A membrane electrode with adjustable wettability, preparation method and application thereof

Abstract

The present invention relates to the field of fuel cells, and provides a membrane electrode with adjustable wettability, a preparation method and an application thereof, wherein the membrane electrode comprises an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer which are sequentially stacked and connected, wherein the anode gas diffusion layer is a single-layer structure, and the single-layer structure is a substrate layer, and a wettability regulating porous layer is provided between the anode gas diffusion layer and the anode catalyst layer, and the wettability regulating porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide and a light-induced wettability change photosensitizer. Advantages: (1) The wettability of the coating surface can be adjusted according to the operating conditions of the membrane electrode by the wavelength of light and the irradiation time to improve the performance of the membrane electrode in a low humidity or high humidity environment. (2) It avoids adding wettability regulating substances to the anode catalyst layer to ensure its normal catalytic ability. (3) The thickness is thinner, and the interface resistance is reduced, while the adjustment range of the membrane electrode operating conditions is expanded.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and more specifically, to a membrane electrode with adjustable wettability, a preparation method and an application thereof. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) consists of multiple single cells connected in series, and the single cell is mainly composed of a membrane electrode assembly (MEA) and a bipolar plate. MEA is the core component of PEMFC and is a key factor affecting the specific power density, energy density distribution and service life of PEMFC. At present, the performance of MEA is related to the temperature, humidity and other conditions of the operating conditions. MEA has poor performance in low humidity environments. To improve this problem, hydrophilic additives are usually added to the catalyst layer. However, adding additives to the catalyst layer may often affect the reaction interface, transmission resistance or mass transfer resistance of the catalyst layer. In a high humidity environment, the performance of MEA may be reduced due to the influence of water on gas transmission.

[0003] Patent CN116207313B discloses a self-humidifying membrane electrode and its preparation method, adding cationic metal oxide compounds to the anode catalyst layer slurry to improve the water retention of the catalyst layer. However, the preparation process of this method uses a non-protonic solvent to prepare the slurry, and the non-protonic solvent is usually a high-boiling point organic solvent containing nitrogen or sulfur. On the one hand, the environmental friendliness is poor in actual production. On the other hand, the high-boiling point solvent containing nitrogen or sulfur is easily adsorbed on the active sites of the catalyst during the slurry preparation process and is difficult to remove, which may affect the performance of the membrane electrode. Patent CN 116387580A discloses a self-humidifying membrane electrode preparation method in which a hydrophilic oxide film is deposited on the surface of the anode catalyst layer of the membrane electrode to obtain a hydrophilic anode. However, the oxide coating on the anode surface usually has poor conductivity, which will lead to an increase in the resistance of the membrane electrode, and when the coating is dense, it may affect the transmission of the reaction gas and water on the anode side, thereby further affecting the performance of the membrane electrode. CN104716351A discloses a method of adding an inorganic hydrophilic oxide to the anode catalyst layer of a membrane electrode and performing ultraviolet light treatment to improve the hydrophilicity of the anode catalyst layer, thereby improving the performance of the battery in a low-humidity environment. However, inorganic hydrophilic oxides are generally difficult to disperse evenly in the catalyst layer slurry, and often agglomerate and disperse unevenly, making it difficult to ensure the uniformity of the product surface wettability.

[0004] Therefore, it is particularly important to study a membrane electrode that can adjust the surface wettability without affecting the performance. Summary of the invention

[0005] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art and provide a membrane electrode with adjustable wettability and a preparation method and application, which can adjust the wettability of the surface of the anode catalyst layer and improve the performance of the membrane electrode under low or high humidity conditions.

[0006] An object of the present invention is to provide a membrane electrode with adjustable wettability, comprising an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer which are sequentially stacked and connected, wherein the anode gas diffusion layer is a single-layer structure, and the single-layer structure is a substrate layer, and a wettability adjusting porous layer is provided between the anode gas diffusion layer and the anode catalyst layer, and the wettability adjusting porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide and a photo-induced wettability changing photosensitizer.

[0007] In the present technical solution, the base layer is carbon paper or carbon cloth, and the ratio of the conductive agent, adhesive, hydrophobic agent and inorganic oxide is 10:(0.5~5):(0.5~5):(0.5~5); the conductive agent is one or more of acetylene black, graphite, carbon black, graphene and carbon nanotubes, which is used to improve the conductivity of the wettability regulating porous layer and prevent the increase of membrane electrode resistance due to the wettability regulating porous layer.

