Membrane-less electrolyzer for converting (BI)carbonate solutions to useful compounds

Abstract

A membrane-less electrolyzer for converting a liquid feed to one or more useful products is disclosed. The membrane-less electrolyzer comprises an anode, a cathode and an internal flow plate separating the anode and the cathode at internal sides thereof. The internal flow plate has an open area formed therein arranged to permit fluid communication between an internal face of an anode and an internal face of a cathode. The internal flow plate comprises at least one fluid inlet configured to direct a liquid flow to the open area. In some embodiments, a hydrophobic film layer is arranged between the anode and an anode flow plate. The hydrophobic film layer may be selectively permeable to species with low water solubility. A method of converting (bi)carbonate solution to one or more carbon-containing compounds using the membrane-less electrolyzer is also disclosed.

Description

MEMBRANE-LESS ELECTROLYZER FOR CONVERTING (BI)CARBONATE SOLUTIONS TO USEFUL COMPOUNDSCross-Reference to Related Application

[0001] This application claims priority from US application No. 63 / 641 ,008 filed 1 May 2024 and entitled MEMBRANE-LESS ELECTROLYZER FOR CARBON DIOXIDE REDUCTION which is hereby incorporated herein by reference for all purposes. For purposes of the United States of America, this application claims the benefit under 35 U.S.C. §119 of US application No. 63 / 641 ,008 filed 1 May 2024 and entitled MEMBRANE-LESS ELECTROLYZER FOR CARBON DIOXIDE REDUCTION which is hereby incorporated herein by reference for all purposes.Field

[0002] The invention pertains to a membrane-less electrolyzer, in particular, one that can be adapted to convert a liquid feed such as an aqueous (bi)carbonate solution to one or more useful products.Background

[0003] The electrochemical reduction of carbon dioxide (CO2RR) is a promising strategy for mitigating global CO2 emissions while simultaneously yielding valuable chemicals and fuels, such as CO, HCOO-, and C2H4. A liquid-fed electrolyzer has been used to overcome challenges associated with gas-fed electrolyzers, where the liquid-feed comprises ionic species such as carbonate and / or bicarbonate which are formed from capture of CO2 gas by contacting the CO2 gas with a capture solution of various types.

[0004] However, in a liquid-fed electrolyzer, an ion exchange membrane is required to prevent ion crossover between the anode and cathode compartments, and to create the necessary isolated acidic and alkaline regions for reactive carbon electrolysis.These membranes increase the operating voltage of the electrolyzer, are costly, can be challenging to source, and can degrade over extended periods of electrolysis.

[0005] The inventors have recognised a general need for improved electrolyzers and methods that are capable of overcoming the challenges associated with ion exchangemembranes such as, changes in the membrane supply chain, variations in membrane properties from batch to batch, and membrane degradation over time during continuous electrolysis, while achieving high efficiency and high product selectivity,Summary

[0006] This application has a number of aspects. These include, without limitation:• membrane-less electrolyzers for converting a liquid feed to one or more useful compounds;• membrane-less electrolyzers for converting (bi)carbonate solution to one or more carbon-containing compounds;• methods for converting (bi)carbonate solution to one or more carbon- containing compounds;• methods for capturing atmospheric carbon dioxide.

[0007] One aspect of the invention provides a membrane-less electrolyzer. The electrolyzer omits an ion exchange membrane which separates the anode from the cathode. An internal flow plate is arranged between the anode and cathode. The internal flow plate has an open area formed therein. The open area is arranged to allow fluid flow between the anode and the cathode.

[0008] A cathode flow plate and an anode flow plate may be arranged to press against the cathode and the anode respectively at an external side of the cathode and the anode opposite to the internal flow plate. The cathode and anode flow plates comprise flow channels configured for fluid flow to the respective cathode and anode, as well as fluid transport into and / or out of the electrolyzer.

[0009] In some embodiments, the internal flow plate comprises one or more fluid inlets arranged to direct a flow of a liquid feed towards the open area. The one or more fluid inlets may be arranged at an inner wall edge of the internal flow plate. In some embodiments, the liquid feed comprises a (bi)carbonate solution. The (bi)carbonate solution may comprise carbonate and / or bicarbonate ions.

[0010] In some embodiments, the anode comprises a porous gas diffusion layer that has hydrophobic properties. An anode catalyst is deposited on the hydrophobic porous gas diffusion layer.

[0011] A hydrophobic film may be arranged to separate the anode and the anode flowplate. In some embodiments, the hydrophobic film is selectively permeable to gas species with low water solubility. An example of such gas species with low solubility is hydrogen gas.

[0012] In some embodiments, the cathode comprises a porous gas diffusion layer that has hydrophilic properties. A cathode catalyst is deposited on the hydrophilic porous gas diffusion layer.

[0013] In some example embodiments, the membrane-less electrolyzer is used in a method of converting (bi)carbonate solution to one or more useful compounds. An oxidation reaction occurs at the anode. A reduction reaction occurs at the cathode. In some embodiments, the oxidation reaction is a hydrogen oxidation reaction (HOR). In some embodiments, the method involves supplying hydrogen gas (H2) through an anode flow plate to the anode to participate in the oxidation reaction to produce protons (H+). In some embodiments, the hydrogen gas is caused to flow through a hydrophobic film to reach the anode. The method also involves supplying (bi)carbonate solution into the electrolyzer through the internal flow plate. The (bi)carbonate solution may be directed to the open area of the internal flow plate. In some embodiments, the (bi)carbonate solution is caused to flow towards the anode. The protons produced at the anode may react with the (bi)carbonate to form in situ CO2 ( / -CO2). In some embodiments, the reaction between the protons and the (bi)carbonate occurs at or near an internal surface of the anode facing the internal flow plate. The / -CO2 may migrate through the solution toward the cathode. The / -CO2 participates in a reduction reaction at the cathode to produce one or more carbon- containing products such as carbon monoxide, methane, formate, ethylene, ethanol, etc. The one or more products may diffuse through the cathode and exit the electrolyzer through the cathode flow plate.

[0014] Proof of concept demonstrations of electrolyzing (bi)carbonate solution using the membrane-less electrolyzer described herein have shown that sustained electrolysis at an industrially relevant electrochemical reaction rate (“current density”) of 100 mA cm-2for 180 hours, while being energy efficient (1.2 V) and highly selective towards CO at a Faradaic efficiency of FEco at 75% can be achieved.

[0015] In some embodiments, a Faradaic efficiency of FEco of at least 10% and up to 100%, and / or a product yield of at least 200 mmol nr2IT1and up to about 1000 mmolrrr2IT1can be achieved by using the described membrane-less electrolyzer to convert bicarbonate-riched capture solutions to CO.

[0016] Further aspects and example embodiments are illustrated in the accompanying drawings and / or described in the following description.

[0017] It is emphasized that the invention relates to all combinations of the above features, even if these are recited in different claims.Brief Description of the Drawings

[0018] The accompanying drawings illustrate non-limiting example embodiments of the invention.

[0019] FIG. 1 is a schematic diagram illustrating an example membrane-less electrolyzer, and the chemical equations that are proposed to occur in an electrolysis using the membrane-less electrolyzer when hydrogen gas is fed at the anode and (bi)carbonate is supplied into the electrolyzer though an internal flow plate according to an example embodiment.

[0020] FIG. 2A is an exploded perspective view of a membrane-less electrolyzer according to an example embodiment.

[0021] FIG. 2B is a schematic diagram illustrating the chemical equations that are proposed to occur in an electrolysis using the FIG. 2A membrane-less electrolyzer when hydrogen gas is fed at the anode and (bi)carbonate is supplied into the electrolyzer through an internal flow plate according to an example embodiment.

[0022] FIG. 3A are top elevation views of different designs of internal flow plates according to some example embodiments of the invention.

[0023] FIG. 3B are perspective views of the FIG. 3A internal flow plates.

[0024] FIG. 4 is a flow chart depicting a method of converting (bi)carbonate to one or more products using the FIG. 1 membrane-less electrolyzer according to an example embodiment of the invention.

