Electrolytic system including a gas diffusion anode and its operation method

Abstract

This specification describes a gas diffusion anode, an electrolytic system including such an anode, and a method of using such a system. The gas diffusion anode includes a current collector, an anode porous substrate, an anode catalyst layer, and an anode-liquid interface layer. During operation, the anode gas chamber receives hydrogen gas, which flows through the current collector into the anode porous substrate. The anode porous substrate provides a uniform distribution of hydrogen gas and a uniform current density. The anode catalyst layer converts the hydrogen gas into protons, returning electrons to the current collector via the anode porous substrate. The protons are transported to the anolyte by the anode-liquid interface layer. This layer also prevents the anolyte from coming into contact with the anode catalyst layer. The anode porous substrate, the anode catalyst layer, and the anode-liquid interface layer help prevent the anolyte from migrating into the anode gas chamber.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to the pending U.S. Provisional Patent Application No. 63 / 495,856, filed on April 13, 2023, and incorporates its entirety by reference herein.

[0002] This application relates to electrochemical systems, and more particularly to gas diffusion anodes, electrolytic systems including the same, and methods thereof. [Background technology]

[0003] Electrolytic cells use an external electrical energy source to drive various chemical reactions. For example, such a cell, or more commonly, an electrolytic system, can be used to convert metal salts (e.g., supplied as part of brine during mineral extraction) into metal hydroxides (e.g., used to produce lithium and sodium). Electrolytic cells / systems are sometimes also referred to as electrolytic devices, electrolytic cells / systems, and electrochemical cells / systems. Such a cell / system includes two electrodes (i.e., an anode / positively charged electrode and a cathode / negatively charged electrode), which are immersed in an electrolyte solution, and a voltage is applied between the electrodes to drive the electrochemical reaction.

[0004] Conventional electrolytic systems / processes for the conversion of metal salts involve (1) decomposing water molecules into protons and oxygen gas at the anode, and (2) decomposing water molecules into hydroxide ions and hydrogen gas at the cathode. In such systems, the anode material must be selected to be stable under acidic operating conditions, while the cathode material must be stable under basic operating conditions. The cathode in such systems can be manufactured from stainless steel or nickel. The anode requires a coating of a conductive metal oxide made from metal, such as an iridium oxide coating or a ruthenium oxide coating, where these coatings act as catalysts for the oxidation of water or chloride, respectively, resulting in reduced power consumption. [Overview of the Initiative]

[0005] Described herein are gas diffusion anodes, electrolytic systems comprising such gas diffusion anodes, and methods of using such systems to convert metal salts into hydroxides. The gas diffusion anode comprises an anode gas chamber, a current collector, an anode porous substrate, an anode catalyst layer, and an anode-liquid interface layer. During operation, the anode gas chamber receives hydrogen gas, which flows through the current collector into the anode porous substrate. The anode porous substrate provides a uniform distribution of hydrogen gas and a uniform current density. The anode catalyst layer converts the hydrogen gas into protons, returning electrons to the current collector via the anode porous substrate. The protons are transported to the anolyte by the anode-liquid interface layer. The anode porous substrate, the anode catalyst layer, and the anode-liquid interface layer help prevent the anolyte from migrating into the anode gas chamber.

[0006] Accordingly, this application includes a gas diffusion anode, the gas diffusion anode comprising: a current collector comprising a conductive mesh; an anode porous substrate disposed adjacent to the current collector and comprising a porous electronically conductive structure; an anode catalyst layer disposed adjacent to the anode porous substrate and comprising a conductive filler, a binder and a catalyst, having a different average porosity from the anode porous substrate and disposed adjacent to the anode porous substrate so as to be disposed between the anode porous substrate and an anode-liquid interface layer; and an anode-liquid interface layer disposed adjacent to the anode catalyst layer so as to be disposed between the anode porous substrate and an anode-liquid interface layer and comprising an ionomer coating configured to conduct protons through a porous polymer substrate and an anode-liquid interface layer.

[0007] This application also includes a gas diffusion anode for use in an electrochemical cell, the gas diffusion anode comprising an anode gas chamber, a current collector disposed adjacent to the anode gas chamber such that it is disposed between the anode gas chamber and an anode porous substrate, the current collector including a conductive mesh, an anode porous substrate disposed adjacent to the current collector and including a porous electron conductive structure, an anode catalyst layer disposed adjacent to the anode porous substrate and including a conductive filler, a binder, and a catalyst, having an average porosity different from that of the anode porous substrate and disposed adjacent to the anode porous substrate such that it is disposed between the anode porous substrate and an anode-liquid interface layer, and an anode-liquid interface layer disposed adjacent to the anode catalyst layer such that the anode catalyst layer is disposed between the anode porous substrate and the anode-liquid interface layer, the anode-liquid interface layer including an ionomer coating configured to conduct protons through a porous polymer substrate and the anode-liquid interface layer.

[0008] Furthermore, an electrochemical system is provided that includes a cathode, the gas diffusion anode of the present application, and a cell membrane disposed between the cathode and the gas diffusion anode, the cathode and the cell membrane defining a cathode liquid channel therebetween, and the gas diffusion anode and the cell membrane defining an anode liquid channel therebetween.

[0009] Furthermore, the present application also includes a method of operating the electrochemical system of the present application, the method comprising flowing a cathode liquid through the cathode liquid channel of the electrochemical system, the cathode liquid including at least water, flowing an anode liquid through the anode liquid channel of the electrochemical system, the anode liquid including a metal salt in the form of metal cations and anions, flowing hydrogen gas through the gas diffusion anode of the electrochemical system, applying a voltage between the cathode and the gas diffusion anode, whereby the hydrogen gas is converted to protons and the protons are released into the anode liquid, and metal cations moving across the cell membrane of the electrolytic cell from the anode liquid to the cathode liquid.

[0010] These and other embodiments will be further described below with reference to the drawings.

[0011] The accompanying drawings are for illustrative purposes only and are useful only for showing one example of the possible structures and operations related to the disclosed system, apparatus, and method of the present invention. These drawings do not limit any changes in shape and details that can be made without departing from the spirit and scope of the disclosed embodiments by those skilled in the art.

Brief Description of the Drawings

[0012] [Figure 1A] An example of an electrolytic cell including a conventional solid anode, which system is used to convert a metal salt to a metal hydroxide. [Figure 1B] Another example of an electrolytic cell including a gas diffusion anode, which system is also used to convert a metal salt to a hydroxide. [Figure 1C] A plot comparing the electrode potentials in the electrolytic cells of FIGS. 1A and 1B. [Figure 2A] A schematic cross-sectional view of an electrolysis system including a gas diffusion anode and other components according to some embodiments. [Figure 2B] A schematic cross-sectional view of an electrolysis system including a gas diffusion anode, a feedstock channel, and other components in addition to anolyte channels and catholyte channels according to some embodiments. [Figure 2C] A block diagram of a catholyte showing various catholyte components according to some embodiments. [Figure 2D] A block diagram of an anolyte showing various anolyte components according to some embodiments. [Figure 2E] A block diagram of a feedstock showing various feedstock components according to some embodiments. [Figure 2F] A schematic flowchart of an electrolysis system showing various connections and flow paths of flows according to some embodiments. [Figure 3A]This is a schematic cross-sectional view of a gas diffusion anode showing various components of this anode according to several embodiments. [Figure 3B] This is a schematic cross-sectional view of a gas diffusion anode in another embodiment, including an anodic liquid thin film flow structure. [Figure 3C] This is a schematic block diagram of the anode catalyst layer in a gas diffusion anode according to several examples, showing the various components of this anode catalyst layer. [Figure 3D] This is a plot of binder concentration and pore size at the thickness within the anodic porous substrate, based on several examples. [Figure 3E] This is a plot of pore diameter at height within an anode porous substrate, based on several examples. [Figure 3F] This is a plot of two pressure profiles in the height direction corresponding to different cell examples. [Figure 4] This is a process flowchart corresponding to a method for forming a gas diffusion anode, based on several examples. [Figure 5] This is a process flowchart corresponding to the operation method of an electrolytic system including a gas diffusion anode, according to several embodiments. [Figure 6] This is a schematic diagram of an electrolytic cell including the gas diffusion anode of the present application, according to an exemplary embodiment. [Figure 7] This plot shows the voltage performance of a gas diffusion anode according to an exemplary embodiment of this application, compared to a commercially available mixed metal oxide (MMO) anode. [Figure 8] This plot shows the specific energy consumption of a gas diffusion anode according to an exemplary embodiment of this application, compared to a commercially available mixed metal oxide (MMO) anode. [Figure 9] This plot shows the current efficiency of a gas diffusion anode according to an exemplary embodiment of this application, compared to a commercially available mixed metal oxide (MMO) anode. [Figure 10] This plot shows the stability of an electrode including a gas diffusion anode according to an exemplary embodiment of this application over 400 hours of operation. [Modes for carrying out the invention]

[0013] definition Unless otherwise noted, the definitions and embodiments set forth in this section and other sections are intended to be applicable to all embodiments and aspects of this application to which they are applicable, as will be understood by those skilled in the art.

[0014] As used in this application and its claims, the terms “comprising” (and all forms including “comprise” and “comprises”), “having” (and all forms including “have” and “has”), “including” (and all forms including “include” and “includes”), or “containing” (and all forms including “contain” and “contains”) are inclusive or open-ended terms and do not exclude any additional or undescribed elements or processes.

[0015] As used herein, "consisting" and its derivatives are intended as closed terms to identify the presence of described features, elements, components, groups, integers, and / or processes, and to exclude the presence of other undescribed features, elements, components, groups, integers, and / or processes.

[0016] As used herein, the term "consisting essentially of" is intended to identify the presence of any feature, element, component, group, integer and / or process described, as well as any element(s) that does not substantially affect the fundamental and novel properties of these features, elements, components, group, integer and / or processes.

[0017] As used herein, the terms “about,” “substantially,” and “approximately” refer to a reasonable degree of deviation of the word being modified, where the result does not change significantly. These degree-indicating terms should be interpreted as including a deviation of at least ±5% from the word being modified, unless the meaning of the word being modified is lost or the context suggests otherwise to a person skilled in the art.

