Self-humidifying CO2 membrane electrode structure and preparation method thereof

Abstract

The invention provides a self-humidifying CO2 membrane electrode structure and a preparation method thereof. The self-humidifying CO2 membrane electrode structure comprises an electrolyte isolation plate, the electrolyte isolation plate is provided with an anode side and a cathode side, the anode side is sequentially provided with a cation exchange membrane, an anode catalyst layer, a current collector and an anode electrode plate, and the cathode side is sequentially provided with an anion exchange membrane, a cathode catalyst layer and a cathode electrode plate; the anode electrode plate is provided with a first inlet, hydrogen enters the anode electrode plate from the first inlet and is subjected to a hydrogen oxidation reaction under the action of an anode catalyst to generate protons and electrons, and the protons are migrated to the electrolyte isolation plate through the cation exchange membrane; the cathode electrode plate is provided with a second inlet, CO2 gas enters the cathode electrode plate from the second inlet and is subjected to a reduction reaction under the action of a cathode catalyst to generate a reduction product and OH <->, and OH <-> is migrated to the electrolyte isolation plate through the anion exchange membrane to react with protons. The long-term operation stability of the membrane electrode structure is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical catalysis, and in particular to a self-humidifying CO2 membrane electrode structure and a preparation method thereof. Background Art

[0002] Currently, CO2 membrane electrode structures typically use iridium oxide as the anode oxygen evolution reaction (OER) catalyst. The anode provides protons through the water oxidation reaction and drives the electron flow to maintain the overall reaction. However, this structure has multiple technical bottlenecks, which seriously restrict its energy efficiency, stability and engineering development:

[0003] First, the energy consumption of the anode reaction is high. The OER reaction itself has a high theoretical potential (1.23V vs. RHE). In actual operation, a higher overpotential is usually required to maintain a stable reaction, which significantly increases the overall energy consumption. At the same time, the by-product of the anode reaction is oxygen. If it is mixed with the cathode product (such as hydrogen or carbon monoxide), there are certain safety risks. In addition, the reaction often requires the use of precious metal catalysts such as iridium oxide, which further increases the system cost and is not conducive to large-scale promotion and application.

[0004] Second, water management is complex and relies on external liquid supply. To maintain the wet state of the ion exchange membrane, the system needs to continuously introduce electrolyte to the anode side with the help of an external peristaltic pump to establish a gas-liquid-solid three-phase interface to ensure the reaction rate. However, this external liquid supply method results in uneven water distribution in actual operation, which can easily lead to phenomena such as cathode flooding or partial drying of the anode. Especially under high current density conditions, it is more likely to induce imbalance in the membrane electrode interface structure, resulting in a significant decline in electrode performance.

[0005] Third, cation migration leads to structural degradation. Existing systems mostly use liquid electrolytes containing alkali metal cations (such as K + 、Na + ), during long-term operation, these cations easily penetrate the proton exchange membrane and migrate to the cathode side, reacting with the carbonate ions (CO3 2- ) ions combine to form insoluble carbonate deposits. These deposits may clog the pores of the catalyst layer or cover the interface of the gas diffusion layer, thereby exacerbating mass transfer limitations, reducing electrode activity, and affecting the overall device stability and lifespan. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a self-humidifying CO2 membrane electrode structure, including an electrolyte separator filled with a solid electrolyte, the electrolyte separator having an anode side and a cathode side opposite to the anode side, the anode side being provided with a cation exchange membrane, an anode catalyst layer, a current collector and an anode electrode plate in sequence from the inside to the outside, and the cathode side being provided with an anion exchange membrane, a cathode catalyst layer and a cathode electrode plate in sequence from the inside to the outside;

[0007] The anode electrode plate has a first inlet and a first outlet. Hydrogen enters the anode electrode plate from the first inlet and undergoes a hydrogen oxidation reaction under the action of the anode catalyst to generate protons and electrons. The protons migrate to the electrolyte separator through the cation exchange membrane.

[0008] The cathode electrode plate has a second inlet and a second outlet. CO2 gas enters the cathode electrode plate from the second inlet and undergoes a reduction reaction under the action of the cathode catalyst. The generated products include reduction products and OH. - , OH - Migrate through the anion exchange membrane to the electrolyte separator to react with protons.

