polytetrafluoroethylene (PTFE) filters are known to be effective cathode substrates due to their hydrophobic properties. However, PTFE filters are not electrically conductive and when they are used as gas diffusion layers, all current is conducted across the plane of the catalyst layer. This strategy is possible for currents below 1 A, but may not be conductive enough for the currents reached in larger current cells (>80 A / cell).

[0086] Other known commercially available GDLs are typically composed of porous carbon fiber paper (0-5% moisture-proof) or felt covered with a microporous layer (composed of a mixture of carbon nanoparticles and 5-30% polytetrafluoroethylene (PTFE)). Nanoparticle catalysts are typically further deposited on the surface of the GDL to form a gas diffusion electrode (GDE). However, with reference to FIG. 4, it was shown that the hydrophobicity of these known GDLs typically decreases over time as the carbon material becomes more hydrophilic through the electroreduction process. The decrease in hydrophobicity can be due to electrowetting, the formation of salt crystals, or the deposition of impurities on the surface of the GDL. This loss of hydrophobicity leads to the GDL becoming flooded with water, electrolyte, or liquid products, limiting the diffusion of CO / CO2 to the catalyst layer and ultimately causing reaction instability. For this reason, these electrodes are found not suitable for use in CO2 MEA electrolyzers that produce carbon products at high current densities over periods of hundreds of hours.

[0087] Proposed herein are electrodes, e.g., cathodes, that include gas diffusion layers that are conductive yet remain hydrophobic for extended periods of time, preventing flooding from electrolyte and products. More specifically, the use of cathodes as proposed herein can increase the duration of operation from at most 10 hours to hundreds of hours, as seen, for example, in FIG. 4, before the gas diffusion layers are unable to provide CO2 / CO to the catalyst due to blockage from being filled with formed salt crystals or flooded with electrolyte or products.

[0088] With reference to FIG. 1, the cathode 32 as proposed herein is a GDE including a GDL 42, a catalyst layer 44, and optionally a stabilization layer 46. With reference to FIGS. 1 and 2, the GDL 42 includes a support layer 48 and a microporous layer (MPL) 50 deposited on the support layer 48. In some implementations, the support layer can include carbon paper, carbon felt, or carbon cloth. Alternatively, the support layer can include metal, such as a metal mesh. The support layer is porous with pore sizes of less than a millimeter. The MPL is designed to be hydrophobic and conductive. The MPL can include conductive nanoparticles, such as carbon nanoparticles. Optionally, the carbon nanoparticles can be or include acetylene black, ketjen black, carbon black, carbon nanotubes, graphite, graphene, or any combination thereof. The MPL can further include a hydrophobic polymer. For example, the hydrophobic polymer can be PTFE, fluorinated ethylene propylene (FEP), perfluoroalcoxy (PFA), polyvinylidene fluoride (PVDF), and polydimethylsiloxane (PDMS).

[0089] More specifically, after testing different substrate materials, the produced GDL and resulting GDE are hydrophobic and provide through-plane conductivity, which should be understood as the conduction of electricity from one layer of the GDL or cathode (GDE) to another adjacent layer.

[0090] In some embodiments, the support layer of the cathode can be a custom PTFE-containing layer, for example, a thin commercially available carbon paper treated with 5% to 60% by weight, optionally at least 30% by weight, and further optionally 30% to 50% by weight PTFE. The resulting treated carbon paper (support layer) has a thickness of 50 μm to 1000 μm, optionally 100 μm to 300 μm. In addition, the cathode further comprises an MPL, which can include conductive nanoparticles such as acetylene black nanoparticles mixed with a high concentration of PTFE, for example, 60% to 99% by weight PTFE, optionally 80% to 95% by weight PTFE, to create a conductive and hydrophobic surface interface for depositing the cathode catalyst. The dry thickness of the MPL can be 0.5 μm to 500 μm, optionally 10 μm to 80 μm. For this reason, the GDE contains a thin PTFE-carbon paper layer and a thin MPL to maximize CO2 availability to the catalyst and allow any potassium carbonate salts formed during the reaction to be dissolved by periodic rinsing with DI water.

[0091] Figures 4 to 9 illustrate the performance of a cathode including a GDL as proposed herein with various parameters such as operating duration (Figures 4 and 5), the nature of the support layer and the presence of an MPL (Figure 6), and the thickness of the MPL (Figures 7 to 9).

[0092] The combination of a hydrophobic MPL and a hydrophobic porous support layer containing microscale pores can ensure (i) gas transport to the reaction sites by preventing flooding of the electrode by liquid products, liquid electrolyte, or condensed water, and (ii) electron transport from the current collector to the cathode. The formed gas diffusion electrode promotes high current density, selectivity (to either single- or multi-carbon gas or liquid products), and stable conversion of CO2 or CO in a gas-phase membrane electrode assembly.

[0093] The cathode further comprises a catalyst layer. In some embodiments, the cathode can further comprise a stabilization layer. Both layers consist of nanoparticles bound with a binder (such as ionomer or PTFE), but their functions are different. The nanoparticles of the catalyst layer are selected to be catalytically active for CO2 / CO electroreduction and can be sized from 1 nm to 10000 nm, optionally from 10 nm to 100 nm. For example, the catalyst layer can comprise Cu nanoparticles. The nanoparticles of the stabilization layer are selected to be stabilizing and conductive, such as titania, ceria, carbon nanoparticles (including carbon nanotubes), graphite, graphene, and silica. Ionomers that can be used to bind the nanoparticles in each one of the catalyst layer and the stabilization layer can be Nation®, Fumion®, or analogs thereof. The ionomers included in the catalyst layer can be the same or different from the ionomers included in the stabilization layer.