[0025] FIG. 5 is an exploded perspective view of an example prototype membraneless electrolyzer.

[0026] FIG. 6 shows computational fluid dynamics (CFD) simulations of the average [ / -CO2]cathode in a membrane-less bicarbonate electrolyzer. The plot in a) shows a simulated relationship between electrolyte flow rate (20 to 200 mL min-1) and averageconcentration at the cathode surface ([ / -CO2]cathode) in a Square flow field geometry. The plot in b) illustrates simulated variation of [ / -CC>2]cathode across different flow field geometries (Circle-Axis, Diamond, Square, and Circle-Tangent) at a fixed electrolyte flow rate of 200 mL min-1, highlighting the impact of geometry on [ / -CO2]cathode.

[0027] FIG. 7 shows fluid dynamics controls CO2RR performance in a membrane-less bicarbonate electrolyzer. The plot in a.) shows faradaic efficiency for CO (FEco) (from experiments) as a function of average [ / -CO2]cathode (from simulations) tuned by varying electrolyte flow rate in a Square flow field geometry. The plot in b.) shows FEco variation with flow field geometries at a fixed electrolyte flow rate of 200 mL min-1. The Diamond flow field achieves the highest FEco, corresponding to an optimal average [ / -CO2]cathode of 1.6 mM. Lower or higher [i-CO2]cathode negatively impacts FEco due to insufficient reactant supply or excessive bubble coverage on the cathode.

[0028] FIG. 8 illustrates the performance and stability of the membrane-less bicarbonate electrolyzer by operating in tandem with a water electrolyzer for green hydrogen production. The schematic diagrams in a.) illustrate the tandem electrolyzer design integrating a membrane-less bicarbonate electrolyzer with a water electrolyzer, where the latter supplies green hydrogen for the anodic HOR. The plot in b.) illustrates variation of cell voltage with current density for the membrane-less electrolyzer using the Diamond flow field geometry. The plot in c.) illustrates FEco and CO2 utilization as functions of the applied current density. The system yields the highest FEco of 75% and CO2 utilization efficiency of ~41 % at the current density of 100 mA cm-2The plot in d.) are results from a stability test at a current density of 100 mA cm-2, showing consistent operation over 180 hours with an FEco greater than 70% and a stable cell voltage below 1 .4 V.

[0029] FIG. 9 illustrates the effect of the flow rate of 3 M KHCO3 on electrolyzer performance for example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The H2 gas flow rate and current density were held constant at 50 seem and 100 mA cm-2, respectively. The electrolysis time was 5 min. Each experiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c = Circle-Tangent; and d = Circle-Axis.

[0030] FIG. 10 illustrates the effect of current density on electrolyzer performance for the example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The H2 gas flow rate and 3 M KHCO3 flow rate were held constant at 50 seem and 200 mL min-1, respectively. The electrolysis time was 5 min. Each experiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c = Circle-Tangent; and d = Circle-Axis.

[0031] FIG. 11 illustrates the effect of the flow rate of H2 gas on electrolyzer performance for example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The current density and 3 M KHCO3 were held constant at 100 mA cm-2and 200 mL min-1, respectively. The electrolysis time was 5 min. Each experiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c = Circle-Tangent; and d = Circle-Axis.Detailed Description

[0032] Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive sense.Definitions

[0033] “Ion exchange membrane” is a membrane that is selectively permeable to certain ions. An example of an ion exchange membrane is a cation exchange membrane such as Nation™. A cation exchange membrane is a membrane that is selectively permeable to cations. Another example of an ion exchange membrane is an anion exchange membrane. An anion exchange membrane is a membrane that is selectively permeable to anions.

[0034] “Bipolar membrane” or “BPM” is a membrane comprising plural layers including an anion exchange layer on one side and a cation exchange layer onanother side. A bipolar membrane may comprise one or more layers between the anion exchange layer and the cation exchange layer. For example, an intermediate layer may comprise a catalyst which facilitates dissociation of water into protons and hydroxide ions. The anion exchange layer may conduct hydroxide ions. The cation exchange layer may conduct protons. An example bipolar membrane is Fumasep® FBM" that is manufactured by FUMATECH BWT GmbH.

[0035] “Flow cell” refers to an electrochemical cell in which an electrolyte, or a catholyte and / or an anolyte are flowed through the cell while the cell is in operation.

[0036] “Flow plate” refers to a structural plate which comprises flow channels that receive a feed. For example, an anode flow plate may be arranged at the anode side of a flow cell and a cathode flow plate is located at the cathode side of the flow cell. The anode and cathode flow plates comprise flow channels that respectively receive an anode feed and a cathode feed.

[0037] “Current density” is total current divided by the geometric surface area of an electrode. For example, an electrode having an area of 100 cm2carrying an electrical current of 20 Amperes would have a current density of 200 mA cm-2.

[0038] “Faradaic efficiency” (FE) is a measure of the efficiency with which an electron transfer reaction generates a desired product. Faradaic efficiency can be reduced by side reactions which create undesired products or by further reactions which consume the desired product after it is produced. FE for a gaseous product k may be determined in accordance with Equation 1.(Eq. 1) where nk is the number of electrons exchanged, F is Faraday’s constant (F = 96,485 C / mol), Xk is the mole fraction of the gas k in the gaseous mixture analyzed, Fm is the molar flow rate in mol / s, and / is the total current in A. The molar flow rate may be derived from the volume flow rate Fvby the relation Fm = pF / RT, with p being the atmospheric pressure in Pa, R the ideal gas constant of 8.314 J mol-1K-1and T the temperature in Kelvin.

[0039] “Hydrogen oxidation reaction” or “HOR” is an electrochemical reaction that involves the oxidation of hydrogen molecules. The reaction products depend on theenvironment in which the reaction occurs. The environment may be acidic or alkaline or neutral.

[0040] “Substantially free of gaseous CO2” when applied to an electrolyte comprising carbonate and bicarbonate ions means that if the electrolyte carries any gaseous CC>2, the molar ratio of gaseous CO2 carried by the electrolyte to carbonate and / or bicarbonate ions in the electrolyte is not more than about 2% per minute at which the electrolyte is delivered into the electrolyzer.

[0041] “Carbon capture system” is a system which comprises suitable one or more apparatuses that are configured to capture carbon dioxide from the atmosphere or a point source. The captured carbon dioxide may be stored and / or converted to useful compounds. For example, the carbon capture system may comprise a contactor. The contactor may be configured to bring a gas comprising carbon dioxide into contact with a capturing solution to form the aqueous solution comprising bicarbonate ions.Example membrane-less electrolyzer

[0042] Aspects of the invention relate to a membrane-less or membrane-free electrolyzer for electrolyzing a liquid feed to produce one or more useful compounds. In some example embodiments, the membrane-less electrolyzer is adapted to convert (bi)carbonate solution to one or more carbon-containing compounds. This is only an example. The membrane-less electrolyzer described herein may be adapted to convert other liquid feeds to form one or more desired useful compounds.

[0043] A membrane-less electrolyzer does not comprise a membrane, such as an ion exchange membrane and / or a bipolar membrane (BPM), to separate the anode chamber from the cathode chamber.

[0044] FIG. 1 illustrates an example membrane-less electrolyzer 10 for electrolyzing (bi)carbonate solution to produce carbon-containing product(s). FIG. 1 depicts some of the chemical reactions that are believed to occur in the electrolyzer 10 according to an example electrochemical method. The example shows the reactions that are believed to occur in the conversion of (bi)carbonate to carbon monoxide. This is only an example. The electrolysis of (bi)carbonate using the electrolyzer 10 may produce other useful chemical products. Different chemical reactions will occur in the production of the other useful chemical products.

[0045] The electrolyzer 10 comprises at least one electrochemical flow cell 12. Flow cell 12 comprises a cathode 16 and an anode 18. An internal flow plate 14 separates the cathode 16 and the anode 18 at internal sides 17, 19 of the cathode 16 and the anode 18. The internal flow plate 14 may be pressed against internal faces 24, 28 of the anode 18 and the cathode 16. The cathode 16 is exposed to a cathode chamber 11. The anode 18 is exposed to an anode chamber 13.