[0009] Optionally, the cathode catalyst layer includes a porous carbon paper layer, an active material layer formed on the surface of the porous carbon paper layer, and an ion polymer layer formed on the surface of the active material layer, and the material of the ion polymer layer is an ion polymer containing a quaternary amine group.

[0010] Optionally, the thickness of the active material layer is 50 nm to 200 nm, and the loading density of the ion polymer layer is 1 mg / cm 2 -3mg / cm 2 .

[0011] Optionally, the material of the active material layer is selected from any one of Ag, Cu, Au, Bi, Pb and Zn, or an alloy or composite material formed by at least two of these metals, or a metal nitrogen-carbon composite material, or a molecular catalyst.

[0012] Optionally, the anion exchange membrane comprises a polymer material whose main chain is polyarylether or polystyrene, and has a quaternary ammonium group, an imidazole group or a piperidine group on the side chain for achieving OH - directional conduction.

[0013] Optionally, the cation exchange membrane is a Nafion membrane, and the thickness of the Nafion membrane is 50 μm-180 μm;

[0014] The material of the anode catalyst layer is Pt / C catalyst, and the loading density of the anode catalyst layer is 0.5 mg / cm 2 -1.5mg / cm 2 .

[0015] Optionally, the electrolyte separator comprises:

[0016] The separator body defines a receiving cavity for filling the solid electrolyte;

[0017] The by-product collecting structure is communicated with the accommodating cavity of the separator body and is used for collecting the by-products generated during the cathode side reaction process.

[0018] In particular, the present invention also provides a method for preparing the aforementioned self-humidifying CO2 membrane electrode structure, comprising the following steps:

[0019] providing an electrolyte separator filled with a solid electrolyte;

[0020] Attaching an anode membrane electrode in a wet state to the anode side of the electrolyte separator, and attaching an anion exchange membrane in a wet state to the cathode side of the electrolyte separator, wherein the anode membrane electrode comprises a cation exchange membrane and an anode catalyst layer formed on the cation exchange membrane, and the cation exchange membrane is close to the anode side;

[0021] A current collector and an anode electrode plate are sequentially stacked on one side of the anode catalyst layer, and a cathode catalyst layer and a cathode electrode plate are sequentially stacked on one side of the anion exchange membrane, thereby obtaining a self-humidifying CO2 membrane electrode structure.

[0022] Optionally, the method for preparing the cathode catalyst layer comprises the following steps:

[0023] Providing porous carbon paper;

[0024] forming an active material layer on the surface of the porous carbon paper;

[0025] An ionic polymer containing a quaternary amine group is sprayed on the surface of the active material layer to form an ionic polymer layer.

[0026] According to the solution of the present invention, the self-humidifying CO2 membrane electrode structure realizes efficient spatial separation and synergistic coupling of hydrogen oxidation reaction (HOR) and CO2 reduction reaction by sequentially arranging a cation exchange membrane, an anode catalyst layer, a current collector and an anode electrode plate on the anode side of the electrolyte separator from the inside to the outside, and sequentially arranging an anion exchange membrane, a cathode catalyst layer and a cathode electrode plate on the cathode side from the inside to the outside. Specifically: First, the present invention adopts the HOR reaction to replace the traditional OER reaction, which significantly reduces the overpotential required for the anode reaction, thereby effectively reducing the overall energy consumption of the system, and avoiding the potential safety hazards caused by the accumulation of oxygen byproducts during the OER reaction, and has higher energy efficiency and operational safety. Secondly, the anode adopts a full gaseous reaction system design, completely abandoning the dependence on the electrolyte, and there is no need to introduce water or electrolyte solution on the anode side, fundamentally eliminating the problem of catalyst layer deactivation or mass transfer limitation caused by "flooding" of the anode, and significantly improving the anode interface stability and reaction sustainability. Thirdly, since this structure does not involve mobile metal cations (such as K + 、Na +), which can effectively prevent metal ions from migrating through the exchange membrane to the cathode side and reacting with CO2 reduction products (such as CO3 2- ) forms carbonate deposition, thus fundamentally solving the common problems of salt precipitation blockage and catalyst pore deactivation, and ensuring the long-term operation stability of the membrane electrode structure. In addition, the protons generated by HOR react with the OH generated in the CO2 reduction reaction. - A neutralization reaction occurs in the electrolyte separator, building an internal self-circulating water management system. This self-humidification mechanism can maintain the moisture balance of the membrane electrode without additional water supply, and continuously supply the water molecules required for the CO2 reduction reaction. The system structure is simpler and is particularly suitable for operating scenarios with high steady-state requirements, such as intermittent power supply from renewable energy. In summary, the present invention significantly improves the energy efficiency, safety and long-term operational stability of the membrane electrode structure through the multi-dimensional collaborative design of "low-energy anode reaction + all-gaseous reaction system + blocking salt precipitation migration + self-humidification water management".

