Preparation method of membrane electrode assembly for water electrolysis of proton exchange membrane

Abstract

The invention belongs to the technical field of proton exchange membrane electrolyzed water, and particularly relates to a preparation method of a membrane electrode assembly for proton exchange membrane electrolyzed water, which comprises the following steps: coating a transfer printing membrane with cathode catalyst slurry by adopting a slit coating process to form a cathode catalyst layer; part of the anode catalyst slurry is ultrasonically sprayed on the transfer printing film to form a first anode catalyst layer, and the remaining anode catalyst slurry is ultrasonically sprayed on the surface of the anode porous transmission layer to form a second anode catalyst layer of an embedded structure; compounding the cathode catalyst layer, the proton exchange membrane and the first anode catalyst layer to form a three-in-one assembly through a heat transfer printing process; the anode side of the three-in-one assembly is attached to the anode porous transmission layer with the second anode catalyst layer, and the cathode side of the three-in-one assembly is attached to the cathode porous transmission layer to form the membrane electrode assembly. Part of the slurry is directly sprayed to the PTL to form a catalyst layer partially embedded into the PTL, so that the transmission efficiency of reactants and products can be improved, and concentration polarization is remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of proton exchange membrane water electrolysis, and in particular relates to a method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis. Background Art

[0002] As the global energy mix accelerates its transition toward cleaner energy, the strategic value of hydrogen as a zero-carbon energy carrier is becoming increasingly prominent. Proton exchange membrane water electrolysis (PEM) technology, due to its high efficiency, rapid response, high current density, and strong adaptability to renewable energy fluctuations, is considered a core technology for the large-scale production of green hydrogen. In recent years, global patent applications related to PEM water electrolysis have seen explosive growth, with technology deployment primarily focused on membrane electrode assembly (MEA) optimization, catalyst cost reduction and efficiency improvement, flow field structure design, and system integration innovation.

[0003] In the actual working conditions of PEM water electrolysis, mass transfer limitation is the key problem that hinders the reaction at high current density. At high current density, a large number of bubbles generated by the reaction cover the original active sites, causing them to fail, thereby increasing the polarization overpotential. Membrane electrode is one of the core components of PEM water electrolysis. Thermal transfer is the current mainstream membrane electrode preparation technology. Usually, the catalyst slurry is coated on the transfer membrane to form a catalytic layer. Subsequently, the cathode catalyst layer, the anode catalyst layer and the polymer proton exchange membrane are compounded together by thermal transfer, and then the porous transport layer is attached to form a membrane electrode assembly. The three-in-one membrane electrode assembly prepared by this thermal transfer process usually causes the catalyst to accumulate too densely on the polymer membrane, especially limiting the conduction of the three-phase interface of the anode part, making it difficult to desorb bubbles under high current density operation. Therefore, spraying part of the anode slurry directly onto the PTL (Porous transport layer) to form a catalyst layer partially embedded in the porous structure enhances the escape channel of bubbles and reduces bubble blockage, which is of great significance for improving reaction efficiency, reducing mass transfer resistance, and further improving the water / gas management efficiency of the gas diffusion layer. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a method for preparing a membrane electrode assembly (MEA) for proton exchange membrane water electrolysis. Because the anode catalyst layer of conventional membrane electrodes is completely coated on the proton exchange membrane, oxygen bubbles rapidly form on the anode side at high current densities (e.g., >2 A / cm²) and are difficult to escape, blocking the transport path of the reactant (water), leading to increased concentration polarization and reduced efficiency. The present invention uses a pre-sprayed PTL slurry to enhance the contact tightness between the catalyst layer and the PTL, reducing interfacial resistance and electron conduction losses, thereby alleviating mass transfer limitations in the high-density region of the PEM membrane electrode for water electrolysis.

[0005] To achieve the above technical objectives, the technical solution adopted in the embodiment of the present invention is: A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis comprises the following steps: Step S1, cathode catalyst layer preparation: cathode catalyst slurry is coated on the transfer film by a slot coating process to form a cathode catalyst layer; Step S2, preparing the anode catalyst layer in steps: ultrasonically spraying a portion of the anode catalyst slurry onto the transfer membrane to form a first anode catalyst layer, and ultrasonically spraying the remaining anode catalyst slurry onto the surface of the anode porous transport layer to form a second anode catalyst layer with an embedded structure; Step S3, thermal transfer of three-in-one component: the cathode catalyst layer, the proton exchange membrane and the first anode catalyst layer are composited to form a three-in-one component through a thermal transfer process; Step S4, final assembly of the membrane electrode assembly: the anode side of the three-in-one assembly is laminated with the anode porous transport layer with the second anode catalyst layer in step S2, and the cathode side is laminated with the untreated cathode porous transport layer to form a membrane electrode assembly.

