An electrode structure for in-situ nitrogen separation, fuel cell and method of manufacture

Abstract

The application provides an electrode structure for in-situ nitrogen separation, a fuel cell and a preparation method, and belongs to the technical field of fuel cells. The electrode structure comprises an anode gas diffusion layer and an anode catalytic layer, and a nitrogen selective separation adsorption layer is arranged between the anode gas diffusion layer and the anode catalytic layer. The separation adsorption layer is a porous film layer with a pore size between the kinetic diameter of a hydrogen molecule and the kinetic diameter of a nitrogen molecule, and is deposited on the side surface of the anode gas diffusion layer facing the anode catalytic layer in an in-situ growth manner. By adopting the technical scheme provided in the embodiment of the application, the problems in the prior art that the system volume increases sharply, the in-situ nitrogen separation cannot be realized at the electrode level, the nitrogen occupies the active sites of the catalytic layer, hinders the diffusion of hydrogen and accelerates the performance decay of the electrode can be solved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to an electrode structure for in-situ nitrogen separation, a fuel cell, and a method for its preparation. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are highly efficient energy conversion devices that directly convert chemical energy into electrical energy through electrochemical reactions. Due to their advantages such as fast start-up speed, low operating temperature, and high power density, they have broad application prospects in transportation, portable power supplies, and distributed power generation. Among various fuel supply solutions, indirect ammonia-hydrogen fuel cells (IAFCs) using ammonia as the hydrogen storage medium have received widespread attention in recent years. This technology converts ammonia into hydrogen through ammonia cracking, which is then used to power the fuel cell. It combines the significant advantages of high hydrogen storage density, convenient transport of liquid ammonia, and wide availability, making it an important development direction in the field of hydrogen energy utilization. However, while producing the target product hydrogen, the ammonia cracking reaction inevitably produces an equimolar amount of nitrogen as a byproduct. Even after the cracked gas undergoes separation and purification treatment to remove trace amounts of residual ammonia, a large amount of nitrogen remains in the mixed gas entering the fuel cell. Since nitrogen molecules themselves lack electrochemical reactivity, when they enter the anode catalyst layer along with hydrogen, they occupy active sites at the three-phase interface of the catalyst, typically represented by Pt / C, severely hindering the effective diffusion of hydrogen molecules to these sites and leading to a significant decrease in catalytic efficiency. Simultaneously, the continuous accumulation of nitrogen within the catalyst layer significantly increases the gas mass transfer resistance inside the electrode, reducing the overall output power and energy conversion efficiency of the battery. Under long-term operating conditions, the presence of nitrogen can also easily induce localized hydrogen depletion in the catalyst, accelerating the irreversible degradation of the electrode materials. Therefore, in indirect ammonia-hydrogen fuel cell systems, efficiently separating and removing nitrogen is a key technical challenge for improving battery performance and ensuring long-term operational stability.

[0003] To address the issue of nitrogen removal from ammonia cracking gas, existing technologies primarily employ the method of installing a separate separation device external to the fuel cell system. A typical approach involves configuring a molecular sieve adsorption purification unit upstream of the fuel cell inlet pipeline. This unit utilizes the molecular sieve material filled in the adsorption tower to selectively adsorb nitrogen, supplying the purified hydrogen-rich gas to the fuel cell. This approach typically requires multiple adsorption towers to achieve pressure swing adsorption (PSA) cycle operation and additional regeneration auxiliary equipment such as vacuum pumps or compressors to ensure periodic desorption and regeneration of the adsorbent. Another approach involves installing a separate polymer membrane separation module at the fuel cell system inlet, utilizing the difference in permeation rates of hydrogen and nitrogen through polymer membrane materials such as polyimide to achieve gas separation. This approach also requires a separate membrane separation module, along with a corresponding booster pump and piping system, installed externally to the fuel cell system to maintain the required pressure differential driving force across the membrane. Both of the above schemes place the nitrogen separation function outside the fuel cell body. The pyrolysis gas is pretreated by an external separation device and then the purified gas is sent into the battery pack through an extended pipeline. This inevitably extends the gas transport path from the pyrolyzer to the battery anode.

[0004] However, the aforementioned existing technologies that place the nitrogen separation structure outside the fuel cell all have significant drawbacks. First, the external molecular sieve adsorption scheme requires additional large-scale adsorption towers, regeneration devices, and supporting piping and valve systems. The size of these auxiliary devices often far exceeds that of the fuel cell itself, resulting in a significant increase in the overall volume and weight of the power system. This severely reduces the system's volumetric energy density and gravimetric energy density, hindering the widespread adoption of indirect ammonia-hydrogen fuel cells in space- and weight-sensitive applications such as vehicle-mounted and portable systems. Second, while the external membrane separation scheme has a relatively compact structure, the traditional polymer membrane materials used, such as polyimide, have poor stability in the highly acidic, high-humidity, and humid-heat operating environment (70-80°C) unique to proton exchange membrane fuel cells. They are prone to swelling, degradation, and even structural collapse, leading to a significant decline in separation performance and making it difficult to meet the reliability requirements for long-term operation. Furthermore, regardless of the external separation scheme used, the extended delivery pipeline from the external separation device to the fuel cell anode not only increases system complexity and pressure drop loss but also reduces system response speed, making it impossible to achieve real-time in-situ nitrogen separation at the electrode level. More fundamentally, after the gas undergoes external pretreatment enters the anode, a small amount of residual nitrogen will still gradually accumulate in the catalyst layer. Existing external separation schemes cannot solve the problem of in-situ retention of nitrogen at the three-phase interface of the catalyst layer from the perspective of electrode microstructure. Therefore, they cannot fundamentally eliminate the occupation of catalytic active sites by nitrogen and the obstruction of hydrogen diffusion. Summary of the Invention

[0005] This invention provides an electrode structure, fuel cell, and preparation method for in-situ nitrogen separation. This addresses the problems in existing technologies, such as a sudden increase in overall system volume, extended gas delivery path, reduced energy density, and the inability to achieve real-time in-situ nitrogen separation at the electrode level. These problems lead to residual nitrogen occupying active sites in the anode catalyst layer, hindering hydrogen diffusion, and accelerating electrode performance degradation. The technical solution is as follows: In a first aspect, an electrode structure for in-situ nitrogen separation includes an anode gas diffusion layer and an anode catalyst layer, wherein a nitrogen selective separation adsorption layer is disposed between the anode gas diffusion layer and the anode catalyst layer. The nitrogen selective separation adsorption layer is a porous thin film layer with a pore size between the dynamic diameter of hydrogen molecules and the dynamic diameter of nitrogen molecules. The nitrogen selective separation adsorption layer is deposited on the side surface of the anode gas diffusion layer facing the anode catalyst layer by in-situ growth.

