A membrane electrode for a solid polymer membrane electrolyzer and a method for manufacturing the same

Abstract

The application discloses a membrane electrode for a solid polymer membrane electrolytic cell and a preparation method thereof. The membrane electrode comprises an anode porous transport layer, an anode catalytic layer, a proton exchange membrane, a cathode catalytic layer and a cathode porous transport layer which are sequentially arranged. The proton exchange membrane is integrally connected with the anode catalytic layer and the cathode catalytic layer in situ. The anode catalytic layer adopts a multi-subset layer structure. Each subset layer contains a composite catalyst and a perfluorosulfonic acid resin. The composite catalyst is composed of a noble metal catalyst and a conductive carrier. The amount of the perfluorosulfonic acid resin, the proportion of the conductive carrier and the noble metal catalyst in the composite catalyst in each subset layer change in a gradient manner. The loading amount of the noble metal catalyst in each subset layer is the same. In the preparation, the anode catalytic layer and the cathode catalytic layer are respectively sprayed on the anode porous transport layer and the cathode porous transport layer, and the proton exchange membrane is formed by being deposited on the catalytic layer in situ. The application has the advantages of improving the water electrolysis performance of the membrane electrode, firmly connecting the catalytic layer and the membrane and the like.

Description

Technical Field

[0001] This invention belongs to the technical field of membrane electrodes, and particularly relates to a membrane electrode for a solid polymer membrane electrolyzer and its preparation method. Background Technology

[0002] Hydrogen is a versatile energy carrier that can help address current critical energy and environmental challenges. Green hydrogen produced by water electrolysis is recognized as one of the cleanest and greenest energy sources, and its combination with renewable energy is considered the most efficient and sustainable form of hydrogen production available today. Developing a "green hydrogen economy" through renewable energy-based water electrolysis will be a core factor in the future decarbonization of the world economy and a key medium for building a reversible, circular integrated energy system.

[0003] Solid polymer membrane electrolyzers (SPEWEs) offer a wider operating range and shorter response times, and are particularly well-suited for coupling with highly dynamic energy sources such as wind and solar power, which can reduce operating costs. With the ever-increasing demand for green energy, there has been significant research interest in SPEWE technology. Currently, SPEWE technology has achieved small-scale commercialization, but its high cost remains a major challenge in becoming a commercially viable large-scale hydrogen production solution.

[0004] Existing membrane electrodes for solid polymer membrane electrolyzers suffer from problems such as low water electrolysis efficiency, easy delamination and cracking between the catalytic layer and the membrane under high current density, leading to reduced water electrolysis performance, and differences in reaction space and large mass transfer resistance in the anode catalytic layer. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the background art and to propose a membrane electrode for a solid polymer membrane electrolyzer and its preparation method, which can improve the water electrolysis performance of the membrane electrode, ensure a strong connection between the catalyst layer and the membrane that is not prone to cracking, and reduce the charge transfer resistance and mass transfer resistance at the membrane electrode interface.

[0006] To achieve the above objectives, this invention proposes a membrane electrode for a solid polymer membrane electrolyzer, comprising a proton exchange membrane, an anode catalyst layer, a cathode catalyst layer, an anode porous transport layer, and a cathode porous transport layer. The anode porous transport layer and the cathode porous transport layer are respectively disposed on the side of the anode catalyst layer and the cathode catalyst layer away from the proton exchange membrane. Both sides of the proton exchange membrane are integrally connected in situ to one side of the anode catalyst layer and the cathode catalyst layer, respectively. The anode catalyst layer adopts a multi-sublayer structure, and each sublayer contains a composite catalyst and perfluorinated material. The ratio of composite catalyst and perfluorosulfonic acid resin in each subset layer is different. The composite catalyst is composed of noble metal catalyst and conductive support. The amount of perfluorosulfonic acid resin in each subset layer decreases from the inside to the outside along the direction away from the proton exchange membrane. The proportion of conductive support in the composite catalyst in each subset layer decreases from the inside to the outside along the direction away from the proton exchange membrane. The proportion of noble metal catalyst in the composite catalyst in each subset layer increases from the inside to the outside along the direction away from the proton exchange membrane, so that the loading of noble metal catalyst in each subset layer is the same.