[0094] More specifically, the particles of the stabilization layer can have a surface that is modified with functional groups to prevent the catalyst layer from restructuring during operation of the multilayer gas diffusion electrode. The functional groups can be ionizing units, imidazolium, sulfonic acid, poly(arylpiperidinium) ion-conducting ionomers, such as Nation®, Fumion®, etc., mentioned above.

[0095] A variety of deposition techniques can be used to deposit the catalyst layer and the stabilization layer. Deposition techniques include drop casting, blade coating, gravure coating, slot die coating, dry pressing, electrodeposition, rolling, sputtering, thermal evaporation, or any combination thereof. For example, the catalyst layer and the stabilization layer can be sprayed directly onto the MPL. For example, the catalyst nanoparticles can be mixed with an ionomer, which acts as a binder as well as increasing the ionic conductivity to all the catalyst nanoparticles and increasing the CO / CO2 availability to the catalyst nanoparticles. In some embodiments, a porous catalyst layer is formed by dispersing the nanoparticle-ionomer mixture within the surface of the MPL, rather than forming a thin continuous film, to increase the active area and current density for the CO / CO2 reduction reaction. The thickness of the catalyst layer can be from 100 nm to 10 μm. The stabilization layer can be formed by mixing the nanoparticles with an ionomer and spraying the mixture onto the catalyst layer. The stabilization layer prevents the catalyst layer from restructuring during operation (i.e., agglomerating the catalyst nanoparticles and changing their oxidation state, exposed crystal orientation, or particle size due to changes in exposed potential or pH) and maintains a uniform voltage distribution. The catalytic environment can be further tailored through the selection of ionomers or other functionalization of the carbon nanoparticles of the stabilization layer.

[0096] The cathode containing the proposed GDL can be used in a liquid flow cell reactor or a membrane electrode assembly reactor.

[0097] Multi-layer gas diffusion electrodes can be manufactured by a variety of methods available to those skilled in the art, however the method developed to manufacture the multi-layer gas diffusion electrodes described herein and claimed is as follows.

[0098] A method for producing a cathode is further provided, the method including forming a gas diffusion layer, optionally forming a catalyst layer on the gas diffusion layer, and further optionally forming a stabilization layer on the catalyst layer. Forming the gas diffusion layer includes forming a support layer and an MPL. For example, forming the support layer can include immersing a carbon paper in a PTFE solution and then heat treating to melt the PTFE on the carbon fibers of the carbon paper to produce a support layer that is a PTFE-treated carbon paper. Forming the MPL then includes mixing a carbon nanoparticle ink with a PTFE solution to form an MPL ink, and blade coating the MPL ink 51 on top of the support layer 48 that is a PTFE-treated carbon paper to form an MPL 50, as seen in FIG. 3. Optionally, the blade coating can be performed to form an MPL having a wet thickness of 400 μm to 1000 μm, which corresponds to a final thickness of 0.5 μm to 500 μm thick when dry. Finally, forming the gas diffusion layer includes heat treating (sintering) the MPL to melt the PTFE therein. Optionally, the heat treating can include exposing the gas diffusion layer to a temperature of 300°C to 400°C in an oven so that the PTFE particles sinter together and form a coherent, uniform layer on top of the support layer with the carbon nanoparticles. Sintering the PTFE also provides the hydrophobicity of the gas diffusion layer.

[0099] In some embodiments, the method can further include forming a catalyst layer by spraying a catalyst ink (e.g., a mixture of Cu nanoparticles and an ionomer that acts as a binder in a solvent such as methanol, ethanol, and isopropanol) on top of the MPL. The catalyst material in the ink can be a metal, metal oxide, or mixed metal. In some embodiments, the method can further include forming a stabilization layer by spraying a stabilization ink (e.g., a mixture of carbon nanoparticles and an ionomer in a solvent such as methanol, ethanol, and isopropanol) on top of the catalyst layer.

[0100] As seen in FIG. 5, the formed multilayer GDE can be used as a cathode to sustain the electrochemical reduction of gaseous CO, CO, or a combination thereof to carbon products. When used as a cathode, the multilayer gas diffusion electrode demonstrated exceptional stability. For example, when combined with salt mitigation (periodic rinsing) and a copper mesh strategy as described herein, the stability was further improved, reaching hundreds of hours of operation (e.g., at least 500 hours) while maintaining selectivity to ethylene products of at least 25%. The unique electrode configuration facilitated all important transport functions (reactants, electrons, ions, products).

[0101] Hydrophilic spacers for electrochemical conversion of CO2 Ion exchange membranes are key components of membrane electrode assemblies for CO2, CO, or other electrolysers. They separate the anode and cathode compartments and complete the ionic circuit between the two by allowing ions to selectively pass through. Membrane stability is critical to the stability of MEA electrolysers. Membranes can fail due to mechanical instability caused by mechanical perforation, drying, chemical decomposition, etc. The current state of the art solution in this field is to use reinforced membranes, however, these reinforced membranes result in increased cell voltage, reduced membrane-electrode contact, and degradation over time.

[0102] The mechanical stability problem can be overcome by the currently proposed MEA design while maintaining good membrane-electrode contact and not degrading over time. To avoid membrane holes and short circuits, a hydrophilic spacer is provided that can be used as at least one layer separating the ion exchange membrane from the anode in the MEA. For example, referring to FIG. 1, a hydrophilic spacer 38 can be provided between and in contact with the anode 34 and the anion exchange membrane 36 (AEM).

