Thickness-controllable gas-water transmission layer and preparation method and application thereof

Abstract

The invention discloses a preparation method of a thickness-controllable gas-water transmission layer, which comprises the following steps: 1) preparing feed liquid: uniformly mixing titanium-containing powder particles with an organic solvent to obtain mixed slurry; 2) silk-screen printing: coating the surface of a titanium-based material with the mixed slurry obtained in the step 1) through a silk screen, and drying to obtain a prefabricated gas-water transmission layer; and 3) vacuum sintering: performing vacuum sintering on the prefabricated gas-water transmission layer obtained in the step 2), and cooling to obtain the thickness-controllable gas-water transmission layer. According to the gas-water transmission layer prepared by the method, the utilization rate of a catalyst can be remarkably improved, the hydrogen production power consumption of the PEM electrolytic cell is reduced, and the operation cost of the PEM electrolytic cell is reduced; besides, the gas-water transmission layer prepared according to the method can also provide additional support for the membrane electrode, and deformation of the PEM caused by the pressure difference between the cathode and the anode in the operation process is reduced, so that the service life of the membrane electrode is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy production technology, specifically relating to a gas-water transport layer with controllable thickness, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis technology is considered one of the key pathways to achieve large-scale green hydrogen production. A PEM electrolyzer mainly consists of key components such as bipolar plates, cathode / anode gas-liquid transport layers, cathode / anode catalyst layers, and ion exchange membranes. The gas-liquid transport layer, typically a conductive porous material, plays multiple roles, including supporting the membrane electrodes, collecting current, and transporting gas and liquid, making it one of the key components affecting the electrolyzer's performance. Among these, the titanium-based anode gas-liquid transport layer plays a crucial role in the oxygen evolution reaction at the anode, acting as a water conveyor, venting agent, heat conductor, and electrical conductor, and has a decisive impact on the amount of precious metals used in the membrane electrodes of the PEM electrolyzer (material cost), power consumption (operating cost), and lifespan.

[0003] Common materials for the anode gas-water transport layer in PEM electrolyzers include sintered titanium, titanium fiber felt, and titanium mesh. Titanium mesh is the cheapest, but its high porosity can lead to poor contact with the membrane electrode assembly, resulting in the worst performance in electrolyzers. Sintered titanium has a porosity of approximately 50% and a thickness of about 0.5 mm. However, the high interfacial resistance of sintered titanium / catalyst layer, high gas-water transport resistance, and high cost make it unsuitable for electrolytic reactor applications. Currently, the most commonly used anode gas-water transport layer material is titanium fiber felt, with a porosity of 50-80% and a thickness of 200-400 micrometers, offering the best performance for electrolyzers. However, existing anode gas-water transport layers still suffer from the following three major problems: 1) The contact between the titanium fiber felt and the catalyst layer is a line contact, and the poor conductivity of the anode catalyst IrO2 leads to excessive contact resistance between the titanium fiber felt and the catalyst layer; the efficiency loss caused by the contact resistance between the titanium fiber felt and the membrane electrode accounts for 30% to 50% of the total loss of the electrolyzer.

[0004] 2) Titanium fiber felt has large pore size and coarse fiber diameter. Electrochemical reactions only occur in a small area near the titanium fiber, while most of the precious metal catalysts that are not in contact with the titanium fiber cannot participate in the electrochemical reaction, thus reducing the utilization rate of precious metal catalysts.

[0005] 3) The surface pore size of titanium fiber felt varies, with larger pores reaching over 150 micrometers; consequently, when the cathode hydrogen is running at high pressure, the presence of the pressure difference between the cathode and anode can easily "squeeze" the membrane electrode into the large pores, causing membrane electrode deformation, cracks in the catalyst layer, catalyst shedding, and shortening the membrane electrode life.

[0006] To address the aforementioned issues, a microporous titanium particle coating is typically added to the surface of the gas-water transport layer. This improves the contact between the gas-water transport layer and the catalyst layer while ensuring that the gas-water transport resistance is not affected, and provides additional support for the catalyst layer. Currently, the main techniques for preparing microporous layers include bonding, ultrasonic spraying, and vacuum sintering. The bonding method uses perfluorosulfonic acid resin or polyvinyl butyral as a binder and isopropanol as a solvent, and sprays the coating onto the surface of the gas-water transport layer using a spray gun to form a porous coating containing the binder and titanium particles. However, due to the electrical insulation and weak adhesion of the binder, the porous titanium coating exhibits poor conductivity and weak bonding strength with the gas-water transport layer, making it prone to detachment. Ultrasonic spraying, using methods such as vacuum plasma spraying, directly sprays titanium particles onto the surface of the gas-water transport layer. However, this method requires specialized and expensive plasma spraying equipment, and the thick coating results in additional ohmic losses in the gas-water transport layer. Vacuum high-temperature sintering, which involves preparing titanium particles through powder compaction and casting, not only has a high sintering temperature leading to high energy consumption, but also results in a thick coating, causing high ohmic resistance and mass transfer losses in the system. Furthermore, to ensure the gas-water transport performance of the microporous titanium particle coating, existing porous coatings are mostly made of titanium particles with a diameter of 25 μm or more. This results in low surface smoothness and excessively large porosity in the prepared microporous titanium particle coating, still failing to solve the problems of high contact resistance between the gas-water transport layer and the catalyst layer, low catalyst utilization, and membrane electrode deformation. Summary of the Invention