[0007] Preferably, the anode catalyst layer is formed by sequentially connecting a first subset layer, a second subset layer, and a third subset layer from the inside out along the direction away from the proton exchange membrane.

[0008] Preferably, the noble metal catalyst is an Ir-containing metal compound or metal oxide, and the mass fraction of the noble metal catalyst in the composite catalyst is 40-80%.

[0009] Preferably, the Ir loading in the first subset layer, the second subset layer, and the third subset layer is the same and is 0.1–0.3 mg each. Ir cm -2 The proportions of noble metal catalysts in the composite catalysts of the first subset layer, the second subset layer, and the third subset layer are 40%, 60%, and 80%, respectively.

[0010] Preferably, the perfluorosulfonic acid resin loadings in the first subset layer, the second subset layer, and the third subset layer are 30-45%, 15-30%, and 1-15% of the Ir loading, respectively.

[0011] Preferably, the conductive carrier includes at least one of TiN and TiO2.

[0012] Preferably, the anode porous transport layer is a porous titanium plate with a porosity of 30-60%, and the cathode porous transport layer is carbon paper with a microporous layer or a porous titanium plate.

[0013] The present invention also proposes a method for preparing the membrane electrode for the above-mentioned solid polymer membrane electrolyzer, comprising the following steps:

[0014] Preparation and spraying of cathode catalyst slurry: Platinum carbon catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, and ultrasonically treated in an ice-water bath. Perfluorosulfonic acid resin is added, and ultrasonic treatment in an ice-water bath is performed again to obtain cathode catalyst slurry. The cathode catalyst slurry is sprayed onto one side of the cathode porous transport layer to form a cathode porous transport layer containing a cathode catalyst layer.

[0015] Preparation and spraying of anode catalyst slurry: The composite catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, perfluorosulfonic acid resin is added, and the mixture is subjected to ultrasonic treatment in an ice-water bath to obtain anode catalyst slurry. The anode catalyst slurry includes multiple sub-layer slurries. The mass ratio of perfluorosulfonic acid resin to composite catalyst in the multiple sub-layer slurries decreases from the inside to the outside. The multiple sub-layer slurries are sprayed and connected together from the inside to the outside. The outermost sub-layer slurry is sprayed onto one side of the anode porous transport layer to form an anode porous transport layer containing an anode catalyst layer.

[0016] Preparation of membrane electrode: The cathode porous transport layer containing the cathode catalyst layer and the anode porous transport layer containing the anode catalyst layer are placed in the grooves of two glass plates, with the cathode catalyst layer and the anode catalyst layer facing upwards. 10-20 wt% Nafion membrane solution is added to the two grooves respectively and placed in an oven at 60-80℃ to form semi-solid proton exchange membrane layers on the surfaces of the cathode catalyst layer and the anode catalyst layer respectively. The two proton exchange membrane layers are then attached to each other and placed in an oven at 100-120℃ to achieve in-situ integrated membrane formation, and finally a solid polymer membrane electrolyzer membrane electrode is obtained.

[0017] The cathode catalyst slurry contains 0.1-0.5% platinum-carbon catalyst by mass, the anode catalyst slurry contains 0.1-0.6% total composite catalyst by mass, and the anode catalyst layer preparation and spraying steps involve mixing deionized water and low-boiling-point pure solvent at a volume ratio of 1:(1-4).

[0018] Preferably, the low-boiling-point pure solvent is at least one of isopropanol, n-propanol, ethanol, and methanol, and the equivalent mass of the perfluorosulfonic acid resin is 700–2100 g / mol.

[0019] Preferably, the spraying flow rate during the spraying process is 1-5 ml / min, the hot plate temperature is 70-100℃, and the thickness of the proton exchange membrane in the membrane electrode of the solid polymer membrane electrolyzer is 10-185 μm.