[0046] The anode 18 and the cathode 16 may be in fluid communication. Referring to FIGS. 1 , 2A, 2B, 3A and 3B, in some embodiments, the internal flow plate 14 has an open area 20 formed therein. The open area 20 of the internal flow plate 14 creates a fluidic path between the anode 18 and the cathode 16 so as to allow a flow of fluid between the anode 18 and the cathode 16. The open area 20 exposes active regions 18A, 16A of the anode 18 and the cathode 16. The fluidic path separates the active region 18A of the anode 18 from the active region 16A of the cathode 16. A distance between the active area 18A of the anode 18 and the active area 16A of the cathode 16 may be a thickness of an inner wall edge 15 of the internal flow plate 14. The inner wall edge 15 of the internal flow plate 14 may define the open area 20.

[0047] The internal flow plate 14 comprises one or more fluid inlets 22. The one or more fluid inlets 22 of the internal flow plate 14 may be fluidly connected to a reservoir containing (bi)carbonate solution. In some embodiments, one or more fluid inlets 22 of the internal flow plate 14 are fluidly connected to a carbon capture system. (Bi)carbonate solution may be delivered to the flow cell 12 by flowing through the internal flow plate 14 via the fluid inlets 22.

[0048] In some embodiments, the one or more fluid inlets 22 are arranged along an inner wall edge 15 of the internal flow plate 14. In some embodiments, the fluid inlet 22 is arranged to direct the (bi)carbonate solution to flow along a first face 21 A and / or a second opposing face 21 B of the internal flow plate 14 and then flow through a second opposing face 21 B. In some embodiments, the fluid inlet 22 is arranged to direct the (bi)carbonate solution at an angle on the inner wall edge 15 of the internal flow plate 14. The angle at which the fluid flow is directed can be adjusted to optimize the fluid dynamics of the electrolyzer 10. In one example embodiment, the angle is about 45°. In some embodiments, the one or more fluid inlets 22 are arranged at a corner of the inner wall edge 15. In some embodiments, the fluid inlet 22 is arrangedto direct the (bi)carbonate solution to flow in a direction to the face 21 A, 21 B of the internal flow plate 14 that is tangent to the inner wall edge 15. In some embodiments, the fluid inlet 22 is arranged to direct the (bi)carbonate solution to flow in a direction of the central axis of the open area 20.

[0049] In some embodiments, the geometric shape of the open area 20 is a circle, an ellipse, quadrilateral (e.g., diamond, square, etc.) and other polygons (e.g., triangle, pentagon, hexagon, etc.).

[0050] In some embodiments, a plurality of fluid inlets 22 are arranged along the inner wall edge 15 of the internal flow plate 14. In some embodiments, at least two of the plurality of fluid inlets 22 are arranged diametrically opposed to one another.

[0051] FIGS. 3A and 3B illustrate non-limiting example embodiments (a, b, c and d) of internal flow plates 14 that may be used.

[0052] For example, referring to embodiment a, the internal flow plate 14 has a square-shaped open area 20 with two fluid inlets 22 arranged at opposite corners of the squared-shaped inner wall edge 15. The fluid inlets 22 are arranged to direct a flow of liquid (e.g., (bi)carbonate solution) along opposing faces 21 A, 21 B of the internal flow plate 14. In the embodiment a example, the side length of the squareshaped open area 20 is about 22 mm. The area of the open area 20 is about 484 mm2. The thickness (or depth) of the square-shaped inner wall edge 15 is about 2 mm.

[0053] Referring to embodiment b, the internal flow plate 14 has a diamond-shaped open area 20 with two fluid inlets 22 arranged at top and bottom vertices of the diamond-shaped inner wall edge 15. Such positioning of the fluid inlets 22 may direct a flow of liquid to initially encounter the inner wall edge 15 of the internal flow plate 14 at an angle of approximately 45°. In the embodiment b example, the side length of the diamond-shaped open area 20 is about 22 mm. The area of the open area 20 is about 484 mm2. The thickness (or depth) of the diamond-shaped inner wall edge 15 is about 2 mm.

[0054] Referring to embodiment c, the internal flow plate 14 has a circular-shaped open area 20 with two fluid inlets 22 arranged to direct a flow of liquid to a face 21 A, 21 B of the internal flow plate 14 that is tangent to the cylindrical inner wall edge 15. Such positioning of the fluid inlets 22 may maximize the vorticity of the fluid flow intothe anode and / or cathode chamber 11 , 12. In the embodiment c example, the diameter of the circular-shaped open area 20 is about 24.82 mm, and the area is 484 mm2. The thickness (or depth) of the circular-shaped inner wall edge 15 is about 2 mm.

[0055] Referring to embodiment d, the internal flow plate 14 has a circular-shaped open area 20 with two fluid inlets 22 arranged to direct the fluid flow in a direction of the central axis of the circular open area 20 to impinge on the cylindrical volume. In the embodiment d example, the diameter of the circular-shaped open area 20 is about 24.82 mm, and the area is 484 mm2. The thickness (or depth) of the circularshaped inner wall edge 15 is about 2 mm.

[0056] The example dimensions of the open area 20 provided in embodiments a-d are adjusted for an internal flow plate 14 with dimensions of 9 cm by 6 cm. These dimensions are only examples.

[0057] In some embodiments, the internal flow plate 14 has more than one open area 20 formed therein.

[0058] The internal flow plate 14 may have one or more fastening holes 23. The one or more fastening holes 23 may be arranged to receive a fastener such as a bolt and the like for securing the internal flow plate 14 with the other structural components discussed herein to form the flow cell 12.

[0059] The internal flow plate 14 may be made from any suitable material(s) that is stable in aqueous (bi)carbonate solution under an electrochemical bias. The internal flow plate 14 may be made from one or more polymers. In some embodiments, the internal flow plate 14 is made from an acrylic polymer such as a methyl acrylate- based resin. Non-limiting examples of other suitable materials that may be used to form the internal flow plate 14 include polypropylene, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), and / or acrylonitrile butadiene styrene (ABS). In some embodiments, the surface of the internal flow plate 14 is not additionally treated and / or comprise a coating. The internal flow plate 14 may be produced using machining, moulding, or with a 3D printer.

[0060] One or more of the following may be adjusted to optimize the fluid dynamics of the reactive solution that is caused to flow into the open area 20 of the internal flow plate 14:- the geometric shape of the open area 20;- the size of the open area 20;- the thickness of the inner wall edge 15 of the internal flow plate 14;- the position at which the fluid inlet 22 is arranged along the inner wall edge 15 of the internal flow plate 14;- the size and / or shape of the port of the fluid inlet 22;- the angle at which the fluid inlet 22 is oriented along the inner wall edge 15 of the internal flow plate 14, thereby the angle at which the fluid enters the open area 20;- the rate at which the fluid flow out of the fluid inlet 22;- the number of fluid inlets 22; and / or- the number of open areas 20 in the internal flow plate 14, etc.

[0061] An anode flow plate 30 may be pressed against the anode 18. The anode flow plate 30 may be arranged to face an external face 26 of the anode 18. The anode flow plate 30 comprises a fluid inlet 36. The fluid inlet 36 of the anode flow plate 30 may be fluidly connected to an anolyte reservoir (not shown). The anolyte reservoir contains any suitable anolyte such as an acidic anolyte. In some example embodiments, the anolyte reservoir contains a gas. The fluid inlet 36 of the anode flow plate 30 may be fluidly connected to a gas tank comprising hydrogen gas (H2). Humidified H2 may be delivered to the anode 18 by flowing through the inlet 36 of the anode flow plate 30. A fluid outlet 40 of the anode flow plate 30 may be fluidly connected to an electrolyte drain (not shown). Unreacted H2 may flow out of electrolyzer 10 through the outlet 40 of the anode flow plate 30.