[0018] In this application, the singular forms "a," "an," and "the" are to be used with the plural form unless the context clearly indicates otherwise. For example, an embodiment including "a component" should be understood to indicate either a form having one component or a form having two or more additional components.

[0019] In embodiments including “additional” or “second” components or effects, “second component” as used herein is different from the other components or the first component. A “third” component is different from the other components, the first component and the second component, and so are any further listed or “additional” components.

[0020] As used herein, the term "and / or" means that the listed items exist or are used individually or in combination. In effect, the term means that "at least one" or "one or more" of the listed items are used or are present.

[0021] As used herein, the term "suitable" means that the selection of a particular component or condition depends on the specific synthesis operation performed, the identification of the component to be transformed, and / or the specific use of that component, but the selection is sufficient for those skilled in the art.

[0022] The battery industry and other industries are experiencing increasing demand for various materials used in their manufacture. Traditional methods for producing these materials are energy-intensive, require significant capital expenditures, and can generate various by-products that need to be utilized. For example, one of the main waste products during the manufacture of lithium-ion battery materials is sodium sulfate (Na2SO4). While sodium sulfate is used in the manufacture of detergents, glass, and lubricants, the global market size for this material is currently around 30 MT / year, and no significant increase in demand is expected in the future. In contrast, a single large-scale battery cathode manufacturing plant can produce up to 250,000 tons / year of anhydrous sodium sulfate (as a by-product). Environmental concerns regarding the proper disposal of such large quantities of sodium sulfate are significant. At the same time, the manufacturing process of battery materials requires various chemicals such as sodium hydroxide (NaOH) and sulfuric acid (H2SO4).

[0023] Sodium sulfate (Na2SO4) can be converted, more specifically, electrochemically decomposed into sodium hydroxide (NaOH) and sulfuric acid (H2SO4). One conventional approach involves a bipolar membrane electrodialysis (BPED) process using a four-chamber electrolytic cell with three membranes: (1) an anion exchange membrane (AEM), (2) a cation exchange membrane (CEM), and a bipolar membrane (BPM). The energy efficiency of such a system is approximately 1500-2500 kWh per ton of sodium hydroxide (NaOH) produced. However, BPED cells have a relatively low current density (approximately 1000 A / m²). 2 It operates at low temperatures, requiring numerous large electrodialysis layers, which drives up capital costs. This process can only produce dilute acid and base solutions (e.g., up to about 4-10% by weight). Furthermore, AEM limits the operating temperature of the BPED system to about 40-50°C. Such low temperatures require more energy for post-processing / solution concentration. Finally, BPM membranes tend to degrade if various impurities (e.g., chlorides and heavy metals) are present in the feedstock.

[0024] Another conventional approach (shown in Figure 1A) uses a two-chamber electrolytic cell 100 comprising an anode 102 (e.g., coated with iridium oxide (IrO2)) and a cathode 110 (e.g., formed from nickel or stainless steel). One embodiment of this cell may be referred to as a DSA-O2 cell. The cell membrane 130 may be a single cation exchange membrane (CEM) and, along with high concentrations of acid and base currents (e.g., up to about 20 wt%), a higher current density (about 3000-4000 A / m²). 2 This can be achieved. The water in the cathode liquid 140 is decomposed / reduced to hydrogen gas (H2) and hydroxide anions (OH - ) The water in the anodic acid 150 is decomposed / oxidized to oxygen gas (O2) and protons (H + The anodic acid 150 also contains feedstock (shown as sodium sulfate (Na2SO4) in this embodiment) and cations (for example, Na + These cations contain protons (H + The ions are replaced into the cathode liquid 140 via the cell membrane 130. Therefore, at the outlet of the electrolytic cell 100, the cathode liquid 140 contains sodium hydroxide (NaOH) and hydrogen gas (H2), and the anode liquid 150 contains sulfuric acid (H2SO4) and oxygen gas (O2). The total theoretical voltage of this electrochemical cell (including the anode and cathode) is 2.06V (as shown in Figure 1C), which is quite high and requires a large amount of energy consumption. Furthermore, the acidic environment of the anode 102 and the basic environment of the cathode 110 can damage these electrodes, especially the anode 102.

[0025] The various problems listed above are solved by an electrolytic cell 100 including a gas diffusion anode 120 as described herein. The electrolytic cell 100 may be part of a two-channel system (having a single membrane) or a three-channel system (having two membranes). One embodiment of such an electrolytic cell 100 is shown in Figure 1B, which shows the gas diffusion anode 120 in addition to the cathode 110 and cell membrane 130. Hydrogen gas (H2) is supplied through the gas diffusion anode 120, thereby generating protons (H2). +) is generated and released into the anolyte 150. A feedstock (e.g., sodium sulfate (Na2SO4)) is introduced into the anolyte 150. For the purposes of the present disclosure, the terms “feedstock” and “metal salt” are used synonymously. Further, it should be noted that the feedstock / metal salt can be introduced into the anolyte 150 (2-channel system) and also into the feedstock solution 160 (3-channel system). Referring to the 2-channel example of FIG. 1B, sodium cations (Na + ) are displaced from the anolyte 150 by protons introduced from the gas diffusion anode 120. Specifically, these sodium cations (Na + ) move through the cell membrane 130 and into the catholyte 140. Water in the catholyte 140 is decomposed / reduced to hydrogen gas (H2) and hydroxide anions (OH - ). Thus, at the outlet of the electrolytic cell 100, the catholyte 140 contains sodium hydroxide (NaOH) and hydrogen gas (H2), and the anolyte 150 contains sulfuric acid (H2SO4).

[0026] Unlike the comparative cell described above with reference to FIG. 1A, oxygen gas (O2) is not generated in the anolyte 150 of the electrolytic cell 100 equipped with the gas diffusion anode 120. Further, the total theoretical voltage of this electrochemical cell (including the anode and cathode) is 0.83 V (as shown in FIG. 1C), which is significantly lower than that of the comparative cell, thereby reducing energy consumption. Further, these gas diffusion anode cells can be operated at temperatures of 75° C. or higher, which is approximately 50% higher than the temperature of the comparative cell. The high temperature aids in increasing various concentrations (e.g., metal hydroxide concentration) in the post-treatment process. Further, operation at high temperature also improves the reaction kinetics of the electrolysis process and reduces the required operating potential. For every 10° C. increase in the operating temperature, approximately 0.1 - 0.3 V can be reduced from the operating voltage.

[0027] One of the challenges in gas diffusion anode cells is controlling / limiting / blocking the movement of anolyte through the gas diffusion anode in such cells. Various characteristics of gas diffusion anodes are utilized to eliminate or at least reduce this potential anolyte movement, which may also be referred to as anolyte flooding (the phenomenon in which a large amount of anolyte passes through the anode and interferes with its operation). Some of these characteristics include the porosity and hydrophobicity of various layers, as well as the distribution of these properties over thickness and / or height.

[0028] Furthermore, uniform distribution of hydrogen to the catalyst site is crucial for efficient cell operation, and this is achieved through various features of the gas diffusion anode. For example, a gas diffusion anode includes an anode gas chamber, a current collector, an anode porous substrate, an anode catalyst layer, and an anode-liquid interface layer. During operation, the anode gas chamber receives hydrogen gas, which flows through the current collector into the anode porous substrate. The anode porous substrate provides a uniform distribution of hydrogen gas and a uniform current density. The anode catalyst layer converts the hydrogen gas into protons, returning electrons to the current collector via the anode porous substrate. The protons are transported to the anolyte by the anode-liquid interface layer. The anode porous substrate, anode catalyst layer, and anode-liquid interface layer help prevent the anolyte from migrating into the anode gas chamber.

[0029] Because the reaction kinetics of the hydrogen oxidation reaction are easy, a small amount of platinum catalyst (0.2-1 mg / cm³) is used. 2 Or 0.05-2 mg / cm³ 2 ) allows for a maximum of 10 kA / m 2 It should be noted that high current densities can be achieved. Furthermore, hydrogen gas is produced at the cathode in stoichiometrically equal proportions.

[0030] Accordingly, this application includes a gas diffusion anode, the gas diffusion anode comprising: a current collector comprising a conductive mesh; an anode porous substrate disposed adjacent to the current collector and comprising a porous electronically conductive structure; an anode catalyst layer disposed adjacent to the anode porous substrate and comprising a conductive filler, a binder and a catalyst, having a different average porosity from the anode porous substrate and disposed adjacent to the anode porous substrate so as to be disposed between the anode porous substrate and an anode-liquid interface layer; and an anode-liquid interface layer disposed adjacent to the anode catalyst layer so as to be disposed between the anode porous substrate and an anode-liquid interface layer and comprising an ionomer coating configured to conduct protons through a porous polymer substrate and an anode-liquid interface layer.

[0031] This application also includes a gas diffusion anode for use in an electrochemical cell, the gas diffusion anode comprising: an anode gas chamber; a current collector disposed adjacent to the anode gas chamber so as to be positioned between the anode gas chamber and the anode porous substrate, the current collector comprising a conductive mesh; an anode porous substrate disposed adjacent to the current collector, the anode porous substrate comprising a porous electronically conductive structure; an anode catalyst layer disposed adjacent to the anode porous substrate, comprising a conductive filler, a binder and a catalyst, having a different average porosity from the anode porous substrate, and disposed adjacent to the anode porous substrate so as to be positioned between the anode porous substrate and the anode-liquid interface layer; and an anode-liquid interface layer disposed adjacent to the anode catalyst layer so as to be positioned between the anode porous substrate and the anode-liquid interface layer, the anode-liquid interface layer comprising a porous polymer substrate and an ionomer coating configured to conduct protons through the anode-liquid interface layer.

[0032] In some embodiments, the anode-liquid interface layer includes an exposed anode-liquid side outer surface.

[0033] In some embodiments, the gas diffusion anode further includes an anodic liquid thin film flow structure positioned adjacent to the anodic liquid interface layer such that the anodic liquid interface layer is located between the anodic catalyst layer and the anodic liquid thin film flow structure. In some embodiments, the thin film flow structure is a 3D mesh structure with a very high degree of opening that controls the flow of the anodic liquid. In other words, those skilled in the art will understand that “thin film flow” refers to a controlled flow. In some embodiments, the anodic liquid interface layer includes a 3D shape printed directly on the anodic liquid interface layer.