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of a self-humidifying CO2 membrane electrode structure according to one embodiment of the present invention is shown;

[0029] Figure 2 A flow chart showing a method for preparing a self-humidifying CO2 membrane electrode structure according to an embodiment of the present invention is shown;

[0030] Figure 3 The self-humidifying CO2 membrane electrode structure according to one embodiment of the present invention is shown in FIG. -2 The data curve of operation under the current density of ;

[0031] In the figure: 1-electrolyte separator, 2-cation exchange membrane, 3-anode catalyst layer, 4-current collector, 5-anode electrode plate, 6-anion exchange membrane, 7-cathode catalyst layer, 8-cathode electrode plate. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0033] Figure 1 FIG. 1 shows a schematic structural diagram of a self-humidifying CO2 membrane electrode structure according to an embodiment of the present invention. Figure 1As shown, the self-humidifying CO2 membrane electrode structure includes an electrolyte separator 1 filled with a solid electrolyte. The electrolyte separator 1 has an anode side and a cathode side opposite to the anode side. The anode side is provided with a cation exchange membrane 2, an anode catalyst layer 3, a current collector 4 and an anode electrode plate 5 in sequence from the inside to the outside. The cathode side is provided with an anion exchange membrane 6, a cathode catalyst layer 7 and a cathode electrode plate 8 in sequence from the inside to the outside. The anode electrode plate 5 has a first inlet and a first outlet. Hydrogen enters the anode electrode plate 5 from the first inlet and undergoes a hydrogen oxidation reaction under the action of the anode catalyst to generate protons and electrons. The protons migrate to the electrolyte separator 1 through the cation exchange membrane 2. The cathode electrode plate 8 has a second inlet and a second outlet. CO2 gas enters the cathode electrode plate 8 from the second inlet and undergoes a reduction reaction under the action of the cathode catalyst. The generated products include reduction products and OH - , OH - The protons migrate through the anion exchange membrane 6 to the electrolyte separator 1 to react with the protons for neutralization.

[0034] According to the solution of the embodiment of the present invention, the self-humidifying CO2 membrane electrode structure realizes efficient spatial separation and synergistic coupling of hydrogen oxidation reaction (HOR) and CO2 reduction reaction by sequentially arranging a cation exchange membrane 2, an anode catalyst layer 3, a current collector 4 and an anode electrode plate 5 on the anode side of the electrolyte separator 1 from the inside to the outside, and sequentially arranging an anion exchange membrane 6, a cathode catalyst layer 7 and a cathode electrode plate 8 on the cathode side from the inside to the outside. Specifically: First, the present invention adopts the HOR reaction to replace the traditional OER reaction, which significantly reduces the overpotential required for the anode reaction, thereby effectively reducing the overall energy consumption of the system, and avoiding the potential safety hazards caused by the accumulation of oxygen byproducts during the OER reaction, and has higher energy efficiency and operational safety. Secondly, the anode adopts a full gaseous reaction system design, completely abandoning the dependence on the electrolyte, and there is no need to introduce water or electrolyte solution on the anode side, fundamentally eliminating the problem of catalyst layer deactivation or mass transfer limitation caused by "flooding" of the anode, and significantly improving the anode interface stability and reaction sustainability. Thirdly, since this structure does not involve mobile metal cations (such as K + 、Na + ), which can effectively prevent metal ions from migrating through the exchange membrane to the cathode side and reacting with CO2 reduction products (such as CO3 2- ) forms carbonate deposition, thus fundamentally solving the common problems of salt precipitation blockage and catalyst pore deactivation, and ensuring the long-term operation stability of the membrane electrode structure. In addition, the protons generated by HOR react with the OH generated in the CO2 reduction reaction. -A neutralization reaction occurs in the electrolyte separator 1, building an internal self-circulating water management system. This self-humidification mechanism can maintain the moisture balance of the membrane electrode without the need for additional water supply, and continuously supply the water molecules required for the CO2 reduction reaction. The system structure is simpler and is particularly suitable for operating scenarios with high steady-state requirements, such as intermittent power supply from renewable energy. In summary, the present invention significantly improves the energy efficiency, safety and long-term stability of the membrane electrode structure through the multi-dimensional collaborative design of "low-energy anode reaction + all-gaseous reaction system + blocking salt precipitation migration + self-humidification water management".