[0062] A cathode flow plate 34 may be pressed against the cathode 16. The cathode flow plate 34 may be arranged to face an external face 29 of the cathode 16. The cathode flow plate 34 comprises one or more fluid outlets 44. The one or more outlets 44 of cathode flow plate 34 may be fluidly connected to a collector (not shown). Useful carbon-containing products may flow out of the cell through the outlet 44 of the cathode flow plate 34. Useful products may be separated from one another in a separator. Some of the separated products may be stored in a collector. Some of the separated products may be recycled back to the flow cell 12.

[0063] The anode and cathode flow plates 30, 34 may be made from any suitablematerial(s) for use as a flow plate that can be configured to collect a current on an external surfaces 26, 29 of the anode 18 and cathode 16 respectively, and / or to transport fluid through the flow plate 30, 34 to provide a flow of fluid to the respective electrode. Suitable materials are materials which are electrically conductive, resistant to the operating conditions of the electrolyzer (e.g., resistant to chemical corrosion, resistant to strong acids or bases under an applied potential, and / or mechanical wear during assembly / disassembly, etc.) such as titanium and steel.

[0064] The example embodiments illustrate that the internal flow plate 14 comprises two fluid inlets 22, the anode flow plate 30 comprises one fluid inlet 36 and one fluid outlet 40, and the cathode flow plate 34 comprises two fluid outlets 44; however, any suitable number of fluid inlets 22, 36 and fluid outlets 40, 44 may be provided at each of the internal flow plate 14, the anode flow plate 30 and cathode flow plate 34. In some embodiments, the internal flow plate 14 comprises one or more fluid outlets. In some embodiments, the cathode flow plate 34 comprises one or more fluid inlets.

[0065] A power supply 46 is connected to apply a potential difference between the cathode 16 and the anode 18. A negative electrical charge is applied to the cathode. A positive electrical charge is applied to the anode. An oxidation reaction 50 takes place at the anode 18. A reduction reaction 54 takes place at the cathode 16. The power source 46 may be configured to maintain a desired electric current between the cathode 16 and the anode 18 and / or to maintain a potential difference between the cathode 16 and the anode 18 at a desired level or in a desired range. In some embodiments, the potential difference introduces a current density of at least 100 mA cm-2. In some embodiments, the potential difference introduces a current density of at least 500 mA cm’2In some embodiments, the potential difference introduces a current density in the range of from 20 to 2000 mA cm’2. In some example embodiments, the electrical potential has a magnitude that does not exceed 1.0 V.

[0066] The anode 18 may comprise any materials suitable for use as an electrode. Such material may comprise a catalyst suitable for driving a hydrogen oxidation reaction (HOR).

[0067] The cathode 16 may comprise any materials suitable for use as an electrode. In some embodiments, such material comprises a catalyst that is suitable for promoting the electrochemical production of desired products from carbon dioxide(CO2).

[0068] The cathode 16 comprises a cathode catalyst. Examples of suitable cathode catalysts are one or more of a metal (e.g., Ag, Cu, Sn, Bi, Au, Zn, etc.), or metal alloys (e.g., Sn-Bi, Cu-Ag, etc.), macrocyclic compounds (e.g., phthalocyanine or porphyrin, such as a phthalocyanine-based or porphyrin-based catalyst where the metal center is a transitional metal (e.g., Co, Cu, Fe, Ni, Zn, etc.), and pyrolyzed metal-nitrogen-carbon.

[0069] The cathode catalyst may be deposited on a porous gas diffusion layer. In some embodiments, the porous gas diffusion layer comprises a carbon felt, carbon paper, carbon cloth, a sintered gas diffusion layer, metal foam (Cu, Ag, Ni, etc.), metal mesh (Cu, Ag, Ni, etc.), etc. In some embodiments, the porous gas diffusion layer is hydrophilic. Hydrophilicity refers to a material’s affinity to liquid or vapor water. A hydrophilic surface is a surface that tends to adsorb water or be wetted by water.

[0070] In some embodiments, the ionomer content in the cathode 16 is in the range of from 0 to about 50% w / w.

[0071] In some embodiments, the cathode catalyst is deposited on the gas diffusion layer with a loading mass in the range of from about 0.1 mg cm-2to about 5 mg cm-2.

[0072] In some example embodiments, the cathode 16 is formed by sputtering one or more layers of a first catalyst such as silver (Ag) on a porous gas diffusion layer such as a hydrophilic carbon paper, followed by electrodepositing a second catalyst such as a cobalt phthalocyanine (CoPc) and carbon nanotubes (CNTs) catalyst on the first catalyst-sputtered carbon paper. In some other example embodiments, the cathode 16 is formed by spray-coating one or more layers of a first catalyst such as silver (Ag) on a porous gas diffusion layer such as hydrophilic carbon paper, followed by further subsequent modification steps.

[0073] The anode 18 comprises an anode catalyst. Examples of suitable anode catalysts are one or more of Pt black, Pt / C nanoparticles, PtM / C where M = Pd, Ru, Ir, Ag, Fe, Co, Ni, Cu, etc., cobalt phthalocyanine (CoPc) and carbon nanotubes (CNTs), noble metals (e.g., Ir, Pd, Pt, Au, etc.), non-noble metals (e.g., Ni, Mn, Cu, etc.), metal oxides supported catalysts (e.g., Pt / TiO2, PtNi / MoO2, PtRu / SnO2, etc.), and Pt-alloy (e.g., Pt-Ru, Pt-Ni, Pt-Co, Pt-Cu-Fe, etc.).

[0074] The anode catalyst may be deposited on a porous gas diffusion layer. In someembodiments, a surface of the porous gas diffusion layer is made of a material that has hydrophobic properties. Hydrophobicity refers to a material’s tendency to repel liquid or vapor water. A hydrophobic surface is a surface that tends to repel water. In some embodiments, the porous gas diffusion layer comprises a carbon felt, carbon paper, carbon cloth, a sintered gas diffusion layer, etc. In an example embodiment, the porous gas diffusion layer 60 comprises a hydrophobic carbon paper.

[0075] In some embodiments, the ionomer content in the anode 18 is in the range of from 0 to about 50% w / w.

[0076] In some embodiments, the anode catalyst is deposited on the gas diffusion layer with a loading mass in the range of from about 0.1 mg cm-2to about 5 mg cm-2.

[0077] In some embodiments, one or more hydrophobic films 68 are arranged between the anode flow plate 30 and the anode 18. The one or more hydrophobic films 68 may be pressed against an internal surface 70 of the anode flow plate 30 and the external surface 26 of the anode 18. The one or more hydrophobic films 68 may be porous. The hydrophobic film 68 may be made of one or more materials that are selectively permeable to certain gas species. In some embodiments, such gas species have low water solubility. In some embodiments, “low water solubility” means a species with a water solubility of less than about 0.0100 g / L at 1 atm at 20°C, and in some embodiments, less than about 0.00500 g / L at 1 atm at 20°C. One example of such a gas species with low water solubility is hydrogen gas. In some embodiments, the hydrophobic film 68 is adapted to block passage of species (e.g., gas and / or aqueous) with a water solubility of more than 0.0100 g / L at 1 atm at 20°C, and in some embodiments, more than 0.00500 g / L at 1 atm at 20°C. Examples of suitable materials that may form the one or more hydrophobic films 68 include polytetrafluoroethylene (PTFE), and polypropylene, polyethylene, ethylene tetrafluoroethylene (ETFE), polyvinylidene difluoride (PVDF).

[0078] Without being bound to theory, the combination of a hydrophobic anode and a hydrophobic film has at least the following three functions in the performance of an electrochemical method using the membrane-less electrolyzer 10: (i) create a triple phase boundary that facilitates the oxidation of the hydrogen-containing species (e.g., hydrogen gas); (ii) facilitates the diffusion of the hydrogen-containing species through the gas diffusion layer of the anode 18 to reach the anode catalyst; and (iii) improvethe gas-liquid separation to prevent the crossover between the aqueous solution (e.g., (bi)carbonate solution) that is supplied to the internal flow plate 14 and the gas (e.g., hydrogen gas) that is supplied to the anode flow plate 30.