[0006] Furthermore, the cathode porous transport layer and the anode porous transport layer are both titanium fiber sintered porous materials or carbon paper, with a porosity of 40%-70% and an average pore size of 10-70 μm.

[0007] Furthermore, the anode catalyst slurry in step S2 includes an iridium-based catalyst, a perfluorosulfonic acid resin and a solvent, the mass proportion of the iridium-based catalyst is 1-5%, the mass proportion of the perfluorosulfonic acid resin is 0.2-0.8%, and the solvent is a mixed solvent of water / n-propanol, and the mass ratio of water to n-propanol is 1:1-3:1.

[0008] Furthermore, the process parameters of the ultrasonic spraying in step S2 include: nozzle movement speed 50-300 mm / s; carrier gas pressure 5-100 psi; flow rate 0.1-10 mL / min, and substrate temperature 60-100°C.

[0009] Furthermore, in step S2, the second anode catalyst layer is first sprayed in a high-loading mode to form a surface enrichment layer; and then sprayed in a low-loading mode to promote slurry penetration.

[0010] Furthermore, the Ir loading during spraying in the high loading mode is 0.1-1.0 mg / cm², and the Ir loading during spraying in the low loading mode is 0.05-0.5 mg / cm².

[0011] Furthermore, the Ir loading of the first anode catalyst layer is 0.1-1.0 mg / cm², and the Ir loading of the second anode catalyst layer is 0.1-1.0 mg / cm².

[0012] The technical solution provided by the embodiment of the present invention has the following beneficial effects: 1. Improve mass transfer capability at high current density Traditional problem: Since the catalyst layer (CL) of the thermal transfer membrane electrode is completely attached to the surface of the proton exchange membrane (PEM), the rapid generation of oxygen bubbles on the anode side in the high current density region (>2 A / cm²) will lead to obstructed mass transfer, increased concentration polarization, and reduced efficiency.

[0013] The improvement of the present invention is that part of the slurry is sprayed directly onto the PTL to form a catalyst layer partially embedded in the porous structure, which enhances the escape channel of bubbles and reduces bubble blockage, thereby improving the transmission efficiency of reactants (water) and products (oxygen, protons) and significantly reducing concentration polarization.

[0014] 2. Enhanced mechanical stability and durability Traditional problem: The catalyst layer of the thermal transfer membrane electrode is in contact with the PTL only through pressing, which may lead to stratification due to interfacial stress or bubble impact after long-term operation.

[0015] Improvement of the present invention: The slurry pre-sprayed on the PTL forms a physical anchoring effect with the PTL, thereby increasing the bonding strength between the catalyst layer and the PTL, reducing the risk of delamination, and extending the life of the membrane electrode.

[0016] 3. Reduce interface contact resistance Traditional problem: There may be incomplete adhesion between the catalyst layer of the transfer membrane electrode and the PTL, resulting in discontinuous electron conduction path and increased contact resistance.

[0017] Improvement of the present invention: The pre-sprayed slurry on the PTL fills the surface pores thereof, forming a tighter electron conduction network, reducing the interface resistance and improving the electrochemical efficiency.

[0018] 4. Process compatibility and cost advantages By retaining some of the transfer process, the direct spray coating process avoids the special requirements for membrane or catalyst slurries (such as solvent compatibility). By flexibly adjusting the slurry distribution ratio, it can adapt to different PTL (such as titanium fiber sintered porous material titanium felt, carbon paper) and catalyst (IrO2, Pt) systems without reconstructing the entire preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Graph showing battery performance of membrane electrode assemblies of Examples 1-2 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1 A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis comprises the following steps: Step S1: Preparation of cathode catalyst layer Slurry composition: Pt / C catalyst (40wt% Pt) and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and isopropanol were mixed at a mass ratio of 1:1 to prepare a cathode catalyst slurry with a solid content of 10%; Coating process: Slit coating (coating speed 20 mm / s, gap height 150 μm) was used to form a uniform wet film on the PTFE transfer membrane. After drying at 80°C, the cathode catalyst layer (Pt loading 0.3 mg / cm²) was obtained.

[0022] Step S2: Preparation of anode catalyst layer in steps Slurry preparation: IrO2 and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and n-propanol were mixed at a mass ratio of 2:1, and ultrasonic dispersion was performed to form an anode catalyst slurry.

[0023] First anode catalyst layer (transfer film side): Ultrasonic spraying parameters: nozzle speed 200 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90 °C.