[0008] The adhesive is an amphiphilic polymer, preferably an amphiphilic polymer that can form intermolecular hydrogen bonds, such as one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, perfluorosulfonic acid resin and amphiphilic block copolymers, which is used to bond the conductive agent, hydrophobic agent, inorganic oxide and photosensitizer to form a wettability regulating porous layer.

[0009] The hydrophobic agent is one or more of polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, and is used to adjust the hydrophobic property of the porous coating.

[0010] The inorganic metal oxide is used to improve wettability and adjust the porosity of the porous layer to ensure normal transmission of substances.

[0011] Photoinduced wettability change photosensitizer is a substance that can change the wettability of the coating surface after light treatment. According to the operating conditions of the membrane electrode, the wettability of the coating surface is adjusted by the wavelength of light and the irradiation time to improve the performance of the membrane electrode in low humidity or high humidity environment.

[0012] The anode gas diffusion layer in the present invention only includes a base layer and does not include a porous layer. The base layer is carbon paper or carbon cloth. The wettability regulating porous layer can be understood as combining the wettability regulating layer and the porous layer into one, so as to achieve wettability regulation of the catalyst layer surface while ensuring normal water vapor transmission.

[0013] Compared with directly adding additives such as photoinduced wettability change photosensitizers into the catalyst layer, the present invention combines the wettability regulating layer and the porous layer into one to avoid the catalyst reaction activity, resistance and mass transfer inside the catalyst layer, thereby ensuring the normal catalytic ability of the anode catalyst layer.

[0014] Furthermore, the conventional anode gas diffusion layer structure is a base layer combined with a porous layer. Compared with setting an adjustment layer between the anode catalyst layer and the conventional anode gas diffusion layer, the present invention combines the wettability adjustment layer and the porous layer into one. Since there is one less layer, its thickness is thinner and the interface resistance between the gas diffusion layer and the catalyst layer can be reduced. In addition, the hydrophilicity and hydrophobicity of the wettability adjustment porous layer in the conventional gas diffusion layer are fixed. After adding a wettability adjustment layer on this basis, the adjustment range will be smaller according to the operating conditions. That is, the present invention uses the wettability adjustment porous layer directly as the wettability adjustment layer to expand the adjustment range of the membrane electrode operating conditions.

[0015] Furthermore, the mass ratio of the inorganic oxide to the photo-induced wettability change photosensitizer is (0.5-5):(0.1-10).

[0016] The appropriate ratio of inorganic oxide and photoinduced wettability change photosensitizer can adjust the wettability of the porous layer while ensuring its porosity, that is, the wettability of the anode catalyst layer surface can be adjusted without affecting the gas diffusion layer and increasing the thickness of the membrane electrode.

[0017] Furthermore, the light-induced wettability change photosensitizer is azobenzene, coumarin, spiropyran, diarylethene or diarylethene derivatives. Coumarin is preferred. After light treatment, the coumarin lactone ring opens or forms dimers with different molecular conformations, thereby changing the wettability of the catalyst layer surface. At the same time, the light-induced wettability change photosensitizer is soluble in low-polarity alcohol or deionized water. The photosensitizer can be effectively and evenly dispersed in the solution, which is conducive to forming a uniform humidity-adjustable porous coating and ensuring the stability of the membrane electrode performance.

[0018] Furthermore, the inorganic oxide is an inorganic metal oxide or an inorganic non-metal oxide, and the inorganic oxide is in a granular form with a particle size of 10 nm to 100 nm.

[0019] In the present technical solution, the inorganic oxide is one or more of TiO2, SiO2, CrO2, Al2O3, ZnO, CeO2, Ce3O2, V2O5, W2O3, etc.

[0020] Furthermore, the conductive agent is one or more of acetylene black, graphite, carbon black, graphene, and carbon nanotubes.

[0021] Furthermore, it also includes low boiling point alcohol and water, and the mass ratio of the low boiling point alcohol to water is (1-15):10.

[0022] The low boiling point alcohol is one or more of ethanol, propanol, butanol, ethylene glycol, ethoxyethanol, and methoxyethanol.