[0103] With reference to FIG. 1, the hydrophilic spacer may consist of a non-conductive porous hydrophilic layer having a thickness of 0.001 mm to 3 mm, a porosity of 10% to 90%, and a pore size of 0.0001 mm to 1 mm. The non-conductive porous hydrophilic layer is placed between the anode and the ion exchange membrane of the MEA by being glued, fixed, hot pressed, placed against, or pressed against the anode and / or ion exchange membrane of the MEA to function as a hydrophilic spacer. The anolyte flows along the spacer and wets its surface. The spacer stabilizes the ion exchange membrane in the MEA system, provides mechanical support to the membrane, provides continuous membrane hydration and ionic connection, and prevents electrical shorting in the event of membrane failure.

[0104] 10, various materials can be used as the hydrophilic spacer layer, with the choice of material affecting the selectivity and voltage of the electroreduction reaction. Materials can also be selected based on compatibility with the pH and electrolyte of the reaction. In some embodiments, the non-conductive porous hydrophilic material can be polyester, rayon, silk, cotton, cheesecloth, PES, nylon, hydrophilic PTFE, cellulose, polypropylene, polyethylene, or any combination thereof.

[0105] In some embodiments, the hydrophilic, porous, non-conductive layer of the spacer can be functionalized with an ionomer or another chemical to increase the ionic conductivity and chemical reaction selectivity of the MEA. More specifically, the spacer can include an ionomer coating. With reference to FIG. 12, it is shown that the ionomer coating reduces the cell voltage and increases the C2H4 selectivity relative to a hydrophilic spacer without the coating.

[0106] With reference to Figures 10, 11A and 11B, it can be seen that the presence of a hydrophilic spacer reduces the effect on ethylene Faradaic efficiency (FE) and increases the effect on cell voltage, even when the hydrophilic spacer is on the anode side of the MEA, for all materials tested in Figure 10. However, with reference to Figures 11A and 11B, which compare the performance lifetime of MEAs with and without hydrophilic spacers, it can be seen that MEAs with hydrophilic spacers can perform with at least 20%, 25% or 30% selectivity for ethylene over extended periods of time compared to MEAs without hydrophilic spacers.

[0107] The non-conductive hydrophilic spacer stabilizes the ion exchange membrane within the membrane electrode assembly, provides mechanical support to the ion exchange membrane, keeps the membrane hydrated and ionically connected, and prevents electrical shorting in the event of membrane failure. The lifetime of MEAs containing hydrophilic spacers can be further explained by the fact that the hydrophilic spacer is perforation resistant, and by separating sharp anode fibers from the ion exchange membrane, this can minimize perforations and extend the lifetime of the MEA.

[0108] Supportive structure for enhanced CO2 delivery, support and thermal management Membrane electrode assemblies (MEAs) can be used for the electrochemical conversion of carbon dioxide (CO2) or carbon monoxide (CO). Reactors using this technology are large in size (>5 cm 2), they use channels (e.g., in a serpentine configuration) to better control the flow of reactants and products along the surface of the MEA. In this approach, unsupported channel regions suffer from reduced electrical contact with the flow field / current collectors and mechanical instabilities in the MEA. In addition, the cathode / anode areas directly above the land areas of the flow field experience reduced mass transport as species must diffuse farther from the channel to reach these areas and vice versa. This reduced mass transport results in limited access to the CO2 / CO reactant gases, compromising reaction efficiency. Furthermore, due to the heat released from the reaction, these regions are more likely to reach higher temperatures that may damage the MEA and / or electrolyzer components.

[0109] The proposed electrolytic reduction reactor can include a conductive porous support structure used in combination with an MEA, such as the MEA described herein, a cathode flow field, and an anode flow field. The support structure can include a pair of opposing support substructures, each of which is provided on one side of the membrane electrode assembly to uniformly maintain the membrane electrode assembly in between the pair of opposing support substructures. For example, each support substructure can be located on either side of the cathode and / or anode of the MEA, between the flow field and the MEA. The support structure provides mechanical support and compression to the MEA, distributing current uniformly from the current collector / flow field of the electrolytic reduction reactor across the cathode and / or anode. When used in combination with the support structure of the present invention, the flow field can be designed to have larger channels (than in the absence of the support structure), facilitating water rinsing to avoid salts and other obstructions while avoiding increased pressure drop in the flow field channels. Thus, the support structures improve mixing along the flow field channels and in the reactor dead spots between the flow field channels, thereby facilitating delivery of CO2 / CO to the catalyst at the cathode, transport of reaction products away from the cathode, and heat transfer to remove excess heat generated from the reaction. Each support substructure can include at least one layer of porous conductive material. The porous conductive material can be a metal mesh that supports the MEA and performs several important functions. For example, at least one mesh support layer can be added to both the cathode and anode sides of the MEA to facilitate flow and compression of reactants to the catalyst. As seen in FIG. 1, the thickness of the support substructure on the cathode side can be different from the thickness of the support substructure on the anode side. With reference to the embodiment shown in FIG. 13, each support substructure can include, for example, three layers of metal mesh.

[0110] The presence of the support structure allows for a large cell area (e.g., at least 100 cm) because the support structure (40a, 40b), which is a layered metal mesh, supports the membrane electrode assembly 30 including the cathode 32, the ion exchange membrane 36, and the anode 34 due to the increased number of channel areas 58 and 60 compared to the existing smaller cell area, as can be seen in FIG. 13, which shows a portion of the large cell area. 2 Or at least 800 cm 2 This is particularly useful for systems having

[0111] The porosity of at least one layer of each supporting substructure may be at least 50% and the pore size may be between 0.1 mm and 10 mm. The shape of the pores of the supporting substructure may vary, including diamond-shaped, circular, square, triangular, hexagonal, and elliptical. The at least one layer may be a perforated mesh, an expanded mesh, a flat mesh, a multi-layer mesh, a welded wire mesh, and a woven wire mesh. Each layer may have a thickness that varies from 100 μm to 5 mm. The material of each layer is a conductive material that may be a metal or alloy. The material may include titanium, copper, aluminum, stainless steel, bronze, brass, galvanized steel, platinum, nickel alloy, carbon, carbon steel, iron, lead, or other electroplated / electroless plated metal mesh. The electrical conductivity and fluid flow dynamics of the supporting substructure may be adjusted by selecting its pore size, pore shape, pore distribution, strand orientation of each layer, and the number of layers of the substructure. Optionally, turbulence enhancers, for example ribbed or spiral elements to disrupt the flow, can be added on at least one layer as part of the supporting substructure.