[0024] Spraying results: The first anode catalyst layer with an Ir loading of 0.5 mg / cm² was formed by spraying on the PTFE transfer membrane.

[0025] Second anode catalyst layer (embedded in PTL): High loading mode (nozzle speed 200 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90°C): First, a surface enrichment layer with an Ir loading of 0.3 mg / cm² was sprayed on the titanium fiber sintered porous material (porosity 50%, average pore size 20 μm).

[0026] Low-load penetration mode (nozzle speed 100 mm / s, carrier gas pressure 5 psi, flow rate 0.5 mL / min, substrate temperature 90°C): Anode catalyst slurry with an Ir loading of 0.2 mg / cm² was sprayed onto the above-mentioned titanium fiber sintered porous material (porosity 50%, average pore size 20 μm) to allow the slurry to penetrate deeply into the pores (total Ir loading 0.5 mg / cm²).

[0027] Step S3: Thermal transfer of three-in-one components The cathode catalyst layer, Nafion115 proton exchange membrane, and first anode catalyst layer were aligned and hot pressed at 140°C and 3 MPa for 5 minutes to form a three-in-one assembly.

[0028] Step S4: Final assembly of membrane electrode assembly Anode side: The anode side of the three-in-one component is directly bonded to the titanium fiber sintered porous material pre-sprayed with the second anode catalyst layer.

[0029] Cathode side: The cathode side is directly bonded to the untreated titanium fiber sintered porous material (porosity 50%, average pore size 20μm) to eventually form a membrane electrode assembly.

[0030] Step S5: testing the water electrolysis performance of the membrane electrode in a water electrolysis cell at 80°C.

[0031] Example 2 A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis comprises the following steps: Step S1: Preparation of cathode catalyst layer Slurry composition: PtCo / C alloy catalyst (50wt% Pt, 5wt% Co) was mixed with 20wt% Nafion solution at a solid mass ratio of 2:1, and water and isopropanol were mixed at a mass ratio of 1:1 to prepare a cathode catalyst slurry with a solid content of 12%.

[0032] Coating process: Slit coating (coating speed 20 mm / s, gap height 150 μm) was used to form a uniform wet film on the PTFE transfer membrane. After drying at 80°C, the cathode catalyst layer (Pt loading 0.3 mg / cm²) was obtained.

[0033] Step S2: Preparation of anode catalyst layer in steps Slurry preparation: IrO2 / TiO2 supported iridium-based catalyst was mixed with 20 wt% Nafion solution at a solid mass ratio of 2:1, water and n-propanol were mixed at a mass ratio of 3:1, and ultrasonic dispersion was performed to form an anode catalyst slurry.

[0034] First anode catalyst layer (transfer film side): Ultrasonic spraying parameters: nozzle speed 150 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90 °C.

[0035] Spraying results: The first anode catalyst layer with an Ir loading of 0.2 mg / cm² was formed by spraying on the PTFE transfer membrane.

[0036] Second anode catalyst layer (PTL embedded structure): High loading mode (nozzle speed 150 mm / s, carrier gas pressure 20 psi, flow rate 2 mL / min, substrate temperature 90°C): First, a surface enrichment layer with an Ir loading of 0.2 mg / cm² was sprayed on the titanium fiber sintered porous material (porosity 65%, average pore size 40 μm).

[0037] Low-load penetration mode (nozzle speed 100 mm / s, carrier gas pressure 5 psi, flow rate 0.5 mL / min, substrate temperature 90°C): The anode catalyst slurry with an Ir loading of 0.1 mg / cm² was sprayed onto the above-mentioned titanium fiber sintered porous material (porosity 65%, average pore size 40 μm) to allow the slurry to penetrate deeply into the pores (total Ir loading 0.3 mg / cm²).

[0038] Step S3: hot pressing and laminating the three-in-one components The cathode catalyst layer, enhanced proton exchange membrane (Gore 80μm), and first anode catalyst layer were aligned and hot pressed at 140°C and 3MPa for 5 minutes to form a three-in-one component.

[0039] Step S4: Final assembly of membrane electrode assembly Anode side: Directly bond the anode side of the three-in-one assembly to the titanium fiber sintered porous material PTL pre-sprayed with the second anode catalyst layer Cathode side: The cathode side is directly bonded to the untreated titanium fiber sintered porous material (porosity 65%, average pore size 40μm) to eventually form a membrane electrode assembly.

[0040] Step S5: testing the water electrolysis performance of the membrane electrode in a water electrolysis cell at 80°C.