[0023] Another object of the present invention is to provide a method for preparing the above-mentioned membrane electrode, comprising the following steps: S1, preparing CCM; S2, preparing wettability regulating porous layer slurry: adding a photoinduced wettability changing photosensitizer to a low-boiling alcohol, stirring, adding an adhesive, stirring, adding a hydrophobic agent, stirring, adding a conductive agent, and ultrasonicating to obtain a wettability regulating porous layer preparatory liquid A; adding an inorganic oxide to water, and ultrasonicating to obtain a wettability regulating porous layer preparatory liquid B; mixing the wettability regulating porous layer preparatory liquid A and the wettability regulating porous layer preparatory liquid B, and ultrasonicating to obtain a wettability regulating porous layer slurry; S3, preparing a membrane electrode: coating the wettability regulating porous layer slurry obtained in step S2 on the surface of the anode catalyst layer of the CCM in step S1, heating and drying to obtain a CCM combined with a wettability regulating porous layer, and laminating it with a support material, a cathode gas diffusion layer, and a base layer of an anode gas diffusion layer to obtain a membrane electrode.

[0024] Furthermore, in step S3, after heating and drying, light treatment is performed, wherein the light treatment is to irradiate the porous coating with ultraviolet light or visible light, wherein the wavelength of the ultraviolet light or visible light is less than 400 nm, preferably in the wavelength range of 350 nm to 400 nm, and the irradiation time is 5 to 60 min.

[0025] Furthermore, in step S2, the solid content of the obtained wettability adjustment porous layer slurry is 0.1% to 20%.

[0026] In the technical scheme, in step S1, the preparation of CCM can be: mixing ionomer, cathode catalyst, low boiling point alcohol, and water to prepare cathode catalyst layer slurry; mixing ionomer, anode catalyst, low boiling point alcohol, and water to prepare anode catalyst layer slurry. The cathode catalyst layer is coated on one side of the proton exchange membrane by coating, spraying, hot pressing transfer, etc., and the anode catalyst layer is coated on the other side of the proton exchange membrane to obtain a three-layer catalyst layer coated proton exchange membrane, namely CCM.

[0027] In step S2, specifically, the following steps may be performed: adding a light-induced wettability change photosensitizer to a low-boiling alcohol, stirring and dissolving, then adding an amphiphilic polymer, continuing stirring for at least 24 hours so that the photosensitizer and the amphiphilic polymer are fully combined through hydrogen bonds, and the stirring time is preferably 24 to 48 hours, adding a hydrophobic agent solution to the solution, stirring for 10 to 60 minutes to mix evenly, and then continuing to add a conductive agent, and ultrasonicating for 10 to 30 minutes to obtain a wettability adjustment porous layer preparatory solution A. Adding an inorganic oxide to water, and ultrasonicating for 10 to 30 minutes to obtain a wettability adjustment porous layer preparatory solution B. Mixing the wettability adjustment porous layer preparatory solution A and the wettability adjustment porous layer preparatory solution B, and ultrasonicating for 10 to 30 minutes to obtain a coating solution.

[0028] In step S3, the coating solution is applied to the surface of the anode catalyst layer of the CCM by spraying, coating or scraping, and then heated and dried and then subjected to light treatment to obtain a CCM with adjustable surface wettability. The membrane electrode is obtained by laminating the CCM with a support material, a cathode gas diffusion layer and an anode carbon paper or carbon cloth.

[0029] Another object of the present invention is to provide application of the membrane electrode in a fuel cell.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) Based on the addition of a photosensitizer that changes wettability in a photosensitive manner, the membrane electrode of the present invention can adjust the wettability of the coating surface by adjusting the wavelength of light and the irradiation time according to the operating conditions of the membrane electrode, so as to improve the performance of the membrane electrode in a low-humidity or high-humidity environment.

[0032] (2) Compared with directly adding additives such as photoinduced wettability change photosensitizers into the catalyst layer, the present invention combines the wettability regulating layer and the porous layer into one, thereby avoiding the catalyst reaction activity, resistance and mass transfer inside the catalyst layer, and ensuring the normal catalytic ability of the anode catalyst layer.