[0112] COMSOL modeling can be used to aid in the selection of mesh size and configuration. More specifically, computer simulations can be used to predict the concentrations of CO2 and CO during electrolytic reduction, with the electrolyzer reactor being fed with 50 mol% CO2 and 50 mol% CO at atmospheric conditions. For example, titanium or copper mesh can be selected for the cathode side to promote uniform compression to the MEA across the flow field channel area and provide CO2 access to the entire catalytic surface of the cathode. One to four layers of titanium or copper mesh with large pores (2-3 mm) can be selected for the cathode side, as it is a poor H2 catalyst and the pores are large enough not to fill with water during operation. Comparing Figures 14 and 15, the mesh substructure on the cathode side provides uniform electrical connection between the cathode and the cathode flow field (e.g., with a voltage difference of up to 160 mV at 240 A across the active area), indicating that the mesh reduces the voltage required to operate the electrolyzer reactor. Comparing Figures 16 and 17, it is shown that the mesh support substructure of the cathode improves the mass transport of reactant CO2 and product CO to and from the catalytic sites, respectively. With reference to Figure 18, the improved mass transport leads to a further improvement in FE for, for example, ethylene production (about 27% FE with the cathode mesh compared to about 19% FE without the cathode mesh). Comparing Figures 19 and 20, the electrolysis cell including the cathode without the mesh support substructure achieves a 100 mA.cm 2 (high FE in H2 and low FE in products), while the cell containing a cathode with one layer of Ti mesh reaches the mass transport limit at 100 mA.cm 2 21 and 22, it is shown that the configuration of the supporting substructure (number of layers and pore size) changes the CO / CO2 hydrodynamics and mass transport, which affects both the selectivity and stability of the reaction. Figure 23 is an example of a substructure that is a copper mesh, showing that different metals can be used to form the substructure.

[0113] On the anode side, at least one mesh layer may also be added to aid in the transport of anolyte to the anode catalyst, thus providing uniform cooling to the cell. The oxidation cell potential on the anode side may favor the use of titanium, for example, as the mesh material due to its corrosion resistance. The mesh support substructure on the anode side typically includes 2-5 layers of fine mesh and can be tailored to the depth of each cell.

[0114] An electrolyzer reactor is provided that includes a support structure as defined herein, including a cathode support substructure sandwiched between the cathode flow field and the cathode, and an anode support substructure sandwiched between the anode flow field and the anode. Each support substructure includes at least one layer of metal mesh that can be welded, glued, fastened, hot pressed to the flow field and / or electrode. Alternatively, the at least one layer of metal mesh can simply be physically placed or pressed against the flow field and electrode. Each support substructure is configured to provide suitable contact between the conductive flow field and the electrode to provide an electrical path with minimal resistance between the flow field and the electrode.

[0115] It should be noted that although the embodiment of the support structure is described above as including two support sub-structures, the support structure may include a single support sub-structure disposed on only one side (e.g., the cathode side or the anode side) of the MEA within the CO electrolyser.

[0116] Electrolyser stack reactor for electrochemical conversion of CO2, CO, and other chemical feedstocks Commercially available CO electrolysis reactors are typically small in area (<5 cm 2) and single cell designs. Such reactors can be useful for testing catalysts and reaction conditions on a laboratory scale, but both the cell size and the number of cells need to be increased if industrial-scale conversion rates are to be realized. When the cells are combined, any defect in a single cell will affect the performance of the whole. Known CO2 and water electrolysers can use a bipolar stack arrangement in which the cells are electrically connected in series. If a single electrochemical cell is defective, the entire stack will not function properly. For example, if one cell has a very large resistance, it will take up most of the voltage supplied to the stack, leaving much less voltage for the other cells. This large resistance can occur during assembly or after some time of operation. In a purely bipolar arrangement, the stack needs to be disassembled to isolate the defective cell.

[0117] Provided herein is a monopolar CO2 electrolyzer stack reactor that is designed and operated to diagnose faulty electrochemical cells and electronically and / or hydrodynamically isolate such cells to achieve efficient performance throughout the stack.

[0118] Referring to FIG. 30, the electrolyzer stack reactor 4 includes two end plates 6 and a plurality of repeating cell units 2, where the end plates 6 are fastened together with a threaded assembly. The electrolytic reduction reactor described herein can be used as repeating cell units 2 that are stacked to form an electrolyzer stack reactor 4 that includes a plurality of repeating cell units 2, thereby designed to carry out electrochemical CO2 reduction reactions in a modular and scalable manner. For example, the electrolyzer stack reactor can include 2 to 100 electrochemical repeating cell units stacked together. The cell area (active surface) of each repeating unit is 5 cm2. 2 ~2m 2 , optionally, 100 cm 2 ~10000cm 2 can be adjusted.

[0119] Further, with reference to Figure 30, each repeating cell unit 2 can comprise two flow field assemblies (e.g., an anode flow field assembly 8 and a cathode flow field assembly 10, either metal or plastic based), a membrane electrode assembly 30 (e.g., as detailed in Figure 1), and optionally a support structure 40 as described herein including cathode substructures 40a and anode substructures 40b on the sides of the membrane electrode assembly (e.g., as detailed in Figure 1, but not clear in Figure 30). The flow field assemblies (8, 10) distribute gas and liquid phase reactants to the cathode and anode, respectively, in the membrane electrode assembly of each repeating cell unit 2.