[0035] It should be explained that in this application, the cathode side not only does not need to rely on a water management system or external humidity control, but also realizes a self-humidification mechanism within the system by cooperating with the electrolyte separator 1 and the anode side. Specifically, in this application, the generated protons migrate to the electrolyte separator through the cation exchange membrane and react with the OH generated by the cathode side. - Water is generated within the solid electrolyte. This water continuously wets the cation exchange membrane and anion exchange membrane, maintaining high ionic conductivity. Some water also diffuses to the cathode catalyst layer surface to participate in the CO2 reduction reaction. Excess water is discharged through fluid channels provided in the electrolyte separator, maintaining localized water content while preventing failures such as anode flooding and cathode drying out.

[0036] Before the membrane electrode structure proposed in this application was finalized, the inventors conducted a lot of scheme exploration and experimental verification work. For example, in the initial experiments, an attempt was made to attach a bipolar membrane structure between the cathode catalyst layer and the anode catalyst layer. The structure includes an anion exchange layer and a cation exchange layer. However, in actual operation, it was found that the water dissociation reaction continued to occur at the interface of this type of bipolar membrane under the working potential, and the generated H + With OH - Neutralization reaction occurs inside the membrane. When carbonate (CO3 2- ) or bicarbonate (HCO3 - ) plasma, the generated H + Further reaction with it continuously releases CO2 gas, which accumulates inside the membrane, causing local bubbling, seriously damaging the integrity of the membrane structure and its interface contact with the electrode, ultimately causing electrochemical performance degradation and reduced operational stability.

[0037] To address the above issues, the inventors further improved the membrane electrode structure, separating the anion exchange layer from the cation exchange layer, using a cation exchange membrane and an anion exchange membrane, respectively. Furthermore, a solid electrolyte separator was added between the two membranes, which was filled with a solid electrolyte material. This improvement effectively avoids the CO2 accumulation caused by the water dissociation reaction during operation of the bipolar membrane structure and effectively suppresses gas accumulation between the anion exchange membrane and the cation exchange membrane, thereby proposing the technical solutions of the embodiments of the present application.

[0038] In some embodiments, the electrolyte separator 1 comprises a separator body and a byproduct collection structure. The separator body defines a cavity for filling a solid electrolyte. The byproduct collection structure communicates with the cavity of the separator body and is used to collect byproducts produced during the cathode-side reaction. The byproduct collection structure actively guides and collects byproducts such as CO2 gas or excess water produced during the electrolysis process, thereby suppressing issues such as electrolyte swelling, interfacial pH fluctuations, or blocked ion migration channels caused by localized water accumulation at the interface. The collected CO2 gas is pure CO2, free of impurities, and can therefore be recovered and redirected to a second inlet. In a preferred embodiment, two byproduct collection structures are provided, one on each side of the separator body, and each is connected to the cavity via a fluid channel. The fluid channel is a microporous channel. In one embodiment, the pore size of the microporous channel is preferably controlled between 500 μm and 1000 μm, enabling the discharge of liquid water and CO2 gas.

[0039] In a further embodiment, the byproduct collection structure can be filled with a hydrophilic polymer material or gel layer that has excellent water absorption properties and does not hinder gas permeability, such as modified polyacrylates, hydrogel-coated hollow fibers, or inorganic adsorbent particles with polar groups. This is used to selectively capture and lock water while maintaining a free diffusion channel for CO2 gas to prevent byproduct accumulation. In other embodiments, the byproduct collection structure can also be designed as a water-conducting structure with unidirectional permeability, allowing water to migrate from the interior of the electrolyte separator into the collection cavity while preventing external moisture from infiltrating in the opposite direction, thereby preventing the migration of solid electrolyte components or secondary contamination.