[0007] This invention aims to at least partially address one of the technical bottlenecks in related technologies. Therefore, the main objective of this invention is to provide a method for preparing a gas-water transport layer with controllable thickness, which can effectively improve catalyst utilization, reduce ohmic losses in the electrolyzer, and reduce the overall cost of the gas-water transport layer while simultaneously lowering the power consumption for hydrogen production in the PEM electrolyzer.

[0008] The present invention also provides the application of the thickness-controllable gas-water transport layer in the gas-water transport layer of a proton exchange membrane electrolyzer; The objective of this invention is achieved through the following technical solution: A method for preparing a gas-water transport layer with controllable thickness includes the following steps: 1) Preparation of the slurry: The titanium-containing metal powder particles are mixed evenly with an organic solvent to obtain a mixed slurry; 2) Screen printing: The mixed paste obtained in step 1) is coated onto the surface of the titanium-based material through a screen. After drying, a prefabricated gas-water transport layer is obtained. 3) Vacuum sintering: The prefabricated gas-water transport layer obtained in step 2) is vacuum sintered and cooled to obtain a gas-water transport layer with controllable thickness.

[0009] In some specific embodiments, the titanium-containing metal powder particles in step 1) are titanium powder or titanium alloy powder, and the particle size of the titanium-containing metal powder particles is 1-60 μm.

[0010] Furthermore, the particle size of the titanium-containing metal powder is 3-50 μm; Furthermore, the particle size of the titanium-containing metal powder is 5-30 μm; In some specific embodiments, the organic solvent mentioned in step 1) includes, but is not limited to, one or more of ethylene glycol, glycerol, propylene glycol, ethylene glycol butyl ether, and diethylene glycol butyl ether.

[0011] In some specific embodiments, the titanium-based material mentioned in step 2) includes, but is not limited to, one or more of titanium felt, sintered titanium plate, and titanium mesh.

[0012] In some specific embodiments, the screen coating method described in step 2) is specifically as follows: S1) First, place the mixed paste in the area outside the screen pattern to make the screen and titanium-based material in close contact; S2) The horizontal scraper blade transfers the mixed slurry through the wire mesh to the surface of the titanium-based material; S3) Depending on the target thickness, the coating can be applied once or multiple times.

[0013] In some specific embodiments, the drying process conditions in step 3) are: drying at 100-250°C for 3-8 hours under vacuum conditions.

[0014] In some specific embodiments, the vacuum sintering process conditions described in step 3) are as follows: under vacuum conditions, the heating rate is set to 3~10℃ / min, and after heating to 500~900℃, the temperature is held for 2~10 hours.

[0015] Furthermore, during the vacuum sintering process, the vacuum degree is ≤10. -3 Pa.

[0016] As part of the same inventive concept, the present invention also provides a gas-water transport layer with controllable thickness.

[0017] As part of the same inventive concept, this invention also provides an application of a gas-water transport layer with controllable thickness in the fields of proton exchange membrane electrolysis for hydrogen production, anion exchange membrane electrolysis for hydrogen production, and proton exchange membrane fuel cells.

[0018] Compared with the prior art, the present invention has at least the following advantages: 1) The gas-water transport layer of this application uses only a slurry system containing titanium metal powder particles and organic solvents, which not only meets the process requirements of screen printing slurry viscosity, consistency, etc., but also avoids the formation of low conductivity titanium compounds in the coating slurry during the subsequent sintering process, thus ensuring the high conductivity of the prepared titanium metal or titanium alloy particle coating.

[0019] 2) This application uses screen printing technology to coat a mixture of titanium metal powders onto the surface of a titanium-based material. This allows for precise control of the thickness of the microporous titanium particle coating within the range of 5-100 μm and an accuracy within ±2 μm. Simultaneously, the prepared microporous titanium particle coating has a uniform and flat surface (surface undulation ≤ ±5 μm), providing a good conductive network and physical support for the PEM electrolytic cell membrane electrode. Furthermore, screen printing is easy to implement for large-scale, continuous production, making it convenient for widespread use.