[0120] For this reason, the repeat cell units are connected in parallel so that a large current is applied to the end of the electrolyzer stack reactor and each repeat cell unit receives a portion of the current and a similar voltage. The current going to each repeat cell unit can be measured and if the repeat cell unit is damaged, the electrical connection to the repeat cell unit is cut off. Cutting the electrical connection to the repeat cell unit reduces the amount of active area but allows the rest of the stacked repeat cell units to continue to operate. In some embodiments, the cathode and anode fluid flows to each repeat cell unit can be individually adjusted through the manifold assembly. As a result, if a membrane rupture occurs in a repeat cell unit, the cathode and / or anode fluid flows to the defective repeat cell unit can be stopped and the repeat cell unit can be electrically disconnected.

[0121] More specifically, if a repeating cell unit in a stack is shorted, the measured cell voltage will be lower for that repeating cell unit than during normal operation to achieve the same current. For example, to achieve a current of at least about 80 A, the cell voltage may be at least about 3.0 V during normal operation, and a short circuit may be detected when a cell voltage of less than about 2 V, typically less than about 1 V, is measured. For example, the current through each repeating cell unit may be measured at the tab using a handheld clamp meter.

[0122] For this purpose, the electrolyzer stack reactor further includes a manifold assembly in fluid communication with the flow field of each repeating cell unit to distribute reactant fluids (i.e., CO2, CO or mixtures thereof, and electrolyte) to the anodes and cathodes of each membrane electrode assembly. For example, the manifold assembly can include two separate inlet manifolds, i.e., an anode inlet manifold and a cathode inlet manifold, for supplying reactant fluids to the multiple cathodes and anodes, respectively. The manifold assembly can further include two separate outlet manifolds, i.e., an anode outlet manifold and a cathode outlet manifold, for recovering product fluids and spent electrolyte from the multiple cathodes and anodes. Each manifold can be internal or external to the repeating cell unit. In addition, the anode manifold can be different from the cathode manifold. For example, the cathode inlet and outlet can be manifolded internally, while the anode inlet and outlet can be manifolded externally.

[0123] In the embodiment illustrated in Figures 25, 27 and 28, the manifolds are internal, meaning that fluids flow only through the distribution channels that are internal to each repeating cell unit. Referring to Figure 24, each one of the internal inlet and outlet manifolds includes an inlet or outlet end port defined by a hole 14 in each of the end plates 6, each hole 14 being in fluid communication with a channel of the corresponding manifold. For example, as illustrated in Figure 29, reactant fluids can be fed to the cathode inlet manifold through an inlet end port 14a defined in each of the two end plates 6, and the cathode outlet manifold can discharge product fluids through an outlet end port 14b defined in each of the two end plates.

[0124] The distribution channels of the internal manifold are further defined through additional ports provided in the cathode flow field and the anode flow field of each one of the stacked repeating cell units. Referring to FIG. 25, the anode flow field (and current collector) assembly 8 can include a housing 80 and an anode flow field (and current collector) insert 81 configured to be received within the housing 80. In the embodiment illustrated in FIG. 25 and FIG. 28, the anode inlet manifold comprises a series of inlet ports 16a defined within the housing 80 of each anode flow field assembly 8 of the repeating cell unit, and the anode outlet manifold comprises a series of outlet ports 16b defined within the housing 80 of each anode flow field assembly 8 of the repeating cell unit. The anode inlet manifold and the anode outlet manifold further include secondary ports 20 in fluid communication with the flow channels of the anode flow field insert 81. As can be better seen in FIG. 28, the secondary ports 20 comprise inlet secondary ports 20a for conducting electrolyte from inlet ports 16a of the anode inlet manifold to the flow channels of the anode flow field insert 81, and outlet secondary ports 20b for conducting spent electrolyte from the flow channels of the anode flow field insert 81 to the anode outlet manifold via outlet ports 16b. The same principle is followed for the cathode inlet manifold and the cathode outlet manifold. Referring to FIG. 27, the cathode inlet manifold comprises a series of inlet ports 18a defined in the housing 100 of each cathode flow field assembly 10 of the repeating cell unit 2, and the cathode outlet manifold comprises a series of outlet ports 18b defined in the housing 100 of each cathode flow field assembly 10 of the repeating cell unit 2. The cathode inlet manifold and the cathode outlet manifold further comprise secondary ports 22 in fluid communication with the flow channels of the cathode flow field insert 101.With further reference to FIG. 27, the secondary ports 22 include inlet secondary ports 22a for conducting reactant fluids from the inlet ports 18a of the cathode inlet manifold to the flow channels of the cathode flow field insert 101, and outlet secondary ports 22b for conducting product fluids from the flow channels of the cathode flow field insert 101 to the cathode outlet manifold via outlet ports 18b.

[0125] In the embodiment illustrated in Figure 26, the manifolds are external, meaning that fluid flows only through distribution channels that may be external to each repeating cell unit and defined by separate tubes or headers. Figure 26 illustrates inlet ports 16a and outlet ports 16b in fluid communication with external distribution channels (not shown) of the anode inlet and anode outlet manifolds. The inlet ports 16a and outlet ports 16b are fluidly connected to secondary inlet ports 20a and secondary outlet ports 20b, respectively, to supply and remove fluids from the flow channels of the anode flow field insert 81.