[0040] The solid electrolyte filled within the electrolyte separator 1 can be, for example, DOWEX 50W×8 hydrogen-type cation exchange resin, which is primarily composed of a cross-linked polystyrene skeleton with grafted sulfonic acid groups forming a strongly acidic cation exchange structure. This resin exhibits excellent proton conductivity and hydration retention properties. When hygroscopic, DOWEX 50W×8 hydrogen-type cation exchange resin forms microscopic hydration channels, providing stable and continuous proton migration pathways without the addition of an external liquid electrolyte. This makes it suitable for ionic connection and charge neutralization between the anode and cathode in solid-state or quasi-solid-state electrolysis systems. Its particle size can be controlled within a range of 100-200 mesh, resulting in a moderate packing density, which helps form a dense and deformable filling layer, facilitating full contact with the separator cavity and reducing interfacial resistance. To optimize the orderliness of its internal ion migration pathways, in some embodiments, DOWEX 50W×8 hydrogen-form cation exchange resin can be packed using directional compaction or electrostatically assisted arrangement methods, resulting in a certain degree of chain-like arrangement or pore connectivity in the resin particles at the microscopic level, further enhancing proton migration rates and reducing the risk of interfacial ion congestion. In preferred embodiments, the cation exchange resin can also be blended with inorganic hydrophilic particles or fluorinated polymer wetting agents such as polytetrafluoroethylene micropowder to improve interfacial wettability and morphological stability during long-term operation, prevent the expansion of voids between particles due to shrinkage, and ensure the continuity of the electrolyte channels.

[0041] In one embodiment, the cation exchange membrane 2 and the anode catalyst layer 3 are an integrated structure, that is, the anode catalyst layer 3 is directly constructed on the surface of the cation exchange membrane 2, avoiding the interface discontinuity problem between the anode catalyst and the proton exchange membrane in the traditional membrane electrode assembly, thereby achieving the coordinated optimization of the ion conduction path, electrocatalytic active sites and reaction gas distribution in the anode reaction area.

[0042] The cation exchange membrane 2 is a Nafion membrane, which has a perfluorosulfonic acid group structure, provides efficient proton conductivity in a hydrated state, and has good chemical stability and mechanical strength. In this embodiment, the thickness of the Nafion membrane is 50 μm to 180 μm, for example, it can be 50 μm, 80 μm, 100 μm, 150 μm or 180 μm. A thinner membrane thickness such as 50 μm helps to reduce the proton migration path length, improve membrane conductivity and reaction response speed, while appropriately increasing the membrane thickness such as 150 μm-180 μm is beneficial to inhibit gas penetration and enhance mechanical stability.

[0043] The anode catalyst layer 3 preferably uses a platinum-supported carbon catalyst (Pt / C), which is a highly dispersed platinum nanoparticle deposited on the surface of the conductive carbon support, forming a rich active site and electron transport network. The catalyst loading density of the anode catalyst layer 3 is 0.5 mg / cm 2 Up to 1.5 mg / cm 2, for example, it can be 0.5 mg / cm 2 , 1.0mg / cm 2 or 1.5 mg / cm 2 The design within this range balances catalytic efficiency, material utilization, and gas diffusion characteristics, avoiding platinum accumulation that could mask activity or low loading that could limit reaction rates. The anode catalyst layer 3 can be directly formed on the Nafion membrane surface by spraying, dipping, or drying the solution. During the formation process, an interfacial binder or intermediate transition layer can be introduced to enhance membrane adhesion and interfacial conductivity.

[0044] In one embodiment, the current collector 4 can be, for example, a porous titanium felt structure. The porous titanium felt structure is a three-dimensional porous felt material made of high-temperature sintering of metal titanium fibers, which has excellent electrical conductivity, structural support and chemical stability. The porosity of the porous titanium felt is preferably 60% to 80%, for example, 65%, 70% or 75%, to ensure smooth diffusion and timely discharge of the gaseous reactants hydrogen or other gases. The thickness of the porous titanium felt is preferably 100μm to 500μm, for example, 150μm, 300μm or 400μm, taking into account both mechanical support strength and low pressure drop requirements. The diameter of the titanium fiber is preferably 10μm to 30μm, which improves the contact density of the porous network and the continuity of electron transmission. Using porous titanium felt as the current collector 4 can significantly improve the conductivity, gas diffusion efficiency and structural stability of the overall electrode structure. Its three-dimensional porous structure not only provides a continuous electron transmission channel, but also provides an efficient path for the migration of gaseous reactants and by-products, which helps to reduce reaction impedance, slow down water accumulation and blockage, and maintain interfacial reaction activity. In addition, porous titanium felt has good flexibility and compressibility, which can enhance the close fit of the membrane electrode assembly. At the same time, it has excellent chemical inertness and can adapt to complex electrochemical environments such as acidic or oxygen-rich environments, effectively extending the operating life of the system. It is particularly suitable for application scenarios in solid-state systems that have high requirements for structural integration and long-term stability.

