Aperture-wettability double-gradient gas diffusion electrode and preparation method thereof

Abstract

The invention provides a gas diffusion electrode with aperture-wettability double gradients and a preparation method of the gas diffusion electrode, and belongs to the technical field of metal-CO2 battery electrodes. The device sequentially comprises a current collector, a hydrophobic macroporous transmission layer, a hydrophobic microporous transmission layer, a hydrophilic transition regulation and control layer and a hydrophilic catalyst layer from a gas side to an electrolyte side. The functional layers with multi-scale apertures are stacked along the axial direction of the electrode, so that the continuous gradient transition of the apertures is realized; and meanwhile, through surface wettability modification, continuous wettability gradient distribution with gradually decreased contact angles is realized on the same spatial dimension. The double gradient structure can form a through gas transmission channel and a catalytic area with a high specific surface area in the electrode, and controllable infiltration of electrolyte is realized. The mass transfer bottleneck of a traditional gas diffusion electrode is overcome, and the stability of a gas-liquid-solid three-phase reaction interface of the gas diffusion electrode is improved.

Description

A gas diffusion electrode with pore size-wetness dual gradient and its preparation method Technical Field

[0001] This invention belongs to the field of metal-CO2 battery electrode technology, specifically, it relates to a gas diffusion electrode with a dual gradient of pore size and wettability and its preparation method. Background Technology

[0002] With the advancement of the "dual carbon" goal, Zn-CO2 flow batteries, which combine carbon dioxide resource utilization with energy storage technology, have attracted widespread attention. In this battery system, the cathode, as the core site of the CO2 electrochemical reduction reaction, typically employs a gas diffusion electrode to construct a stable gas-liquid-solid three-phase reaction interface, aiming to achieve efficient CO2 mass transfer and electron conduction, thereby completing the conversion and utilization of carbon dioxide while storing energy. However, during high-current-density electrolysis, the hydrophobic layer of the gas diffusion electrode is prone to degradation, leading to problems such as electrolyte overflow, carbonate blockage of pores, and instability of the three-phase interface, severely restricting battery performance and cycle life.

[0003] The overall pore size distribution and wettability gradient of the gas diffusion electrode are key factors affecting the cathode performance of Zn-CO2 flow batteries. While traditional gas diffusion electrodes have improved gas-liquid distribution through layered design, surface modification, or localized hydrophobic agent regulation, their pore size and wettability distribution often exhibit discrete or abrupt characteristics. This makes it difficult to form a continuous gradient transition from the gas side to the electrolyte side along the electrode axis, hindering the electrode from simultaneously achieving efficient CO2 transport and stable liquid phase supply. This severely limits the high power density output and long-term stable operation of Zn-CO2 flow batteries. Therefore, there is an urgent need for a gas diffusion electrode with both continuous pore size and wettability gradients along the electrode axis to establish a stable gas-liquid-solid three-phase reaction interface and improve the mass transfer performance of the flow battery cathode, thereby effectively enhancing the CO2 electrochemical reduction efficiency of Zn-CO2 flow batteries. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a gas diffusion electrode with a dual gradient of pore size and wettability, and its preparation method. This invention can effectively optimize the CO2 transport path and electrolyte distribution, enhance the stability of the gas-liquid-solid three-phase reaction interface, and provide sufficient active sites for the CO2 electrochemical reduction reaction. This invention helps to improve the conversion efficiency of the CO2 electrochemical reduction reaction and enhances the electrode stability and overall energy efficiency of Zn-CO2 flow batteries during long-term operation, providing an innovative technical path for the electrode structure design and controllable preparation of high-performance Zn-CO2 flow batteries.

[0005] This invention is achieved through the following technical solution: a gas diffusion electrode with a pore size-wetness dual gradient: the gas diffusion electrode includes: a current collector, a hydrophobic macroporous transport layer, a hydrophobic microporous transport layer, a hydrophilic transition control layer, and a hydrophilic catalytic layer; the current collector is disposed on the gas input side of the electrode and is in electrical contact with the hydrophobic macroporous transport layer, used to achieve efficient electronic conduction between the external circuit and the internal reaction zone of the electrode, while providing mechanical support for the entire structure; the hydrophobic macroporous transport layer is located between the current collector and the hydrophobic microporous transport layer; used to achieve uniform distribution of CO2 reaction gas and serve as a seepage barrier on the gas side.