[0006] Optionally, the pore size of the nitrogen selective separation adsorption layer is 0.30~0.35 nm.

[0007] Optionally, the thickness of the nitrogen selective separation adsorption layer is 50~500 nm.

[0008] Optionally, the core material of the nitrogen selective separation adsorption layer is selected from at least one of heteroatom-doped microporous carbon, pore size-controlled metal-organic framework materials, functionalized covalent organic framework materials, and modified zeolite molecular sieves.

[0009] Optionally, the pore size-controlled metal-organic framework material is a zeolite imidazole ester framework material, which is formed by the coordination of zinc ions and 2-methylimidazolium to form a sodalite topology. The methyl side group on the 2-carbon atom in the 2-methylimidazolium points to the center of the pore window, and the effective sieving pore size is limited to 0.34 nm through the steric hindrance effect.

[0010] In a second aspect, a fuel cell includes the aforementioned in-situ nitrogen separation electrode structure, and further includes an anode bipolar plate, a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer, and a cathode bipolar plate, wherein the anode bipolar plate, the anode gas diffusion layer, the nitrogen selective separation adsorption layer, the anode catalyst layer, the proton exchange membrane, the cathode catalyst layer, the cathode gas diffusion layer, and the cathode bipolar plate are stacked sequentially.

[0011] Optionally, the anode bipolar plate is provided with an air inlet, a flow channel and an air outlet, and the air outlet is provided with a purge valve, which is connected to the air outlet.

[0012] Thirdly, a method for preparing an electrode structure for in-situ nitrogen separation as described above includes the following steps: Step 1: Using the anode gas diffusion layer as a growth substrate, hydrophilize the surface of the anode gas diffusion layer facing the anode catalyst layer by introducing oxygen-containing functional groups onto the surface. Step 2: Prepare metal salt precursor solution and organic ligand precursor solution separately, and mix them to obtain reaction mother liquor; Step 3: Immerse the activated anolyte gas diffusion layer into the reaction mother liquor and react at a set temperature for a set time to allow metal ions and organic ligands to coordinate and nucleate in situ on the activated surface of the anolyte gas diffusion layer and grow into a continuous and dense nanofilm. By controlling the reaction time, the thickness of the nanofilm is controlled to be between 50 and 500 nm. The nanofilm is the nitrogen selective separation adsorption layer. Step 4: Remove the anode gas diffusion layer on which the nitrogen selective separation adsorption layer is grown on the surface, use solvent to clean and remove unreacted precursors and loosely attached particles, dry and activate under vacuum conditions to remove residual solvent molecules in the channels and release the sieve channels. Step 5: Coat the surface of the nitrogen selective separation adsorption layer on the side opposite to the anode gas diffusion layer with an anode catalyst slurry and dry it to form the anode catalyst layer, thus obtaining the anode gas diffusion layer, nitrogen selective separation adsorption layer and anode catalyst layer stacked in sequence.

[0013] Optionally, in step one, the hydrophilization treatment involves bombarding the surface of the anode gas diffusion layer facing the anode catalyst layer with oxygen plasma, using a radio frequency power of 30~80W and a treatment time of 120~300s, thereby introducing hydroxyl and carboxyl groups as oxygen-containing functional groups onto the surface.

[0014] Optionally, in step two, the metal salt precursor solution is an alcoholic solution of zinc nitrate hexahydrate, and the organic ligand precursor solution is an alcoholic solution of 2-methylimidazole; in step three, the set temperature is 20~80℃, and the set time is 60~300min; in step four, the drying and activation temperature is 50~100℃, the vacuum degree is less than 0.1Pa, and the activation time is 8~16h; in step five, the anode catalyst slurry contains a Pt / C catalyst and a perfluorosulfonic acid resin dispersion, the coating is done by spraying, and the drying temperature is 40~80℃.

[0015] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: This invention provides an electrode structure, fuel cell, and preparation method for in-situ nitrogen separation. By setting a nitrogen selective separation adsorption layer between the anode gas diffusion layer and the anode catalyst layer, the nitrogen separation function is transferred from the outside of the traditional fuel cell system to the microstructure level inside the electrode. This achieves in-situ real-time retention of nitrogen before it reaches the anode catalyst layer, fundamentally eliminating nitrogen's occupation of active sites at the catalyst's three-phase interface and its obstruction of hydrogen diffusion, significantly improving catalytic efficiency and the overall output power of the battery. Specifically, since the nitrogen selective separation adsorption layer is located between the anode gas diffusion layer and the anode catalyst layer, it is directly embedded inside the electrode structure as a functional interface layer. This eliminates the need for a bulky molecular sieve adsorption tower, regeneration device, and supporting piping and valve system outside the fuel cell system, as well as the need for independent membrane separation modules and booster pumps. This significantly reduces the overall volume and weight of the indirect ammonia-hydrogen fuel cell system, and significantly improves the system's volumetric energy density and gravimetric energy density, which is beneficial for its application in space- and weight-sensitive scenarios such as vehicle-mounted and portable applications. Meanwhile, because the nitrogen selective separation adsorption layer is a porous thin film layer with a pore size between the dynamic diameters of hydrogen and nitrogen molecules, it utilizes the size difference between the dynamic diameters of hydrogen and nitrogen molecules to achieve physical sieving of the two gases: hydrogen molecules, with their smaller dynamic diameter, smoothly pass through the separation adsorption layer to reach the catalyst layer and participate in the electrochemical reaction, while nitrogen molecules, with their larger dynamic diameter, are trapped on the upstream side of the catalyst layer. This molecular-size-based physical sieving mechanism achieves in-situ real-time separation of nitrogen at the electrode level, allowing continuous operation without external energy input. This effectively avoids the increased mass transfer resistance, decreased battery output power, and irreversible performance degradation of electrode materials caused by the continuous accumulation of nitrogen in the catalyst layer. Furthermore, the nitrogen selective separation adsorption layer is deposited on the surface of the anode gas diffusion layer facing the anode catalyst layer through in-situ growth, forming a chemical bond-level interfacial bond between the separation adsorption layer and the anode gas diffusion layer. The bonding strength is far higher than that of traditional physical coating or adhesive bonding methods. This robust interfacial anchoring relationship formed by in-situ growth enables the separation adsorption layer to effectively resist the scouring of high-speed airflow inside the proton exchange membrane fuel cell, corrosion from strong acidic environments, and thermal stress under high humidity and heat alternating conditions. It is less prone to swelling, degradation, peeling, or structural collapse, ensuring the reliability and stability of the separation function during long-term operation. Simultaneously, the in-situ growth method achieves integrated construction of the separation adsorption layer and the micron-scale electrode structure. This effectively solves the problems of existing technologies, such as a sharp increase in overall system volume, extended gas delivery paths, reduced energy density, and the inability to achieve in-situ real-time nitrogen separation at the electrode level, leading to residual nitrogen occupying active sites in the anode catalyst layer, hindering hydrogen diffusion, and accelerating electrode performance degradation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is an exploded view of the fuel cell structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the fuel cell workflow provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the preparation method provided in the embodiments of the present invention.