[0045] In one embodiment, the anode electrode plate 5 is etched or milled in its main body to form a first inlet and a first outlet, and a multi-channel flow field structure is arranged between the two to optimize the distribution of hydrogen in the anode catalyst layer and the rapid discharge of reaction products (protons and trace water vapor). Specifically, the multi-channel flow field channel can adopt an equal-width tooth type, a winding bend or a divergent convergence design, and the channel width is preferably 0.5mm-2mm and the depth is 0.2mm-1mm, so as to achieve uniform distribution of hydrogen while ensuring low pressure drop. The multi-channel flow field structure can also be combined with a hydrophobic surface treatment such as PTFE coating or microporous sandblasting process to further enhance the ability to remove water vapor in the channel and inhibit liquid phase aggregation.

[0046] In some embodiments, the cathode catalyst layer 7 includes a porous carbon paper layer, an active material layer formed on the surface of the porous carbon paper layer, and an ion polymer layer formed on the surface of the active material layer, wherein the material of the ion polymer layer is an ion polymer containing a quaternary amine group. The porous carbon paper layer serves as a gas diffusion layer, has good electronic conductivity and gas permeability, can effectively support the upper structure and achieve rapid diffusion and uniform distribution of reaction gases such as CO2. The active material layer is directly formed on the surface of the porous carbon paper, and the selected material is any one of Ag, Cu, Au, Bi and Pb, or an alloy or composite material formed by at least two of these metals. The active material layer can also be other catalytically active materials, such as Zn, metal nitrogen carbon composites (M-NC) and molecular catalysts, and molecular catalysts can be, for example, CoPc (cobalt phthalocyanine), Co-HITP (cobalt-based nitride / phosphide material), etc. The active material layer can also be other catalysts that catalyze the CO2 reduction reaction. The thickness of the active material layer is preferably 50nm-200nm to form a nanoscale continuous film layer or a nanoparticle array structure. Different metal materials exhibit different CO2 reduction selectivity. Ag and Au materials have excellent CO selectivity, while Bi, Pb and their complexes tend to generate formate ions (HCOO - ), while Cu can catalyze the formation of a variety of reduction products, including methane (CH4), ethylene (C2H4), methanol (CH3OH) and ethanol (C2H5OH). It should be noted that when the catalyst is Bi, Pb or their complexes, humidified CO2 gas must be introduced to maintain the hydration state of the catalytic interface and promote the long-term progress of the formate pathway reaction. When the catalyst is Ag, Au or Cu-based materials, the reaction system is introduced with completely dry CO2 gas and completely dry H2 gas to maintain the moisture required for the operation of the membrane electrode.

[0047] The ion polymer layer covers the surface of the active material layer to activate CO2 and inhibit the shedding or aggregation of the catalyst. The ion polymer layer is made of a cation exchange polymer containing quaternary ammonium groups, such as polydiallyldimethylammonium chloride, polyethyleneimine, polymethacryloyloxyethyltrimethylammonium chloride or polystyrenetrimethylbenzylammonium chloride, with a loading density of 1 mg / cm 2 -3mg / cm 2 , for example, it can be 1 mg / cm 2 , 2mg / cm 2 or 3 mg / cm 2 .

[0048] In the above structure, the reduction products generated by different catalytic materials have different migration paths and discharge methods. For gaseous products such as carbon monoxide (CO), methane (CH4), ethylene (C2H4), methanol (CH3OH) and ethanol (C2H5OH) generated by catalytic materials such as Ag, Au, and Cu, as well as liquid products such as methanol and ethanol, these products are directly discharged and collected from the second outlet of the cathode electrode plate. When Bi, Pb or a composite material containing Bi and Pb is used as the catalyst, the main product generated is formate ions (HCOO - ), after being generated in the cathode catalyst layer, the anion passes through the anion exchange membrane into the intermediate solid electrolyte layer, where it combines with the protons generated by the oxidation of H2 on the anode side to form formic acid (HCOOH). The generated liquid formic acid is discharged through the discharge channel in the electrolyte separator.