[0006] The hydrophobic microporous transport layer is disposed between the hydrophobic macroporous transport layer and the hydrophilic transition control layer to prevent electrolyte from permeating to the gas side; the hydrophilic transition control layer is disposed between the hydrophobic microporous transport layer and the hydrophilic catalytic layer; through its hydrophilic porous network structure, it can slowly release and regulate the distribution of electrolyte, and stabilize the position of the three-phase reaction interface; the hydrophilic catalytic layer is located on the innermost side of the electrode structure, directly in contact with the electrolyte, and provides active sites for the catalytic reaction.

[0007] The gas diffusion electrode has a dual gradient distribution along its axis, with the pore size continuously decreasing from the gas side to the electrolyte side and the wettability transitioning from hydrophobic to hydrophilic.

[0008] Furthermore, the current collector is made of graphite plate or surface-modified titanium-based porous metal sheet; the hydrophobic macroporous transport layer is made of porous carbon paper or carbon cloth, and after being impregnated or sprayed with a hydrophobic agent, it has excellent hydrophobic properties.

[0009] Furthermore, the hydrophobic microporous transport layer is made of porous carbon material rich in hydrophobic agents; the hydrophobic agents are polytetrafluoroethylene or polyvinylidene fluoride, which, through coating and film formation on the surface of the carbon skeleton, construct a stable three-dimensional hydrophobic network.

[0010] Furthermore, the hydrophilic transition control layer is surface-modified with a hydrophilic agent, giving it durable and stable hydrophilic properties; the hydrophilic catalytic layer is composed of microporous carbon material with a high specific surface area.

[0011] Furthermore, the gas diffusion electrode also includes a metal nanocatalyst supported on the surface of the hydrophilic catalyst layer by impregnation-thermal reduction or electrochemical deposition.

[0012] A method for fabricating a gas diffusion electrode with a dual pore size-wetness gradient: The fabrication method is a layer-by-layer construction method based on 3D printing: a hydrophobic macroporous transport layer is fixed on a current collector to form a substrate; a hydrophobic microporous transport layer, a hydrophilic transition control layer, and a hydrophilic catalytic layer are sequentially 3D printed on the substrate to form a composite electrode; the composite electrode is dried and carbonized at high temperature to obtain a pure carbon porous framework; a surface wettability gradient is constructed on the carbonized electrode, that is, the hydrophilic transition control layer and the hydrophilic catalytic layer are hydrophilically modified, and the hydrophobic macroporous transport layer and the hydrophobic microporous transport layer are hydrophobically modified; a metal nanocatalyst is loaded on the hydrophilic catalytic layer.

[0013] A method for fabricating a gas diffusion electrode with a pore size-wetness dual gradient: The fabrication method is a hot pressing molding method based on pre-fabricated functional layers: a current collector, a hydrophobic macroporous transport layer, a hydrophobic microporous transport layer, a hydrophilic transition control layer, and a hydrophilic catalytic layer without catalyst loading are prepared independently; the functional layers are stacked in sequence and hot pressed; and a metal nanocatalyst is loaded onto the hydrophilic catalytic layer of the hot-pressed electrode.

[0014] Furthermore, the hydrophilic transition control layer is a pre-fabricated porous material in the hot pressing molding method, and is formed in situ by printing and carbonizing hydrophilic carbon slurry in 3D printing.

[0015] An electronic device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the above method.