[0126] The manifold assembly of the electrolyzer reactor stack ensures the supply of reactants to the anode and cathode flow fields and the collection of products from the anode and cathode flow fields in parallel. It is further understood that the distribution channels (external or internal) of the manifold assembly are configured such that the cathode fluid flows through the anode plate of the repeating cell unit and the anode fluid flows through the cathode plate of the repeating cell unit. The manifold assembly can be tailored to each individual repeating cell unit. The flow direction of reactants through the anode inlet manifold and the cathode inlet manifold as illustrated in the figure is provided as an example, and such direction of reactants can be changed to parallel flow or counter flow with each other through the anode inlet manifold and the cathode inlet manifold.

[0127] It should be noted that the orientation of the manifolds can affect the overall reactor performance. The reactant feed can enter the top of each repeat cell unit through the cathode inlet manifold and exit near the bottom of each repeat cell unit through the cathode outlet manifold, so that any liquid products and condensate can be easily removed using gravity. The electrolyte feed can enter the bottom of each repeat cell unit through the anode inlet manifold and exit near the top of each repeat cell unit through the anode outlet manifold, so that any gas bubbles can flow up and out without blocking the flow and distribution channels. The inlet manifolds can feed the cells from the front or back of the stack in one location (unidirectional), or from both the front and back of the stack (bidirectional, as seen in FIG. 29). It has been observed that bidirectional feeding of CO2 to the electrolyzer reactor stack can improve the uniformity of CO2 distribution between the repeat cell units, especially as the electrolyzer reactor stack grows in number of repeat cell units.

[0128] Regarding the electrical connection, referring to the stack reactor 70 in FIG. 30, current is applied to each repeat cell unit 2 in parallel through common bus bars 24 and 26 connected to the current collectors of the anode flow field (and current collector) assembly 8 and the cathode current collectors 28. This parallel connection allows low voltage, high current operation. Operation can include monitoring the stack voltage to detect short circuits and further monitoring the current at each repeat cell unit tab to detect particularly faulty repeat cell units. Referring to FIG. 24, the parallel arrangement allows the cell fuses 52 to be cut to isolate a failed repeat cell unit 2 from the rest of the stack. For example, the fuses 52 can be provided on the anode side in series with the anode bus bar 24.

[0129] Depending on the type of manifold selected for the electrolyzer stack reactor, the material of the anode flow field assembly can be tailored to avoid current shunting. If an internal manifold is used, the fluid must travel through plastic parts to avoid such current shunting. For example, the anode flow field assembly can include a plastic housing when used in combination with an internally manifolded electrolyte, an electrolyte that is therefore not exposed to the cell. With reference to FIG. 25, the anode housing 80 of the anode flow field (and current collector) assembly 8 can be made of plastic with an internal anode inlet manifold and an internal anode outlet manifold, while the current collector / flow field insert 81 can be made of metal. In another example, with reference to FIG. 26, the anode flow field (and current collector) assembly 8 can be designed entirely of metal and used in combination with an externally manifolded electrolyte. These two designs overcome the current shunting problem, with the current applied to the cell traveling through the conductive electrolyte rather than participating in the electrochemical reaction, potentially shorting the reactor.

[0130] CATHODE REFILL METHOD AND SYSTEM FOR ELECTROLYZER - Patent application Cations migrating through the ion exchange membrane during CO2 electroreduction can form solid salts with bicarbonate or carbonate anions on the cathode side of the CO2 electrochemical reactor. If the gas diffusion layer, flow field, or mesh support substructure of the cathode fills with solid salt, CO2 cannot reach the catalyst, the CO2 reduction reaction stops, and no new CO2 reduction products are produced. The reactor cannot be operated continuously because disassembly, salt removal, and reassembly of a large reactor can take 1-2 hours and may be required several times per day. Typical metals used as CO2 reduction catalysts can be irreversibly altered by the momentary positive potential seen from the electrolyzer reactor discharge when the electrolyzer reactor is turned off and salt formation is cleaned up. The objective of this invention is to remove these blockages so that the reactor can continue to operate at its maximum capacity.

[0131] A system is provided for rinsing any salt formation or other obstructions in the gas diffusion electrode (cathode), support structure (mesh), and / or flow field of an electrolyzer reactor as described herein. At least the rinsing operation may be performed manually or automatically.

[0132] 31, the electrolytic reduction system includes a water distribution assembly 62 configured to periodically provide a rinse fluid 64, e.g., water, to a cathode compartment of a reactor 70 (e.g., a CO2 electrolyzer in FIG. 30 including a cathode flow field assembly (housing+insert) 10) when the electrolytic reduction is running for a certain electrolytic reduction period. The distribution assembly 62 can include a rinse water reservoir 66 and piping 68, which is in fluid communication with the cathode compartment of the reactor 70 to provide the rinse water 64 from the reservoir 66 to the cathode compartment of the electrolyzer reactor 70. The distribution assembly 62 further includes a pump 72 and a valve 74 mounted on the piping 68 to open the flow in the piping and control the flow rate of the rinse water 64 in the piping 68 to the cathode compartment.

[0133] For example, the system can be automated to periodically rinse with water using automatic valves and pumps, or manually using manual valves and pumps. This system avoids the need to disassemble and reassemble the electrolyzer reactor every time there is an obstruction, and acts as preventative maintenance to mitigate the creation of obstructions before such obstructions completely block the available channels in the cathode compartment.

[0134] Thus, operation of the rinse system, referred to as a rinse run, can increase the stability of the electrolyzer reactor by removing any obstructions in the cathode compartment (cathode, mesh support substructure, and / or flow field) with the rinse fluid, increasing the hydration of the ion exchange membrane of the electrolyzer reactor. For example, the electrolyzer reactor can be operated with stable performance for at least 100 hours.