[0049] In some embodiments, the anion exchange membrane 6 is constructed of functionalized polymer materials, the main chain substrate of which is polyarylether such as polyarylethersulfone, polyaryletherketone, or polystyrene, and functional groups with alkaline or quaternary ammonium properties are introduced into the main chain or side chain of the molecule, especially quaternary ammonium groups (-NR4 + ), imidazole groups or piperidine groups to give the membrane selective OH - Directional conduction capability. This type of membrane material can be modified by grafting functional groups through methods such as bromomethylation, amination, or cyclization, so that the ion exchange membrane has the following structural characteristics:

[0050] 1) Strong backbone structure rigidity and high thermochemical stability. The polyarylether and polystyrene backbones possess excellent heat resistance and mechanical strength, ensuring the anion exchange membrane's ability to maintain its morphology under high pH and high voltage conditions.

[0051] 2) Side chain functionalization. By introducing quaternary ammonium groups, imidazole groups or piperidine groups, the OH groups can be functionalized. - Highly efficient selective adsorption and conduction, forming a continuous anion migration channel.

[0052] 3) Uniform ion channel distribution. The multi-point grafting strategy can form a three-dimensional cross-linked or microphase-separated structure, which is conducive to building a stable and highly connected anion transport network and improving the overall conductivity.

[0053] The anion exchange membrane 6 introduces quaternary ammonium, imidazole or piperidine functional groups on the main chain of polyarylether or polystyrene to achieve OH - The membrane not only maintains structural and performance stability under harsh operating conditions such as high pH and high temperature, but also exhibits excellent water management capabilities and membrane electrode interface compatibility, effectively avoiding failure issues such as interfacial carbonate precipitation and catalyst deactivation.

[0054] In particular, the embodiment of the present invention also provides a method for preparing the self-humidifying CO2 membrane electrode structure, such as Figure 2 As shown, the preparation method comprises:

[0055] Step S100, providing an electrolyte separator filled with a solid electrolyte;

[0056] Step S200, attaching the anode membrane electrode in a wet state to the anode side of the electrolyte separator, and attaching the anion exchange membrane in a wet state to the cathode side of the electrolyte separator, the anode membrane electrode comprising a cation exchange membrane and an anode catalyst layer formed on the cation exchange membrane, the cation exchange membrane being close to the anode side;

[0057] In step S300, a current collector and an anode electrode plate are sequentially stacked on one side of the anode catalyst layer, and a cathode catalyst layer and a cathode electrode plate are sequentially stacked on one side of the anion exchange membrane, thereby obtaining a self-humidifying CO2 membrane electrode structure.

[0058] In one embodiment, a method for preparing a cathode catalyst layer includes the following steps: providing porous carbon paper; forming an active material layer on the surface of the porous carbon paper; and spraying an ionic polymer containing a quaternary ammonium group on the surface of the active material layer to form an ionic polymer layer.

[0059] According to the solution of the embodiment of the present invention, the membrane electrode structure prepared by this preparation method has excellent structural density, interfacial stability, and ion-guiding ability. Not only does it achieve in-situ migration of cathode water and anode wetting during operation, effectively alleviating the problem of membrane electrode dry-out failure, but it also suppresses local pH fluctuations and reduces the risk of catalyst passivation, thereby improving the conversion efficiency and operational stability of the CO2 reduction reaction. This method is characterized by simple operation, high degree of structural integration, and strong adaptability, making it suitable for the mass production of large-area, high-performance CO2 membrane electrode devices.

[0060] Figure 3 The self-humidifying CO2 membrane electrode structure according to one embodiment of the present invention is shown in FIG. -2 The black line represents the voltage and the red dotted line represents the Faradaic efficiency. Figure 3 In the embodiment shown, silver is deposited on hydrophobic carbon paper as the cathode catalyst layer, platinum carbon is used as the anode catalyst layer, and after the membrane electrode is assembled, dry CO2 and H2 are introduced into the cathode and anode respectively for self-humidification operation. Figure 3 It can be seen that at 100mAcm -2At a current density of , the membrane electrode structure can operate stably for more than 90 hours, and throughout the entire operating cycle, the Faraday efficiency of the CO product is always maintained at more than 95%, showing excellent selectivity and long-term operational stability. This result fully demonstrates that the self-humidifying CO2 membrane electrode structure proposed in the embodiment of the present invention relies on the membrane electrode multi-layer collaborative design to achieve efficient water management without an external humidifying gas source, which can effectively alleviate the performance degradation problems caused by membrane drying and electrode dehumidification in traditional CO2 electroreduction systems. By optimizing the catalyst layer structure and matching the hydrophilicity of the interface, the directional migration of the reaction water and the continuous wetting of the anode side membrane are achieved, thereby ensuring the overall ion conduction efficiency and electrocatalytic reaction activity of the membrane electrode.