[0020] 3) The prefabricated gas-water transport layer in this application, under vacuum conditions at medium and low temperatures (500-900℃) (≤10 -3 The Pa) sintering method can ensure the formation of sintering necks between titanium particles while maintaining the integrity of the coating microporous structure and the bonding strength with the titanium-based porous material. Compared with the existing titanium sintering temperature ≥1000℃, it can not only significantly reduce sintering energy consumption, but also avoid problems such as reduced porosity of titanium particle coating caused by over-sintering.

[0021] 4) The method of this application is not only suitable for traditional titanium felt and sintered titanium substrates, but also for cheaper titanium mesh substrates, making it highly versatile. It can transform rough surfaces into highly smooth surfaces. Compared to the titanium felt, which is the most commonly used material in the prior art and costs as much as 4,500 to 8,000 yuan per square meter, the gas-water transport layer prepared by titanium mesh can be as low as 2,000 yuan per square meter under the same hydrogen production energy consumption conditions. The low cost of the substrate helps to reduce the cost of PEM electrolyzer equipment. The gas-water transport layer prepared by this method can not only significantly improve the utilization rate of the catalyst and reduce the hydrogen production power consumption of the PEM electrolyzer, but also help to reduce the operating cost of the PEM electrolyzer. In addition, the gas-water transport layer prepared according to the method of this application can also provide additional support for the membrane electrode, reduce the deformation of the PEM caused by the pressure difference between the anode and cathode during operation, and thus improve the service life of the membrane electrode. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 The images show a surface SEM image (a) and a cross-sectional SEM image (b) of the gas-water transport layer in Embodiment 1 of the present invention. Figure 2This is a test diagram of the polarization curve of the gas-water transport layer in Embodiment 1 of the present invention; Figure 3 This is a diagram showing the thickness and flatness test results of the air-water transport layer in this invention; Figure 4 This is a cross-sectional SEM image of the sintered neck of the gas-water transport layer in this invention. Figure 5 To compare with the traditional anodic loading of 2mg Ir / cm 2 And the ultra-low anodic loading of 0.2 mg in this application Ir / cm 2 Diagram showing the performance of the lower electrolytic cell. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.

[0025] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0026] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0027] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0028] The objective of this invention is achieved through the following technical solution: A method for preparing a gas-water transport layer with controllable thickness includes the following steps: 1) Preparation of the slurry: Pure titanium or titanium alloy powder particles are mixed evenly with an organic solvent to obtain titanium powder slurry; Specifically, pure titanium or titanium alloy powder particles are mixed with organic solvent in a container. After initial mixing by mechanical stirring, they are ultrasonically dispersed for 10-20 minutes to ensure that the titanium powder particles are uniformly dispersed in the organic solvent without agglomeration, forming a paste-like slurry with suitable viscosity. 2) Screen printing: The paste obtained in step 1) is coated onto the surface of the titanium-based material through a screen. After drying, a prefabricated gas-water transport layer is obtained. 3) Vacuum sintering: The prefabricated gas-water transport layer obtained in step 2) is vacuum sintered and cooled to obtain a gas-water transport layer with controllable thickness.

[0029] The particle size of the titanium powder particles mentioned in step 1) is 1-50 μm, and may be one of 1-3 μm, 3-15 μm and 15-50 μm or a mixture of any two or more thereof; The organic solvents mentioned in step 1) include, but are not limited to, one or more of ethylene glycol, glycerol, propylene glycol, ethylene glycol butyl ether, and diethylene glycol butyl ether. The paste-like slurry in this application comprises a mixed solvent consisting of one or more of ethylene glycol, glycerol, propylene glycol, ethylene glycol butyl ether, and diethylene glycol butyl ether, and pure titanium or titanium alloy powder particles. It does not contain any pore-forming agents or other fillers or reagents. The paste-like slurry in this application not only ensures that all other substances except pure titanium or titanium alloy powder particles are completely removed during the subsequent drying process, but also ensures that pure titanium or titanium alloy will not generate other titanium oxides, nitrides, or carbides during the subsequent vacuum sintering process, thus avoiding or reducing the impact on its electrical conductivity.

[0030] In some specific embodiments, the titanium-based material mentioned in step 2) includes, but is not limited to, one or more of titanium felt, sintered titanium plate, and titanium mesh, and may also be other titanium-based porous materials that meet the requirements and can be conceived or used by those skilled in the art.