[0016] A computer-readable storage medium for storing computer instructions that, when executed by a processor, implement the steps of the above-described method.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: The gas diffusion electrode with a dual pore size-wetness gradient proposed in this invention adopts a multi-layer composite structure design, which includes a current collector, a hydrophobic macroporous transport layer, a hydrophobic microporous transport layer, a hydrophilic transition control layer, and a hydrophilic catalytic layer sequentially from the gas side to the electrolyte side. By stacking functional layers with different pore sizes along the electrode axis, a gradient transition of multi-scale pore sizes is achieved from the gas side to the electrolyte side, thereby constructing a through-hole gas transport channel and a high specific surface area catalytic region inside the electrode. At the same time, a gradient distribution of hydrophobicity decreasing layer by layer from the gas side to the electrolyte side and hydrophilicity increasing accordingly is achieved in this spatial dimension, thereby effectively suppressing electrolyte leakage and maintaining a stable and efficient three-phase reaction interface. The electrode structure and its controllable preparation method provided by this invention will provide a key electrode structure and process preparation path for high-performance Zn-CO2 flow batteries, and are expected to improve their CO2 electrochemical reduction conversion efficiency and long-term operational stability.

[0018] This invention overcomes the mass transfer bottleneck of traditional gas diffusion electrodes by constructing a multi-scale pore size gradient transition and a hydrophobic-hydrophilic smooth transition wettability gradient distribution from the gas side to the electrolyte side. This ensures sufficient active sites for efficient CO2 gas transport and catalytic reactions, while also enabling controllable wetting and stable regulation of the electrolyte, thus forming a stable gas-liquid-solid three-phase reaction interface within the electrode. Furthermore, this electrode structure effectively suppresses electrolyte overflow and gas transport blockage, significantly improving the CO2 electrochemical reduction conversion efficiency and long-term operational stability of Zn-CO2 flow batteries at high current densities. Simultaneously, the 3D printing and thermoforming electrode fabrication processes provided by this invention offer the dual advantages of flexible design and mature technology, providing feasible technical solutions for customized electrode development. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the three-dimensional structure of the gas diffusion electrode with pore size-wetness dual gradient according to the present invention; Figure 2 is a schematic diagram of the two-dimensional structure of the gas diffusion electrode with pore size-wetness dual gradient according to the present invention; wherein 1-current collector, 2-hydrophobic macroporous transport layer, 3-hydrophobic microporous transport layer, 4-hydrophilic transition control layer, 5-hydrophilic catalytic layer, 6-metal nanocatalyst; Figure 3 is the preparation process of the present invention based on the layer-by-layer construction method of 3D printing; Figure 4 is the preparation process of the present invention based on the hot pressing molding method of prefabricated functional layer. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0022] A gas diffusion electrode with a pore size-wetness dual gradient adopts a multilayer composite structure design, which includes a current collector 1, a hydrophobic macroporous transport layer 2, a hydrophobic microporous transport layer 3, a hydrophilic transition control layer 4, and a hydrophilic catalytic layer 5 from the gas side to the electrolyte side.

[0023] In this embodiment, a continuous gradient transition of pore size is achieved by stacking functional layers with multi-scale pore sizes of 50-70 μm, 5-50 μm, 0.1-5 μm, and 2-100 nm along the electrode axis. Simultaneously, through surface wettability modification, a continuous wettability gradient distribution with decreasing contact angle is achieved in the same spatial dimension. The electrode exhibits a dual gradient distribution along its axis, with continuously decreasing pore size from the gas side to the electrolyte side and a wettability transition from hydrophobic to hydrophilic. This dual gradient structure enables the formation of a through-hole gas transport channel and a high specific surface area catalytic region within the electrode, and allows for controllable electrolyte wetting.

[0024] The current collector 1 serves as the supporting substrate and core component for current conduction of the electrode. After being ultrasonically cleaned with organic solvent, rinsed with deionized water, and dried, it is placed on the gas input side of the electrode and makes electrical contact with the hydrophobic macroporous transport layer 2. This enables efficient electronic conduction between the external circuit and the internal reaction zone of the electrode, while also providing stable mechanical support for the entire multilayer electrode structure.

[0025] The current collector 1 is preferably a graphite plate with a thickness of 0.2~1.0 mm (0.5 mm is preferred in the example) or a surface-modified titanium-based porous metal sheet to improve its interfacial conductivity and long-term corrosion resistance in the electrolyte environment.

[0026] The hydrophobic macroporous transport layer 2 serves as the gas distribution and support substrate for the electrode, located between the current collector 1 and the hydrophobic microporous transport layer 3. After being modified with a hydrophobic agent, this layer exhibits high hydrophobicity and excellent gas permeability. Its function is to achieve uniform distribution of CO2 reaction gas and to act as a seepage barrier on the gas side.