[0018] In the figure: 1-Anode gas diffusion layer; 2-Anode catalyst layer; 3-Nitrogen selective separation adsorption layer; 4-Anode bipolar plate; 41-Inlet; 42-Flow channel; 43-Outlet; 5-Proton exchange membrane; 6-Cathode catalyst layer; 7-Cathode gas diffusion layer; 8-Cathode bipolar plate; 9-Purge valve. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] Figure 1 This is an exploded view of the fuel cell structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the fuel cell workflow provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the preparation method provided in an embodiment of the present invention. Figures 1 to 3 The electrode structure, fuel cell, and preparation method for in-situ nitrogen separation shown include an anode gas diffusion layer 1 and an anode catalyst layer 2. A nitrogen selective separation adsorption layer 3 is disposed between the anode gas diffusion layer 1 and the anode catalyst layer 2. The nitrogen selective separation adsorption layer 3 is a porous thin film layer with a pore size between the dynamic diameter of hydrogen molecules and the dynamic diameter of nitrogen molecules. The nitrogen selective separation adsorption layer 3 is deposited on the surface of the anode gas diffusion layer 1 facing the anode catalyst layer 2 by in-situ growth.

[0021] Exemplarily, in this embodiment of the invention, the anode gas diffusion layer 1 serves as a porous substrate for gas transport. Its surface facing the anode catalyst layer 2 serves as the growth substrate for the nitrogen selective separation adsorption layer 3. The nitrogen selective separation adsorption layer 3 is chemically bonded to the surface of the anode gas diffusion layer 1, forming a robust, integrated structure. The other side of the nitrogen selective separation adsorption layer 3 is tightly bonded to the anode catalyst layer 2, thus forming a complete functional interface layer between the anode gas diffusion layer 1 and the anode catalyst layer 2. Because the nitrogen selective separation adsorption layer 3 is directly deposited on the anode gas diffusion layer 1 through in-situ growth, rather than through physical coating or adhesive bonding, the separation adsorption layer and the substrate possess chemical bond-level bonding strength, capable of resisting the risk of peeling under high-speed airflow and humid heat alternating conditions inside the fuel cell. When the hydrogen and nitrogen mixture generated from ammonia cracking enters the anode gas diffusion layer 1 from the flow channel of the anode bipolar plate, the mixture is first uniformly distributed and initially diffused within the porous carbon fiber structure of the anode gas diffusion layer 1. Subsequently, the mixed gas reaches the surface of the nitrogen selective separation adsorption layer 3, where a molecular sieving process occurs: Since the pore size of the nitrogen selective separation adsorption layer 3 is strictly between the dynamic diameter of hydrogen molecules (0.289 nm) and the dynamic diameter of nitrogen molecules (0.364 nm), hydrogen molecules, due to their smaller dynamic diameter, can efficiently pass through the sieving channels of the nitrogen selective separation adsorption layer 3, continuing to diffuse towards the anode catalyst layer 2 and reaching the active sites at the three-phase interface of the Pt / C catalyst, where an electrochemical oxidation reaction (H2→2H2O) occurs. + +2e - Nitrogen molecules, due to their larger kinetic diameter than the pore size of the selective nitrogen separation adsorption layer 3, are physically trapped on the side of the nitrogen selective separation adsorption layer 3 facing the anode gas diffusion layer 1, and cannot enter the anode catalyst layer 2. The trapped nitrogen gradually accumulates in the nitrogen selective separation adsorption layer 3. Through temperature fluctuations (e.g., 60–80°C) or small pressure fluctuations caused by fuel cell start-up and shutdown processes or operating conditions, nitrogen undergoes thermal desorption or pressure swing desorption from the nitrogen selective separation adsorption layer 3, and diffuses counter-currently along the porous channels of the anode gas diffusion layer 1 towards the anode flow channel, ultimately being discharged from the battery system with the anode exhaust gas through the outlet. This in-situ separation mechanism effectively intercepts nitrogen before it reaches the catalyst layer, fundamentally avoiding the problems of nitrogen occupying catalyst active sites, hindering hydrogen diffusion, and increasing mass transfer resistance, significantly improving the battery's catalytic efficiency, output power, and long-term operational stability.

[0022] Optionally, the pore size of the nitrogen selective separation adsorption layer 3 is 0.30~0.35 nm.