[0033] (3) Compared with setting a regulating layer between the anode catalyst layer and the anode gas diffusion layer, the present invention combines the wettability regulating layer and the porous layer into one. Since there is one less layer, the thickness is thinner and the interface resistance between the gas diffusion layer and the catalyst layer can be reduced. In addition, the hydrophilicity and hydrophobicity of the wettability regulating porous layer in the traditional gas diffusion layer are fixed. After adding a wettability regulating layer on this basis, the adjustment range will be smaller according to the operating conditions. That is, the present invention uses the wettability regulating porous layer directly as the wettability regulating layer to expand the adjustment range of the membrane electrode operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the CCM contact angle test result of Example 1.

[0035] Figure 2 This is the CCM contact angle test result of Example 2.

[0036] Figure 3 This is the CCM contact angle test result of Example 3.

[0037] Figure 4 This is the CCM contact angle test result of Example 4.

[0038] Figure 5 This is the CCM contact angle test result of Comparative Example 1.

[0039] Figure 6 The membrane electrode structure is assembled from the CCM of Example 3 or Example 4.

[0040] Figure 7 The electrical performance test curves of the membrane electrode assembled by the CCM of Example 3 and Comparative Example 1.

[0041] Figure 8 The electrical performance test curves of the membrane electrode assembled by the CCM of Example 4 and Comparative Example 1.

[0042] Reference numerals: carbon paper 1 , wettability regulating porous layer 2 , anode catalyst layer 3 , proton exchange membrane 4 , cathode catalyst layer 5 , cathode gas diffusion layer 6 . DETAILED DESCRIPTION

[0043] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0044] An object of the present invention is to provide a membrane electrode with adjustable wettability, comprising an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer which are sequentially stacked and connected, wherein the anode gas diffusion layer is a single-layer structure, and the single-layer structure is a substrate layer, and a wettability adjusting porous layer is provided between the anode gas diffusion layer and the anode catalyst layer, and the wettability adjusting porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide and a photo-induced wettability changing photosensitizer.

[0045] In some embodiments, the mass ratio of the inorganic oxide to the photo-induced wettability change photosensitizer is (0.5-5):(0.1-10).

[0046] The appropriate ratio of the inorganic oxide and the photoinduced wettability change photosensitizer can adjust the wettability of the porous layer while ensuring the porosity of the wettability adjustment porous layer.

[0047] In some embodiments, the photoinduced wettability change photosensitizer is azobenzene, coumarin, spiropyran, diarylethene or diarylethene derivatives. Coumarin is preferred. After light treatment, the coumarin lactone ring opens or forms dimers with different molecular conformations, thereby changing the surface wettability of the catalyst layer. At the same time, the photoinduced wettability change photosensitizer is soluble in low-polarity alcohol or deionized water. The photosensitizer can be effectively and evenly dispersed in the solution, which is conducive to forming a uniform humidity-adjustable porous coating and ensuring the stability of the membrane electrode performance.

[0048] In some embodiments, the inorganic oxide is an inorganic metal oxide or an inorganic non-metal oxide, and the inorganic oxide is in a granular form with a particle size of 10 nm to 100 nm.

[0049] In some embodiments, the inorganic oxide is one or more of TiO2, SiO2, CrO2, Al2O3, ZnO, CeO2, Ce3O2, V2O5, W2O3, etc.

[0050] In some embodiments, the conductive agent is one or more of acetylene black, graphite, carbon black, graphene, and carbon nanotubes.

[0051] In some embodiments, low boiling point alcohol and water are further included, and the mass ratio of the low boiling point alcohol to water is (1-15):10.

[0052] In some embodiments, the low boiling point alcohol is one or more of ethanol, propanol, butanol, ethylene glycol, ethoxyethanol, and methoxyethanol.

[0053] Another object of the present invention is to provide a method for preparing the above-mentioned membrane electrode, comprising the following steps: S1, preparing CCM; S2, preparing wettability regulating porous layer slurry: adding a photoinduced wettability changing photosensitizer to a low-boiling alcohol, stirring, adding an adhesive, stirring, adding a hydrophobic agent, stirring, adding a conductive agent, and ultrasonicating to obtain a wettability regulating porous layer preparatory liquid A; adding an inorganic oxide to water, and ultrasonicating to obtain a wettability regulating porous layer preparatory liquid B; mixing the wettability regulating porous layer preparatory liquid A and the wettability regulating porous layer preparatory liquid B, and ultrasonicating to obtain a wettability regulating porous layer slurry; S3, preparing a membrane electrode: coating the wettability regulating porous layer slurry obtained in step S2 on the surface of the anode catalyst layer of the CCM in step S1, heating and drying to obtain a CCM combined with a wettability regulating porous layer, and laminating it with a support material, a cathode gas diffusion layer, and a base layer of an anode gas diffusion layer to obtain a membrane electrode.