[0135] Referring to FIG. 32, the rinse operation involves simultaneously feeding the rinse fluid 64 and CO, CO2 or a mixture thereof 76 to the cathode compartment of the electrolyzer reactor 70. Thus, the rinse system rinses the cathode compartment while the electrolytic reduction reaction is still ongoing. This means that no reactor disassembly is required, minimizing lost productivity time. During rinsing, the rinse fluid is forced into the cathode inlet together with the gaseous reactants, and is further pushed out of the cathode outlet as salt-enriched water (as gas-liquid mixture 78) together with the electrolytic reduction products and remaining CO2. By periodically rinsing the cathode, salts can be effectively removed and stable operation could be maintained for hundreds of hours. Thus, the system can further include a collection tank or waste container for storing and / or recirculating the salt-enriched water.

[0136] In some embodiments, referring to Figure 31, the rinse operation may include, among other things, opening the valve and further operating the pump to move water from the reservoir to the cathode inlet of the electrolyzer reactor and carry it through the cathode flow field along with the CO2, CO or mixtures thereof. After a certain period of time, referred to as the rinse period, the pump may be stopped and the valve may be closed. For example, the rinse period may have a duration of 20 seconds to 30 minutes, optionally 1 to 3 minutes.

[0137] It should be noted that during the rinse period, the CO / CO flow rate supplied with the rinse water can be reduced and selected according to the water flow rate. For example, the ratio of the volumetric flow rate of the rinse water to the volumetric flow rate of CO, CO or their mixture (CO / CO flow rate) can be selected between 0.001 and infinity (CO / CO flow rate), with a further typical range being 0.05-0.5. FIG. 33 illustrates the effect of opening the valve to trigger a rinse run on the CO flow rate, where the current and CO supply are maintained while the rinse run is in progress. In some embodiments, the CO flow can be reduced during the rinse (due to an increase in pressure drop through the stack) and the cell voltage can also be reduced while maintaining the same current (due to a large increase in hydrogen generation activity). It should be further noted that even if electrolytic reduction can be maintained during the rinse period, the operation of the electrolyzer reactor can generate increased amounts of H since the rinse water can temporarily block the CO / CO transport.

[0138] In another embodiment, the CO / CO gas supply lines can be disconnected from the electrolyzer reactor during the rinse period so that only rinse water is supplied to the cathode compartment. Thus, a pump can be connected directly to the cathode inlet or outlet for rinsing. Once the rinse run is completed, the CO / CO supply lines can be reconnected and normal operation can resume.

[0139] The system may further include a controller for triggering the valves (e.g., controlled solenoid valves) and pumps of the distribution assembly so that the rinse water can be automatically pumped through the cathode inlet and out the cathode outlet and then directed to a collection tank or waste container.

[0140] In some embodiments, the injection of the rinsing fluid can be performed at a flow rate to volume of the cathode compartment of 20-200 per minute, optionally 50-80 per minute, where the volume of interest is the volume of the channels of the cathode compartment (i.e., the flow field).

[0141] The electrolytic reduction system can be adapted to facilitate the rinsing operation. For example, the cathode compartment can include a porous support plate and the cathode gas diffusion layer can have pores, the pore size being selected to avoid accumulation of the rinsing fluid or salt-enriched fluid in the pores. The cathode compartment can be as described in connection with the membrane electrode assembly described herein, the electrolyzer reactor described herein, or the electrolyzer reactor stack described herein.

[0142] In some embodiments, the method can include monitoring the pH and conductivity of the salt-enriched water to measure the effectiveness of the rinse operation.

[0143] Referring to FIG. 34, the rinse operation was shown to successfully contribute to a decrease in hydrogen production and an increase in CO production due to an increase in CO2 mass transport once the salt was rinsed.

[0144] A comparison of Figures 35 and 36 shows that in the absence of any rinsing operation, hydrogen production can be increased rapidly, while the stability of the electrolyzer reactor is improved when regular rinsing of the cathode compartment of the electrolyzer reactor is performed. Regarding the effect of rinsing frequency, a comparison of Figures 37 and 38 shows that hydrogen production increases and electrolytic reduction products decrease when the rinsing operation is not frequent enough.

[0145] It should be noted that the rinse system may be adapted to any electrolytic cell reactor, including electrolytic cell reactors as described herein and electrolytic cell reactor stacks as described herein.

[0146] It should be noted that the same reference numbers refer to similar elements. Moreover, for the sake of brevity and clarity, i.e., so as not to overload the drawings with several reference numbers, not all drawings include reference numbers to all components and features, and references to some components and features may be found only in one drawing, from which the components and features of the present disclosure illustrated in other drawings can be easily inferred. The embodiments, geometric configurations, materials referred to, and / or dimensions shown in the figures are optional and are given for illustrative purposes only. Thus, the descriptions, examples, methods and materials presented in the claims and the specification should not be construed as limiting, but rather as illustrative only.

[0147] When the specification states that a component, feature, structure, characteristic, or step "can" be included or "could" be included, it is understood that the particular component, feature, structure, characteristic, or step need not be included.

[0148] Although the embodiments of the electrolyzer stack reactor, membrane electrode assembly, and gas diffusion electrodes, and their corresponding components, as described and illustrated herein, are of certain geometric configurations, not all of these components and geometries are required and therefore should not be construed in a limiting sense. It should be understood that other suitable components and cooperations therebetween, as well as other suitable geometric configurations, may be used, as would be apparent to one skilled in the art, and as would be readily inferred from the present specification by one skilled in the art. Furthermore, it should be understood that descriptions of positions such as "top", "bottom", "upper", "bottom", "left", "right", etc., should be interpreted in the context of the figures, unless otherwise indicated, and should not be considered limiting.

[0149] In this description, the term "about" means within an acceptable error range for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined, i.e., the limitations of the measurement system. It is generally accepted that a measure of accuracy of 10% is acceptable and encompasses the term "about."