[0034] In some embodiments, the conductive mesh is formed from a metal or metal alloy. In some embodiments, the conductive mesh is formed from titanium, high-alloy stainless steel (e.g., 2205, 2507, 904L, alloy 28), stainless steel (e.g., 316L, 304L), Hastelloy alloys (B, B-2, C and D series), high-Si iron, lead, tantalum, zirconium, or titanium carbide. In some embodiments, the conductive mesh is formed from a conductive carbon substrate, such as braided carbon fiber, felt, or foam.

[0035] In some embodiments, the conductive mesh is coated with a conductive material such as graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, titanium carbide, diamond-like carbon, silicon carbide, titanium carbide, gold, platinum, iridium, or a combination thereof. In some embodiments, the conductive mesh is coated with a conductive carbon material, i.e., a carbon-containing material. In some embodiments, the conductive carbon material is graphene, carbon black, carbon nanotubes, diamond-like carbon, silicon carbide, titanium carbide, or a combination thereof.

[0036] In some embodiments, the conductive mesh has an average mesh opening size of about 0.1 mm to about 5 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 1 mm to about 2 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 1.2 mm to about 1.6 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 0.5 mm to about 1 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 2 mm to about 3.6 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 3.6 mm to about 5 mm. In some embodiments, the conductive mesh has an average mesh opening size of about 0.5 mm to about 2.5 mm, or about 0.5 mm to about 1.5 mm, or about 0.1 mm to about 0.25 mm.

[0037] In some embodiments, the wire forming the conductive mesh has a thickness of about 0.1 mm to about 4 mm. In some embodiments, the wire forming the conductive mesh has a thickness of about 0.1 mm to about 0.25 mm. In some embodiments, the wire forming the conductive mesh has a thickness of about 0.25 mm to about 0.5 mm. In some embodiments, the wire forming the conductive mesh has a thickness of about 0.5 mm to about 1 mm. In some embodiments, the wire forming the conductive mesh has a thickness of about 1 mm to about 2 mm. In some embodiments, the wire forming the conductive mesh has a thickness of about 2 mm to about 4 mm.

[0038] In some embodiments, the anodic porous substrate has a variable porosity across the thickness and / or cell height of the anodic porous substrate. In some embodiments, the varying porosity ranges from about 20% to about 90%. In some embodiments, the maximum porosity is about 55% to about 90%, or about 65% to about 85%, or about 75% to about 90%. In some embodiments, the minimum porosity is about 20% to about 35%, or about 35% to about 55%, or about 20% to about 45%.

[0039] In some embodiments, the anodic porous substrate has a thickness of about 100 μm to about 700 μm. In some embodiments, the anodic porous substrate has a thickness of about 200 μm to about 400 μm. In some embodiments, the anodic porous substrate has a thickness of about 250 μm to about 350 μm. In some embodiments, the anodic porous substrate has a thickness of about 350 μm to about 700 μm.

[0040] In some embodiments, the anode porous substrate is formed from a polymer and a carbon material. In some embodiments, the anode porous substrate is formed from about 20% to about 60% by weight of polymer and about 40% to about 80% by weight of carbon material. In some embodiments, the anode porous substrate is formed from about 25% to about 55% by weight of polymer and about 45% to about 75% by weight of carbon material. In some embodiments, the anode porous substrate is formed from about 30% to about 50% by weight of polymer and about 50% to about 70% by weight of carbon material.

[0041] In some embodiments, the polymer is polytetrafluoroethylene (PTFE), such as PTFE wax, PTFE fibers or PTFE paste, polyvinylidene fluoride (PVDF), or a combination thereof. In some embodiments, the carbon material is graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, graphene, titanium carbide, or a combination thereof.

[0042] In some embodiments, the anode porous substrate is configured to (a) be electrically conductive, (b) permeable to gases, particularly hydrogen, and (c) impermeable to electrolytes.

[0043] In some embodiments, the anodic catalyst layer further includes a structural conductive support. In some embodiments, the conductive support is formed of carbon particles configured to receive precipitates of the noble metal catalyst.

[0044] In some embodiments, the catalyst is a material having catalytic properties for the oxidation of hydrogen, and these include carbon-supported platinum (Pt-C), platinum black, iridium oxide, nickel, palladium, rhodium, ruthenium, and Ti (general formula). (n) O (2n-1) This includes, but is not limited to, titanium oxides or combinations thereof.

[0045] In some embodiments, the conductive filler is graphite powder, carbon black, mesocarbon microbeads, activated carbon, graphene, carbon nanotubes, diamond-like carbon, silicon carbide, titanium carbide, or a combination thereof.

[0046] In some embodiments, the binder is polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PTFE wax, PTFE fiber, PTFE paste, or a combination thereof.

[0047] In some embodiments, the anode catalyst layer has a thickness of about 1 μm to about 75 μm. In some embodiments, the anode catalyst layer has a thickness of about 2 μm to about 25 μm. In some embodiments, the anode catalyst layer has a thickness of about 10 μm to about 45 μm. In some embodiments, the anode catalyst layer has a thickness of about 35 μm to about 75 μm.

[0048] In some embodiments, the anode-liquid interface layer has a thickness of about 100 μm to about 600 μm. In some embodiments, the anode-liquid interface layer has a thickness of about 200 μm to about 350 μm. In some embodiments, the anode-liquid interface layer has a thickness of about 220 μm to about 320 μm. In some embodiments, the anode-liquid interface layer has a thickness of about 250 μm to about 300 μm. In some embodiments, the anode-liquid interface layer has a thickness of about 350 μm to about 500 μm. In some embodiments, the anode-liquid interface layer has a thickness of about 450 μm to about 600 μm.

[0049] In some embodiments, the porous polymer substrate includes polyethylene (PE), polypropylene (PP), PTFE, PVDF, PBI (polybenzimidazole), sulfonated tetrafluoroethylene-based fluoropolymer copolymers (Nafion®), or combinations thereof.

[0050] In some embodiments, the ionomer coating comprises perfluorosulfonic acid (PFSA), sulfonated tetrafluoroethylene-based fluoropolymer copolymer (Nafion®), sulfuric acid-doped s-PBI (polybenzimidazole) polymer, sulfonated s-PBI (polybenzimidazole) polymer, or a combination thereof.

[0051] In some embodiments, the ionomer coating has a thickness of about 1 μm to about 100 μm. In some embodiments, the ionomer coating has a thickness of about 2 μm to about 15 μm. In some embodiments, the ionomer coating has a thickness of about 10 μm to about 50 μm. In some embodiments, the ionomer coating has a thickness of about 20 μm to about 40 μm. In some embodiments, the ionomer coating has a thickness of about 60 μm to about 80 μm.

[0052] In some embodiments, the operating voltage of a unit electrochemical cell including the gas diffusion anode of this application is 70°C and 4000 A / m 2 The voltage is approximately 1.2V to 4.2V. In some embodiments, the operating voltage is 70°C and 4000A / m 2 The voltage is approximately 1.5V to 2.8V. In some embodiments, the operating voltage is 70°C and 4000A / m 2 The voltage is approximately 2.0V to 3.2V. In some embodiments, the operating voltage is 70°C and 4000A / m 2 The voltage is approximately 2.2V to 3.8V.

[0053] In some embodiments, the specific energy consumption is 70°C and 4000 A / m 2In this case, the specific energy consumption is approximately 1200 kWh / ton of Na2SO4 to approximately 5000 kWh / ton of Na2SO4. In some embodiments, the specific energy consumption is 70°C and 4000 A / m 2 In this case, the specific energy consumption is approximately 1500 kWh / ton of Na2SO4 to approximately 3500 kWh / ton of Na2SO4. In some embodiments, the specific energy consumption is 70°C and 4000 A / m 2 In this case, the amount of Na2SO4 ranges from approximately 1800 kWh / ton to approximately 4500 kWh / ton.

[0054] In some embodiments, the current efficiency for a conversion rate of 0-60% is 70°C and 4000 A / m 2 The efficiency is approximately 70% to 98%. In some embodiments, the current efficiency for a conversion rate of 0-60% is 70°C and 4000 A / m 2 The efficiency is approximately 80% to 98%. In some embodiments, the current efficiency for a conversion rate of 0-50% is 70°C and 4000 A / m 2 The efficiency is approximately 65% ​​to 80%. In some embodiments, the current efficiency for a conversion rate of 0-50% is 70°C and 4000 A / m 2 The percentage is approximately 85% to 98%.

[0055] Furthermore, an electrochemical system is also provided, comprising a cathode, a gas diffusion anode of the present application, and a cell membrane disposed between the cathode and the gas diffusion anode, wherein the cathode and the cell membrane define a cathodelime channel between them, and the gas diffusion anode and the cell membrane define an anolime channel between them.

[0056] Furthermore, the present application also includes a method for operating the electrochemical system of the present application, the method comprising: flowing a cathodelime into a cathodelime channel of the electrochemical system, wherein the cathodelime contains at least water; flowing an anodelime into an anodelime channel of the electrochemical system, wherein the anodelime contains metal salts in the form of metal cations and anions; flowing hydrogen gas into a gas diffusion anode of the electrochemical system; applying a voltage between the cathode and the gas diffusion anode, thereby converting the hydrogen gas into protons, which are released into the anodelime; and moving metal cations across the cell membrane of the electrolytic cell from the anodelime to the cathodelime.

[0057] Figures 2A-2F - Examples of Electrolytic Systems Figure 2A is a schematic diagram of an electrolytic system 200 according to several embodiments. This type of system is sometimes referred to as a two-channel system to distinguish it from the three-channel system shown in Figure 2B and described below. However, many of the components of the two-channel and three-channel systems are identical.

[0058] Referring to Figure 2A, the electrolysis system 200 includes an electrolytic cell 100, a power supply 210, a cathode liquid recovery device 220, an anode liquid recovery device 230, and a hydrogen supply device 240. As previously mentioned, the electrolytic cell 100 includes a cathode 110, a gas diffusion anode 120, and a cell membrane 130 disposed between the cathode 110 and the gas diffusion anode 120.