[0027] The hydrophobic macroporous transport layer 2 is made of porous carbon paper or carbon cloth with a porosity of 60%~80% and a pore size range of 50~70 μm. After being impregnated or sprayed with a hydrophobic agent, it has excellent hydrophobic properties.

[0028] The hydrophobic microporous transport layer 3 serves as the core hydrophobic barrier and main gas channel inside the electrode. After being impregnated or sprayed with a hydrophobic agent, it is placed between the hydrophobic macroporous transport layer 2 and the hydrophilic transition control layer 4. Through its higher hydrophobic agent loading and specific pore structure, this layer effectively blocks the electrolyte from permeating to the gas side. It is a key functional layer for maintaining the smooth flow of the gas phase channel and preventing liquid resistance.

[0029] The hydrophobic microporous transport layer 3 is made of porous carbon material rich in hydrophobic agents, with a porosity of 65% to 85% and a pore size distribution of 5 to 50 μm. The hydrophobic agent is preferably at least one of polytetrafluoroethylene or polyvinylidene fluoride, which, through coating and film formation on the surface of the carbon skeleton, constructs a stable three-dimensional hydrophobic network.

[0030] If high-temperature carbonization is involved in the preparation of this layer, a carbonizable polymer binder is used for molding, and its hydrophobic properties are acquired through surface modification after carbonization. If it does not participate in high-temperature carbonization, hydrophobic agents such as polytetrafluoroethylene or polyvinylidene fluoride can be used as both binder and hydrophobic agent.

[0031] The hydrophobic macroporous transport layer 2 and hydrophobic microporous transport layer 3 are modified with polytetrafluoroethylene or polyvinylidene fluoride hydrophobic agents, with a target contact angle of 110°~130°. The hydrophilic transition control layer 4, serving as a buffer and control zone for the gas-liquid-solid three-phase reaction, is disposed between the hydrophobic microporous transport layer 3 and the hydrophilic catalyst layer 5. Through its hydrophilic porous network structure, it enables the slow release and distribution control of the electrolyte, stabilizes the three-phase reaction interface, provides a stable ion conduction pathway for the hydrophilic catalyst layer 5, and buffers flow fluctuations.

[0032] When the hydrophilic transition control layer 4 is prepared by 3D printing, it is formed in situ by printing and carbonizing a special hydrophilic carbon slurry. Its pore size and thickness are similar to those prepared by hot pressing, and the hydrophilic properties are achieved through subsequent surface modification processes such as electrochemical oxidation.

[0033] When the hydrophilic transition control layer 4 is prepared by hot pressing, a pre-made carbon felt, porous carbon fiber membrane or electrospun carbon nanofiber membrane (preferably an electrospun fiber membrane with a porosity of 65%~85%, pore size of 0.1~5 μm, and thickness of 50~300 μm, preferably 100~200 μm) is selected as the substrate. After surface modification treatment with hydrophilic agents such as perfluorosulfonic acid resin or hydroxyl / carboxyl modified carbon nanomaterials, it has durable and stable hydrophilic properties.

[0034] The hydrophilic transition control layer 4 is modified with hydrophilicity, and the target contact angle is 70°~90°.

[0035] The hydrophilic catalytic layer 5 is located on the innermost side of the electrode structure and is in direct contact with the electrolyte. Its abundant micro- and nano-pores and high specific surface area provide ample active sites for the catalytic reaction; simultaneously, its high hydrophilicity ensures effective wetting of the active sites and ion transport by the electrolyte.

[0036] The hydrophilic catalyst layer 5 is composed of microporous carbon material with a high specific surface area, including at least one of activated carbon, carbon nanotubes, or graphene, with a porosity of 50%–70%, a pore size range of 2–100 nm, and a thickness of 10–50 μm (preferably 20–30 μm in the examples). Copper, tin, bismuth, silver, or other metal nanocatalysts 6 are loaded using impregnation-thermal reduction, in-situ growth, or electrochemical deposition methods, with a loading amount of 0.5–5.0 mg / cm³. 2 The preferred dosage is 1.0~2.5 mg / cm³. 2After hydrophilic modification, the target contact angle is 40°~70°. It is located on the innermost side of the gas diffusion electrode structure, directly in contact with the electrolyte, and serves as the core region for the CO2 electrochemical reduction reaction.