[0020] The beneficial effects of this invention are as follows: By employing a porous transport layer as the catalyst layer support and directly depositing the membrane on the catalyst layer, an inter-layer interface embedding structure is constructed, increasing the contact interface bonding force, reducing the charge transfer resistance and mass transfer resistance at the membrane electrode interface, achieving zero interface gap, and avoiding cracking between the catalyst layer and the membrane. Under the condition of constant absolute loading of noble metal catalyst, the content of noble metal catalyst and conductive support and the content of ionomer are matched with different gradient distributions. The content gradient of conductive support is used to improve catalyst utilization and enhance water-gas transport, while the gradient change of ionomer content is used to expand the reaction interface and reduce the amount of noble metal used. This membrane electrode adopts in-situ film formation combined with multi-dimensional gradient distribution of the anode catalyst layer, which is conducive to the construction of effective proton, electron, water and gas transport channels in the anode catalyst layer, while improving the construction of the three-phase reaction interface and improving catalyst activity, thereby achieving high-efficiency SPEWE water electrolysis.

[0021] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a structural schematic diagram of an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the installation structure of the anode catalyst layer and the anode porous transport layer according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the composition ratio of each subset layer in the anode catalyst layer of this invention.

[0025] Figure 4 This is a schematic diagram comparing the electrolytic cell voltages of each membrane electrode under different current densities according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram comparing the electrolytic cell voltages of each membrane electrode under a specific current density according to an embodiment of the present invention.

[0027] In the figure: 1-proton exchange membrane, 2-anode catalyst layer, 3-anode porous transport layer, 4-cathode catalyst layer, 5-cathode porous transport layer, 21-first subset layer, 22-second subset layer, 23-third subset layer. Detailed Implementation

[0028] See Figure 1This invention provides a membrane electrode for a solid polymer membrane electrolyzer, comprising a proton exchange membrane 1, an anode catalyst layer 2, a cathode catalyst layer 4, an anode porous transport layer 3, and a cathode porous transport layer 5. The anode porous transport layer 3 and the cathode porous transport layer 5 are respectively disposed on the side of the anode catalyst layer 2 and the cathode catalyst layer 4 away from the proton exchange membrane 1. The two sides of the proton exchange membrane 1 are in-situ integratedly connected to one side of the anode catalyst layer 2 and the cathode catalyst layer 4, respectively. The anode catalyst layer 2 adopts a multi-sublayer structure, and each sublayer contains a composite catalyst and perfluorosulfonic acid resin, with different ratios of composite catalyst and perfluorosulfonic acid resin in each sublayer. The composite catalyst is composed of a noble metal catalyst and a conductive support. In this composite catalyst, the amount of perfluorosulfonic acid resin in each subset layer decreases gradually from the inside out along the direction away from the proton exchange membrane. The proportion of conductive support in the composite catalyst in each subset layer decreases gradually from the inside out along the direction away from the proton exchange membrane 1. The proportion of noble metal catalyst in the composite catalyst in each subset layer increases gradually from the inside out along the direction away from the proton exchange membrane 1. This results in the same loading of noble metal catalyst in each subset layer. The anode catalyst layer 2 adopts a multi-subset structure, which includes, but is not limited to, bi-subset and tri-subset structures. In the composite catalyst, the noble metal catalyst provides catalytic activity, while the conductive support, as the support for the noble metal catalyst, mainly provides a large reaction area.

[0029] The noble metal catalyst is an Ir-containing metal compound or metal oxide. The mass fraction of the noble metal catalyst in the composite catalyst is 40-80%, and the Ir loading in each sub-base is the same and is 0.1-0.3 mg. Ir cm -2 Ir-containing metal compounds include IrRu x O2, and Ir-containing metal oxides include IrO2.

[0030] The conductive carrier includes at least one of TiN and TiO2.

[0031] The anode porous transport layer 3 is a porous titanium plate with a porosity of 30-60%, and the cathode porous transport layer 5 is carbon paper or a porous titanium plate containing a microporous layer.

[0032] The membrane electrode for a solid polymer membrane electrolyzer employs in-situ film formation combined with a multi-dimensional gradient distribution of the anode catalyst layer. Specifically, an anode catalyst layer structure with multiple layers of varying component ratios is formed on the porous anode transport layer. Under the condition of constant absolute noble metal loading, different gradient distributions are used for the content of noble metal, conductive support, and ionomer. The gradient change in conductive support content improves catalyst utilization and enhances water-gas transport, while the gradient change in ionomer content expands the reaction interface, reducing the amount of noble metal required. Then, a solid polymer membrane is in-situ deposited on the catalyst layer, achieving in-situ integrated preparation of the catalyst layer and membrane. This enhances the bonding strength between the catalyst layer and membrane, reduces their contact resistance, and solves the problems of easy cracking and high contact resistance in existing technologies, ultimately improving the efficiency of water electrolysis in the electrolyzer.