[0059] The cathode 110 may be formed from stainless steel (e.g., 316, 316L) or a nickel alloy (e.g., Hastelloy). The cathode 110 may be in the form of one or more plates, meshes, and / or expanded metal forms. In some embodiments, a gap between the cathode 110 and the cell membrane 130 (sometimes referred to as a cathode liquid channel 104) is used to allow hydrogen gas bubbles to escape from the electrolytic cell 100. Alternatively, the cathode 110 may be in direct contact with the cell membrane 130, for example, to reduce the overall resistance of the electrolytic cell 100. For example, a gap behind the cathode 110 (opposite the cell membrane 130) may be used to accumulate gas bubbles away from the membrane / cathode interface. In some embodiments, the cathode 110 is porous (for example, formed using powder processing and by adjusting the water repellency of the layer over its thickness). Some structural features of the cathode 110 may be similar to those of the gas diffusion anode 120 (described later). In these embodiments, instead of generating hydrogen gas as a secondary phase within the cathode liquid channel 104, the hydrogen gas may be generated directly within a gas chamber in contact with the "back surface" of the cathode 110.

[0060] The cell membrane 130 may be referred to as a primary membrane to distinguish it from the various membrane structures of the gas diffusion anode 120. The cell membrane 130 may also be referred to as a cation exchange membrane (CEM), more specifically a cation selective membrane (e.g., NAFION® 424, NAFION® 324, NAFION® 2030, NAFION® 2050 (The Chemours Company, Wilmington, Delaware)). For example, the cell membrane 130 may be a proton selective membrane, and may be a bilayer membrane having (1) a high conductivity / low equivalent weight (EW) ionomer composition on the anolyte side and (2) a hydroxide-blocking, low water absorption, low conductivity ionomer coating on the cathode side. A secondary layer can be used on the cathode side to block hydroxide ions, which is configured to be formed from a high EW ionomer (1400-1600 EW) (e.g., N424, N324) or a carboxylic acid layer (N2030 and N2050). This blocking ability can be used in the aforementioned applications because acids and bases are generated on the opposite side of the membrane (e.g., in a two-chamber design). Neutralization can occur when hydroxides begin to move from the cathode 140 to the anode 150 through the cell membrane 130, resulting in a significant and undesirable decrease in the process's current efficiency. The cell membrane 130 can allow various cations to pass through, such as sodium cations, lithium cations, potassium cations, and hydrogen cation / protons. In some embodiments, the cell membrane 130 is reinforced with woven polytetrafluoroethylene (PTFE) yarn or a 3D printed inflatable mesh to provide better structural stability to the membrane and to facilitate the removal of turbulence and gas bubbles. In some examples, the cell film 130 is temperature-stable at temperatures below 80°C, below 90°C, and even below 100°C.

[0061] Referring to Figure 2A, in some embodiments, the electrolytic cell 100 also includes a cathodelime channel 104 and an anodelime channel 105. The cathodelime channel 104 is located between the cathode 110 and the cell membrane 130 and is used to flow the cathodelime 140 into the electrolytic cell 100. As previously mentioned, the cathodelime channel 104 may be used to remove hydrogen gas and metals from the electrolytic cell 100. The cathodelime channel 104 may also be used to supply water to the electrolytic cell 100. The anodelime channel 105 is located between the gas diffusion anode 120 and the cell membrane 130 and is used to flow the anodelime 150 into the electrolytic cell 100 (for example, to supply raw material / metal salts to the cathodelime channel 104 and remove acid from the cathodelime channel 104, which may be used to remove hydrogen gas and metals from the electrolytic cell 100). As shown in Figure 2A, the cell membrane 130 can separate the cathodelime channel 104 and the anodic membrane channel 105, for example, in a two-channel system. A two-channel system can also be referred to as a single-membrane system.

[0062] Figure 2B shows an embodiment of a three-channel system in which the electrolytic cell 100 includes an additional membrane 132 and a feedstock channel 106. The feedstock channel 106 is located between the cell membrane 130 and the additional membrane 132. Specifically, the additional membrane 132 is located between the feedstock channel 106 and the cathodelime channel 104, while the cell membrane 130 is located between the feedstock channel 106 and the anodelime channel 105. In the three-channel system, the feedstock channel 106 is used to flow the feedstock solution 160 into the electrolytic cell 100. In this system, the feedstock / metal salt may be supplied as part of the feedstock solution 160 rather than the anodelime 150 (as in the two-channel system).

[0063] The catholyte recovery device 220 is used to process the catholyte 140 after it has been discharged from the electrolytic cell 100, and this may also be referred to as processed / spent catholyte. For example, the catholyte recovery device 220 is used to remove metal hydroxides and / or hydrogen gas from spent catholyte. The catholyte recovery device 220 may also be used to introduce more water (for example, to replenish any water that has been consumed). In some embodiments, the catholyte recovery device 220 is used to control the temperature of the catholyte 140, for example, to heat the catholyte 140 to a desired processing temperature.

[0064] The anode recovery device 230 is used to process the anode 150 after it has been discharged from the electrolytic cell 100, and this anode 150 may also be referred to as processed / used cathode. For example, the anode recovery device 230 may remove acids (e.g., sulfuric acid, hydrochloric acid) from the anode 150 and introduce metal salts (e.g., in the form of brine). In some embodiments, the anode recovery device 230 is used to control the temperature of the anode 150, for example, to heat the anode 150 to a desired processing temperature.

[0065] The hydrogen supply device 240 is directly fluid-connected to the gas diffusion anode 120 and is used to introduce hydrogen gas into the gas diffusion anode 120. As will be further described below, this hydrogen gas passes through the gas diffusion anode 120 and is converted into protons which are introduced into the anodic acid 150. The hydrogen supply device 240 can be configured to supply hydrogen gas at a set pressure, which is determined by the configuration of the gas diffusion anode 120. Furthermore, the hydrogen supply device 240 can be configured to supply hydrogen gas at a set flow rate, which is also determined by the configuration of the gas diffusion anode 120 and the processing speed of the electrolytic cell 100 (e.g., the current flowing through the electrolytic cell 100). The hydrogen source for the hydrogen supply device may be recovered hydrogen gas generated at the cathode of the same electrochemical cell.

[0066] Referring to Figure 2C, the inflow of the cathode liquid 140 contains water 144 from the cathode liquid side. Other components in the inflow may be metal hydroxide 142 and / or hydrogen gas 146 (e.g., retained in the cathode liquid 140 as it circulates within the electrolytic cell 100). To maintain a constant concentration of various cathode liquid components (e.g., the concentration of metal hydroxide 142) and prevent the system voltage from rising over time, a monitoring system is implemented in the cathode liquid flow and adds the required amount of water 144 from the cathode liquid side (e.g., deionized (DI) water) to the cathode liquid 140 to maintain a constant concentration of various components. This means that the volume of the cathode liquid 140 increases as it passes through the electrolytic cell 100 over time / multiple times. This excess cathode liquid 140 (in the form of caustic solution) can be continuously removed as a product. This method may be referred to as a "feed-and-bleed" method / system / process. The concentration of metal hydroxide 142 in the outflow stream of the cathode liquid 140 can be maintained at 5–30% by weight, for example, below the maximum solubility of metal hydroxide 142 in water (e.g., 1M–9M). In some embodiments, metal hydroxide 142 (or other optional conductive additive) is added to the cathode liquid 140 to increase its conductivity. Hydrogen gas 146 can be removed from the cathode liquid 140 using gas-liquid separation, for example, within a cathode liquid recovery device 220 in addition to supplying water 144 on the cathode liquid side and removing metal hydroxide 142 (e.g., a portion of the cathode liquid 140).

[0067] Alternatively, those skilled in the art will understand that a "feed-and-bleed" method / system / process can be applied to an anodeliquid flow, and that the flow described above is integrated on the anodeliquid flow. In this way, the total salt concentration of the anodeliquid flow can be kept constant by continuously adding water. During operation, continuous acidification occurs in the anodeliquid flow, so it is also necessary to continuously add sodium sulfate in order to keep the molar ratio of acid to salt below 60%.

[0068] Referring to Figure 2D, in some embodiments, the anodelite 150 contains metal salts 152 (e.g., sodium sulfate (Na2SO4), lithium sulfate (Li2SO4), sodium chloride (NaCl), lithium chloride (LiCl), potassium chloride (KCl), potassium sulfate (K2SO4), and sodium acetate (CH3COONa)). The concentration of metal salts 152 in the anodelite 150 can be 5-25% by weight or 5-75% by weight, and may be, for example, below the maximum solubility limit of the metal salt in water at the applicable processing temperature (e.g., 2M-4.5M or 2M-10M). Higher salt concentrations result in higher conductivity in the system, consequently lowering the operating potential. Also, higher salt concentrations simplify the various post-treatment operations performed on the anodelite 150. Higher salt concentrations require less water 154 on the anodelite side, reducing the total volume of the anodelite 150, and consequently lowering flow rate and pump requirements. It should be noted that during the operation of the electrolytic system 200, the composition of the anolyte 150 and cathode 140 changes in the electrolytic cell 100, the cathode recovery device 220, and the anolyte recovery device 230. For the purposes of this disclosure, unless otherwise stated, all references to the composition of the anolyte 150 and cathode 140 are made in the context of the inflow delivered to the electrolytic cell 100.

[0069] Referring to Figure 2E, in some embodiments (where the electrolytic cell 100 includes a feedstock channel 106), the feedstock solution 160 contains the feedstock metal salt 162 and the feedstock water 164 at both the inlet and outlet sides. In this embodiment, the anode 150 may or may not contain the metal salt 152 (for example, the metal salt 152 may be present in the anode 150 to ensure conductivity). The composition of the feedstock solution 160 and other embodiments will be understood by those skilled in the art from the above-described descriptions of the cathode 140 and anode 150.

[0070] Figure 2F is a schematic flowchart of the electrolytic system 200 showing various connections and flow paths in several embodiments. Several embodiments of the electrolytic system 200 are described above with reference to Figure 2A.