[0037] Metal nanocatalysts 6 are loaded onto the surface of the hydrophilic catalyst layer 5 by impregnation-thermal reduction or electrochemical deposition.

[0038] The overall pore structure and wettability gradient of the electrode of the present invention are achieved through two controllable preparation processes: Process A (layer-by-layer construction method based on 3D printing): 1. Functional layer slurry preparation and substrate pretreatment (1) Current collector 1 pretreatment: Select graphite plates or titanium-based porous metal sheets with a thickness of 0.2~1.0 mm, and sequentially perform ultrasonic cleaning with organic solvent, rinsing with deionized water and drying treatment.

[0039] (2) Preparation of hydrophobic macroporous transport layer 2: Porous carbon paper or carbon cloth with a porosity of 60%~80% is used as substrate, pre-drying treatment is performed, and polytetrafluoroethylene emulsion with a mass fraction of 20~30 wt% is used to spray or briefly impregnate the gas side. After further drying, it is calcined at 340~380 ℃ for 10~30 min to form a stable hydrophobic skeleton.

[0040] (3) Preparation of hydrophobic microporous transport layer 3 slurry: Conductive carbon powder and carbonizable polymer binder (mass ratio 75:25) are mixed, and 5~20 wt% of polyethylene glycol is added as a pore-forming agent and an appropriate amount of organic solvent as a dispersant. After ultrasonic dispersion and mechanical grinding, a uniform and stable slurry is obtained. This slurry layer is dispersed and mixed with conductive carbon powder and binder through pore-forming agent, aiming to form a pore structure with a pore size of 5~50 μm after carbonization.

[0041] (4) Preparation of the hydrophilic transition control layer 4: 30-40 wt% hydrophilic carbon powder and 4-8 wt% carbonizable polymer binder are mixed and dispersed in an appropriate amount of alcohol solvent. The mixture is ultrasonically dispersed and mechanically stirred to obtain a uniformly viscous slurry. This slurry layer utilizes the self-accumulation of hydrophilic carbon powder and the carbonization shrinkage characteristics of the binder to form a transition pore structure with a pore size of 0.1-5 μm after carbonization.

[0042] (5) Preparation of hydrophilic catalyst layer 5 slurry: Microporous carbon support with pore size of 2~100 nm and carbonizable polymer binder are dispersed in organic solvent at a mass ratio of 85~95:5~15 and ultrasonically dispersed to form a uniform catalyst layer slurry.

[0043] 2. 3D printing layer-by-layer stacking: The pre-treated hydrophobic macroporous transport layer 2 is fixed onto the current collector 1 as a substrate. Using a 3D printer equipped with a multi-channel extrusion system, the above-prepared mixed slurries with different pore-forming properties are loaded into individual barrels. Subsequently, on the hydrophobic macroporous transport layer 2 substrate, the hydrophobic microporous transport layer 3, the hydrophilic transition control layer 4, and the hydrophilic catalytic layer 5 are sequentially printed.

[0044] 3. Drying, Heat Treatment, and Carbonization: The printed electrodes are dried in a vacuum environment at 60–120°C for 6–12 h to completely remove the solvent. Subsequently, under an inert atmosphere, they are heated to 800–1000°C at a heating rate of 2–5°C / min and held at that temperature for 1–3 h to complete carbonization, ultimately obtaining a pure carbon porous electrode framework with a continuous gradient transition from macropores to micropores.

[0045] 4. Surface wettability gradient construction and catalyst loading: For the carbonized electrode, oxygen-containing hydrophilic functional groups were introduced into its hydrophilic transition control layer 4 and hydrophilic catalyst layer 5 using electrochemical oxidation to give it hydrophilic to superhydrophilic properties, with target contact angles controlled at 70°~90° and 40°~70°, respectively. Simultaneously, the surfaces of the hydrophobic macroporous transport layer 2 and the hydrophobic microporous transport layer 3 were coated with polytetrafluoroethylene (PTFE) to give them high hydrophobic properties, with target contact angles controlled at 110°~130°. Subsequently, copper, tin, bismuth, or silver nanocatalysts 6 were loaded onto the hydrophilically modified hydrophilic catalyst layer 5 using impregnation-thermal reduction, in-situ growth, or electrochemical deposition methods.