[0033] The present invention also proposes a method for preparing the membrane electrode for the above-mentioned solid polymer membrane electrolyzer, comprising the following steps:

[0034] S01. Preparation and spraying of cathode catalyst slurry: Platinum carbon catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, and ultrasonically treated in an ice-water bath. Perfluorosulfonic acid resin is added, and ultrasonic treatment in an ice-water bath is performed again to obtain cathode catalyst slurry. The cathode catalyst slurry is sprayed onto one side of the cathode porous transport layer to form a cathode porous transport layer containing a cathode catalyst layer.

[0035] S02. Preparation and spraying of anode catalyst slurry: The composite catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, perfluorosulfonic acid resin is added, and the mixture is subjected to ultrasonic treatment in an ice-water bath to obtain an anode catalyst slurry. The anode catalyst slurry includes multiple sub-layer slurries. The mass ratio of perfluorosulfonic acid resin to composite catalyst in the multiple sub-layer slurries decreases from the inside to the outside. The multiple sub-layer slurries are sprayed and connected together from the inside to the outside. The outermost sub-layer slurry is sprayed onto one side of the anode porous transport layer to form an anode porous transport layer containing an anode catalyst layer.

[0036] S03. Preparation of membrane electrode: The cathode porous transport layer containing the cathode catalyst layer and the anode porous transport layer containing the anode catalyst layer are placed in the grooves of two glass plates, with the cathode catalyst layer and the anode catalyst layer facing upwards. 10-20 wt% Nafion membrane solution is added to the two grooves respectively and placed in an oven at 60-80℃ to form semi-solid proton exchange membrane layers on the surfaces of the cathode catalyst layer and the anode catalyst layer. The two proton exchange membrane layers are then attached together and placed in an oven at 100-120℃ to achieve in-situ integrated membrane formation, and finally a solid polymer membrane electrolyzer membrane electrode is obtained.

[0037] In this process, the mass percentage of platinum-carbon catalyst in the cathode catalyst slurry is 0.1-0.5%, the mass percentage of total composite catalyst in the anode catalyst slurry is 0.1-0.6%, the platinum content in the platinum-carbon catalyst is 40-60%, in step S01 deionized water and low-boiling-point pure solvent are mixed at a volume ratio of 1:9, and in step S02 deionized water and low-boiling-point pure solvent are mixed at a volume ratio of 1:(1-4).

[0038] In steps S01 and S02, the low-boiling-point pure solvent is at least one of isopropanol, n-propanol, ethanol, and methanol, and the equivalent mass of the perfluorosulfonic acid resin is 700–2100 g / mol.

[0039] During the spraying process, the spraying flow rate is 1-5 ml / min, the hot table temperature is 70-100℃, and the thickness of the proton exchange membrane in the membrane electrode of the solid polymer membrane electrolyzer is 10-185 μm.

[0040] The present invention will be further illustrated by specific embodiments below. These embodiments are for illustrative purposes only and do not limit the scope of the invention:

[0041] Example 1

[0042] See Figure 1 , Figure 2 and Figure 3 This embodiment provides a membrane electrode for a solid polymer membrane electrolyzer, including a proton exchange membrane 1, an anode catalyst layer 2, a cathode catalyst layer 4, an anode porous transport layer 3, and a cathode porous transport layer 5. The anode porous transport layer 3 and the cathode porous transport layer 5 are respectively disposed on the side of the anode catalyst layer 2 and the cathode catalyst layer 4 away from the proton exchange membrane 1. The right and left sides of the proton exchange membrane 1 are integrally connected in situ to one side of the anode catalyst layer 2 and the cathode catalyst layer 4, respectively. The anode catalyst layer 2 is formed by sequentially connecting a first subset layer 21, a second subset layer 22, and a third subset layer 23 from the inside out along the direction away from the proton exchange membrane. The first subset layer 21, the second subset layer 22, and the third subset layer 23 all contain a composite catalyst and perfluorosulfonic acid resin, and the composite catalyst in the three subset layers is... The ratio of the catalyst and perfluorosulfonic acid resin is different. The composite catalyst consists of a noble metal catalyst and a conductive support. The amount of perfluorosulfonic acid resin in the first subset layer 21, the second subset layer 22, and the third subset layer 23 decreases. The mass ratio of perfluorosulfonic acid resin to the composite catalyst in each subset layer 21, the second subset layer 22, and the third subset layer 23 decreases sequentially. The proportion of the conductive support in the composite catalyst in the first subset layer 21, the second subset layer 22, and the third subset layer 23 decreases. The proportion of the noble metal catalyst in the composite catalyst in the first subset layer 21, the second subset layer 22, and the third subset layer 23 increases, resulting in the same loading of noble metal catalyst in the first subset layer 21, the second subset layer 22, and the third subset layer 23. Figure 3Subset layer one, subset layer two, and subset layer three correspond to the first subset layer 21, the second subset layer 22, and the third subset layer 23 of this embodiment, respectively.

[0043] In this embodiment, the noble metal catalyst is IrO2, the conductive support is TiN, and the cathode porous transport layer is carbon paper with a microporous layer. The proportions of noble metal catalyst in the composite catalyst of the first subset layer 21, the second subset layer 22, and the third subset layer 23 are 40%, 60%, and 80%, respectively. The Ir loading in the first subset layer 21, the second subset layer 22, and the third subset layer 23 is the same and is 0.2 mg each. Ir cm -2 The perfluorosulfonic acid resin loadings in the first subset layer 21, the second subset layer 22, and the third subset layer 23 are 30-45%, 15-30%, and 1-15% of the Ir loading, respectively.

[0044] This embodiment also provides a method for preparing the membrane electrode for the above-mentioned solid polymer membrane electrolyzer, which specifically includes the following steps:

[0045] S01. Preparation and spraying of cathode catalyst slurry: 80 mg of a platinum-carbon catalyst (Pt / C catalyst) with a platinum content of 60% was added to 40 ml of a mixture of deionized water and isopropanol at a volume ratio of 1:9. The mixture was ultrasonically treated in an ice-water bath for 30 min. Then, 108 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated again in an ice-water bath for 30 min to obtain the cathode catalyst slurry. The cathode catalyst slurry was sprayed onto one side of a 220 μm carbon paper using a spraying machine at a spray flow rate of 3 ml / min and a hot plate temperature of 90 °C, forming a cathode catalyst layer on one side of the carbon paper. The Pt loading in the cathode catalyst layer was 0.1 mg. Pt cm -2 ;

[0046] S02. Preparation and spraying of anode catalyst slurry: 100 mg of IrO2 / TiN catalyst (the mass percentage of IrO2 in the composite catalyst is 40%) was added to 40 ml of a mixture of deionized water and isopropanol in a volume ratio of 1:1. The mixture was treated in an ice-water bath for 30 min, and then 71.4 μl of Nafion D2020 ionomer was added. The mixture was then ultrasonically treated in an ice-water bath for 30 min to obtain the first subset layer slurry.

[0047] 100 mg of IrO2 / TiN catalyst (the mass percentage of IrO2 in the composite catalyst is 60%) was added to 40 ml of a mixture of deionized water and isopropanol in a volume ratio of 1:1. The mixture was treated in an ice-water bath for 30 min. Then, 53.5 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated in an ice-water bath for 30 min to obtain the second subset layer slurry.

[0048] 100 mg of IrO2 / TiN catalyst (IrO2 accounts for 80% of the mass of the composite catalyst) was added to 40 ml of a mixture of deionized water and isopropanol in a volume ratio of 1:1. The mixture was treated in an ice-water bath for 30 min. Then, 20.8 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated in an ice-water bath for 30 min to obtain the third subset layer slurry.