[0071] Figures 3A-3F: Examples of gas diffusion anodes Referring to Figure 3A, in some embodiments, the gas diffusion anode 120 includes an anode gas chamber 170, a current collector 124, a porous anode substrate 126, an anode catalyst layer 180, and an anode-liquid interface layer 190. The current collector 124 is located adjacent to the anode gas chamber 170. The porous anode substrate 126 is located adjacent to the current collector 124. Specifically, the current collector 124 is located between the anode gas chamber 170 and the porous anode substrate 126. The anode catalyst layer 180 is located adjacent to the porous anode substrate 126. Specifically, the anode catalyst layer 180 is located between the porous anode substrate 126 and the anode-liquid interface layer 190. The anode-liquid interface layer 190 is located adjacent to the anode catalyst layer 180. In some embodiments, the anode-liquid interface layer 190 is one of the outer structures of the gas diffusion anode 120. Specifically, the anode-liquid interface layer 190 forms the exposed anode-liquid side outer surface 122.

[0072] Referring to Figure 3B, in some embodiments, the gas diffusion anode 120 includes an anolyte thin film flow structure 195 positioned adjacent to the anode-liquid interface layer 190. Specifically, the anode-liquid interface layer 190 is positioned between the anode catalyst layer 180 and the anolyte thin film flow structure 195. In these embodiments, the anolyte thin film flow structure 195 is the outer structure of the gas diffusion anode 120. Specifically, the anolyte thin film flow structure 195 forms the exposed anolyte-side outer surface 122. Additional features of the anolyte thin film flow structure 195 are described below.

[0073] The anode gas chamber 170 is a chamber for supplying hydrogen gas. The anode gas chamber 170 may be filled with current collectors 124 (e.g., multiple metal current collectors of different sizes) to provide electrical contact between the gas diffusion anode 120 and the power supply 210 (e.g., a voltage-transmitting contactor plate connecting the gas diffusion anode 120 and the power supply 210). In some embodiments, the anode gas chamber 170 includes a hydrogen receiving gas inlet 172 (fluidically connected to the hydrogen supply device 240). In some embodiments, the anode gas chamber 170 includes a liquid outlet 174 for removing any liquid passing through the gas diffusion anode 120. The various layers of the gas diffusion anode 120 are configured to prevent liquid (e.g., anodeliquid 150) from flowing into the anode gas chamber 170, but some liquid may still pass through. This liquid can be collected by gravity at the bottom of the anode gas chamber 170 and removed through the liquid outlet 174.

[0074] In some embodiments, the current collector 124 includes a metal or conductive mesh. The current collector 124 allows hydrogen gas to pass from the anode gas chamber 170 to the anode porous substrate 126. In some embodiments, the current collector 124 also provides a mechanical support function, for example, to support other components of the gas diffusion anode 120. In some embodiments, the current collector 124 has a multilayer structure, for example, multiple metal or conductive current collectors of different sizes forming a laminate.

[0075] In some embodiments, the anode porous substrate 126 is a porous, electron-conductive structure. The anode porous substrate 126 ensures uniform distribution of hydrogen gas to the anode catalyst layer 180 and provides electron conductivity (uniform current density) between the anode catalyst layer 180 and the current collector 124. For example, the anode porous substrate 126 may be an open-cell metal foam or a similar structure. In some embodiments, the anode porous substrate 126 has a variable porosity over its thickness (e.g., a higher porosity on the current collector side and a lower porosity on the catalyst layer side). In some embodiments, the anode porous substrate 126 has a variable pore size over its thickness (e.g., a larger pore size (porosity) on the current collector side and a smaller pore size on the catalyst layer side).

[0076] In some embodiments, the average porosity of the anode porous substrate 126 may be 60% to 85% or 20% to 90%. In some embodiments, the porosity of the anode porous substrate 126 varies with respect to its thickness and / or height. For example, the porosity may decrease from the side of the anode porous substrate 126 facing the current collector to the side facing the catalyst layer. In some embodiments, the pore size may decrease from the side of the anode porous substrate 126 facing the current collector to the side facing the catalyst layer. In some embodiments, the pore size may decrease from the top to the bottom of the anode porous substrate 126, for example, as schematically shown in Figure 3E. The top and bottom are defined by the height of the anode porous substrate 126 corresponding to the vertical in the direction of gravity. In some embodiments, the porosity decreases from the top to the bottom of the anode porous substrate 126.

[0077] Referring to Figure 3C, in some embodiments, the anode catalyst layer 180 comprises a conductive filler 182, a binder 184, and / or a catalyst 186. Some examples of materials suitable for the conductive filler 182 include, but are not limited to, graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, graphene, titanium carbide, or combinations thereof. Furthermore, powders and fibers of conductive oxides of stainless steel (e.g., 316, 316L), titanium, nickel, and other metals may also be used. These materials are conductive and chemically stable under the anode potential of the hydrogen evolution reaction (HER) (e.g., -0.5V to 1V relative to a standard hydrogen reference electrode). The proportion of conductive filler 182 in the anode catalyst layer 180 may be 50% to 98% by weight, or more specifically, 75% to 95% by weight.

[0078] Some examples of materials suitable for catalyst 186 include, but are not limited to, carbon-supported platinum (Pt-C), platinum black, iridium oxide, nickel, palladium, rhodium, ruthenium, and Ti (general formula). (n) O (2n-1) Examples include titanium oxides represented by , or combinations thereof, and other HOR catalysts. Catalyst 186 may be in the form of particles with a particle size in the range of 8 to 500 nanometers. If catalyst particles are supported on other structures, the size of these catalyst particles may be 2 to 8 micrometers. Due to their small size, catalyst particles tend to aggregate over time, causing a loss of active area. Therefore, in some embodiments, these particles are stabilized (e.g., attached) on a secondary structure (e.g., carbon particles) to maintain their small size for longer periods. In this embodiment, platinum (Pt) catalyst particles are in the nanometer range, and larger carbon particles are in the micrometer range. The proportion of catalyst 186 in the anode catalyst layer 180 (this may be referred to as the catalyst load) may be in the range of 0.1% to 5% by weight.

[0079] In some embodiments, the anode catalyst layer 180 has a lower average porosity than the anode porous substrate 126. For example, the average porosity of the anode catalyst layer 180 may be in the range of 85% to 98%, or 5% to 60%. In some embodiments, the porosity of the anode catalyst layer 180 varies over its thickness and / or height, as schematically shown in Figure 3D, for example. For example, the porosity may decrease from the side of the anode catalyst layer 180 facing the porous substrate towards the side facing the liquid interface layer. In some embodiments, the pore size may decrease from the side of the anode catalyst layer 180 facing the porous substrate towards the side facing the liquid interface layer. In some embodiments, the pore size may decrease from the top to the bottom of the anode catalyst layer 180. Similar to the anode porous substrate 126 (above), the top and bottom are defined by the height of the anode catalyst layer 180 corresponding to the direction of gravity. In some embodiments, the porosity decreases from the top to the bottom of the anode catalyst layer 180. Another variability may be due to water repellency, for example, the water repellency may increase from the side of the anode catalyst layer 180 facing the porous substrate to the side facing the liquid interface layer. In some embodiments, the water repellency is determined by the concentration of the binder 184 in the anode catalyst layer 180, for example, the concentration of the binder 184 may increase from the side of the anode catalyst layer 180 facing the porous substrate to the side facing the liquid interface layer.

[0080] Some examples of materials suitable for the anode-liquid interface layer 190 include, but are not limited to, PTFE and NAFION ionomers (EW1100-1800). The anode-liquid interface layer 190 should be able to withstand temperatures of 80°C or less, 100°C or less, and even 120°C or less. In some examples, the anode-liquid interface layer 190 has low water transportability (e.g., given by porosity and / or hydrophobicity). In some examples, the anode-liquid interface layer 190 has high proton conductivity (e.g., given by its composition).

[0081] In some embodiments, the anode-liquid interface layer 190 comprises a porous polymer substrate and an ionomer coating, configured to conduct protons through the anode-liquid interface layer 190. Some examples of materials suitable for the porous polymer substrate include, but are not limited to, polypropylene (PP), polyethylene (PE), or polyvinylidene fluoride (PVDF), PBI (polybenzimidazole), Nafion®, and / or polytetrafluoroethylene (PTFE). Some examples of materials suitable for the porous ionomer coating include, but are not limited to, NAFION®-based ionomers (e.g., EW800-1600), sulfuric acid-doped PBI (polybenzimidazole) polymers, and sulfonated s-PBI (s-polybenzimidazole). Depending on the application, other long-chain and short-chain proton-conducting ionomers may be used.

[0082] Overall, the gas diffusion anode 120 employs a multilayer approach to generate different hydrophobic properties on the gas side (i.e., within the anode gas chamber 170) and the liquid side (e.g., the anode liquid channel 105 and / or the anode liquid thin film flow structure 195). For example, the gas side (e.g., the anode porous substrate 126) is significantly more hydrophobic than the liquid side (e.g., the anode-liquid interface layer 190), preventing the anode liquid 150 from moving to the gas side. Furthermore, this variation in hydrophobicity can exist within the same component (e.g., the anode porous substrate 126 and / or the anode-liquid interface layer 190) and can vary along the thickness (i.e., the X direction in Figures 3A and 3B) and / or height (i.e., the Y direction in Figures 3A and 3B). For example, variations in water repellency can be achieved by using different ratios of water-repellency enhancing materials (e.g., polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silane). For instance, the amount of PTFE on the gas side can be as high as 5-10% or 5-50% by weight relative to the total weight of the anode porous substrate 126, while the PTFE ratio on the electrolyte side can be approximately 0.5-4% by weight.

[0083] The water repellency of two opposing surfaces can be measured using a contact angle measurement test on both sides. Alternatively, the gas diffusion anode 120 is exposed to a liquid / gas cell and pressurized until the liquid enters the electrode, and the pressure difference is measured. A pressure difference of at least 150–300 mBar or 100–500 mBar should not cause any penetration of the liquid into the pores.

[0084] In some embodiments, the gas diffusion anode 120 has hydrodynamic stability corresponding to the pressure difference between the gas side and the liquid side, at least 100 mBar, more precisely at least 150 mBar, for example, 250 mBar or less, and even 300 mBar or 500 mBar or less. In other words, the anolyte 150 can apply this pressure to the liquid side of the gas diffusion anode 120 without leaking to the gas side. This hydrodynamic stability is achieved using a combination of porous and hydrophobic properties of different components of the gas diffusion anode 120, which are described above in relation to specific components.