[0054] In some embodiments, in step S3, light treatment is performed after heating and drying, and the light treatment is to irradiate the porous coating with ultraviolet light or visible light, the wavelength of the ultraviolet light or visible light is less than 400nm, preferably in the wavelength range of 350nm to 400nm, and the irradiation time is 5 to 60min.

[0055] In some embodiments, in step S2, the solid content of the obtained wettability adjustment porous layer slurry is 0.1% to 20%.

[0056] In some embodiments, in step S1, the preparation of CCM can be: mixing ionomer, cathode catalyst, low boiling alcohol, and water to prepare cathode catalyst layer slurry; mixing ionomer, anode catalyst, low boiling alcohol, and water to prepare anode catalyst layer slurry. The cathode catalyst layer is coated on one side of the proton exchange membrane by coating, spraying, hot pressing transfer, etc., and the anode catalyst layer is coated on the other side of the proton exchange membrane to obtain a three-layer catalyst layer coated proton exchange membrane, i.e., CCM.

[0057] In step S2, specifically, the following steps may be performed: adding a photosensitive agent for changing wettability to a low-boiling alcohol, stirring and dissolving, then adding an amphiphilic polymer, continuing stirring for at least 24 hours so that the photosensitizer and the amphiphilic polymer are fully combined through hydrogen bonds, and the stirring time is preferably 24 to 30 hours, adding a hydrophobic agent solution to the solution, stirring for 10 to 60 minutes to mix evenly, and then continuing to add a conductive agent, and ultrasonicating for 10 to 30 minutes to obtain a wettability adjustment porous layer preparatory solution A. Adding an inorganic oxide to water, and ultrasonicating for 10 to 30 minutes to obtain a wettability adjustment porous layer preparatory solution B. Mixing the wettability adjustment porous layer preparatory solution A and the wettability adjustment porous layer preparatory solution B, and ultrasonicating for 10 to 30 minutes to obtain a coating solution.

[0058] In step S3, the coating solution is applied to the surface of the anode catalyst layer of the CCM by spraying, coating or scraping, and then heated and dried and then subjected to light treatment to obtain a CCM with adjustable surface wettability. The membrane electrode is obtained by laminating the CCM with a support material, a cathode gas diffusion layer and an anode carbon paper or carbon cloth.

[0059] Another object of the present invention is to provide application of the membrane electrode in a fuel cell.

[0060] The present invention is now further described in conjunction with specific examples. The following examples are only for explaining the present invention, but do not constitute a limitation of the present invention. The test samples and test processes used in the following examples include the following (if the specific experimental conditions are not indicated in the examples, they are usually in accordance with conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following examples, if not otherwise specified, can all be obtained from commercial channels).

[0061] Example 1

[0062] This embodiment provides a CCM combined with a wettability regulating porous layer, wherein the wettability regulating porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide, and a photoinduced wettability change photosensitizer. The CCM combined with a wettability regulating porous layer is made by the following method:

[0063] S1: Dispersing the cathode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain a cathode catalyst layer slurry;

[0064] S2: dispersing the anode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain the anode catalyst layer slurry;

[0065] S3: coating the cathode catalyst slurry and the anode catalyst slurry on both sides of the proton exchange membrane by a slit coater to obtain a CCM;

[0066] S4: Add 1g of coumarin (Aladdin, C104165) to 20g of ethanol and stir magnetically until completely dissolved; add 2g of polyvinyl alcohol resin (Aladdin, P434371) to the solution and continue stirring for 24h; then add 5g of polytetrafluoroethylene suspension (MacKlin, P816262) to the solution and stir magnetically for 30min until it is evenly mixed, then add 5g of acetylene black to the mixed solution and ultrasonically treat the solution for 30min until it is evenly dispersed to obtain wettability adjustment porous layer preparatory solution A. Add 0.5g of ZnO (Aladdin, Z431821) to 80g of water and ultrasonically treat for 10min to obtain porous layer preparatory solution B. Mix wettability adjustment porous layer preparatory solution A and wettability adjustment porous layer preparatory solution B and ultrasonically treat for 20min to obtain wettability adjustment porous layer slurry;

[0067] S5, spraying the wettability regulating porous layer slurry of step S4 on the outer surface of the CCM anode catalyst layer with a thickness of 1 μm, and drying at 90° C. to obtain a CCM combined with a wettability regulating porous layer.