[0049] A third subset layer slurry with a porosity of 60% and a spray flow rate of 3 ml / min was sprayed onto a porous titanium plate with a thickness of 1 mm using a spraying machine at a hot plate temperature of 90°C. Then, a second subset layer slurry was sprayed onto the third subset layer slurry, and a first subset layer slurry was sprayed onto the second subset layer slurry. This resulted in an anode catalyst layer with a three-layer subset layer structure forming on one side of the porous titanium plate. The Ir loading in each subset layer was the same and 0.2 mg. Ir cm -2 ;

[0050] S03. Preparation of membrane electrode: Carbon paper containing the cathode catalyst layer is placed in the groove of the glass plate (groove depth is 310 μm), and a porous titanium plate containing the anode catalyst layer is placed in the groove of the glass plate (groove depth is 1100 μm), with the cathode catalyst layer and the anode catalyst layer facing upwards. 20 wt% Nafion membrane solution is added to the two grooves respectively and placed in a 60℃ oven to form semi-solid proton exchange membrane layers on the surfaces of the cathode catalyst layer and the anode catalyst layer respectively. The two glass plates are then attached to each other so that the two proton exchange membrane layers are attached to each other and placed in a 120℃ oven for 8 hours to achieve in-situ film formation and integrated connection, finally obtaining the membrane electrode of the solid polymer membrane electrolyzer.

[0051] The solid polymer membrane electrolyzer electrode prepared by the above method has the characteristics of gradient and zero interface gap. Zero interface gap means that the connection interface between the proton exchange membrane and the cathode catalyst layer, the anode catalyst layer, the connection interface between each subset layer inside the anode catalyst layer, the connection interface between the anode catalyst layer and the anode porous transport layer, and the connection interface between the cathode catalyst layer and the cathode porous transport layer achieve zero gap connection. Gradient means that the anode catalyst layer has a multi-layer component ratio gradient structure. The components with the ratio gradient include composite catalyst and perfluorosulfonic acid resin.

[0052] Compare with Example 1

[0053] This comparative example provides a method for preparing a membrane electrode, which specifically includes the following steps:

[0054] S01. Preparation of cathode catalyst slurry: 80 mg of Pt / C catalyst with a platinum content of 60% was added to 40 ml of a mixture of isopropanol and deionized water at a volume ratio of 9:1. The mixture was ultrasonically treated in an ice-water bath for 30 min. Subsequently, 108 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated in an ice-water bath for 30 min to obtain the cathode catalyst slurry. The cathode catalyst slurry was sprayed onto one side of a 220 μm carbon paper using a sprayer at a spray flow rate of 3 ml / min and a hot plate temperature of 90 °C, forming a cathode catalyst layer on one side of the carbon paper. The Pt loading in the cathode catalyst layer was 0.1 mg. Pt cm -2 ;

[0055] S02. Preparation of anode catalyst slurry: 100 mg of IrO2 / TiN catalyst (the mass percentage of IrO2 in the composite catalyst is 60%) was added to a mixture of 20 ml of deionized water and 20 ml of isopropanol, and treated in an ice-water bath for 30 min. Then, 54 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated in an ice-water bath for 30 min to obtain the anode catalyst slurry.

[0056] S03. Preparation of the membrane electrode: The cathode catalyst slurry was sprayed onto one side of the Nafion 117 membrane using a sprayer at a flow rate of 3 ml / min and a hot plate temperature of 90℃. Then, the prepared anode catalyst slurry was sprayed onto the other side of the Nafion 117 membrane to form the membrane electrode. The Pt loading in the cathode catalyst layer was 0.1 mg. Pt cm -2 The Ir loading in the anode catalyst layer is 0.6 mg. Ir cm -2 .

[0057] The membrane electrode obtained using this preparation method is a conventional membrane electrode.

[0058] Compare with Example 2

[0059] This comparative example provides a method for preparing a membrane electrode for a solid polymer membrane electrolyzer, except for SO2. Preparation of the anode catalyst slurry: 100 mg of IrO2 / TiN catalyst (the mass percentage of IrO2 in the composite catalyst is 60%) was added to a mixture of 20 ml deionized water and 20 ml isopropanol, and treated in an ice-water bath for 30 min. Then, 54 μl of Nafion D2020 ionomer was added, and the mixture was ultrasonically treated in an ice-water bath for 30 min to obtain the anode catalyst slurry. Using a sprayer at a flow rate of 3 ml / min and a hot plate temperature of 90°C, the anode catalyst slurry was sprayed onto a porous titanium plate with a thickness of 1 mm and a porosity of 60%, resulting in a single-layer anode catalyst layer on one side of the porous titanium plate. The Ir loading in the anode catalyst layer was 0.6 mg. Ir cm -2 Apart from the steps described above, the remaining steps are the same as in Example 1.