[0085] In some embodiments, the gas diffusion anode 120 is configured to withstand temperatures below 90°C, e.g., 60-75°C, 78-84°C, or 85-88°C, or below 100°C, e.g., 60-75°C, 76-84°C, 85-88°C, or 85-98°C. It should be noted that the anolyte 150 is maintained at a temperature of at least 50°C (e.g., 70-85°C) to ensure high kinetic and mass transfer levels. All materials should have a melting / softening temperature higher than the desired operating temperature, and the catalyst should not dissolve in the anolyte over time.

[0086] In some embodiments, the gas diffusion anode 120 has a current density of 6000 A / m². 2 It is configured to maintain stable operation at the following frequencies, most likely 4000-5500 A / m 2 Or 3000-5500 A / m 2This range is based on the surface area of ​​the gas diffusion anode 120. Note that the current density corresponds to the generation rate of the electrolysis system 200.

[0087] Referring to Figure 3F, in some embodiments, the pressure exerted by the anolyte 150 on the gas diffusion anode 120 is limited to the weight of the anolyte 150 (effectively eliminating any pump pressure / hydrodynamic pressure). This pressure control can be achieved by using an "open cell" design, which is sometimes referred to as "thin-film flow electrolysis." In these embodiments, the anolyte 150 flows over the gas diffusion anode 120 with the help of gravity (rather than pressurized pumping). In some embodiments, the electrode angles within the electrolytic cell may be substantially parallel to the direction of gravity. In some cases, the electrolytic cell 100 can be operated at angles of 45° or less with respect to the direction of gravity, more specifically 30-45°. Furthermore, in these embodiments, an anode-liquid interface layer 190 may or may not be required. The anolyte thin-film flow structure 195 can be coated directly onto the anode catalyst layer 180.

[0088] In this "open" cell design, control of mass transport of chemical species can be used to maintain a high current density. To achieve this, thin-film flow-type fabric materials are used to facilitate mass transport and regulate the hydrodynamic pressure of the liquid electrolyte flow. This fabric material may consist of knitted or woven patterned fibers with controlled hydrophobicity and liquid absorption. The material may be fluorinated polymers such as TEFLON®, PVDF, polyvinyl chloride (PVC), and ethylene propylene diene monomer (EPDM), as well as other chemical-resistant polymers. Furthermore, thin-film flow structures can be printed directly onto the anode-liquid interface layer as 3D structures and geometric patterns.

[0089] Figure 3B - Example of anode thin film flow In some embodiments, the gas diffusion anode 120 includes an anodic acid thin film flow structure 195 to prevent flooding of the gas chamber of the gas diffusion anode 120, and more specifically, to prevent the anodic acid 150 from flowing into the gas chamber from the anodic acid side of the gas diffusion anode 120. This flood prevention may also be referred to as the hydrodynamic stability of the gas diffusion anode 120. For example, adjusting the water repellency of the anode-liquid interface layer 190 and the porous anode substrate 126, and / or other components of the gas diffusion anode 120, may not be sufficient to prevent the anodic acid 150 from penetrating into the pores of the anode-liquid interface layer 190.

[0090] In some embodiments, an anolyte thin film flow structure 195 can be placed on the anode-liquid interface layer 190. The anolyte thin film flow structure 195 may be a porous structure formed from polypropylene (PP), and / or polyethylene (PE), polyvinylidene fluoride (PVDF), PBI (polybenzimidazole), Nafion (trademark), and / or polytetrafluoroethylene (PTFE). The pore size may be in the range of 50 to 200 nanometers or 40 to 500 nanometers. In more specific embodiments, the anolyte thin film flow structure 195 includes an ionomer coating, which is applied to the porous structure to create a protective barrier between the anode-liquid interface layer 190 and the anolyte 150. The ionomer coating may include a proton-conducting fluoropolymer (e.g., NAFION® type material), thereby enabling the transport of protons from the anode-liquid interface layer 190 to the anosolite 150, creating additional hydrodynamic resistance to the anosolite 150 and preventing the anosolite 150 from entering the gas chamber.

[0091] Even with the presence of the anodic liquid thin film flow structure 195 and / or the anodic-liquid interface layer 190, the hydrodynamic pressure of the anodic liquid 150 may cause some of the anodic liquid 150 (e.g., water molecules) to pass through the gas diffusion anode 120 into the anode gas chamber 170. This phenomenon may be referred to as "flooding," resulting in reduced performance (high voltage and low efficiency).

[0092] Figure 4 - Example of GDE preparation (specific to sulfate electrolysis) Figure 4 is a process flowchart corresponding to Method 400 for fabricating a gas diffusion anode 120 according to several embodiments.

[0093] Method 400 may begin with forming an anode catalyst layer 180 (block 410). For example, this operation may involve mixing a conductive filler 182 (e.g., in powder form), a binder 184 (e.g., a polymer binder in powder form), and / or a catalyst 186 (e.g., in powder form). Various embodiments of these components are described above.

[0094] Some examples of suitable catalysts include carbon-supported platinum (Pt-C), platinum black, iridium oxide, nickel, palladium, rhodium, ruthenium, and Ti (general formula). (n) O (2n-1) The titanium oxide represented by , or combinations thereof, and other hydrogen oxidation reaction (HOR) catalysts, with particle size ranges of 8 to 200 nanometers. In some examples, the polymer base is PTFE powder with particle size ranges of 20 to 80 micrometers or 5 to 90 micrometers. The filler material shall be conductive under HOR anode potential and chemically stable. Powders and fibers of graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, graphene, titanium carbide, or combinations thereof, as well as powders and fibers of conductive oxides of stainless steel (e.g., 316, 316L), titanium, nickel, and other metals can be used.

[0095] Method 400 proceeds to compressing the mixture (block 420), for example by applying pressure to the mixture (for example by passing the mixture through a roll press / calender). Specifically, this calendering process applies pressure to the powder mixture and compresses the components of the catalyst layer.

[0096] Method 400 proceeds to laminating the compressed mixture onto a conductive support layer (block 430), thereby forming a support-catalyst layer subassembly. This operation may involve passing the laminate of the compressed mixture and the conductive support layer through another roll press / second calendering process, thereby promoting bonding between the support layer and the catalyst-containing layer. In some embodiments, the support layer can be made from a mesh or expanded sheet form of a metal or conductive material such as titanium, stainless steel (e.g., 316, 316L), nickel, and other chemically resistant metals or conductive materials. In other embodiments, the conductive support layer can also be made from metal fibers such as stainless steel and titanium. The porosity of the support layer can be varied with its thickness, thereby enabling controlled transport of gaseous and liquid species.

[0097] Method 400 proceeds to laminating the support layer-catalyst layer subassembly onto a protective layer (block 440), which may also be referred to as a hydrophobic coating layer. This hydrophobic layer may have an ionomer coating to improve proton transport and, at the same time, generate hydrodynamic pressure to prevent flooding of the gas diffusion anode 120.

[0098] Method 400 proceeds to performing a heat treatment (block 450) to strengthen the interlayer bonding and help remove any solvent impurities. For example, the electrodes can be treated at a temperature of 120°C to 240°C or 80°C or higher using an oven or belt heater type process or a hot press process.

[0099] In some embodiments, each of the operations described above is performed in a sequential manner (e.g., "roll-to-roll").

[0100] Figure 5 - Example of operation method Figure 5 is a process flowchart corresponding to Method 500 for operating the electrolytic system 200 according to several embodiments. Various embodiments of the electrolytic system 200 are described above. Note that Method 500 can be used to convert various salts (e.g., sulfates (Li2SO4, Na2SO4, K2SO4, etc.), chlorides (LiCl, NaCl, and KCl, etc.), and organic salts (e.g., sodium acetate (CH3COONa))) into acids (e.g., sulfuric acid (H2SO4), hydrochloric acid (HCl), acetic acid (CH3COOH), etc.) and metal hydroxides (e.g., LiOH, NaOH, etc.).

[0101] In some embodiments, method 500 includes flowing cathodic solution 140 into the cathodic solution channel 104 of the electrolytic cell 100 (block 510). For example, the cathodic solution 140 flows over an area of ​​1 m² of the cathode 110. 2 Hitting distance: 0.5-5m 3 At a flow rate of / hr, or more specifically, 1-3m 3 / hr-m 2 It can be flowed at a flow rate of . The cathode liquid 140 may be at a temperature of 60-90°C, or more specifically 75-85°C, when it reaches the cathode liquid channel 104.

[0102] In some embodiments, method 500 includes flowing anodic acid 150 into the anodic acid channel 105 of the electrolytic cell 100 (block 520). For example, the anodic acid 150 flows over an area of ​​1 m² of the gas diffusion anode 120. 2 Hitting distance: 0.5-5m 3 At a flow rate of / hr, or more specifically, 1-3m 3 / hr-m 2 It can be flowed at a flow rate of . The anolyte 150 may be at a temperature of 60-90°C, or more specifically 75-85°C, when it reaches the anolyte channel 105.

[0103] In some embodiments, method 500 involves feeding 0.5 to 3 m of raw material into the feed channel 106 of the electrolytic cell 100 (block 525). 3 / hr-m 2This includes flowing the feedstock solution 160 within the flow rate range. The feedstock solution 160 may be at a temperature of 60-90°C, or more specifically, 75-85°C, when it reaches the feedstock channel 106. As described above, this operation is performed in a three-channel system and is optional.

[0104] In some embodiments, method 500 includes (block 530) flowing hydrogen gas into a gas diffusion anode 120. The pressure may be up to 1.5 bar, or more specifically 400 mBar to 900 mBar. The temperature may be above 50°C, for example 60 to 90°C. The operating current density is 4000 A / m². 2 In this case, the flow rate is a maximum of 50 L / min-m 2 , more preferably 25-40 L / min-m 2 That's fine.

[0105] In some embodiments, Method 500 proceeds to applying a voltage between the cathode 110 and the gas diffusion anode 120 (block 540). The voltage is determined based on the electrochemical reactions in the system, as described above with reference to Figure 1C. The resistance within the system is also another factor to consider. The application of the voltage drives various electrochemical reactions in the cathode 110 and the gas diffusion anode 120, driving metal cations from the anolyte 150 to the cathodelyte 140.