[0068] Example 2

[0069] This embodiment provides a CCM combined with a wettability regulating porous layer. The difference from Embodiment 1 is that after the CCM combined with a wettability regulating porous layer is prepared according to the preparation method of Embodiment 1, the wettability regulating porous layer is irradiated with ultraviolet light with a wavelength of 355nm for 1min, and then with ultraviolet light with a wavelength of 254nm for 1min, and the two wavelengths of ultraviolet light are alternately treated 5 times.

[0070] Example 3

[0071] This embodiment provides a CCM combined with a wettability regulating porous layer, wherein the wettability regulating porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide, and a photoinduced wettability change photosensitizer. The CCM combined with a wettability regulating porous layer is made by the following method:

[0072] S1: Dispersing the cathode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain a cathode catalyst layer slurry;

[0073] S2: dispersing the anode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain an anode catalyst layer slurry;

[0074] S3: coating the cathode catalyst slurry and the anode catalyst slurry on both sides of the proton exchange membrane by a slit coater to obtain a CCM;

[0075] S4: Add 6g of spiropyran (Macklin, H864447) to 50g of ethanol and stir magnetically until completely dissolved; add 4g of perfluorosulfonic acid resin (Chemours, D2020) to the solution and continue stirring for 24h; then add 6g of polytetrafluoroethylene suspension (MacKlin, P816262) to the solution and stir magnetically for 30min until it is evenly mixed, add 8g of acetylene black to the mixed solution, and ultrasonicate the solution for 30min until it is evenly dispersed to obtain wettability adjustment porous layer preparatory solution A. Add 0.5g of ZnO (Aladdin, Z431821) to 150g of water and ultrasonicate for 10min to obtain porous layer preparatory solution B. Mix wettability adjustment porous layer preparatory solution A and wettability adjustment porous layer preparatory solution B and ultrasonicate for 20min to obtain wettability adjustment porous layer slurry;

[0076] S5, spraying the wettability regulating porous layer slurry of step S4 on the outer surface of the CCM anode catalyst layer with a thickness of 2 μm, and drying at 90° C. to obtain a CCM combined with a wettability regulating porous layer.

[0077] Example 4

[0078] This embodiment provides a CCM combined with a wettability regulating porous layer, which differs from Embodiment 3 in that after the CCM combined with a wettability regulating porous layer is prepared according to the preparation method of Embodiment 3, the outer coating of the anode catalyst layer is irradiated with ultraviolet light with a wavelength of 310 nm for 30 minutes.

[0079] Comparative Example 1

[0080] This comparative example provides a CCM structure, wherein the CCM structure is a proton exchange membrane coated with a cathode catalyst layer and an anode catalyst layer on both sides, respectively. The preparation method of the CCM structure is:

[0081] S1: Dispersing the cathode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain a cathode catalyst layer slurry;

[0082] S2: dispersing the anode catalyst, ionomer, ethanol and water by a Beads mill disperser, the speed of the disperser is 1000 rpm, the dispersion time is 10 min, and then collecting the dispersed catalyst slurry for degassing to obtain the anode catalyst layer slurry;

[0083] S3: The cathode catalyst slurry and the anode catalyst slurry are respectively coated on both sides of the proton exchange membrane by a slit coater to obtain a CCM.

[0084] The preparation process of the CCM structure of this comparative example is the same as that of the CCM structure in the embodiment, so as to compare the CCM structure before and after combining it with the wettability regulating porous layer of the present invention.

[0085] Figure 1 to Figure 5 The contact angle test results of Examples 1 to 4 and Comparative Example 1 are listed in order. The results show that in Comparative Example 1, there is no wettability regulating porous layer outside the anode catalyst layer, and the contact angle is 143.2°. In Examples 1 and 3, a wettability regulating porous layer is combined with the outside of the anode catalyst layer, and the contact angles are 141.9° and 142.8° respectively without light treatment, and the surface of the anode catalyst layer is still hydrophobic. In Examples 2 and 4, a wettability regulating porous layer is combined with the outside of the anode catalyst layer and light treatment is performed, and the contact angles are 118.4° and 97.5° respectively. This indicates that the photoinduced wettability changes after light treatment, or the photosensitizer reacts, so that the wettability of the coating is improved, which is beneficial to the performance improvement of the membrane electrode under low-humidity conditions.