[0079] A (bi)carbonate solution is supplied to the internal flow plate 14 as an electrolyte. The (bi)carbonate solution is supplied into the flow cell 12 through the one or more fluid inlets 22 of the internal flow plate 14. The fluid inlets 22 are arranged so as to cause the (bi)carbonate solution to flow towards and / or through the opening area 20 of the internal flow plate 14. In some embodiments, the fluid inlets 22 are arranged so as to cause the (bi)carbonate solution to flow towards and / or along the internal surface 24 of the anode 18.

[0080] The (bi)carbonate solution is in some embodiments supplied in the absence of a gaseous CO2 feed. In some embodiments, the internal flow plate 14 is supplied with (bi)carbonate solution that is substantially free of gaseous CO2.

[0081] A suitable anolyte may be supplied to the anode 18. The anolyte may be supplied to the anode 18 by flowing through the anode flow plate 30. A suitable anolyte facilitates the oxidation reaction 50 at the anode 18. In some embodiments, the anolyte provides electrons to humidified hydrogen gas (H2) to yield protons (H+).

[0082] In some embodiments, humidified hydrogen gas (H2) is supplied to the anode 18. Hydrogen gas undergoes an oxidation reaction 50 at the anode 18. In some example embodiments, the oxidation reaction 50 is a hydrogen oxidation reaction (HOR). HOR at the anode 18 yields hydrogen ions (H+). The HOR may occur in accordance with Equation 2 below.H2(g) 2H+(g) + 2e_(Eq. 2)

[0083] The hydrogen ions participate in an acid / base reaction 51 by reacting with (bi)carbonate ions to form in situ carbon dioxide ( / -CO2). This acid / base reaction 51 between (bi)carbonate ions and hydrogen ions may occur at or near the catalyst surface of the anode 18. Such a catalyst surface of the anode 18 may be the internal surface 24 of the anode 18 oriented to face the internal flow plate 14. This acid / base reaction may occur in accordance with Equation 3 below.H+(aq) + HCOs'faq) —> / -CO2(g) + H2O0(Eq. 3)

[0084] The in-situ carbon dioxide may migrate through the (bi)carbonate solution towards the cathode 16 to participate in a reduction reaction 54 to form one or more useful compounds. The one or more useful compounds may for example include carbon-containing compounds such as carbon monoxide, methane, formate, ethanol, etc. Examples of in situ carbon dioxide reduction reactions may occur in accordance with Equation 4 below. / -CO2(g) + H2O(|) + 2e~ —> CO(g) + 2OH'(aq)(Eq. 4)

[0085] The one or more useful compounds may diffuse through the cathode 16, and flow through the cathode flow plate 34 to exit the flow cell 12 from the one or more cathode flow plate outlets 44.

[0086] Cathode and anode housings (not shown) may be arranged to press against cathode and anode flow plates 34, 30 respectively.

[0087] One or more accessories may be connected to the flow cell 12 to support the operation thereof. The one or more accessories may include without limitation:- electrolyte pump arranged to deliver the (bi)carbonate solution through the internal flow plate 14;- anolyte pump and / or mass flow controller arranged to deliver anolyte to the anode 18 through the anode flow plate 30;- reactant pump arranged to deliver hydrogen gas to the anode 18 through the anode flow plate 30;- one or more flow meters, which may be communicatively connected to the pumps, to monitor the flow rates at which (bi)carbonate solution, hydrogen gas and / or anolyte are delivered to the cathode 16 and the anode 18; and / or- pressure sensors connected to measure the pressure of the (bi)carbonate solution being supplied through the internal flow plate 14, etc.

[0088] In some embodiments, a source of gas is delivered to the reservoir containing (bi)carbonate solution to increase the pressure of the (bi)carbonate solution before the solution is supplied to the flow cell 12 through the internal flow plate 14. Othersuitable methods and technologies of increasing the pressure of the (bi)carbonate solution may alternatively be used.Example methods of electrolyzing (bi)carbonate using a membrane-less electrolyzer

[0089] Aspects of the invention relate to a method of electrolyzing (bi)carbonate solution using a membrane-less electrolyzer. An example of such a membrane-less electrolyzer is the electrolyzer 10 of the type as illustrated in FIG. 1. The method involves generating in situ carbon dioxide ( / -CO2) at or near the electrocatalyst surface of an anode of the electrolyzer from reacting bicarbonate with hydrogen ions that are produced from an oxidation reaction at the anode. (Bi)carbonate solution is supplied to an internal flow plate arranged between the anode and the cathode. The in situ carbon dioxide participates in a reduction reaction at the cathode to produce one or more useful compounds such as carbon monoxide, methane, formate, ethanol, etc.

[0090] FIG. 4 is a flow chart illustrating the steps of an example electrochemical method 100. In block 102, an electrical current and / or potential is applied between an anode and a cathode. In block 104, a hydrogen-containing species such as hydrogen gas (H2) or pure hydrogen gas is supplied at the anode. The hydrogen-containing species may be delivered into the electrolyzer through one or more fluid inlets of an anode flow plate. The anode flow plate may be arranged to press against an external surface of the anode. In block 106, the hydrogen-containing species undergoes an oxidation reaction to produce hydrogen ions (protons). Other hydrogen-containing species that may be supplied to the anode include for example CH4, C2H6, C2H4, C2H2, C3H8, C3H6, C3H4, C4H10, C4H8, C4H6, etc.). In block 108, (bi)carbonate solution is delivered into the electrolyzer through one or more fluid inlets of the internal flow plate. In block 110, (bi)carbonate ions react with the protons that are produced at the anode to generate in situ carbon dioxide. In some embodiments, such chemical reactions between the (bi)carbonate ions and the protons occur at or near an electrocatalyst surface of the anode. Such a surface may be an internal surface of the anode which faces the internal flow plate. In block 112, the generated in situ carbon dioxide migrates through the liquid toward the cathode. The generated in situ carbon dioxide undergoes a reduction reaction to form one or more useful chemical products(block 114). In block 116, the useful chemical products may be caused to flow through the cathode and the one or more fluid outlets of the cathode flow plate to be removed from the electrolyzer. The useful chemical products may be one or both of a gaseous and liquid product.

[0091] The electrochemical method 100 may be tuned to optimize the fluid dynamics within the reactor and thereby, one or more of product selectivity, current efficiency and reaction rate of each of the electrolysis reaction by adjusting one or more of:• conditions of the flow cell such as temperature, pH, pressure, etc.; and / or• flow rate and / or composition of the bi(carbonate) solution and / or anolyte and / or proton-generating gas (e.g., hydrogen gas); and / or• characteristics of the internal flow plate as discussed in detail elsewhere herein, etc.; and / or• electrical operating conditions such as the applied electrical potential; and / or• characteristics of the cathode and / or anode electrodes such as the material and method of fabrication; and / or• nature of the cathode and / or anode catalyst; etc.

[0092] Optimum fluid dynamics within the reactor can minimize the interference of leaked gases from the anode with the reactions at the cathode and / or hydrogen crossover from the anode to the cathode through the electrolyte.

[0093] The flow rates at which the (bi)carbonate solution and the hydrogen-containing species such as hydrogen gas (H2) are delivered to the electrolyzer may be scaled according to the area of the electrode. In some embodiments, the flow rate at which (bi)carbonate solution is delivered is in the range of from about 20 mL min-1to about 200 mL min-1for a cathode having a geometric surface area in the range of from 4 cm2to 100 cm2. In some embodiments, the flow rate at which the proton-generating gas such as hydrogen gas (H2) is delivered to the anode is in the range of from about 10 seem to about 200 seem for an anode having a geometric surface area in the range of from 4 cm2to 100 cm2.

[0094] In some embodiments, the pH of the (bi)carbonate solution is at least 7, and in some embodiments, in the range of from about 7 to 12. In some embodiments, the concentration of the (bi)carbonate solution that is supplied to the fluid inlet of the internal flow plate is in the range of from about 0.5 M to about 3 M.