[0023] Exemplarily, in this embodiment of the invention, the pore size of the nitrogen selective separation adsorption layer 3 is precisely controlled within the range of 0.30~0.35 nm, which is strictly between the dynamic diameter of hydrogen molecules (0.289 nm) and the dynamic diameter of nitrogen molecules (0.364 nm). The lower limit of the pore size, 0.30 nm, ensures that it is greater than the dynamic diameter of hydrogen molecules (0.289 nm), allowing hydrogen molecules to pass smoothly through the sieve channels with low mass transfer resistance; the upper limit of the pore size, 0.35 nm, ensures that it is less than the dynamic diameter of nitrogen molecules (0.364 nm), allowing nitrogen molecules to be effectively blocked under this pore size condition. This pore size range acts like a precisely customized molecular gate, utilizing the 0.075 nm difference in dynamic diameter between hydrogen and nitrogen to achieve highly selective physical separation of the two gases. When the hydrogen-nitrogen mixture reaches the nitrogen selective separation adsorption layer 3, the kinetic diameter of hydrogen molecules (0.289 nm) is smaller than the minimum pore size of the separation adsorption layer (0.30 nm). Therefore, hydrogen molecules can pass through the sieve channels without obstruction and reach the anode catalyst layer 2 to participate in the electrochemical reaction. However, the kinetic diameter of nitrogen molecules (0.364 nm) is larger than the maximum pore size of the separation adsorption layer (0.35 nm), so nitrogen molecules are physically trapped at the pore inlet. By precisely limiting the pore size to a narrow window of 0.30~0.35 nm, both high hydrogen permeability to maintain the battery's power output and near-complete nitrogen trapping are achieved, effectively preventing localized hydrogen depletion and catalyst performance degradation caused by nitrogen accumulation after entering the catalyst layer.

[0024] Optionally, the thickness of the nitrogen selective separation adsorption layer 3 is 50~500 nm.

[0025] For example, in this embodiment of the invention, the thickness of the nitrogen selective separation adsorption layer 3 is controlled within the nanometer range of 50-500 nm. This thickness range balances mechanical strength and hydrogen mass transfer resistance. When the thickness is less than 50 nm, it is difficult for the film layer to form a continuous and dense covering structure, and pinhole defects are prone to occur, causing nitrogen to leak from the defects and penetrate into the catalyst layer, resulting in loss of separation function. When the thickness exceeds 500 nm, although the mechanical strength is further enhanced, the mass transfer path required for hydrogen to cross the separation adsorption layer is too long, and the gas diffusion resistance increases significantly, resulting in a severe decrease in the overall output power of the battery. The thickness range of 50-500 nm enables the nitrogen selective separation adsorption layer 3 to form a continuous, defect-free, and dense nanofilm, ensuring sufficient mechanical strength to resist the internal airflow erosion and pressure differential load of the battery while controlling the translayer permeation mass transfer resistance of hydrogen at a low level. When hydrogen molecules pass through this nanometer-thick separation and adsorption layer, the diffusion resistance is significantly lower than that of traditional micrometer-thick films due to the extremely short mass transfer path. Therefore, they can reach the Pt / C active sites of the anode catalyst layer 2 with high flux, maintaining a highly efficient electrochemical oxidation reaction rate. Simultaneously, the thickness range of 50–500 nm ensures sufficient continuity and density of the film, preventing nitrogen molecules from entering the catalyst layer through any physical defects or gaps. This achieves efficient hydrogen permeation while maintaining complete nitrogen retention.

[0026] Optionally, the core material of the nitrogen selective separation adsorption layer 3 is selected from at least one of heteroatom-doped microporous carbon, pore size-controlled metal-organic framework materials, functionalized covalent organic framework materials, and modified zeolite molecular sieves.

[0027] For example, in this embodiment of the invention, the core material system of the nitrogen selective separation adsorption layer 3 encompasses four types of porous materials with precise sub-nanometer pore size control capabilities. Heteroatom-doped microporous carbon introduces heteroatoms such as nitrogen, boron, and sulfur into the carbon framework to adjust the size and surface chemical properties of the micropores, ensuring that the pore size falls within the target range between the kinetic diameters of hydrogen and nitrogen. Pore-controlled metal-organic framework materials form highly regular crystalline porous structures through the coordination self-assembly of metal ions and organic ligands, and their pore size can be precisely designed through the steric hindrance effect of the ligands. Functionalized covalent organic framework materials construct an ordered porous framework through covalently linked organic units, and adjust the pore size through functionalization modification. Modified zeolite molecular sieves utilize the natural microporous structure of inorganic aluminosilicate crystals, achieving pore size fine-tuning through ion exchange or framework element replacement. All four types of materials possess excellent chemical and thermal stability, enabling them to adapt to the highly acidic and humid working environment inside proton exchange membrane fuel cells, maintaining separation performance without significant degradation under long-term operating conditions. Simultaneously, all four types of materials can be grown in situ on the surface of the anode gas diffusion layer 1 using either liquid-phase or gas-phase methods, forming a robust chemical bond interface with the substrate. Regardless of which of the four core materials or their combination is chosen, the nitrogen selective separation adsorption layer 3 achieves molecular sieving through its inherent sub-nanometer-scale regular pore structure. Driven by pressure difference and concentration gradient, hydrogen molecules diffuse through the regular pores of the separation adsorption layer to reach the anode catalyst layer 2 and participate in the electrochemical reaction; nitrogen molecules, due to size effect, are blocked upstream of the separation adsorption layer and eventually diffuse backward along the anode gas diffusion layer 1 into the flow channel for discharge. The availability of multiple material options provides flexibility for material adaptation under different application conditions.

[0028] Optionally, the pore size-controlled metal-organic framework material is a zeolite imidazole ester framework material. The zeolite imidazole ester framework material is formed by the coordination of zinc ions and 2-methylimidazolium to form a sodalite topology. The methyl side group on the 2-carbon atom in 2-methylimidazolium points to the center of the pore window, and the effective sieving pore size is limited to 0.34 nm through the steric hindrance effect.