[0061] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A self-humidifying CO2 membrane electrode structure, characterized in that: The electrolyte separator is filled with a solid electrolyte, the electrolyte separator has an anode side and a cathode side opposite to the anode side, the anode side is sequentially provided with a cation exchange membrane, an anode catalyst layer, a current collector and an anode electrode plate from the inside to the outside, and the cathode side is sequentially provided with an anion exchange membrane, a cathode catalyst layer and a cathode electrode plate from the inside to the outside; The anode electrode plate has a first inlet and a first outlet. Hydrogen enters the anode electrode plate from the first inlet and undergoes a hydrogen oxidation reaction under the action of the anode catalyst to generate protons. The protons migrate to the electrolyte separator through the cation exchange membrane. The cathode electrode plate has a second inlet and a second outlet. CO2 gas enters the cathode electrode plate from the second inlet and undergoes a reduction reaction under the action of the cathode catalyst. The generated products include reduction products and OH. - , OH - Migrate through the anion exchange membrane to the electrolyte separator to react with protons.

2. The self-humidifying CO2 membrane electrode structure according to claim 1, characterized in that: The cathode catalyst layer includes a porous carbon paper layer, an active material layer formed on the surface of the porous carbon paper layer, and an ion polymer layer formed on the surface of the active material layer. The material of the ion polymer layer is an ion polymer containing a quaternary amine group.

3. The self-humidifying CO2 membrane electrode structure according to claim 2, characterized in that: The thickness of the active material layer is 50nm-200nm, and the loading density of the ion polymer layer is 1mg / cm 2 -3mg / cm 2 .

4. The self-humidifying CO2 membrane electrode structure according to claim 3, characterized in that: The material of the active material layer is selected from any one of Ag, Cu, Au, Bi, Pb and Zn, or an alloy or composite material formed by at least two of these metals, or a metal nitrogen-carbon composite material, or a molecular catalyst.

5. The self-humidifying CO2 membrane electrode structure according to any one of claims 1 to 4, characterized in that: The anion exchange membrane comprises a polymer material whose main chain is polyarylether or polystyrene, and has a quaternary ammonium group, an imidazole group or a piperidine group on the side chain for achieving OH - directional conduction.

6. The self-humidifying CO2 membrane electrode structure according to claim 5, characterized in that: The cation exchange membrane is a Nafion membrane, and the thickness of the Nafion membrane is 50 μm-180 μm; The material of the anode catalyst layer is Pt / C catalyst, and the loading density of the anode catalyst layer is 0.5 mg / cm 2 -1.5mg / cm 2 .

7. The self-humidifying CO2 membrane electrode structure according to claim 6, characterized in that: The electrolyte separator comprises: The separator body defines a receiving cavity for filling the solid electrolyte; The by-product collecting structure is communicated with the accommodating cavity of the separator body and is used for collecting the by-products generated during the cathode side reaction process.

8. A method for preparing a self-humidifying CO2 membrane electrode structure according to any one of claims 1 to 7, characterized in that: The steps include: providing an electrolyte separator filled with a solid electrolyte; Attaching an anode membrane electrode in a wet state to the anode side of the electrolyte separator, and attaching an anion exchange membrane in a wet state to the cathode side of the electrolyte separator, wherein the anode membrane electrode comprises a cation exchange membrane and an anode catalyst layer formed on the cation exchange membrane, and the cation exchange membrane is close to the anode side; A current collector and an anode electrode plate are sequentially stacked on one side of the anode catalyst layer, and a cathode catalyst layer and a cathode electrode plate are sequentially stacked on one side of the anion exchange membrane, thereby obtaining a self-humidifying CO2 membrane electrode structure.

9. The method for preparing a self-humidifying CO2 membrane electrode structure according to claim 8, characterized in that: The method for preparing the cathode catalyst layer comprises the following steps: Providing porous carbon paper; forming an active material layer on the surface of the porous carbon paper; An ionic polymer containing a quaternary amine group is sprayed on the surface of the active material layer to form an ionic polymer layer.

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