[0031] In some specific embodiments, the screen coating method described in step 2) is specifically as follows: S1) First, place the paste-like material in the area outside the screen pattern, and then, under certain pressure, use a scraper to make the screen and the titanium-based material come into close contact. S2) The horizontal scraper blade transfers the paste-like material through the mesh onto the surface of the titanium-based material. S3) Depending on the target thickness, the coating can be applied once or multiple times.

[0032] This application uses screen printing technology to coat the paste obtained in step 1) onto the surface of a titanium-based material. This screen printing technology is suitable for titanium substrates with various surface morphologies and roughnesses, and is especially effective in handling low-cost substrates with uneven surfaces (such as titanium mesh), transforming their rough surfaces into smooth interfaces. By selecting different mesh sizes (e.g., ≥300 mesh for 1-3μm titanium powder, 200-300 mesh for 3-15μm titanium powder, and 100-200 mesh for 15-50μm titanium powder) and controlling the number of coating passes, a thickness range of 5-100µm can be precisely achieved. Further optimization is to control the thickness of the titanium particle pre-coating to 15-25µm, which can be adjusted according to actual application needs. In some specific embodiments, the drying process conditions in step 3) are: drying at 100-250°C for 3-8 hours under vacuum to completely remove the solvent.

[0033] Furthermore, the prefabricated gas-water transport layer is dried in a vacuum environment. The vacuum environment can accelerate solvent evaporation and promote the formation of a loose and porous titanium particle prefabricated coating. Drying can completely remove the organic solvent in the prefabricated gas-water transport layer, thereby obtaining a loose, porous and uniform titanium particle prefabricated coating.

[0034] In some specific embodiments, the vacuum sintering process conditions in step 3) are: a vacuum degree ≤10 - 3 Under Pa, the heating rate is set to 3~10℃ / min, and after reaching 500~900℃, it is held for 2~10 hours; further, the sintering temperature is 500-700℃ and held for 3-8 hours, so as to form a strong sintering neck between titanium particles and between titanium particles and titanium substrate.

[0035] The sintering temperature used in this invention (e.g., 500°C) is significantly lower than the minimum temperature required for sintering traditional titanium powder particles (900°C, generally >900°C).

[0036] This invention achieves this by using a pre-fabricated gas-water transport layer at a vacuum level of ≤10. -3 Sintering under Pa conditions and at sintering temperatures of 500-900℃ not only forms a strong sintering neck between the titanium particles in the pre-coated titanium particles and the titanium-based porous material, providing sufficient mechanical strength and conductive bonding between the coating and the titanium substrate, but also minimizes: a) collapse or blockage of the loose microporous structure of the titanium coating caused by high temperatures during sintering; b) oxidation of the titanium material (high vacuum environment further inhibits oxidation), preserving the high conductivity of titanium; c) excessive energy consumption and equipment requirements. In summary, low-temperature sintering helps maintain the fine porous conductive structure constructed by micron-sized titanium particles, which is beneficial for subsequent gas-water transport and conductivity.

[0037] In some specific embodiments, the cooling process conditions in step 3) are as follows: cooling to room temperature at a cooling rate of 3~10℃ / min, while maintaining a vacuum degree ≤10 inside the furnace during the cooling process. -3 Pa.

[0038] Example 1 This embodiment provides a gas-water transport layer with controllable thickness, which includes the following steps: 1) Preparation of the liquid: Add titanium powder particles (particle size of 1-50μm) with a mass ratio of 5:3 to ethylene glycol solvent. After mixing by mechanical stirring, ultrasonically disperse for 15 minutes until the titanium powder particles reach a uniform and non-agglomerated dispersion state in the ethylene glycol solvent, forming a paste-like slurry with suitable viscosity, i.e. titanium powder slurry. 2) Screen printing: The titanium powder slurry obtained in step 1) is placed in the area outside the screen pattern. Then, under a pressure of 2kN, a scraper is used to make the screen and the titanium-based porous material (titanium felt) come into close contact. Subsequently, the scraper is horizontally scraped at a stable speed and angle to transfer the titanium powder slurry through the screen holes to the surface of the titanium-based porous material substrate. In the specific operation, depending on the required thickness, the scraping process can be repeated once or multiple times until the desired target thickness is obtained (the target thickness is generally 30-60um, the same below), thus obtaining the prefabricated gas-water transport layer. 3) Place the pre-coated gas-water transport layer from step 2) into a vacuum drying oven and dry it at a vacuum of 20 Pa and a temperature of 100 °C for 8 hours to completely remove the solvent, thereby obtaining a loose, porous and uniform titanium particle pre-coated layer. 4) Place the titanium particle pre-coated material from step 3) into a vacuum furnace, seal it, and simultaneously maintain the vacuum level inside the furnace at 10. -3 Pa, set the heating rate of the vacuum furnace to 5℃ / min, and hold it at 900℃ for 4 hours to ensure a firm bond between titanium particles and between titanium particles and titanium substrate. 5) After the heating and holding processes are completed, cool to room temperature at a cooling rate of 5℃ / min, maintaining a vacuum of 10℃ inside the furnace during the cooling process. -3 Pa; After cooling to room temperature of 100°C, release the vacuum in the furnace and remove the sintered gas-water transport layer.