[0060] The membrane electrode prepared by this method has the characteristic of zero interfacial gap.

[0061] Compare with Example 3

[0062] This comparative example provides a method for preparing a membrane electrode for a solid polymer membrane electrolyzer. Except that 100 mg of IrO2 / TiN catalyst (the mass percentage of IrO2 in the composite catalyst is 60%) is used in the preparation of the first, second, and third subset layer slurries, the remaining steps are the same as in Example 1.

[0063] The membrane electrode prepared by this method has the characteristics of ionomer gradient and zero interfacial gap.

[0064] Compare with Example 4

[0065] This comparative example provides a method for preparing a membrane electrode for a solid polymer membrane electrolyzer. Except that 53.5 μl of Nafion D2020 ionomer is used in the preparation of the first subset layer slurry, the second subset layer slurry, and the third subset layer slurry, the other steps are the same as in Example 1.

[0066] The membrane electrode prepared by this method has the characteristics of catalyst gradient and zero interfacial gap.

[0067] Performance testing of membrane electrodes

[0068] Five types of membrane electrodes, prepared according to the methods described in Example 1 and Comparative Examples 1 to 4, were taken in equal quantities. Each of the five membrane electrodes was placed in one of five identical electrolytic cell fixtures. After energizing, the voltage changes in the five electrolytic cells under different current densities were recorded, and the polarization curves of each membrane electrode were plotted. The polarization curves are shown below. Figure 4 As shown, 1A cm -2 and 3A cm-2 The electrolytic cell voltage results for each membrane electrode under different current densities are as follows: Figure 5 As shown.

[0069] Depend on Figure 4 It can be seen that when the current density increases, especially when it is greater than 2A cm⁻¹, -2 Under the given current density, the electrolytic cell voltage corresponding to the membrane electrode prepared according to the preparation method in Example 1 is significantly lower, indicating that the gradient membrane electrode with zero interfacial gap prepared according to the preparation method in Example 1 has good water electrolysis performance.

[0070] Depend on Figure 5 It can be seen that at 1A cm -2 Under the given current density, the electrolytic cell voltages corresponding to each membrane electrode are basically the same, at 3A cm⁻¹. -2 Under the given current density, the electrolytic cell voltages corresponding to the five membrane electrodes prepared according to the preparation methods in Examples 1 and Comparative Examples 1 to 4 were 2.118V, 2.346V, 2.206V, 2.176V, and 2.146V, respectively. It can be seen that the conventional membrane electrode prepared by the preparation method in Comparative Example 1 has poor water electrolysis performance, while the gradient membrane electrode with zero interface gap prepared by the preparation method in Example 1 has good water electrolysis performance, and its water electrolysis performance is better than that of the membrane electrodes prepared by the preparation methods in Comparative Examples 2 to 4.