[0046] Process B: Hot pressing molding method based on prefabricated functional layer: 1. Pre-preparation of functional layer (1) Pretreatment of current collector 1: Same as the method described in step (1) of process A.

[0047] (2) Preparation of hydrophobic macroporous transport layer 2: Porous carbon paper or carbon cloth with a porosity of 60%~80% is immersed in 20~30wt% polytetrafluoroethylene emulsion for 5 min for hydrophobic treatment, and then calcined at 340~380 ℃ for 10~30 min to allow polytetrafluoroethylene to adhere to the pore wall of the carbon paper to form a stable hydrophobic skeleton.

[0048] (3) Preparation of hydrophobic microporous transport layer 3: Conductive carbon powder and polytetrafluoroethylene emulsion are mixed at a mass ratio of 75:25, and 5~20 wt% polyethylene glycol is added as a pore-forming agent and an appropriate amount of organic solvent as a dispersant. After ultrasonic dispersion and mechanical grinding, a uniform and stable hydrophobic slurry is obtained. A wet film with a thickness of about 80~120 μm is formed on the surface of the dried hydrophobic macroporous transport layer 2. After drying again, it is sintered by heat treatment at 340-360 °C for 10-20 min under an inert atmosphere to construct a hydrophobic microporous transport layer 3 with a pore size of 5~50 μm.

[0049] (4) Preparation of hydrophilic transition control layer 4: Prepare an electrospun carbon nanofiber membrane with a porosity of 65%~85% and a thickness of 100~200 μm, immerse it in a 1~5 wt% perfluorosulfonic acid resin solution or a 0.1~0.5 wt% hydrophilic carbon nanomaterial dispersion, take it out and dry it under vacuum to complete the hydrophilic modification.

[0050] (5) Preparation of hydrophilic catalyst layer 5: Microporous carbon support with pore size of 2~100 nm and polyvinylidene fluoride binder are dispersed in N-methylpyrrolidone solvent at a mass ratio of 85~95:5~15, and a uniform catalyst layer slurry is formed by ultrasonic dispersion. A thin film is prepared by blade coating and then dried and cured.

[0051] 2. Hot pressing: The pre-fabricated current collector 1, hydrophobic macroporous transport layer 2, hydrophobic microporous transport layer 3, hydrophilic transition control layer 4, and hydrophilic catalyst layer 5 are precisely stacked in sequence. Subsequently, hot pressing is performed at a temperature of 120~180 °C and a pressure of 5~15 MPa to finally obtain a porous electrode structure with a continuous gradient transition from macropores to micropores.

[0052] 3. Construction of Surface Wetting Gradient and Catalyst Loading: If the hot pressing process leads to a decrease in the hydrophilicity of the hydrophilic transition control layer 4 and the hydrophilic catalyst layer 5, surface modification treatment can be performed using step 4 of process A to complete the construction of the surface wettability gradient. Subsequently, metal nanocatalysts 6 are loaded onto the surface of the hydrophilic catalyst layer 5 by impregnation-thermal reduction, in-situ growth, or electrochemical deposition.

[0053] An electronic device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the above method.

[0054] A computer-readable storage medium for storing computer instructions that, when executed by a processor, implement the steps of the above-described method.