[0039] Example 2 This embodiment provides a gas-water transport layer with controllable thickness, which includes the following steps: 1) Preparation of the liquid: Add titanium powder particles (particle size of 5-15μm) with a mass ratio of 5:3 to ethylene glycol butyl ether solvent. After mixing by mechanical stirring, ultrasonically disperse for 10-20 minutes until the titanium powder particles reach a uniform and non-agglomerated dispersion state in the ethylene glycol butyl ether solvent, forming a paste-like slurry with suitable viscosity, i.e., titanium powder slurry. 2) Screen printing: The titanium powder slurry obtained in step 1) is placed in the area outside the screen pattern. Then, under a pressure of 2 kN, a scraper is used to make the screen and the titanium-based porous material (titanium felt) come into close contact. Subsequently, the scraper is horizontally scraped at a stable speed and angle to transfer the titanium powder slurry through the screen holes to the surface of the titanium-based porous material substrate. In the specific operation, depending on the required thickness, the scraping process can be repeated once or multiple times until the desired target thickness is obtained, thus obtaining the prefabricated gas-water transport layer. 3) Place the pre-coated gas-water transfer layer from step 2) in a vacuum drying oven and dry it at a vacuum of 25 Pa and a temperature of 150 °C for 5 h to completely remove the solvent and avoid over-oxidation of the titanium particles, thereby obtaining a loose, porous and uniform titanium particle pre-coated layer. 4) Place the titanium particle pre-coated material from step 3) into a flat, high-temperature resistant vacuum furnace, seal it, and simultaneously maintain the vacuum level inside the furnace at 10. -3 Pa, set the heating rate of the vacuum furnace to 5℃ / min, and hold it at 800℃ for 4 hours to fully sinter the titanium particles and the titanium particles and the titanium substrate. 5) After the heating and holding processes are completed, cool to room temperature at a cooling rate of 5℃ / min, maintaining a vacuum of 10℃ inside the furnace during the cooling process. -3 Pa; After cooling to room temperature of 100°C, release the vacuum in the furnace and remove the sintered gas-water transport layer.

[0040] Example 3 This embodiment provides a gas-water transport layer with controllable thickness, which includes the following steps: 1) Preparation of the liquid: Add titanium powder particles (particle size of 10-25μm) with a mass ratio of 5:3 to a mixed solvent of ethylene glycol and propylene glycol with a mass ratio of 1:2. After mixing by mechanical stirring, ultrasonically disperse for 10-20 minutes until the titanium powder particles reach a uniform and non-agglomerated dispersion in the mixed solvent, forming a paste-like slurry with suitable viscosity, i.e., titanium powder slurry; 2) Screen printing: The titanium powder slurry obtained in step 1) is placed in the area outside the screen pattern. Then, under a pressure of 2 kN, a scraper is used to make the screen and the titanium-based porous material (sintered titanium) come into close contact. Subsequently, the scraper is horizontally scraped at a stable speed and angle to transfer the titanium powder slurry through the screen holes to the surface of the titanium-based porous material substrate. In the specific operation, depending on the required thickness, the scraping process can be repeated once or multiple times until the desired target thickness is obtained, thus obtaining the prefabricated gas-water transport layer. 3) Place the pre-coated gas-water transfer layer from step 2) in a vacuum drying oven and dry it for 5 hours at a vacuum of 20 Pa and a temperature of 150 °C to completely remove the solvent and avoid over-oxidation of the titanium particles, thereby obtaining a loose, porous and uniform titanium particle pre-coated layer. 4) Place the titanium particle pre-coated material from step 3) into a flat, high-temperature resistant vacuum furnace, seal it, and simultaneously maintain the vacuum level inside the furnace at 10. -3 Pa, set the heating rate of the vacuum furnace to 5℃ / min, and hold it at 750℃ for 5 hours to allow the titanium particles to be fully sintered together and between the titanium particles and the titanium substrate. 5) After the heating and holding processes are completed, cool to room temperature at a cooling rate of 5℃ / min. During the cooling process, maintain a vacuum of 10℃ inside the furnace. -3 Pa; After cooling to room temperature of 100°C, release the vacuum in the furnace and remove the sintered gas-water transport layer.