[0041] Comparative Example 1 A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis comprises the following steps: Step S1: Preparation of cathode catalyst layer Slurry composition: Pt / C catalyst (40wt% Pt) and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and isopropanol were mixed at a mass ratio of 1:1 to prepare a cathode catalyst slurry with a solid content of 10%.

[0042] Coating process: Slit coating (coating speed 20 mm / s, gap height 150 μm) was used to form a uniform wet film on the PTFE transfer membrane. After drying at 80°C, the cathode catalyst layer (Pt loading 0.3 mg / cm²) was obtained.

[0043] Step S2: Preparation of anode catalyst layer Slurry preparation: IrO2 and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and n-propanol were mixed at a mass ratio of 2:1, and ultrasonic dispersion was performed to form an anode catalyst slurry.

[0044] Ultrasonic spraying parameters: nozzle speed 200 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90 °C.

[0045] Spraying results: An anode catalyst layer with an Ir loading of 1.0 mg / cm² was formed by spraying on the PTFE transfer membrane.

[0046] Step S3: Thermal transfer of three-in-one components The cathode catalyst layer, Nafion115 proton exchange membrane, and anode catalyst layer were aligned and hot pressed at 140°C and 3 MPa for 5 minutes to form a three-in-one component.

[0047] Step S4: Final assembly of membrane electrode assembly The anode side and cathode side of the three-in-one assembly were directly bonded to untreated titanium fiber sintered porous material (porosity 50%, average pore size 20μm) to finally form a membrane electrode assembly.

[0048] Step S5: testing the water electrolysis performance of the membrane electrode in a water electrolysis cell at 80°C.

[0049] Comparative Example 2 A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis comprises the following steps: Step S1: Preparation of cathode catalyst layer Slurry composition: Pt / C catalyst (40wt% Pt) and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and isopropanol were mixed at a mass ratio of 1:1 to prepare a cathode catalyst slurry with a solid content of 10%.

[0050] Coating process: Slit coating (coating speed 20 mm / s, gap height 150 μm) was used to form a uniform wet film on the PTFE transfer membrane. After drying at 80°C, the cathode catalyst layer (Pt loading 0.3 mg / cm²) was obtained.

[0051] Step S2: Preparation of anode catalyst layer in steps Slurry preparation: IrO2 and 20wt% Nafion solution were mixed at a solid mass ratio of 2:1, and water and n-propanol were mixed at a mass ratio of 2:1, and ultrasonic dispersion was performed to form an anode catalyst slurry.

[0052] First anode catalyst layer (transfer film side): Ultrasonic spraying parameters: nozzle speed 200 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90 °C.

[0053] Spraying results: The first anode catalyst layer with an Ir loading of 0.5 mg / cm² was formed by spraying on the PTFE transfer membrane.

[0054] Second anode catalyst layer (embedded PTL): Ultrasonic spraying parameters: nozzle speed 200 mm / s, carrier gas pressure 30 psi, flow rate 2 mL / min, substrate temperature 90 °C.

[0055] Spraying results: Sprayed on titanium fiber sintered porous material (porosity 50%, average pore size 20μm), the Ir loading is 0.5mg / cm².

[0056] Step S3: Thermal transfer of three-in-one components The cathode catalyst layer, Nafion115 proton exchange membrane, and first anode catalyst layer were aligned and hot pressed at 140°C and 3 MPa for 5 minutes to form a three-in-one assembly.

[0057] Step S4: Final assembly of membrane electrode assembly Anode side: The anode side of the three-in-one component is directly bonded to the titanium fiber sintered porous material pre-sprayed with the second anode catalyst layer.

[0058] Cathode side: The cathode side is directly bonded to the untreated titanium fiber sintered porous material (porosity 50%, average pore size 20μm) to eventually form a membrane electrode assembly.

[0059] Step S5: testing the water electrolysis performance of the membrane electrode in a water electrolysis cell at 80°C.

[0060] Compared with traditional membrane electrode, the electrolytic water membrane electrode assembly of the present invention adopts a dual anode catalyst layer structure design, that is, part of the anode catalyst is coated on the transfer membrane (first anode catalyst layer), and the remaining part is sprayed on the titanium fiber sintered porous material to form an embedded second anode catalyst layer. This structural design has a significant effect on improving the binding force between the catalyst and PTL, reducing the interface resistance, and improving the charge transfer efficiency. On this basis, the second anode catalyst layer adopts a combination strategy of high-load mode spraying and low-load mode spraying. First, the high-load mode forms a surface enrichment layer, and then the low-load mode is used to promote penetration, optimize the iridium distribution, reduce the amount of precious metals, and promote the formation of a gradient distribution, expand the three-phase reaction interface, and improve the hydrogen production efficiency.