[0095] In some embodiments, the electrolysis is operated at a temperature in the range of from 20°C to about 80°C.

[0096] The invention is further described with reference to the following specific examples, which are not meant to limit the invention, but rather to further illustrate it.EXAMPLES

[0097] A membrane-less electrolyzer of the type illustrated in FIGS. 1 and 2A, and the method of performing electrolysis illustrated in FIG. 4 were used to convert (bi)carbonate solution to one or more useful compounds.

[0098] In these examples, the cathode 16 comprises a gas-diffusion electrode (GDE). The cathode 16 was prepared by spray coating a concentrated solution (“ink”) of cobalt phthalocyanine supported on carbon nanotubes (CoPc-CNTs) onto a 2 cm x 2 cm silver-sputtered carbon gas diffusion layer. The anode 18 comprises a GDE. The anode 18 was prepared by spray coating a Pt / C nanoparticle ink onto a hydrophobic carbon gas-diffusion layer. To enhance the hydrophobicity of the anode 18 and to prevent electrolyte leakage, a 2 cm x 2 cm piece of a porous polytetrafluoroethylene (PTFE) film (about 130 pm in thickness) was used as a hydrophobic film 68. The hydrophobic film 68 was arranged between the anode GDE and the anodic titanium flow plate. FIG. 5 is an exploded view of the prototype membrane-less electrolyzer 10 that was used in the examples.

[0099] The electrolysis method began with a 3 M potassium hydroxide (KOH) solution which served as the carbon capture medium. This solution reacts with CO2 gas bubbled through it to form HCOs- and COs2-ions. When the pH of the capture solution decreases to approximately 8.416, a bicarbonate-riched carbon capture solution is formed. The bicarbonate-riched carbon capture solution was introduced into the electrolyzer 10 through the internal flow plate 14 at a controlled flow rate. High-purity H2 gas was simultaneously supplied to the anode 18.

[0100] The H2 gas participates in a hydrogen oxidation reaction (HOR) at the anode 18, thus generating protons (H+ions, Eq. 2). The generated protons react with HCOs' ions to produce / -CO2 gas (Eq. 3). As directly observed in-situ using an optical imaging technique, the / -CO2 gas was transported by the flowing electrolyte to the surface of the cathode 16, where i-CO2 are electrochemically reduced to a COproduct (Eq. 4).

[0101] The inventors believe that the performance of a CO2 electrolyzer is strongly influenced by the behavior of CO2 gas bubbles during the electrolysis process. In a conventional CO2 electrolyzer, an ion-exchange membrane separates the anolyte and catholyte chambers. This adds complexity to bubble management. The membraneless electrolyzer design described herein is believed to eliminate the physical barrier, enabling the precise manipulation of CO2 gas bubbles through tuning the fluid dynamics alone.

[0102] To investigate how fluid dynamics influence the / -CO2 concentration at the cathode surface ([ / -CC>2]cathode) and the overall performance of the described membrane-less electrolyzer, the inventors first conducted computational fluid dynamics (CFD) simulations using a COMSOL Multiphysics™ software. The CFD simulations employed an average / -CO2 gas bubble size of approximately 30 pm, with the flow chamber thickness fixed at 2 mm.

[0103] Initially, the inventors evaluated the impact of electrolyte flow rate using a Square flow field geometry with an active cross-sectional area of 2.2 cm x 2.2 cm (FIG. 6a). The simulation revealed an inverse relationship between average [ / - CO2]cathode and electrolyte flow rate, where increasing the electrolyte flow rate from 20 mL min-1to 200 mL min-1reduced the average [ / -CC>2]cathode from 44.4 mM to 3.7 mM. The simulation results of other flow field geometries (Circle-axis, Diamond, and Circle-tangent) also demonstrated similar variation trends of the average [ / -CO2]cathode with varying flow rate.

[0104] The effect of the flow field geometry on [ / -CO2]cathode was explored by designing and 3D-printing flow chambers with Circle-axial (Circle-A), Diamond, Square, and Circle-tangential (Circle-T) geometries, each with a consistent cross-sectional area of 2 cm x 2 cm. The results demonstrated that at a fixed flow rate of 200 mL min-1, Circle-A geometry produced the lowest [ / -CO2]cathode (~1.0 mM), while the Circle-T geometry achieved the highest [ / -CO2]cathode (4.4 mM) (FIG. 6b). Diamond and Square geometries resulted in intermediate [ / -CO2]cathode of 1.6 mM and 3.7 mM, respectively.

[0105] To validate the CFD simulation findings, a series of laboratory experiments for the membrane-less bicarbonate electrolyzer were conducted at 100 mA cm-2, varying electrolyte flow rates and flow field geometries.

[0106] The experimental results mirrored the simulations, highlighting the strong dependence of CO2RR performance metrics, such as FEco, CO2 utilization efficiency, and cell voltage, on fluid dynamics conditions. For example, in a Square flow field geometry, reducing the flow rate from 200 mL min-1to 20 mL min-1increased the average [ / -CC>2]cathode, but decreased FEco from 67% to 15%, presumably due to bubble accumulation on the cathode and mass-transport limitations (FIG. 7a). Similarly, experiments using different flow field geometries at a fixed flow rate of 200 mL min-1revealed that the Diamond geometry achieved the highest FEco of 73% at 100 mA cm-2with an average [ / -CC>2]cathode of 1.6 mM (FIG. 7b).

[0107] This synergistic analysis of CFD simulations and experimental results identified the optimal operating conditions for the prototype membrane-less electrolyzer: a Diamond flow field geometry with an electrolyte flow rate of 200 mL min-1 , ensuring efficient CO2 utilization and high product selectivity.

[0108] The membrane-less bicarbonate electrolyzer described herein may be adapted to directly receive hydrogen that is sourced from a water electrolyzer in a tandem design (FIG. 8a). In these experiments, a water electrolyzer was constructed using a catalyst-coated proton exchange membrane with lrO2 and Pt / C nanoparticle catalysts applied to the anode and cathode, respectively. These catalysts facilitated the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. The water electrolyzer was operated with deionized water and at the same current density of 100 mA cm-2, as the membrane-less bicarbonate electrolyzer, ensuring sufficient hydrogen gas supply for bicarbonate conversion.

[0109] With the combination of the membrane-less design, ultra-hydrophobic HOR anode, and optimal fluid dynamics, an exceptional cell voltage of approximately 1.1 V at 100 mA cm-2was achieved (FIG. 8b), the lowest ever reported for producing CO in bicarbonate electrolyzers. At a higher current density of 500 mA cm-2, the cell voltage gradually increased to 2.3 V, which remains significantly lower than the typical values for conventional BPM- and CEM-based electrolyzers by approximately 10 V and 0.5 V, respectively.

[0110] Further evaluations demonstrated the performance metrics for FEco and CO2 utilization efficiency at varying current densities (FIG. 8c). At 100 mA cm-2, themembrane-less electrolyzer produced a FEco of approximately 74%. While FEco decreased with increasing current density, dropping to approximately 13% at 500 mA cm-2, this trend aligns with prior findings in the literature. The system also produced a CO2 utilization efficiency of approximately 41 % at 100 mA cm-2, among the highest values reported in conversion of bicarbonate solutions to CO to date. Although CO2 utilization decreased with increasing current density, it maintained a respectable 26% at 500 mA cm-2.

[0111] The durability of the membrane-less electrolyzer as tested. Using a Diamond flow field geometry and an electrolyte flow rate of 200 mL min-1at 100 mA cm-2, the membrane-less electrolyzer consistently converted the bicarbonate-riched capture solutions to CO with an FEco greater than 70% at a stable cell voltage of ~1.4 V over an unprecedented 180-hour electrolysis duration (FIG. 8d). This result outperforms all membrane-involved bicarbonate electrolyzers that have been reported to date.

[0112] FIG. 9 illustrates the effect of the flow rate of 3 M KHCO3 on electrolyzer performance for example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The H2 gas flow rate and current density were held constant at 50 seem and 100 mA cm-2, respectively. The electrolysis time was 5 min. Each experiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c= Circle-Tangent; and d = Circle-Axis.