[0041] Example 4 This embodiment provides a gas-water transport layer with controllable thickness, which includes the following steps: 1) Preparation of liquid: Add titanium powder particles (particle size of 15-50μm) at a mass ratio of 5:3 to glycerol, mix by mechanical stirring, and then ultrasonically disperse for 10-20 minutes until the titanium powder particles are uniformly dispersed in glycerol without agglomeration, forming a paste-like slurry with suitable viscosity, i.e. titanium powder slurry. 2) Screen printing: The titanium powder slurry obtained in step 1) is placed in the area outside the screen pattern. Then, under a pressure of 2 kN, a scraper is used to make the screen and the titanium-based porous material (titanium felt) come into close contact. Subsequently, the scraper is horizontally scraped at a stable speed and angle to transfer the titanium powder slurry through the screen holes to the surface of the titanium-based material. In the specific operation, depending on the required thickness, the scraping process can be repeated once or multiple times until the desired target thickness is obtained, thus obtaining the prefabricated air-water transport layer. 3) Place the pre-coated gas-water transfer layer from step 2) into a vacuum drying oven and dry it for 3 hours at a vacuum of 20 Pa and a temperature of 250 °C to completely remove the solvent and avoid over-oxidation of the titanium particles, thereby obtaining a loose, porous and uniform titanium particle pre-coated layer. 4) Place the titanium particle pre-coated material from step 3) into a flat, high-temperature resistant vacuum furnace, seal it, and simultaneously maintain the vacuum level inside the furnace at 10. -3 Pa, set the heating rate of the vacuum furnace to 5℃ / min, and hold it at 600℃ for 4 hours to fully sinter the titanium particles and the titanium particles and the titanium substrate. 5) After the heating and holding processes are completed, cool to room temperature at a cooling rate of 5℃ / min. During the cooling process, maintain a vacuum of 10℃ inside the furnace. -3 Pa; After cooling to room temperature of 100°C, release the vacuum in the furnace and remove the sintered gas-water transport layer.

[0042] Example 5 This embodiment provides a gas-water transport layer with controllable thickness, which includes the following steps: 1) Preparation of the liquid: Add titanium powder particles (particle size of 1-5μm) with a mass ratio of 5:2 to a mixed solvent of ethylene glycol and diethylene glycol butyl ether with a mass ratio of 2:3. After mixing by mechanical stirring, ultrasonically disperse for 15 minutes until the titanium powder particles reach a uniform and non-agglomerated dispersion in the mixed solvent, forming a paste-like slurry with suitable viscosity, i.e., titanium powder slurry; 2) Screen printing: The titanium powder slurry obtained in step 1) is placed in the area outside the screen pattern. Then, under a pressure of 2kN, a scraper is used to make the screen and the titanium-based porous material (titanium mesh) come into close contact. Subsequently, the scraper is horizontally scraped at a stable speed and angle to transfer the titanium powder slurry through the screen holes to the surface of the titanium-based porous material substrate. In the specific operation, depending on the required thickness, the scraping process can be repeated once or multiple times until the desired target thickness is obtained, thus obtaining the prefabricated gas-water transport layer. 3) Place the pre-coated gas-water transfer layer from step 2) in a vacuum drying oven and dry it for 5 hours at a vacuum of 20 Pa and a temperature of 150 °C to completely remove the solvent and avoid over-oxidation of the titanium particles, thereby obtaining a loose, porous and uniform titanium particle pre-coated layer. 4) Place the titanium particle pre-coated material from step 3) into a flat, high-temperature resistant vacuum furnace, seal it, and simultaneously maintain the vacuum level inside the furnace at 10. -3 Pa, set the heating rate of the vacuum furnace to 5℃ / min, and hold it at 500℃ for 3 hours to allow the titanium particles to be fully sintered together and between the titanium particles and the titanium substrate. 5) After the heating and holding processes are completed, cool to room temperature at a cooling rate of 5℃ / min. During the cooling process, maintain a vacuum of 10℃ inside the furnace. -3 Pa; After cooling to room temperature of 100°C, release the vacuum in the furnace and remove the sintered gas-water transport layer.