[0029] Exemplarily, in this embodiment of the invention, the nitrogen selective separation adsorption layer 3 uses zeolite imidazole ester framework material (ZIF-8) as the core material. ZIF-8 consists of zinc ions (Zn... 2+Zinc ions (ZIF-8) and 2-methylimidazole (C4H6N2) self-assemble via coordination bonds to form a sodalite (SOD) topology. In this structure, each zinc ion coordinates with the nitrogen atoms of four 2-methylimidazole molecules, constructing a three-dimensional ordered porous framework network. The methyl side group (-CH3, van der Waals radius approximately 0.20 nm) attached to the 2-carbon atom in the 2-methylimidazole molecule rigidly points towards the center of the pores in the sodalite topology after the structure is formed. Through direct steric hindrance, it occupies part of the pore space, precisely reducing the effective sieving pore size of the ZIF-8 crystal from the theoretical sodalite topology pore size to 0.34 nm. This 0.34 nm pore size lies precisely between the molecular dynamics diameter of hydrogen (0.289 nm) and the molecular dynamics diameter of nitrogen (0.364 nm), like a custom-designed molecular gate. The Zn-N coordination bonds in the ZIF-8 framework exhibit extremely high chemical stability, and its hydrophobic framework effectively resists the attack of water molecules in high-humidity environments. Through the steric hindrance effect of 2-methylimidazolium and the highly compact hydrophobic interface formed by dense crystal stacking, it restricts the penetration of acidic droplets into the membrane layer, enabling it to exhibit excellent stability under the strong acidity and high humidity and heat conditions characteristic of proton exchange membrane fuel cells. When the hydrogen-nitrogen mixture reaches the nitrogen selective separation adsorption layer 3 composed of ZIF-8, hydrogen molecules (kinetic diameter 0.289 nm) are smaller than the effective sieving pore size of ZIF-8 (0.34 nm). Driven by both pressure difference and concentration gradient, they smoothly pass through the highly regular sodalite topological pore network in the ZIF-8 crystals, reaching the active sites of the Pt / C catalyst three-phase interface in the anode catalyst layer 2 for electrochemical oxidation. Nitrogen molecules (kinetic diameter 0.364 nm) are larger than the effective sieving pore size of ZIF-8 (0.34 nm) and are trapped upstream of the separation adsorption layer by the steric barrier formed by the methyl side groups. During the start-up and shutdown process of the fuel cell or under conditions of temperature fluctuation (60~80℃) or slight pressure fluctuation caused by fluctuations in operating conditions, nitrogen molecules trapped and adsorbed near the ZIF-8 channels can be released in situ through thermal desorption or pressure swing desorption mechanisms. The desorbed nitrogen diffuses in the reverse direction along the anode gas diffusion layer 1 towards the anode flow channel and is eventually discharged from the battery system with the anode exhaust gas, thereby restoring the active sites of the ZIF-8 channels in the nitrogen selective separation adsorption layer 3 and realizing the self-regeneration cycle of the separation function.

[0030] A fuel cell includes the aforementioned in-situ nitrogen separation electrode structure, and further includes an anode bipolar plate 4, a proton exchange membrane 5, a cathode catalyst layer 6, a cathode gas diffusion layer 7, and a cathode bipolar plate 8, wherein the anode bipolar plate 4, the anode gas diffusion layer 1, the nitrogen selective separation adsorption layer 3, the anode catalyst layer 2, the proton exchange membrane 5, the cathode catalyst layer 6, the cathode gas diffusion layer 7, and the cathode bipolar plate 8 are stacked sequentially.

[0031] Exemplarily, in this embodiment of the invention, the layers of the fuel cell are stacked and assembled sequentially from the anode side to the cathode side. The anode bipolar plate 4 is located at the outermost anode end, and its inner surface has a flow channel structure for uniformly distributing the hydrogen-nitrogen mixture generated from ammonia cracking to the anode gas diffusion layer 1. The anode gas diffusion layer 1 is closely attached to the inner side of the anode bipolar plate 4, serving as a porous carbon fiber matrix and playing a dual role in uniform gas distribution and electron collection and conduction. A nitrogen selective separation adsorption layer 3 is grown in situ on the surface of the anode gas diffusion layer 1 facing the anode catalyst layer 2, serving as a key molecular sieving interface layer. The anode catalyst layer 2 is closely attached to the other side of the nitrogen selective separation adsorption layer 3, where the supported Pt / C catalyst provides three-phase interfacial active sites for the hydrogen oxidation reaction. A proton exchange membrane 5 is located between the anode catalyst layer 2 and the cathode catalyst layer 6, serving as the core membrane layer for proton conduction and gas isolation. The cathode catalyst layer 6 is located on the cathode side of the proton exchange membrane 5, providing catalytic active sites for the oxygen reduction reaction. The cathode gas diffusion layer 7 is closely attached to the cathode catalyst layer 6 and is used to uniformly distribute the oxidant gas and conduct electrons. The cathode bipolar plate 8 is located at the outermost cathode end, and its inner flow channel structure is used to transport air or oxygen. The hydrogen-nitrogen mixture produced by ammonia cracking enters from the inlet of the anode bipolar plate 4, and after being uniformly distributed through the flow channel, it enters the anode gas diffusion layer 1 for diffusion. After the mixture reaches the nitrogen selective separation adsorption layer 3, hydrogen molecules pass through the separation adsorption layer into the anode catalyst layer 2, where an electrochemical oxidation reaction (H2→2H2O) occurs at the three-phase interface of the Pt / C catalyst. + +2e - The process generates protons and electrons. Protons are conducted to the cathode side via the proton exchange membrane 5, while electrons flow from the anode to the cathode through an external circuit, forming an output current. On the cathode side, air or oxygen enters through the inlet of the cathode bipolar plate 8, diffuses through the cathode gas diffusion layer 7 to the cathode catalyst layer 6, and undergoes a reduction reaction on the cathode catalyst with protons from the proton exchange membrane 5 and electrons from the external circuit (O2 + 4H2O). + +4e - →2H2O), producing water. During fuel cell start-up and shutdown or when temperature fluctuations (e.g., 60–80℃) or small pressure fluctuations occur due to fluctuations in operating conditions, the nitrogen retained by the nitrogen selective separation adsorption layer 3 will be released through thermal desorption or pressure swing desorption. The desorbed nitrogen diffuses counter-currently along the anode gas diffusion layer 1 to the anode channel 42 and is discharged with the exhaust gas. Throughout the entire electrochemical reaction process, nitrogen is always isolated outside the anode catalyst layer 2, ensuring the complete availability of the catalyst active sites, and significantly improving the battery's output power and energy conversion efficiency.

[0032] Optionally, the anode bipolar plate 4 is provided with an air inlet 41, a flow channel 42 and an air outlet 43, and the air outlet 43 is provided with a purge valve 9, which is connected to the air outlet 43.