[0113] FIG. 10 illustrates the effect of current density on electrolyzer performance for the example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The H2 gas flow rate and 3 M KHCO3 flow rate were held constant at 50 seem and 200 mL min-1, respectively. The electrolysis time was 5 min. Each experiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c= Circle-Tangent; and d = Circle-Axis.

[0114] FIG. 11 illustrates the effect of the flow rate of H2 gas on electrolyzer performance for example open area internal flow plate embodiments a-d illustrated in FIGS. 3A and 3B. (a) / -CO2 volume fraction; (b) FEco; (c) FEH2; (d) CO2 utilization; and (e) cell voltage. The current density and 3 M KHCO3 were held constant at 100 mA cm-2and 200 mL min-1, respectively. The electrolysis time was 5 min. Eachexperiment was performed in triplicate. Open area internal flow plate embodiment a = Square; b = Diamond; c= Circle-Tangent; and d = Circle-Axis.

[0115] In the described membrane-less bicarbonate electrolyzer for electrolyzing (bi)carbonate solution, only the carbon capture solution is fed into the electrolyzer and the generation of / -CO2 bubbles is driven by protons produced by the anodic HOR (FIGS. 1 and 2A). The rate of / -CO2 generation is directly proportional to the current density and the availability of hydrogen at the anode. Under constant current density and sufficient hydrogen supply, variations in the average [ / -CO2]cathode are predominantly determined by fluid dynamics metrics, such as electrolyte flow rate and flow field geometry. The control-flow diagram illustrates how fluid dynamics influence CO2RR performance by modulating average [ / -CO2]cathode (FIGS. 6 and 7). At low average [ / -CO2]cathode values, as observed with high electrolyte flow rate or with Circle- A geometry, FEco is limited due to insufficient reactant availability at the cathode surface. Conversely, high average [ / -CO2]cathode values, achieved with low flow rates or Square / Circle-T geometries, are also suboptimal for CO2RR. This is believed to be attributed to the saturation of / -CO2 bubbles on the cathode surface, which increases Ohmic resistance and limits the mass transport for H+ions and H2O.

[0116] The prototype membrane-less bicarbonate electrolyzer design comprises an ultra-hydrophobic HOR anode. The combination of both the hydrophobic H23C8 gas diffusion layer and the gas-permeable porous PTFE film on the backside of the anode demonstrates effective prevention of aqueous electrolyte leakage. The hydrophobic nature of hydrogen gas, coupled with its low solubility in water, are believed to further reduce the likelihood of electrolyte permeating through the anode. This ensures efficient gas-liquid separation which allows sufficient hydrogen gas to reach the Pt / C catalyst, triggering HOR and enabling continuous generation of / -CO2, to stably convert into CO.

[0117] The fast kinetics and low anodic overpotential of HOR significantly reduce the overall cell voltage in the described membraneless electrolyzer, compared to water oxidation reaction, which is typically employed in conventional bicarbonate electrolyzers using BPMs. The present membrane-less electrolyzer has both flow- through and flow-by configuration which resulted in marked improvement in performance, achieving the lowest cell voltage of 1.2 V at 100 mA cm-2. Furthermore,the reactor maintained stable operation for over a week, far exceeding the less than half-hour stability reported in previously reported bicarbonate electrolyzers.Interpretation of Terms

[0118] Unless the context clearly requires otherwise, throughout the description and the claims:• “comprise”, “comprising”, and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”;• “connected”, “coupled”, or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof;• “herein”, “above”, “below”, and words of similar import, when used to describe this specification, shall refer to this specification as a whole, and not to any particular portions of this specification;• “or”, in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list;• the singular forms “a”, “an”, and “the” also include the meaning of any appropriate plural forms. These terms (“a”, “an”, and “the”) mean one or more unless stated otherwise;• “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes both (A and B) and (A or B);• “approximately” when applied to a numerical value means the numerical value ± 10%;• where a feature is described as being “optional” or “optionally” present or described as being present “in some embodiments” it is intended that the present disclosure encompasses embodiments where that feature is present and other embodiments where that feature is not necessarily present and other embodiments where that feature is excluded. Further, where anycombination of features is described in this application this statement is intended to serve as antecedent basis for the use of exclusive terminology such as "solely," "only" and the like in relation to the combination of features as well as the use of "negative" limitation(s)” to exclude the presence of other features; and• “first” and “second” are used for descriptive purposes and cannot be understood as indicating or implying relative importance or indicating the number of indicated technical features.

[0119] Words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description and any accompanying claims (where present), depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0120] Where a range for a value is stated, the stated range includes all sub-ranges of the range. It is intended that the statement of a range supports the value being at an endpoint of the range as well as at any intervening value to the tenth of the unit of the lower limit of the range, as well as any subrange or sets of sub ranges of the range unless the context clearly dictates otherwise or any portion(s) of the stated range is specifically excluded. Where the stated range includes one or both endpoints of the range, ranges excluding either or both of those included endpoints are also included in the invention.

[0121] Certain numerical values described herein are preceded by "about". In this context, "about" provides literal support for the exact numerical value that it precedes, the exact numerical value ±5%, as well as all other numerical values that are near to or approximately equal to that numerical value. Unless otherwise indicated a particular numerical value is included in “about” a specifically recited numerical value where the particular numerical value provides the substantial equivalent of the specifically recited numerical value in the context in which the specifically recited numerical value is presented. For example, a statement that something has the numerical value of “about 10” is to be interpreted as: the set of statements:• in some embodiments the numerical value is 10;• in some embodiments the numerical value is in the range of 9.5 to 10.5; and if from the context the person of ordinary skill in the art would understand that values within a certain range are substantially equivalent to 10 because the values with the range would be understood to provide substantially the same result as the value 10 then “about 10” also includes:• in some embodiments the numerical value is in the range of C to D where C and D are respectively lower and upper endpoints of the range that encompasses all of those values that provide a substantial equivalent to the value 10.

[0122] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and / or acts with equivalent features, elements and / or acts; mixing and matching of features, elements and / or acts from different embodiments; combining features, elements and / or acts from embodiments as described herein with features, elements and / or acts of other technology; and / or omitting combining features, elements and / or acts from described embodiments.

[0123] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any other described embodiment(s) without departing from the scope of the present invention.

[0124] Any aspects described above in reference to apparatus may also apply to methods and vice versa.

[0125] Any recited method can be carried out in the order of events recited or in any other order which is logically possible. For example, while processes or blocks are presented in a given order, alternative examples may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocksmay be deleted, moved, added, subdivided, combined, and / or modified to provide alternative or sub combinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, simultaneously or at different times.

[0126] Various features are described herein as being present in “some embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or any combination of two or more of such features. All possible combinations of such features are contemplated by this disclosure even where such features are shown in different drawings and / or described in different sections or paragraphs. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that “some embodiments” possess feature A and “some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible). This is the case even if features A and B are illustrated in different drawings and / or mentioned in different paragraphs, sections or sentences.

[0126] It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

WHAT IS CLAIMED IS:1 . An electrochemical reactor comprising: an anode; a cathode; an internal flow plate separating the anode and the cathode at internal sides of the anode and cathode, the internal flow plate configured to permit fluid communication between an internal face of the anode and an internal face of the cathode through at least a portion of the internal flow plate, the internal flow plate comprising at least one fluid inlet; a power supply connected to apply a potential difference between the anode and the cathode; an anode flow plate configured to collect a current on an external side of the anode, the anode flow plate comprising at least one fluid inlet and at least one fluid outlet; a cathode flow plate configured to collect a current on an external side of the cathode, the cathode flow plate comprising at least one fluid outlet; a hydrophobic film between the anode and the anode flow plate; a (bi)carbonate solution supply configured to provide (bi)carbonate solution to the internal flow plate via a fluid inlet of the internal flow plate; and a hydrogen supply configured to supply a hydrogen-containing species to the anode flow plate via a fluid outlet of the anode flow plate, the anode configured to accept a feed of the hydrogen-containing species through the hydrophobic film and to oxidize the hydrogen-containing species to form hydrogen ions and to permit diffusion of the hydrogen ions into the internal flow plate, the cathode configured to reduce carbon dioxide to form carbon- containing product(s) and to permit diffusion of the carbon-containing product(s) into the cathode flow plate.