[0106] In some embodiments, method 500 includes recovering at least some of the cathodic acid 140 using, for example, a cathodic acid recovery device 220 (block 550). This is an optional operation. During the cathodic acid recovery operation, metal hydroxides and / or hydrogen gas may be removed from the cathodic acid 140. Water may be introduced into the cathodic acid 140 to replenish the water consumed during the operation of the system.

[0107] In some embodiments, method 500 includes recovering at least a portion of the anode 150 using, for example, an anode recovery device 230 (block 560). This may be an optional operation. During the anode recovery operation, acid may be removed from the anode 150. A metal salt may be introduced into the cathode 140 to replenish metal cations that have moved to the cathode 140 during the operation of the system. Water may be introduced into the anode 150 to replenish water consumed during the operation of the system.

[0108] In some embodiments, the anodic acid side of the electrolytic cell 100 operates in batch mode. In this mode, a fixed amount of anodic acid 150 is introduced into the electrolytic cell 100 (i.e., the anodic acid chamber) and continuously recirculated within the electrolytic cell 100 for a certain period of time. The applied voltage (between the gas diffusion anode 120 and the cathode 110) drives cations across the cell membrane 130 (from anodic acid 150 to cathode). For example, sodium ions (Na) traversing the cell membrane 130. + ) For each reaction at the gas diffusion anode 120, one proton (H) is released into the anosol 150. + ) is generated, thereby maintaining the charge balance in the anode 150. Thus, during this batch operation period, the anode 150 becomes "acidified". In some embodiments, this batch process has a current efficiency of over 90% and a molar conversion rate of up to 70% (e.g., Na2SO4 to H2SO4). For the purposes of this disclosure, current efficiency is the ratio of electrons supplied to the system that are actually used to produce chemical substances (e.g., H2SO4 and NaOH). For example, a current efficiency of 90% means that 90% of the current supplied to the electrolytic unit actually produced acids and caustic substances (molarly stoichiometrically). It should be noted that a higher conversion rate corresponds to an increase in the proton concentration in the anode 150, which drives protons through the cell membrane 130 and significantly reduces efficiency. Thus, when the conversion rate of the metal salt 152 is approximately 60-75%, the batch process is stopped and the anode 150 is replaced.

[0109] In the same or other embodiments, a feed-and-bleed method may be used on both the cathode and anode sides of the electrolytic cell 100. The objective is to maintain a stable / constant concentration of metal hydroxide 142 in the cathode 140 and a stable / constant concentration of acid in the anode 150. This concentration stabilization is achieved by continuously monitoring the concentration of the cathode 140 using conductivity probes and density probes, where conductivity and density indicate the concentration of metal hydroxide 142. Specifically, cations (e.g., Na) + or Li + ) passes through the cell membrane 130 and OH at the cathode 110 - When ions are generated, the output of the conductivity probe is used to operate the drug delivery pump, delivering more water (e.g., DI water) to the cathode 140. This approach allows the concentration of metal hydroxide 142 in the cathode 140 to be maintained at the same level. However, the volume of the cathode 140 increases with the supply of water, and some of it is removed, resulting in an overall feed-and-bleed effect.

[0110] Figure 6 is a schematic diagram showing an example embodiment of an electrochemical cell 600 with a gas diffusion anode according to the present application. A rod 610 is welded to a conductive mesh 620 that functions as a current collector. A spring-shaped compression structure 630 is mounted to uniformly distribute compression over the gas diffusion anode, ensuring good electrical contact (low contact resistance) and resulting in a uniform distribution of current. The gas diffusion anode is sandwiched between gaskets / O-rings 635 to seal the liquid chamber 640 from the hydrogen gas chamber 650. A 3D structure 660 is adjacent to the anode-liquid opposing layer 670 to ensure that the flow is controlled. A cation exchange membrane 680 is sandwiched between gaskets / O-rings 635' to seal the liquid anode chamber 685 from the cathode chamber 690. A stainless steel or nickel-based cathode mesh 695 is pressed against the cation exchange membrane 680.

[0111] Figure 7 is a plot showing the 1-hour average voltage measurements for two different cell configurations. One cell includes the unused gas diffusion electrode of this application, with 0.5 g / m³ of gas on the anode. 2 The Pt catalyst is supported in one cell, and the other cell, i.e., the comparison cell, is 20 g / m³ 2 It included an unused DSA-O2 anode mesh with an iridium oxide catalyst coating (MMO anode). 25cm 2 Using a lab-scale electrochemical cell with an active area of ​​4000 A / m², 2 The test was conducted at a constant temperature of 70°C under the specified conditions. 500 liters of 2.5 M sodium sulfate solution were supplied to the anosolite chamber and circulated in batch mode. 4 M sodium hydroxide solution was supplied to the cathodeite chamber and circulated under "feed-and-bleed" operation. The voltage response of the electrochemical cell was recorded over 12 hours. These results indicate that a voltage reduction of approximately 1.0 V can be achieved by incorporating the anode of this application. After 10 hours of operation, as the anosolite batch became acidified and the conductivity of the anosolite increased, the operating voltage of the cell of this application fell below 3.0 V, while the comparative MMO anode cell consistently remained above 4 V.

[0112] Figure 8 is a plot showing the specific energy consumption per ton of sodium sulfate against the acid conversion rate (molar equivalent) of the anode liquid flow for two different cell configurations under the same operating conditions as described above. The specific energy in the anode of this application is approximately 1500 kWh lower than that of the comparative MMO anode configuration, which means that the energy required for salt decomposition is reduced by 35%. Although not bound by theory, the increase in specific energy in both cell configurations (when the molar conversion rate exceeds 60%) may be due to batch circulation of the anode liquid flow, and as a result, when the molar conversion rate exceeds 60%, excess protons migrate to the cathode liquid chamber side via the cation exchange membrane. When protons migrate instead of sodium ions, the protons neutralize the hydroxide produced at the cathode, resulting in a decrease in current efficiency.

[0113] Figure 9 is a plot showing the current efficiency against the acid conversion rate (molar equivalent) of the anode liquid flow for two different cell configurations under the same operating conditions as described above. The current efficiency of the anode of this application reaches over 90%, while the efficiency of the comparative MMO anode configuration is slightly lower at approximately 82%, indicating a 10% improvement in process efficiency by using the anode of this application. Although not bound by theory, the decrease in current efficiency in both cell configurations (when the molar conversion rate exceeds 60%) may be due to batch circulation of the anode liquid flow, and as a result, when the molar conversion rate exceeds 60%, excess protons migrate to the cathode liquid chamber side via the cation exchange membrane. When protons migrate instead of sodium ions, the protons neutralize the hydroxide produced at the cathode, resulting in a decrease in current efficiency.

[0114] Figure 10 is a plot showing the measured voltage of the anode configuration of this application under the same operating conditions as described above. The average operating voltage of the electrochemical cell of this application was maintained relatively stably at around 3V for 440 hours. Although not bound by theory, this dataset demonstrates that no flooding occurred during prolonged operation, and that if flooding had occurred, it would have caused a significant increase in the operating cell voltage. Furthermore, the stable voltage measurements also demonstrate that the GDE of this application is robust enough to withstand corrosive conditions inside the electrochemical cell and is maintained relatively stably without performance degradation.

[0115] conclusion While the above concepts are explained in some detail for clarity, it will be apparent that certain changes and modifications may be made within the scope of the attached claims. It should be noted that many alternative methods exist for carrying out the processes, systems, and apparatus. Therefore, the embodiments described herein are illustrative and should not be construed as limiting.

Claims

1. A gas diffusion anode, wherein the gas diffusion anode is A current collector including a conductive mesh, An anode porous substrate, which is disposed adjacent to the current collector and includes a porous electronically conductive structure, An anode catalyst layer, which is disposed adjacent to the anode porous substrate, comprises a conductive filler, a binder, and a catalyst, has a different average porosity from the anode porous substrate, and is disposed adjacent to the anode porous substrate so as to be positioned between the anode porous substrate and the anode-liquid interface layer, A gas diffusion anode, comprising an anode-liquid interface layer, wherein the anode catalyst layer is disposed adjacent to the anode catalyst layer such that the anode catalyst layer is positioned between the anode porous substrate and the anode-liquid interface layer, and the anode-liquid interface layer includes an ionomer coating configured to conduct protons through the porous polymer substrate and the anode-liquid interface layer.

2. A gas diffusion anode for use in an electrochemical cell, wherein the gas diffusion anode is Anode gas chamber and A current collector comprising a conductive mesh, positioned adjacent to the anode gas chamber so as to be placed between the anode gas chamber and the anode porous substrate, An anode porous substrate, which is disposed adjacent to the current collector and includes a porous electronically conductive structure, An anode catalyst layer, which is disposed adjacent to the anode porous substrate, comprises a conductive filler, a binder, and a catalyst, has a different average porosity from the anode porous substrate, and is disposed adjacent to the anode porous substrate so as to be positioned between the anode porous substrate and the anode-liquid interface layer, A gas diffusion anode, comprising an anode-liquid interface layer, wherein the anode catalyst layer is disposed adjacent to the anode catalyst layer such that the anode catalyst layer is positioned between the anode porous substrate and the anode-liquid interface layer, and the anode-liquid interface layer includes an ionomer coating configured to conduct protons through the porous polymer substrate and the anode-liquid interface layer.

3. The gas diffusion anode according to claim 1 or 2, wherein the anode-liquid interface layer includes an exposed anode liquid side outer surface.

4. The gas diffusion anode according to any one of claims 1 to 3, further comprising an anode-liquid thin film flow structure disposed adjacent to the anode-liquid interface layer such that the anode-liquid interface layer is positioned between the anode catalyst layer and the anode liquid thin film flow structure.

5. The gas diffusion anode according to any one of claims 1 to 4, wherein the conductive mesh is formed from titanium, high-alloy stainless steel, stainless steel, Hastelloy alloy, high-Si iron, lead, tantalum, zirconium, titanium carbide, conductive carbon substrate, or a combination thereof.

6. The gas diffusion anode according to any one of claims 1 to 5, wherein the conductive mesh is coated with a conductive material.