[0033] Exemplarily, in this embodiment of the invention, the inlet 41 on the anode bipolar plate 4 is located at one end of the bipolar plate and is used to receive the hydrogen-nitrogen mixture from the ammonia cracking system. A flow channel 42 is disposed on the inner surface of the anode bipolar plate 4, connecting the inlet 41 and the outlet 43, providing an orderly channel path for the flow of the mixed gas and ensuring that the gas is evenly distributed to the entire effective area of ​​the anode gas diffusion layer 1. The outlet 43 is located at the other end of the bipolar plate and is used to discharge unreacted tail gas. A purge valve 9 is installed at and connected to the outlet 43, opening when a purge operation is required and closing during normal operation. The flow channel 42 can adopt an interdigitated flow field or a biomimetic flow field design to enhance the gas convection and permeation capacity, providing a stronger mechanical driving force for hydrogen to cross the nitrogen selective separation adsorption layer 3. During normal operation of the fuel cell, a hydrogen-nitrogen mixture enters through inlet 41 and flows along channel 42 towards outlet 43. During this flow, the gas permeates from channel 42 into the anode gas diffusion layer 1, and then reaches the nitrogen selective separation adsorption layer 3 for molecular sieving. Hydrogen permeates through the separation adsorption layer and participates in the anode electrochemical reaction, while nitrogen is trapped and adsorbed on the nitrogen selective separation adsorption layer 3. When nitrogen accumulation reaches a certain level, the system controller issues a purge command. Fuel cell start-up and shutdown processes or fluctuations in operating conditions may cause temperature fluctuations (e.g., 60–80℃) or small pressure fluctuations. The purge valve 9 opens, and the nitrogen selective separation adsorption layer 3 releases the captured nitrogen through thermal desorption or pressure swing desorption mechanisms. The desorbed nitrogen diffuses counter-currently along the anode gas diffusion layer 1 towards channel 42. The nitrogen-rich exhaust gas accumulated in channel 42 is rapidly discharged from outlet 43 driven by the pressure difference between the inlet and outlet. After the purge operation is completed, the purge valve 9 closes, and the battery returns to normal operation. By adjusting the opening and closing frequency of the purge valve 9 at regular intervals, nitrogen blockage in the flow channel and anode gas diffusion layer can be effectively eliminated. Combined with the in-situ regeneration mechanism of the nitrogen selective separation adsorption layer 3, the trapped nitrogen is released through thermal desorption or pressure swing desorption and then promptly discharged through the purge operation, keeping the entire anode-side gas channel unobstructed and ensuring that the fuel cell maintains efficient and stable energy output during long-term operation.

[0034] A method for preparing an electrode structure for in-situ nitrogen separation as described above includes the following steps: S1: Using an anode gas diffusion layer 1 as a growth substrate, the surface of the anode gas diffusion layer 1 facing the anode catalyst layer 2 is hydrophilically treated to introduce oxygen-containing functional groups onto the surface; S2: Metal salt precursor solution and organic ligand precursor solution are prepared separately and mixed to obtain a reaction mother liquor; S3: The activated anode gas diffusion layer 1 is immersed in the reaction mother liquor, and the reaction is carried out at a set temperature for a set time, so that metal ions and organic ligands are in-situ coordinated and nucleated on the activated surface of the anode gas diffusion layer 1 and grown into a continuous and dense nanofilm. The thickness of the nanofilm is controlled to be between 50 and 500 nm by controlling the reaction time. nm, the nanofilm is the nitrogen selective separation adsorption layer 3; S4: Take out the anode gas diffusion layer 1 on which the nitrogen selective separation adsorption layer 3 is grown, use solvent to clean and remove unreacted precursors and loosely attached particles, dry and activate under vacuum conditions to remove residual solvent molecules in the channels and release the sieve channels; S5: Coat the anode catalyst slurry on the side of the nitrogen selective separation adsorption layer 3 away from the anode gas diffusion layer 1 and dry it to form the anode catalyst layer 2, and obtain the anode gas diffusion layer 1, nitrogen selective separation adsorption layer 3 and anode catalyst layer 2 stacked in sequence.

[0035] Specifically, in this embodiment of the invention, the preparation method directly grows a nitrogen selective separation adsorption layer 3 on the surface of the anolyte gas diffusion layer 1 using a liquid-phase in-situ growth process, achieving integrated preparation of the separation functional layer and the electrode substrate. The hydrophilic treatment in S1 is a key step in establishing a strong interfacial bond between the separation adsorption layer and the substrate. By introducing oxygen-containing functional groups (such as hydroxyl and carboxyl groups) onto the surface of the anolyte gas diffusion layer 1, the originally hydrophobic carbon-based surface is transformed into a hydrophilic activated surface with a high density of nucleation sites. These oxygen-containing functional groups anchor metal ions in the metal salt precursor through electrostatic attraction, providing dense attachment sites for the heterogeneous nucleation of the porous framework material. The metal salt precursor solution and organic ligand precursor solution prepared in S2 respectively ensure the controllability of the reaction system. The organic ligand molecules, through the steric hindrance effect of their side groups, precisely control the pore size of the generated porous framework material during subsequent coordination self-assembly, ensuring it falls within the target sieving range of 0.30~0.35 nm. In step S3, the two precursor solutions are mixed to form a reaction mother liquor, into which the activated anode gas diffusion layer 1 is immersed. Metal ions first form chemical bonds with oxygen-containing functional groups on the substrate surface, and then, starting from this, undergo coordination reactions with organic ligands, nucleating in situ and gradually growing into a continuous and dense nanofilm. This "bottom-up" chemical bond-level anchoring method allows the separation adsorption layer to be deeply "rooted" on the substrate surface, giving the film layer extremely high interfacial bonding strength. By strictly controlling the reaction time and using reaction kinetics to precisely "stop" crystal growth, the film thickness is controlled within an ultrathin range of 50-500 nm. In step S4, solvent cleaning removes surface impurities and loose particles, and then vacuum drying and activation completely remove residual solvent molecules from the channels, fully releasing the effective sieving channels and giving the separation adsorption layer the final molecular sieve activity. In step S5, an anode catalyst slurry is coated on the surface of the separation adsorption layer to form the anode catalyst layer 2, completing the assembly of the three-layer integrated electrode structure. The surface activation of S1 lays the interfacial chemical foundation for the in-situ nucleation of S3; the precursor preparation of S2 provides precise raw material conditions for the coordination self-assembly reaction of S3; the in-situ liquid-phase growth of S3 is the core step in forming the separation adsorption layer; the cleaning and activation of S4 releases the pore function of the separation adsorption layer; and the coating of the catalytic layer in S5 completes the construction of the final electrode structure. These five steps are sequentially linked, with the output of one step becoming the input of the next, forming a complete fabrication process chain.