[0086] The CCM of Example 3 and Example 4 was combined with carbon paper and cathode gas diffusion layer to form a membrane electrode for electrical performance testing. The membrane electrode structure is as follows: Figure 6 As shown, the membrane electrode comprises a carbon paper 1, a wettability regulating porous layer 2, an anode catalyst layer 3, a proton exchange membrane 4, a cathode catalyst layer 5 and a cathode gas diffusion layer 6 which are stacked and connected in sequence; the CCM, anode gas diffusion layer and cathode gas diffusion layer of comparative example 1 are combined into a membrane electrode for electrical performance testing. Figure 7 The polarization curves of Example 3 and Comparative Example 1 under high humidity conditions (80% RH) show that adding an ultra-thin super-hydrophobic coating on the surface of the anode catalyst layer can facilitate drainage under high humidity conditions and improve the performance of the membrane electrode. Figure 8 Polarization curves of Example 4 and Comparative Example 1 under relatively dry conditions show that the performance of Example 4 after light treatment is significantly better than that of the sample of Comparative Example 1 without spraying wettability regulating porous layer, indicating that the method of the present invention can significantly improve the wettability and water retention of membrane electrode under dry conditions, which is beneficial to improving the performance of membrane electrode.

[0087] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A membrane electrode with adjustable wettability, comprising an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer which are sequentially stacked and connected, characterized in that: The anode gas diffusion layer is a single-layer structure, the single-layer structure is a substrate layer, a wettability regulating porous layer is provided between the anode gas diffusion layer and the anode catalyst layer, the wettability regulating porous layer comprises a conductive agent, an adhesive, a hydrophobic agent, an inorganic oxide and a light-induced wettability changing photosensitizer, The mass ratio of the inorganic oxide to the photoinduced wettability change photosensitizer is (0.5-5):(0.1-10); The light-induced wettability change photosensitizer is azobenzene, coumarin, spiropyran, diarylethene or a diarylethene derivative.

2. The membrane electrode according to claim 1, characterized in that: The inorganic oxide is an inorganic metal oxide or an inorganic non-metal oxide, and the inorganic oxide is in a granular form with a particle size of 10 nm to 100 nm.

3. The membrane electrode according to claim 1, characterized in that: The wettability adjusting porous layer has a thickness of 0.1 μm to 5 μm.

4. The method for preparing a membrane electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Prepare CCM; S2, preparing wettability regulating porous layer slurry: adding a photosensitive agent for changing wettability to a low-boiling alcohol, stirring, adding an adhesive, stirring, adding a hydrophobic agent, stirring, adding a conductive agent, ultrasonicating, and obtaining a wettability regulating porous layer preparatory liquid A; adding an inorganic oxide to water, ultrasonicating, and obtaining a wettability regulating porous layer preparatory liquid B; mixing the wettability regulating porous layer preparatory liquid A and the wettability regulating porous layer preparatory liquid B, ultrasonicating, and obtaining a wettability regulating porous layer slurry; S3, preparing a membrane electrode: coating the wettability-adjusting porous layer slurry obtained in step S2 on the surface of the anode catalyst layer of the CCM in step S1, heating and drying to obtain a CCM combined with a wettability-adjusting porous layer, and laminating the CCM with a supporting material, a cathode gas diffusion layer, and a base layer of an anode gas diffusion layer to obtain a membrane electrode; In step S3, after heating and drying, a light treatment is performed. The light treatment is to irradiate the wettability regulating porous layer with ultraviolet light for 5 to 60 minutes.

5. The method for preparing a membrane electrode according to claim 4, characterized in that: The mass ratio of the low boiling point alcohol to water is (1-15):

10.

6. The preparation method according to claim 4, characterized in that: In step S2, the solid content of the obtained wettability adjustment porous layer slurry is 0.1% to 20%.

7. Use of the membrane electrode according to any one of claims 1 to 3 in a fuel cell.

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