[0055] The above provides a detailed description of the gas diffusion electrode with a pore size-wetness dual gradient and its preparation method proposed in this invention. The principles and implementation methods of this invention have been explained. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A gas diffusion electrode with a dual pore size-wetness gradient, characterized in that: The gas diffusion electrode includes: a current collector (1), a hydrophobic macroporous transport layer (2), a hydrophobic microporous transport layer (3), a hydrophilic transition control layer (4), and a hydrophilic catalytic layer (5); the current collector (1) is disposed on the gas input side of the electrode and is in electrical contact with the hydrophobic macroporous transport layer (2) to achieve efficient electronic conduction between the external circuit and the internal reaction zone of the electrode, while providing mechanical support for the entire structure; the hydrophobic macroporous transport layer (2) is located between the current collector (1) and the hydrophobic microporous transport layer (3); it is used to achieve uniform distribution of CO2 reaction gas and to serve as a seepage barrier on the gas side. The hydrophobic microporous transport layer (3) is disposed between the hydrophobic macroporous transport layer (2) and the hydrophilic transition control layer (4) to block the electrolyte from permeating to the gas side; the hydrophilic transition control layer (4) is disposed between the hydrophobic microporous transport layer (3) and the hydrophilic catalytic layer (5); through its hydrophilic porous network structure, it can slowly release and regulate the distribution of the electrolyte, and stabilize the position of the three-phase reaction interface; the hydrophilic catalytic layer (5) is located on the innermost side of the electrode structure and is in direct contact with the electrolyte, providing active sites for the catalytic reaction. The gas diffusion electrode has a dual gradient distribution along its axis, with the pore size continuously decreasing from the gas side to the electrolyte side and the wettability transitioning from hydrophobic to hydrophilic.

2. The gas diffusion electrode according to claim 1, characterized in that: The current collector (1) is made of graphite plate or surface-modified titanium-based porous metal sheet; the hydrophobic macroporous transport layer (2) is made of porous carbon paper or carbon cloth, and has excellent hydrophobic properties after being impregnated or sprayed with a hydrophobic agent.

3. The gas diffusion electrode according to claim 2, characterized in that: The hydrophobic microporous transport layer (3) is made of porous carbon material rich in hydrophobic agents; the hydrophobic agents are polytetrafluoroethylene or polyvinylidene fluoride, which form a stable three-dimensional hydrophobic network by coating and film formation on the surface of the carbon skeleton.

4. The gas diffusion electrode according to claim 3, characterized in that: The hydrophilic transition control layer (4) is surface modified by a hydrophilic agent and has durable and stable hydrophilic properties; the hydrophilic catalytic layer (5) is composed of microporous carbon material with high specific surface area.

5. The gas diffusion electrode according to claim 4, characterized in that: The gas diffusion electrode also includes a metal nanocatalyst (6) supported on the surface of the hydrophilic catalyst layer (5) by impregnation-thermal reduction or electrochemical deposition.

6. A method for preparing a gas diffusion electrode with a pore size-wetness dual gradient as described in any one of claims 1 to 5, characterized in that: The preparation method is a layer-by-layer construction method based on 3D printing: a hydrophobic macroporous transport layer (2) is fixed on a current collector (1) to form a substrate; a hydrophobic microporous transport layer (3), a hydrophilic transition control layer (4) and a hydrophilic catalytic layer (5) are sequentially 3D printed on the substrate to form a composite electrode; the composite electrode is dried and carbonized at high temperature to obtain a pure carbon porous framework; the surface wettability gradient of the carbonized electrode is constructed, that is, the hydrophilic transition control layer (4) and the hydrophilic catalytic layer (5) are hydrophilized, and the hydrophobic macroporous transport layer (2) and the hydrophobic microporous transport layer (3) are hydrophobized; a metal nanocatalyst (6) is loaded on the hydrophilic catalytic layer (5).

7. A method for preparing a gas diffusion electrode with a pore size-wetness dual gradient as described in any one of claims 1 to 5, characterized in that: The preparation method is based on the hot pressing molding method of pre-made functional layers: the current collector (1), the hydrophobic macroporous transport layer (2), the hydrophobic microporous transport layer (3), the hydrophilic transition control layer (4) and the hydrophilic catalytic layer (5) without catalyst are prepared independently; the functional layers are stacked in sequence and hot-pressed; metal nanocatalysts are loaded on the hydrophilic catalytic layer (5) of the electrode after hot pressing molding.

8. The method according to claim 6 or 7, characterized in that: The hydrophilic transition control layer (4) is a pre-made porous material in the hot pressing molding method, and is formed in situ by printing and carbonization of hydrophilic carbon slurry in 3D printing.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method of claim 6 or 7.

10. A computer-readable storage medium for storing computer instructions, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method of claim 6 or 7.

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