2. The electrolyzer according to claim 1 , wherein the cathode flow plate is configured to remove at least some of the carbon-containing product(s) via an outlet of the cathode flow plate.

3. The electrolyzer according to claim 1 or 2, wherein the anode flow plate and the cathode flow plate are configured to conduct electrical current.

4. The electrolyzer according to any one of claims 1 to 3, wherein one or both of the anode and the cathode comprises a porous gas diffusion layer.

5. The electrolyzer according to any one of claims 1 to 4, wherein one or both of the anode and the cathode comprises a free-standing layer of carbon.

6. The electrolyzer according to any one of claims 1 to 5, wherein the anode is hydrophobic or comprises a hydrophobic coating.

7. The electrolyzer according to any one of claims 1 to 6, wherein the anode comprises a catalyst to promote oxidation of a hydrogen-containing species.

8. The electrolyzer according to any one of claims 1 to 7, wherein the cathode comprises a catalyst to promote reduction of carbon dioxide.

9. The electrolyzer according to any one of claims 1 to 8, wherein in the hydrophobic film is porous.

10. The electrolyzer according to any one of claims 1 to 9, wherein the internal flow plate comprises an open area defining a quadrilateral or ellipse shape.11 . The electrolyzer according to any one of claims 1 to 10, further comprising a gas-liquid separator arranged downstream from the electrolyzer to collect the product(s) produced from the electrolyzer.

12. The electrolyzer according to any one of claims 1 to 11 , further comprising a contactor having a fluid inlet and a fluid outlet, the contactor configured to bring a gas comprising carbon dioxide into contact with an aqueous solution provided at the fluid inlet to produce the (bi)carbonate solution.

13. The electrolyzer according to claim 12, wherein the fluid outlet of the contactor is in fluid communication with the fluid inlet of the internal flow plate to supply the (bi)carbonate solution to the internal flow plate.

14. A method for converting (bi)carbonate solutions to carbon-containing product(s), the method comprising: applying an electrical potential between an anode and a cathode of an electrochemical cell, wherein the anode and cathode are separated by an internal flow plate; supplying a hydrogen-containing species to the anode; oxidizing the hydrogen-containing species, at the anode, to form hydrogen ions;supplying a (bi)carbonate solution to the internal flow plate; reacting the (bi)carbonate ions with the hydrogen ions to form gaseous carbon dioxide; and reducing the carbon dioxide, at the cathode, to form one or more carbon-containing products.

15. The method according to claim 14, wherein the hydrogen-containing species is supplied to the anode via an anode flow plate located on the opposite side of the anode from the internal flow plate.

16. The method according to claim 15, further comprising diffusing the hydrogencontaining species to the anode through a hydrophobic layer present between the anode and the anode flow plate.

17. The method according to any one of claims 14 to 16, further comprising flowing the carbon-containing product(s) from the cathode into a cathode flow plate.

18. The method according to any one of claims 14 to 17, wherein the electrical potential has a magnitude that does not exceed 1.0 V.

19. The method according to any one of claims 14 to 18, wherein a current density has a magnitude of at least 100 mA cm-2.

20. The method according to any one of claims 14 to 19, wherein the concentration of the (bi)carbonate solution at the fluid inlet of the internal flow plate is in the range of from about 0.1 M to about 3 M.21 . The method according to claim 20, wherein a flow rate of the (bi)carbonate solution at the fluid inlet of the internal flow plate ranges from about 20 mL min-1to about 200 mL min-1.

22. The method according to any one of claims 14 to 21 , wherein the hydrogen containing species may be composed of pure hydrogen gas.

23. The method according to claim 22, wherein the flow rate of the hydrogen gas is in the range of from about 10 seem to 150 seem.

24. The method according to any one of claims 14 to 23, wherein the carbon- containing product(s) comprises one or both of a gaseous and liquid product.

25. The method according to any one of claims 14 to 24, wherein the reacting of the (bi)carbonate ions with the hydrogen ions to form gaseous carbon dioxideoccurs at or near an internal face of the anode, the internal face being proximate to the internal flow plate.

26. An electrolyzer comprising: an anode; a cathode; an internal flow plate separating the anode and the cathode at internal sides of the anode and cathode, the internal flow plate having an open area formed therein arranged to permit fluid communication between an internal face of the anode and an internal face of the cathode, the internal flow plate comprising at least one fluid inlet configured to direct a liquid flow to the open area; an anode flow plate configured to collect a current on an external side of the anode, the anode flow plate comprising at least one fluid inlet and at least one fluid outlet; a cathode flow plate configured to collect a current on an external side of the cathode, the cathode flow plate comprising at least one fluid outlet arranged for discharge of one or more products formed at the cathode; a hydrophobic film arranged between the anode and the anode flow plate, the hydrophobic film being selectively permeable to one or more species with low water solubility; and a power supply connected to apply a potential difference between the anode and the cathode.

27. The electrolyzer according to claim 26, wherein the open area of the internal flow plate defines a quadrilateral or elliptical shape.

28. The electrolyzer according to claim 26 or 27, wherein the internal flow plate defines a diamond shape.

29. The electrolyzer according to any one of claims 26 to 28, wherein the at least one fluid inlet is positioned at an inner wall edge of the open area of the internal flow plate, wherein the inner wall edge defines the open area.

30. The electrolyzer according to claim 29, wherein the at least one fluid inlet is positioned at a corner of a quadrilateral-shaped inner wall edge.31 . The electrolyzer according to any one of claims 29 or 30, wherein the at least one fluid inlet comprises two fluid inlets, and wherein the two fluid inlets are positioned at opposing vertices of a diamond-shaped inner wall edge.

32. The electrolyzer according to any one of claims 26 to 31 , the anode and / or the cathode comprises a gas diffusion electrode.

33. The electrolyzer according to any one of claims 26 to 32, wherein the anode comprises a hydrophobic porous gas diffusion layer and an anode catalyst deposited on the hydrophobic porous gas diffusion layer.

34. The electrolyzer according to any one of claims 26 to 33, wherein the cathode comprises a hydrophilic porous gas diffusion layer and a cathode catalyst deposited on the hydrophilic porous gas diffusion layer.

35. The electrolyzer according to any one of claims 26 to 34, wherein the anode is adapted to oxidize the hydrogen-containing species to form protons.

36. The electrolyzer according to claim 35, wherein the anode is adapted to oxidize hydrogen gas to form protons.

37. The electrolyzer according to any one of claims 26 to 36, wherein the fluid inlet of the internal flow plate is fluidly connected to a (bi)carbonate supply, the (bi)carbonate supply being configured to supply (bi)carbonate solution to the internal flow plate.

38. The electrolyzer according to any one of claims 26 to 37, wherein the cathode is adapted to reduce carbon dioxide to form the one or more products comprising one or more carbon-containing compounds.

39. The electrolyzer according to any one of claims 26 to 38, wherein the hydrophobic film is porous.

40. The electrolyzer according to any one of claims 26 to 39, wherein the hydrophobic film is selected from one or more of polytetrafluoroethylene (PTFE), polypropylene, polyethylene, ethylene tetrafluoroethylene (ETFE), and polyvinylidene difluoride (PVDF).41 . The electrolyzer according to any one of claims 26 to 40, wherein the one or more species with low water solubility has a water solubility of less than about 0.0100 g / L at 1 atm at 20°C.

42. The electrolyzer according to any one of claims 26 to 40, wherein the one or more species with low water solubility has a water solubility of less than about 0.0050 g / L at 1 atm at 20°C.

43. The electrolyzer according to any one of claims 26 to 42, wherein the one or more species with low water solubility comprise hydrogen gas.

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