[0036] Optionally, in S1, the hydrophilization treatment involves bombarding the surface of the anode gas diffusion layer 1 facing the anode catalyst layer 2 with oxygen plasma, using a radio frequency power of 30~80W and a treatment time of 120~300s, to introduce hydroxyl and carboxyl groups as oxygen-containing functional groups on the surface.

[0037] Exemplarily, in this embodiment of the invention, S1 employs oxygen plasma bombardment as a specific method for hydrophilication treatment. The anolyte gas diffusion layer 1 is placed inside the cavity of the plasma cleaning equipment, with its surface facing the anolyte catalyst layer 2 exposed to the oxygen plasma. The radio frequency power is set in the range of 30~80W, which is sufficient to generate enough high-energy oxygen active groups to effectively bombard the carbon-based surface without damaging the microstructure of the carbon fiber in the anolyte gas diffusion layer 1 due to excessive power. The treatment time is controlled within 120~300s to ensure that the surface functionalization reaction proceeds fully. During plasma bombardment, the high-energy oxygen active groups react with the carbon-based surface, forcibly grafting a large number of hydroxyl (-OH) and carboxyl (-COOH) groups onto the carbon fiber surface and within the micropores. These oxygen-containing functional groups transform the originally hydrophobic carbon-based surface into a hydrophilic surface. Simultaneously, they act as chemical anchoring sites, preferentially capturing metal ions from the metal salt precursor solution through electrostatic attraction and chemical chelation during the subsequent in-situ liquid-phase growth of S3. This provides a high density of attachment sites for the heterogeneous nucleation of the porous framework material, ensuring a strong chemical bond-level bond between the separated adsorption layer and the substrate. Surface activation using a dry process with oxygen plasma offers advantages over wet chemical treatment, including better uniformity, no chemical residue, and higher efficiency, while also providing controllable damage to the substrate's microstructure. The process window, consisting of 30–80 W of RF power and 120–300 s of processing time, provides adaptable adjustment space for anolyte gas diffusion layers of different specifications, ensuring ideal surface functionalization effects under various substrate conditions.

[0038] Optionally, in S2, the metal salt precursor solution is an alcoholic solution of zinc nitrate hexahydrate, and the organic ligand precursor solution is an alcoholic solution of 2-methylimidazole; in S3, the set temperature is 20~80℃, and the set time is 60~300min; in S4, the drying and activation temperature is 50~100℃, the vacuum degree is less than 0.1Pa, and the activation time is 8~16h; in S5, the anode catalyst slurry contains Pt / C catalyst and perfluorosulfonic acid resin dispersion, the coating is done by spraying, and the drying temperature is 40~80℃.

[0039] For example, in this embodiment of the invention, S2 uses zinc nitrate hexahydrate [Zn(NO3)2·6H2O] as the metal salt precursor, which is dissolved in an alcohol solvent (such as anhydrous methanol) to prepare a metal salt precursor solution. Zinc ions (Zn...) 2+In subsequent reactions, it serves as the metal node of the metal-organic framework material. The organic ligand used is 2-methylimidazole (C4H6N2), which is dissolved in an alcohol solvent to prepare an organic ligand precursor solution. An alcohol solvent is chosen as the reaction medium because it can simultaneously dissolve both the metal salt and the organic ligand, and does not chemically corrode the materials of the anolyte gas diffusion layer 1 and the anolyte catalyst layer. When the methyl side group (-CH3) on the 2-carbon atom of the 2-methylimidazole molecule coordinates with zinc ions to form a ZIF-8 sodalite topology, it rigidly points towards the center of the pore, precisely limiting the effective sieve pore size to 0.34 nm through direct steric hindrance, falling within the target range of 0.30~0.35 nm. In S3, the two precursor solutions are mixed to obtain the reaction mother liquor, and the activated anolyte gas diffusion layer 1 is vertically immersed in the mother liquor. The set temperature of 20~80℃ covers the reaction conditions from room temperature to mild heating; the higher the temperature, the faster the nucleation rate and crystal growth rate. The time range of 60–300 min provides controllable space for the preparation of films with different thickness requirements. During the reaction, zinc ions first chemically chelate with the hydroxyl and carboxyl oxygen-containing functional groups introduced on the substrate surface in S1, forming nucleation sites on the activated surface. Subsequently, zinc ions undergo coordination reactions with 2-methylimidazole molecules, nucleating in situ and gradually growing into a continuous and dense ZIF-8 nanofilm. By precisely controlling the reaction time and utilizing reaction kinetics to control the crystal growth process, the film thickness is precisely controlled within the range of 50–500 nm. In S4, after removing the anolyte gas diffusion layer 1 with the separated adsorption layer grown on its surface, it is repeatedly cleaned with pure alcohol solvents to remove residual unreacted precursors and loosely attached particles. Subsequently, a drying and activation treatment is carried out continuously for 8–16 h under strict vacuum conditions of 50–100 °C and a vacuum degree of less than 0.1 Pa. The purpose of this process is to completely remove residual alcohol solvent molecules from the ZIF-8 framework channels, fully releasing the effective sieve channels of 0.30~0.35nm and achieving the final molecular sieve activity state. The temperature is set at 50~100℃, providing sufficient thermal driving force to desorb solvent molecules from the channels without causing thermal decomposition of the ZIF-8 framework structure due to excessive temperature. A high vacuum environment of less than 0.1Pa further lowers the desorption energy barrier for solvent molecules, accelerating the channel emptying process. In S5, the anode catalyst slurry is prepared by mixing a Pt / C catalyst and a perfluorosulfonic acid resin (Nafion) dispersion. The Pt / C catalyst provides electrocatalytic activity for the hydrogen oxidation reaction, while the perfluorosulfonic acid resin acts as a proton-conducting binder, binding the catalyst particles into layers and establishing a proton conduction network. The catalyst slurry is uniformly coated onto the surface of the nitrogen selective separation adsorption layer 3, opposite to the anode gas diffusion layer 1, using a spraying method. This spraying method enables uniform thin-layer deposition of the catalyst and precise control of the loading.After coating, drying at 40-80℃ allows the solvent to evaporate and the catalyst layer to solidify, resulting in a complete electrode structure with the anode gas diffusion layer 1, nitrogen selective separation adsorption layer 3, and anode catalyst layer 2 stacked sequentially. Plasma activation in S1 provides a substrate surface with high-density nucleation sites for S3; the zinc nitrate hexahydrate and 2-methylimidazole precursor solution prepared in S2 provides precise chemical raw materials for the coordination self-assembly reaction of S3; in-situ liquid-phase growth of S3 under mild conditions of 20-80℃ is the core film-forming step for the ZIF-8 separation adsorption layer; solvent cleaning and vacuum activation in S4 ensure the complete opening of the pores in the separation adsorption layer and the activation of the molecular sieve function; and the catalyst layer spraying in S5 completes the assembly of the final integrated electrode structure. The process parameters of all five steps are interconnected and progressively advanced, jointly ensuring the chemical bond strength between the separation adsorption layer and the substrate, precise pore size control of 0.30-0.35 nm, ultra-thin film thickness of 50-500 nm, and the complete functionality of the final electrode structure.