[0071] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a membrane electrode for a solid polymer membrane electrolyzer, characterized in that, It includes the following steps: Preparation and spraying of cathode catalyst slurry: Platinum carbon catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, and ultrasonically treated in an ice-water bath. Perfluorosulfonic acid resin is added, and ultrasonic treatment in an ice-water bath is performed again to obtain cathode catalyst slurry. The cathode catalyst slurry is sprayed onto one side of the cathode porous transport layer to form a cathode porous transport layer containing a cathode catalyst layer. Preparation and spraying of anode catalyst slurry: The composite catalyst is added to a mixture of deionized water and low-boiling-point pure solvent, perfluorosulfonic acid resin is added, and the mixture is subjected to ultrasonic treatment in an ice-water bath to obtain anode catalyst slurry. The anode catalyst slurry includes multiple sub-layer slurries. The mass ratio of perfluorosulfonic acid resin to composite catalyst in the multiple sub-layer slurries decreases from the inside to the outside. The multiple sub-layer slurries are sprayed and connected together from the inside to the outside. The outermost sub-layer slurry is sprayed onto one side of the anode porous transport layer to form an anode porous transport layer containing an anode catalyst layer. Preparation of membrane electrode: The cathode porous transport layer containing the cathode catalyst layer and the anode porous transport layer containing the anode catalyst layer are placed in the grooves of two glass plates, with the cathode catalyst layer and the anode catalyst layer facing upwards. 10-20 wt% Nafion membrane solution is added to the two grooves respectively and placed in an oven at 60-80℃ to form semi-solid proton exchange membrane layers on the surfaces of the cathode catalyst layer and the anode catalyst layer. The two proton exchange membrane layers are then attached to each other and placed in an oven at 100-120℃ to achieve in-situ integrated membrane formation, and finally a solid polymer membrane electrolyzer membrane electrode is obtained. The cathode catalyst slurry contains 0.1-0.5% platinum-carbon catalyst by mass, and the anode catalyst slurry contains 0.1-0.6% total composite catalyst by mass. The solid polymer membrane electrolyzer electrode comprises a proton exchange membrane, an anode catalyst layer, a cathode catalyst layer, an anode porous transport layer, and a cathode porous transport layer. The anode porous transport layer and the cathode porous transport layer are respectively disposed on the side of the anode catalyst layer and the cathode catalyst layer away from the proton exchange membrane. The two sides of the proton exchange membrane are in-situ integratedly connected to one side of the anode catalyst layer and the cathode catalyst layer, respectively. The anode catalyst layer adopts a multi-sublayer structure, and each sublayer contains a composite catalyst and perfluorosulfonic acid resin, with different ratios of composite catalyst and perfluorosulfonic acid resin in each sublayer. The composite catalyst consists of a noble metal catalyst and a conductive support. In each subset layer, the amount of perfluorosulfonic acid resin decreases gradually from the inside out along the direction away from the proton exchange membrane. Similarly, the proportion of the conductive support in the composite catalyst decreases gradually from the inside out along the direction away from the proton exchange membrane, while the proportion of the noble metal catalyst in the composite catalyst increases gradually from the inside out along the direction away from the proton exchange membrane. This ensures that the loading of the noble metal catalyst is the same in each subset layer. The conductive support includes at least one of TiN and TiO2. The noble metal catalyst is an Ir-containing metal compound or metal oxide. The mass fraction of the noble metal catalyst in the composite catalyst of each subset layer is 40–80%, and the Ir loading in each subset layer is the same and is 0.1–0.3 mg. Ir cm -2 .

2. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 1, characterized in that: The anode catalyst layer is formed by sequentially connecting the first subset layer, the second subset layer, and the third subset layer from the inside out along the direction away from the proton exchange membrane.

3. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 2, characterized in that: The Ir loading is the same in the first subset layer, the second subset layer, and the third subset layer, and is 0.1–0.3 mg in each case. Ir cm -2 The proportions of noble metal catalysts in the composite catalysts of the first subset layer, the second subset layer, and the third subset layer are 40%, 60%, and 80%, respectively.

4. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 3, characterized in that: The perfluorosulfonic acid resin loadings in the first subset layer, the second subset layer, and the third subset layer are 30-45%, 15-30%, and 1-15% of the Ir loading, respectively.

5. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 1, characterized in that: The anode porous transport layer is a porous titanium plate with a porosity of 30-60%, and the cathode porous transport layer is carbon paper with a microporous layer or a porous titanium plate.

6. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 1, characterized in that: The low-boiling-point pure solvent is at least one of isopropanol, n-propanol, ethanol, and methanol, and the equivalent mass of the perfluorosulfonic acid resin is 700–2100 g / mol.

7. The method for preparing the membrane electrode for a solid polymer membrane electrolyzer as described in claim 1, characterized in that: During the spraying process, the spraying flow rate is 1-5 ml / min, the hot plate temperature is 70-100 ℃, and the thickness of the proton exchange membrane in the membrane electrode of the solid polymer membrane electrolyzer is 10-185 μm.

Images