7. The gas diffusion anode according to claim 6, wherein the conductive material is graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, titanium carbide, diamond-like carbon, silicon carbide, titanium carbide, gold, platinum, iridium, or a combination thereof.

8. The gas diffusion anode according to any one of claims 1 to 7, wherein the conductive mesh has an average mesh opening size of about 0.1 mm to about 5 mm.

9. The gas diffusion anode according to any one of claims 1 to 8, wherein the wire forming the conductive mesh has a diameter of about 0.1 mm to about 4 mm.

10. The gas diffusion anode according to any one of claims 1 to 9, wherein the anode porous substrate has a variable porosity over its thickness and / or cell height.

11. The gas diffusion anode according to claim 10, wherein the variable porosity is in the range of about 20% to about 90%.

12. The gas diffusion anode according to claim 10 or 11, wherein the maximum porosity is approximately 55% to approximately 90%.

13. A gas diffusion anode according to any one of claims 10 to 12, wherein the minimum porosity is approximately 20% to approximately 45%.

14. The gas diffusion anode according to any one of claims 1 to 13, wherein the anode porous substrate has a thickness of about 100 μm to about 700 μm.

15. The gas diffusion anode according to any one of claims 1 to 14, wherein the anode porous substrate is formed from a polymer and a carbon material.

16. The gas diffusion anode according to claim 15, wherein the anode porous substrate is formed from about 20% to about 60% by weight of a polymer and about 40% to about 80% by weight of a carbon material.

17. The gas diffusion anode according to claim 15 or 16, wherein the polymer is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), PTFE wax, PTFE fiber, PTFE paste, or a combination thereof.

18. The gas diffusion anode according to any one of claims 15 to 17, wherein the carbon material is graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, graphene, titanium carbide, diamond-like carbon, silicon carbide, or a combination thereof.

19. The gas diffusion anode according to any one of claims 1 to 18, wherein the anode catalyst layer further comprises a structurally conductive support.

20. The catalyst is carbon-supported platinum (Pt-C), platinum black, iridium oxide, nickel, palladium, rhodium, ruthenium, and general formula Ti （ｎ） O （２ｎ－１） A gas diffusion anode according to any one of claims 1 to 19, wherein the anode is a titanium oxide or a combination thereof.

21. The gas diffusion anode according to any one of claims 1 to 20, wherein the conductive filler is graphite powder, carbon black, mesocarbon microbeads, activated carbon, carbon nanotubes, titanium carbide, diamond-like carbon, silicon carbide, titanium carbide, or a combination thereof.

22. The gas diffusion anode according to any one of claims 1 to 21, wherein the binder is polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PTFE wax, PTFE fiber, PTFE paste, or a combination thereof.

23. The gas diffusion anode according to any one of claims 1 to 22, wherein the anode catalyst layer has a thickness of about 1 μm to about 75 μm.

24. The gas diffusion anode according to any one of claims 1 to 23, wherein the anode-liquid interface layer has a thickness of about 100 μm to about 600 μm.

25. The gas diffusion anode according to any one of claims 1 to 24, wherein the porous polymer substrate comprises polyethylene (PE), polypropylene (PP), PTFE, PVDF, PBI (polybenzimidazole), sulfonated tetrafluoroethylene-based fluoropolymer copolymer, or a combination thereof.

26. The gas diffusion anode according to any one of claims 1 to 25, wherein the ionomer coating comprises perfluorosulfonic acid (PFSA), sulfonated tetrafluoroethylene-based fluoropolymer copolymer, sulfuric acid-doped s-PBI (polybenzimidazole) polymer, sulfonated s-PBI (polybenzimidazole) polymer, or a combination thereof.

27. The gas diffusion anode according to any one of claims 1 to 26, wherein the ionomer coating has a thickness of about 1 μm to about 100 μm.

28. The operating voltage of the electrochemical cell including the gas diffusion anode is 70°C and 4000 A / m. ２ A gas diffusion anode according to any one of claims 1 to 27, wherein the voltage is approximately 1.2V to approximately 4.2V.

29. The specific energy consumption of the electrochemical cell including the gas diffusion anode is 70°C and 4000 A / m ２ In Na ２ SO ４ A gas diffusion anode according to any one of claims 1 to 27, wherein the capacity is approximately 1200 kWh / ton to approximately 5000 kWh / ton per unit.

30. The current efficiency of the electrochemical cell including the aforementioned gas diffusion anode is 0-60% for conversion at 70°C and 4000 A / m ２ A gas diffusion anode according to any one of claims 1 to 27, wherein the concentration is approximately 70% to approximately 98%.

31. Cathode and, A gas diffusion anode according to any one of claims 1 to 30, An electrochemical system comprising a cell membrane disposed between the cathode and the gas diffusion anode, wherein the cathode and the cell membrane define a cathodelime channel between them, and the gas diffusion anode and the cell membrane define an anodelime channel between them.

32. A method for operating the electrochemical system described in claim 31, The process involves flowing cathodic solution into the cathodic solution channel of the electrochemical system, wherein the cathodic solution contains at least water. The process involves flowing an anodic acid into the anodic acid channel of the electrochemical system, wherein the anodic acid contains metal salts in the form of metal cations and anions. A method comprising: flowing hydrogen gas into the gas diffusion anode of the electrochemical system; and applying a voltage between the cathode and the gas diffusion anode, thereby converting the hydrogen gas into protons which are released into the anodic solution, and driving the metal cations across the cell membrane of the electrolytic cell from the anodic solution to the cathode solution.

33. A gas diffusion anode used in an electrolytic cell for converting metal salts to metal hydroxides, The aforementioned gas diffusion anode, Anode gas chamber and A current collector comprising a metal mesh and positioned adjacent to the anode gas chamber, An anode porous substrate having a porous electronically conductive structure, The current collector is positioned adjacent to the current collector so as to be located between the anode gas chamber and the anode porous substrate, An anode catalyst layer comprising a conductive filler, a binder, and a catalyst, having an average porosity smaller than that of the anode porous substrate, and positioned adjacent to the anode porous substrate so as to be placed between the anode porous substrate and the anode-liquid interface layer, A gas diffusion anode comprising an anode-liquid interface layer comprising a porous polymer substrate and an ionomer coating configured to conduct protons through the anode-liquid interface layer, the anode-liquid interface layer being disposed adjacent to the anode catalyst layer.

34. The gas diffusion anode according to claim 33, wherein the anode-liquid interface layer forms the exposed anode liquid side outer surface.

35. The gas diffusion anode according to claim 33, further comprising an anode-liquid thin film flow structure disposed adjacent to the anode-liquid interface layer such that the anode-liquid interface layer is positioned between the anode catalyst layer and the anode-liquid thin film flow structure.

36. The gas diffusion anode according to claim 33, wherein the anode gas chamber includes a hydrogen receiving gas inlet.

37. The gas diffusion anode according to claim 36, wherein the anode gas chamber includes a liquid outlet for removing any liquid passing through the gas diffusion anode.

38. The gas diffusion anode according to claim 33, wherein the current collector is formed from titanium.

39. The gas diffusion anode according to claim 33, wherein the anode porous substrate has a variable porosity over the thickness and / or cell height of the anode porous substrate.

40. The gas diffusion anode according to claim 33, wherein the anode catalyst layer further comprises a structurally conductive support.

41. The gas diffusion anode according to claim 33, wherein the porous polymer substrate comprises at least one of polyethylene (PE), polypropylene (PP), PTFE, or PVDF.

42. The gas diffusion anode according to claim 33, wherein the ionomer coating comprises perfluorosulfonic acid (PFSA) or PBI (polybenzimidazole).

43. An electrolytic system, wherein the system Cathode and, The gas diffusion anode according to claim 33, The cell film is disposed between the cathode and the gas diffusion anode, The cathode and the cell membrane define a cathode liquid channel between them. An electrolytic system in which the gas diffusion anode and the cell membrane define an anodic solution channel between them.

44. A method for operating an electrolytic system including an electrolytic cell, The method involves flowing cathodic solution into the cathodic solution channel of the electrolytic cell, The cathode liquid is a cathode liquid containing at least water, and the process involves flowing the cathode liquid. The method involves flowing anodic acid into the anodic acid channel of the electrolytic cell, The anode liquid contains metal salts in the form of metal cations and anions, and the anode liquid is flowed through the system. The process involves flowing hydrogen gas into the gas diffusion anode of the electrolytic cell, A method comprising applying a voltage between the cathode and the gas-diffusing anode, thereby converting hydrogen gas into protons which are released into the anodic solution and driving the metal cations across the cell membrane of the electrolytic cell from the anodic solution to the cathode solution.

45. The method according to claim 32 or 43, wherein the cathode liquid is flowed into the cathode liquid channel of the electrolytic cell at a temperature of 40 to 90°C.

46. The method according to claim 32 or 43, wherein the anode liquid is flowed into the cathode liquid channel of the electrolytic cell at a temperature of 40 to 90°C.

47. The method according to claim 32 or 43, wherein the hydrogen gas passes through a portion of the gas diffusion anode and is converted into protons by the gas diffusion anode.

48. The method according to claim 32 or 43, further comprising recovering the cathodic liquid using a cathodic liquid recovery device.

49. The method according to claim 32 or 43, further comprising recovering the anodic acid using an anodic acid recovery device.

50. The method according to claim 32 or 43, wherein the electrolytic cell is operated in batch mode on the anodic acid side.

51. The method according to claim 32 or 43, wherein the electrolytic cell is operated in a feed-and-bleed mode on the cathode side.

52. The method according to claim 43, wherein the gas diffusion anode is Anode gas chamber and A current collector comprising a metal mesh and positioned adjacent to the anode gas chamber, An anode porous substrate having a porous electronically conductive structure, The current collector is positioned adjacent to the current collector so as to be located between the anode gas chamber and the anode porous substrate, An anode catalyst layer comprising a conductive filler, a binder, and a catalyst, having an average porosity smaller than that of the anode porous substrate, and positioned adjacent to the anode porous substrate so as to be placed between the anode porous substrate and the anode-liquid interface layer, A method comprising a porous polymer substrate and an ionomer coating configured to conduct protons through the anode-liquid interface layer, wherein the anode-liquid interface layer is located adjacent to the anode catalyst layer.

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