[0040] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0041] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrode structure for in-situ nitrogen separation, comprising an anode gas diffusion layer (1) and an anode catalyst layer (2), characterized in that, A nitrogen selective separation adsorption layer (3) is provided between the anode gas diffusion layer (1) and the anode catalyst layer (2). The nitrogen selective separation adsorption layer (3) is a porous thin film layer with a pore size between the dynamic diameter of hydrogen molecules and the dynamic diameter of nitrogen molecules. The nitrogen selective separation adsorption layer (3) is deposited on the side surface of the anode gas diffusion layer (1) facing the anode catalyst layer (2) by in-situ growth.

2. The electrode structure for in-situ nitrogen separation according to claim 1, characterized in that, The pore size of the nitrogen selective separation adsorption layer (3) is 0.30~0.35nm.

3. The electrode structure for in-situ nitrogen separation according to claim 1, characterized in that, The thickness of the nitrogen selective separation adsorption layer (3) is 50~500nm.

4. The electrode structure for in-situ nitrogen separation according to claim 1, characterized in that, The core material of the nitrogen selective separation adsorption layer (3) is selected from at least one of heteroatom-doped microporous carbon, pore size-controlled metal-organic framework materials, functionalized covalent organic framework materials, and modified zeolite molecular sieves.

5. The electrode structure for in-situ nitrogen separation according to claim 4, characterized in that, The pore size-controlled metal-organic framework material is a zeolite imidazole ester framework material. The zeolite imidazole ester framework material is formed by the coordination of zinc ions and 2-methylimidazolium to form a sodalite topology. The methyl side group on the 2-carbon atom in the 2-methylimidazolium points to the center of the pore window, and the effective sieving pore size is limited to 0.34 nm through the steric hindrance effect.

6. A fuel cell comprising the electrode structure for in-situ nitrogen separation as described in any one of claims 1 to 5, characterized in that, It also includes an anode bipolar plate (4), a proton exchange membrane (5), a cathode catalytic layer (6), a cathode gas diffusion layer (7), and a cathode bipolar plate (8), wherein the anode bipolar plate (4), the anode gas diffusion layer (1), the nitrogen selective separation adsorption layer (3), the anode catalytic layer (2), the proton exchange membrane (5), the cathode catalytic layer (6), the cathode gas diffusion layer (7), and the cathode bipolar plate (8) are stacked in sequence.

7. The fuel cell according to claim 6, characterized in that, The anode bipolar plate (4) is provided with an air inlet (41), a flow channel (42) and an air outlet (43). The air outlet (43) is provided with a purge valve (9), and the purge valve (9) is connected to the air outlet (43).

8. A method for preparing an electrode structure for in-situ nitrogen separation as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Using the anode gas diffusion layer (1) as a growth substrate, the surface of the anode gas diffusion layer (1) facing the anode catalyst layer (2) is hydrophilized to introduce oxygen-containing functional groups onto the surface. Step 2: Prepare metal salt precursor solution and organic ligand precursor solution separately, and mix them to obtain reaction mother liquor; Step 3: Immerse the activated anode gas diffusion layer (1) into the reaction mother liquor, and react at a set temperature for a set time to allow metal ions and organic ligands to coordinate and nucleate in situ on the activated surface of the anode gas diffusion layer (1) and grow into a continuous and dense nanofilm. By controlling the reaction time, the thickness of the nanofilm is controlled at 50~500nm. The nanofilm is the nitrogen selective separation adsorption layer (3). Step 4: Take out the anode gas diffusion layer (1) on which the nitrogen selective separation adsorption layer (3) is grown on the surface, use solvent to clean and remove unreacted precursors and loose attached particles, dry and activate under vacuum conditions, remove residual solvent molecules in the pores, and release the sieve pores. Step 5: Coat the surface of the nitrogen selective separation adsorption layer (3) on the side opposite to the anode gas diffusion layer (1) and dry it to form the anode catalyst layer (2), thus obtaining the anode gas diffusion layer (1), nitrogen selective separation adsorption layer (3) and anode catalyst layer (2) stacked in sequence.

9. The preparation method according to claim 8, characterized in that, In step one, the hydrophilization treatment is to bombard the surface of the anode gas diffusion layer (1) facing the anode catalyst layer (2) with oxygen plasma, the radio frequency power is 30~80W, the treatment time is 120~300s, and hydroxyl and carboxyl groups are introduced on the surface as oxygen-containing functional groups.

10. The preparation method according to claim 8, characterized in that, In step two, the metal salt precursor solution is an alcoholic solution of zinc nitrate hexahydrate, and the organic ligand precursor solution is an alcoholic solution of 2-methylimidazole; in step three, the set temperature is 20~80℃, and the set time is 60~300min; in step four, the drying and activation temperature is 50~100℃, the vacuum degree is less than 0.1Pa, and the activation time is 8~16h; in step five, the anode catalyst slurry contains Pt / C catalyst and perfluorosulfonic acid resin dispersion, the coating is done by spraying, and the drying temperature is 40~80℃.

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