[0043] Performance testing: This application uses Example 1 as an example to conduct performance tests on the gas-water transport layer with controllable thickness prepared therefrom. Specifically: 1) Microscopic morphology diagram SEM image of the titanium metal particle microporous layer in Example 1 is shown below. Figure 1 As shown, where Figure 1 a) SEM image of the microporous layer surface; Figure 1 b) SEM images of the microporous layer and the cross-section of the titanium-based material. The images show that the titanium metal particle microporous layer in this application is uniformly coated on the titanium-based porous material, exhibiting abundant pores.

[0044] 2) Electrochemical performance This application performs polarization curve testing on the titanium particle microporous coating prepared in Example 1, specifically: Test samples: In this application, titanium felt, titanium mesh, and sintered titanium substrate were selected as control groups, and titanium particle microporous coatings prepared on titanium felt, titanium mesh, and sintered titanium substrate were selected as test groups (the preparation method of the test group with titanium mesh and sintered titanium as substrates is the same as that in Example 1, the only difference being the substrate material). Polarization curve tests were conducted under the same experimental conditions. The results are as follows Figure 2 As shown, from Figure 2As can be seen from the above, under the same voltage, the sample with titanium particle metal coating has a higher current density than the sample without coating, and the performance of the coated sample is similar. The titanium particle microporous coating in this application significantly improves the performance of porous layers of different titanium substrates (titanium felt, titanium mesh and sintered titanium).

[0045] 3) Thickness and flatness test This test uses the gas-water transport layer prepared in Example 1 as an example. The coating thickness of the prepared gas-water transport layer is measured using a spiral micrometer. The control sample is titanium felt, and the test sample is titanium felt with a coating of titanium particles and micropores. Specifically: a) Select a control sample (titanium felt) of the same area size from the same batch of substrates, and use a micrometer to measure the thickness at multiple points on the sample (≥5), and take the average value to obtain the substrate thickness; b) Select test samples with titanium particle microporous coatings prepared from the same batch of substrates (the gas-water transport layer prepared in this application), and use a micrometer to measure the thickness (≥5) at multiple points on the test samples. Take the average value to obtain the thickness of the substrate with titanium particle microporous coating; subtract the two values ​​to obtain the coating thickness. The measured thickness is: Based on the data in the table, the average thickness of the titanium particle microporous coating in the gas-water transport layer of this application is calculated to be 40.9 μm.

[0046] Simultaneously, this application performs laser confocal microscopy testing on the titanium particle microporous coating in the gas-water transport layer prepared in Example 1, specifically: Cut the sample to a suitable size (not less than 20×20 mm) 2 ); Place the sample on the laser confocal stage and turn on the equipment to perform the test; c) An X50 laser confocal lens was used for testing to obtain the three-dimensional morphology of the sample surface. Figure 3 The surface roughness is calculated according to the national standard (GB / T131-93) and the arithmetic mean deviation Ra of the profile is taken.

[0047] The calculated coating Ra = 4.4 μm indicates that the titanium particle microporous coating in the gas-water transport layer of this application has excellent smoothness.

[0048] 4) Testing of sintered neck or bond strength This test uses the gas-water transport layer prepared in Example 1 as an example to analyze the prepared gas-water transport layer using cross-sectional SEM images ( Figure 4 The sintered neck size was statistically analyzed and tested, specifically as follows: a) Obtain the sample cross-section by resin curing, cutting, and grinding; b) Microscopic images of the coating on the cross section were obtained using a scanning electron microscope; c) Statistical analysis of the sintering neck width between particles to obtain the sintering strength results; As shown in the figure, sintered necks are formed between titanium particles and between titanium particles and the titanium substrate in the gas-water transport layer of this application. The formation of sintered necks ensures the bonding strength between the titanium particles and the titanium substrate; the wider the sintered neck, the higher the bonding strength between the titanium particles. Statistical calculations of the sintered neck size show that the average sintered neck size obtained in this titanium particle microporous coating is 0.87 μm. In summary, the titanium particle microporous coating and the titanium substrate in this application exhibit excellent bonding strength.