[0150] In this description, the embodiments are examples. The various occurrences of "several embodiments" do not necessarily all refer to the same embodiment. Although various features of the present technology and components may be described in the context of a single embodiment, these features may also be provided separately or in any suitable combination. Conversely, although the present technology and components may be described herein in the context of separate embodiments for clarity, they may also be implemented in a single embodiment.

Claims

1. Gaseous CO ２ 1. A multi-layer gas diffusion electrode (GDE) for sustaining the electrochemical reduction of CO, CO, or a combination thereof to multi-carbon products, comprising: A gas diffusion layer (GDL), support layer, The gaseous CO usable for electrolytic reduction ２ a gas diffusion layer comprising a microporous layer (MPL) having pores sized to retain CO, CO, or a combination thereof; The CO ２ a catalyst layer comprising a catalyst favorable for the reduction of CO, CO, or said combination thereof; A multilayer gas diffusion electrode (GDE) wherein each one of the support layer and the MPL is hydrophobic and conductive, and the GDE is conductive from one layer to another.

2. The support layer is a first hydrophobic polymer; and a first conductive material selected from the group consisting of carbon paper, carbon felt, carbon cloth, and metal mesh.

3. The multilayer GDE of claim 1 or 2, wherein the support layer has a thickness of 50 μm to 1000 μm.

4. The MPL is a second hydrophobic polymer; and and a second conductive material comprising carbon nanoparticles.

5. The multilayer GDE of claim 1 or 2, wherein the MPL has an MPL thickness of 0.5 μm to 500 μm.

6. The catalyst is provided as particles, and the catalyst layer binds the catalyst particles together and provides ionic conductivity and CO ２ 3. The multilayer GDE of claim 1 or 2, further comprising a binder that promotes utilization.

7. 7. The multi-layer GDE of claim 6, wherein the catalyst particles are metal, metal oxide, or mixed metal.

8. 3. The multilayer GDE of claim 1 or 2, further comprising a stabilization layer comprising solid particles having surfaces modified with functional groups to prevent the catalyst layer from rebuilding during operation of the multilayer gas diffusion electrode.

9. 10. The multi-layer GDE of claim 8, wherein the solid particles of the stabilization layer are particles of carbon, graphite, graphene, titania, silica, ceria, or any combination thereof.

10. 9. The multilayer GDE of claim 8, wherein the functional group is an ionized unit of an ion-conducting ionomer, imidazolium, sulfonic acid, poly(arylpiperidinium).

11. 1. A method for producing a gas diffusion electrode (GDE) comprising a gas diffusion layer (GDL) and a catalyst layer, comprising: providing a hydrophobic and conductive support layer; blade coating a microporous layer ink onto the support layer, the microporous layer ink comprising conductive particles and a hydrophobic polymer to form a microporous layer (MPL); heat treating the MPL to sinter the hydrophobic polymer within the conductive particle network and form the GDL; spraying a catalyst ink comprising catalyst particles and a binder onto said GDL to form said catalyst layer.

12. CO ２ 1. A method for facilitating operation of an electrolytic reduction system for converting CO, CO, or mixtures thereof into carbon products, comprising: The CO ２ , CO or the mixture thereof into the inlet of the cathode compartment of the electrolytic reduction system, ２ performing an electrolytic reduction of the oxidized carbon dioxide, CO, or the mixture thereof to the carbon product, the electrolytic reduction comprising forming carbonate salts within the cathode compartment along a flow path; injecting a rinse fluid into the inlet of the cathode compartment to dissolve and remove at least a portion of the carbonate salt along the flow path to form a salt-enriched fluid; and recovering at least one of the carbon product and the salt-enriched fluid from an outlet of the cathode compartment.

13. The injection of the rinsing fluid ２ 13. The method of claim 12, wherein the injection of CO alternates with the injection of CO or the mixture thereof.

14. The CO ２ 13. The method of claim 12, wherein the injection of CO, CO or the mixture thereof is maintained during the injection of the rinse fluid.

15. The method of any one of claims 12 to 14, wherein the rinsing fluid is water, deionized water, a mixture of water and surface tension reducing molecules, or waste electrolyte.

16. The method according to any one of claims 12 to 14, wherein the injection of the rinsing fluid is carried out at a rinsing frequency of between 30 minutes and 12 hours.

17. CO ２ 1. An electrolytic reduction system for converting CO, CO, or mixtures thereof into carbon products, comprising: The CO ２ a cathode compartment including a gas diffusion electrode that sustains the electrolytic reduction of CO, CO, or said mixture thereof, and an inlet in fluid communication with said gas diffusion electrode; A distribution assembly comprising: The CO ２ , CO, or said mixture thereof, and ２ , CO or the mixture thereof to the inlet of the cathode compartment, ２ a first supply pipe for performing electrolytic reduction of CO, CO, or the mixture thereof to the carbon product, the electrolytic reduction comprising forming carbonate salts along a flow path within the cathode compartment; a second supply line in fluid communication with a source of rinsing fluid; a valve operable to fluidly connect the inlet of the cathode compartment to the second supply line for injecting the rinse fluid into the inlet of the cathode compartment, thereby dissolving and removing at least a portion of the carbonate salts along the flow path to form a salt-enriched fluid; a pump operable to control a volumetric flow rate of the rinsing fluid to the cathode compartment.

18. 20. The system of claim 17, further comprising a controller operably connected to the valve and the pump for automatic operation of the valve and the pump, and for periodically triggering injection of the rinse fluid at a rinse frequency and for a rinse period.

19. 19. The system of claim 17 or 18, wherein the cathode compartment further comprises a porous mesh support substructure in contact with and in fluid communication with the cathode flow field and the catalyst-containing gas diffusion electrode to define the flow path.

Images