[0061] The membrane electrodes of Examples 1-2 and Comparative Examples 1-2 were tested for their water electrolysis performance. Figure 1As shown. The embedded anode catalyst layer design and high / low loading gradient spraying of Examples 1-2 show obvious advantages. Compared with Comparative Examples 1-2, Example 1 has a more significant advantage in high current density, and the overpotential is reduced by about 50-80mV at 4 A / cm². At the same time, Example 1 has a higher current density upper limit at the same voltage, indicating that the gradient loading design effectively alleviates the mass transfer limitations of traditional MEA at high currents. It is proved that high surface loading can ensure reaction kinetics, and low bottom loading helps to maintain the pore smoothness of PTL, synergistically reducing activation polarization and ohmic polarization. Example 2 uses a more active catalyst. Compared with Example 1, the loaded catalyst used in the anode can effectively inhibit IrO2 agglomeration and increase the active sites of the catalytic layer. At the same time, the Gore membrane used has high proton conductivity. Combined with the original structural design, the amount of precious metals used can be greatly reduced while maintaining high current density performance.

[0062] The present invention enhances the bonding strength between the catalyst and PTL by designing an embedded catalytic layer in the anode part, thereby reasonably improving the mass transfer and conductivity of electrolyzed water. By controlling the slurry ratio and ultrasonic spraying parameters, precise regulation is achieved in the PTL to achieve high and low loading distribution. The high loading of the surface layer provides high surface activity, ensuring rapid charge transfer, and the low loading of the bottom layer avoids pore blockage, maintaining the gas diffusion and liquid water transmission capacity of the PTL, forming a stable structure of "surface enrichment + deep anchoring", which adapts to bubble scouring and mechanical stress during the electrolysis process. The membrane electrode assembly design reduces the amount of precious metals while improving the catalytic activity, interface stability and overall performance of the membrane electrode, and is suitable for large-scale proton exchange membrane water electrolysis hydrogen production applications.

[0063] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis, characterized in that: The following steps are involved: Step S1, cathode catalyst layer preparation: cathode catalyst slurry is coated on the transfer film by a slot coating process to form a cathode catalyst layer; Step S2, preparing the anode catalyst layer in steps: ultrasonically spraying a portion of the anode catalyst slurry onto the transfer membrane to form a first anode catalyst layer, and ultrasonically spraying the remaining anode catalyst slurry onto the surface of the anode porous transport layer to form a second anode catalyst layer with an embedded structure; Step S3, thermal transfer of three-in-one component: the cathode catalyst layer, the proton exchange membrane and the first anode catalyst layer are composited to form a three-in-one component through a thermal transfer process; Step S4, final assembly of the membrane electrode assembly: the anode side of the three-in-one assembly is laminated with the anode porous transport layer with the second anode catalyst layer in step S2, and the cathode side is laminated with the untreated cathode porous transport layer to form a membrane electrode assembly.

2. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 1, characterized in that: The cathode porous transport layer and the anode porous transport layer are both titanium fiber sintered porous materials or carbon paper, with a porosity of 40%-70% and an average pore size of 10-70 μm.

3. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 1, characterized in that: The anode catalyst slurry in step S2 includes an iridium-based catalyst, a perfluorosulfonic acid resin and a solvent, wherein the mass of the iridium-based catalyst accounts for 1-5%, the mass of the perfluorosulfonic acid resin accounts for 0.2-0.8%, and the solvent is a mixed solvent of water / n-propanol, and the mass ratio of water to n-propanol is 1:1-3:

1.

4. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 1, characterized in that: The process parameters of the ultrasonic spraying in step S2 include: nozzle movement speed 50-300 mm / s; carrier gas pressure 5-100 psi; flow rate 0.1-10 mL / min, and substrate temperature 60-100° C.

5. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 1, characterized in that: In step S2, the second anode catalyst layer is first sprayed in a high-loading mode to form a surface enrichment layer; and then sprayed in a low-loading mode to promote slurry penetration.

6. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 5, characterized in that: When spraying in the high-load mode, the Ir loading is 0.1-1.0 mg / cm², and when spraying in the low-load mode, the Ir loading is 0.05-0.5 mg / cm².

7. The method for preparing a membrane electrode assembly for proton exchange membrane water electrolysis according to claim 1, characterized in that: The Ir loading of the first anode catalyst layer is 0.1-1.0 mg / cm², and the Ir loading of the second anode catalyst layer is 0.1-1.0 mg / cm².

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