[0049] 5) Catalyst utilization rate This application also conducted performance tests on the catalyst utilization rate of the gas-water transport layer prepared in Example 1, specifically: Test Samples: Since the IrO2 loading in the anode catalyst layer has a decisive influence on electrolysis performance, the test samples were compared with those of a traditional anode with a loading of 2 mg. Ir / cm 2 and ultra-low anodic loading of 0.2 mg Ir / cm 2 The performance of the electrolyzer was assessed, specifically by employing the gas-water transport layer and low-loading catalyst exchange membrane combination described in this application (i.e., a loading of 0.2 mg). Ir / cm 2 + Titanium felt with a titanium particle microporous coating), and a control group consisting of a titanium felt without a titanium particle microporous coating and an exchange membrane with a high catalyst loading (i.e., 2 mg). Ir / cm 2 (+Titanium felt without titanium particle microporous coating) was used to test whether the gas-water transport layer with titanium particle microporous coating maintained the same performance after a significant reduction in catalyst loading, and to measure whether adding titanium particle microporous coating under low catalyst loading conditions could achieve better performance, determining the coating's contribution to improving catalyst utilization. The proton exchange membrane used in the test membrane electrode was Nafion N115, all prepared using a slurry ultrasonic spraying method. The catalyst loading of the prepared membrane electrode was adjusted by regulating the amount of catalyst slurry sprayed. Compared to traditional loaded membrane electrodes, the ultra-low loading catalyst layer has a thinner catalyst layer. Due to the smaller cross-section of the catalyst layer, the intralayer transport resistance of the ultra-low loading catalyst layer is larger, making it more prone to the problem of decreased catalyst utilization due to the "island phenomenon".

[0050] This application employs a two-electrode system, with the anode side serving as the working electrode and the cathode side as both the counter and reference electrodes. The electrolytic performance of the electrolyzer was evaluated using LSV testing, the electrochemically active area of ​​the anode catalyst layer was calculated using CV testing, and the high-frequency resistance of different samples was analyzed using constant-current EIS testing. The results are as follows Figure 5 As shown, after using titanium felt MPL (gas-water transport layer), the conventional anode loading is 2mg. Ir / cm 2 and ultra-low anodic loading of 0.2 mg Ir / cm 2 The performance of the lower electrolyzers was almost identical, indicating that 2mg Ir / cm 2 The catalyst was not fully utilized at the initial loading, but it maintained the same performance even after reducing the loading by 10 times. In summary, this indicates that at low loading, the MPL effectively improves the catalyst utilization rate to achieve the same performance, and the MPL layer can avoid the "island effect" caused by reducing the catalyst loading.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a gas-water transport layer with controllable thickness, characterized in that, Includes the following steps: 1) Preparation of the slurry: The titanium-containing metal powder particles are mixed evenly with an organic solvent to obtain a mixed slurry; 2) Screen printing: The mixed paste obtained in step 1) is coated onto the surface of the titanium-based material through a screen. After drying, a prefabricated gas-water transport layer is obtained. 3) Vacuum sintering: The prefabricated gas-water transport layer obtained in step 2) is vacuum sintered and cooled to obtain a gas-water transport layer with controllable thickness.

2. The method for preparing a thickness-controllable gas-water transport layer according to claim 1, characterized in that, The titanium-containing metal powder particles mentioned in step 1) are titanium powder or titanium alloy powder, and the particle size of the titanium-containing metal powder particles is 1-60μm.

3. The method for preparing a thickness-controllable gas-water transport layer according to claim 1, characterized in that, The organic solvents mentioned in step 1) include, but are not limited to, one or more of ethylene glycol, glycerol, propylene glycol, ethylene glycol butyl ether, and diethylene glycol butyl ether.

4. The method for preparing a thickness-controllable gas-water transport layer according to claim 1, characterized in that, The titanium-based materials mentioned in step 2) include, but are not limited to, one or more of titanium felt, sintered titanium plate, and titanium mesh.

5. The method for preparing the thickness-controllable gas-water transport layer according to claim 4, characterized in that, The screen coating method described in step 2) is as follows: S1) First, place the mixed paste in the area outside the screen pattern to make the screen and titanium-based material in close contact; S2) The horizontal scraper blade transfers the mixed slurry through the wire mesh to the surface of the titanium-based material; S3) Depending on the target thickness, the coating can be applied once or multiple times.

6. The method for preparing a thickness-controllable gas-water transport layer according to claim 1, characterized in that, The drying process conditions described in step 3) are: drying at 100-250℃ for 3-8 hours under vacuum conditions.

7. The method for preparing a gas-water transport layer with controllable thickness according to claim 1, characterized in that, The vacuum sintering process conditions described in step 3) are as follows: under vacuum conditions, the heating rate is set to 3~10℃ / min, and after heating to 500~900℃, the temperature is held for 2~10 hours.

8. The method for preparing a thickness-controllable gas-water transport layer according to claim 4, characterized in that, During the vacuum sintering process, the vacuum level is ≤10. -3 Pa.

9. A gas-water transport layer with controllable thickness prepared by the preparation method according to any one of claims 1-8, characterized in that, The thickness of the porous transport layer is 5-100 μm.

10. The application of a gas-water transport layer with controllable thickness according to claim 9 in the fields of proton exchange membrane electrolysis for hydrogen production, anion exchange membrane electrolysis for hydrogen production, and proton exchange membrane fuel cells.

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