A proton exchange membrane electrode and its preparation method, and a proton exchange membrane fuel cell.

Abstract

This disclosure relates to a proton exchange membrane electrode (PEMED) and its preparation method, as well as a PEMED fuel cell. The PEMED includes a catalyst layer comprising a composite hygroscopic agent. The composite hygroscopic agent comprises a core and a shell. The core comprises microcrystalline cellulose, and the shell comprises a zeolite imidazole organic framework material. The PEMED of this disclosure can achieve long-term stable operation under dry conditions, and the PEMED fuel cell exhibits excellent durability.

Description

Technical Field

[0001] This disclosure relates to proton exchange membrane fuel cell technology, specifically to a proton exchange membrane electrode and its preparation method, and a proton exchange membrane fuel cell. Background Technology

[0002] The efficient and stable operation of proton exchange membrane fuel cells (PEMFCs) under zero humidification (0%RH) conditions is an important research direction in the current new energy field. Traditional proton exchange membrane electrodes (MEAs) heavily rely on external humidification to maintain proton conductivity, leading to a significant increase in system complexity and cost. The core challenges of dry operation are: the contradiction between proton conductivity and water balance—the proton conductivity of perfluorosulfonic acid ionomers is exponentially related to water content, decreasing sharply under low humidity; increased oxygen mass transfer resistance—the ionomer volume shrinks under dry conditions, causing catalyst / ionomer interface contact failure; and reduced electrochemical reaction efficiency—the platinum catalyst surface activity decreases due to sulfonate adsorption poisoning. In recent years, domestic and international research has mainly addressed these problems by developing self-humidifying membrane electrodes, optimizing ionomer structures, and innovating slurry formulations. However, the practical effects still have many limitations, and the problem of long-term stable operation of membrane electrodes under dry conditions urgently needs to be solved. Summary of the Invention

[0003] The purpose of this disclosure is to provide a proton exchange membrane electrode and its preparation method, as well as a proton exchange membrane fuel cell. The membrane electrode can achieve long-term stable operation under dry conditions, and the proton exchange membrane fuel cell has excellent durability.

[0004] To achieve the above objectives, a first aspect of this disclosure provides a proton exchange membrane electrode, including a catalyst layer comprising a composite hygroscopic agent comprising a core and a shell, wherein the core comprises microcrystalline cellulose and the shell comprises a zeolite imidazole organic framework material.

[0005] Optionally, in the composite desiccant, the mass ratio of the core to the shell is (1~3):1;

[0006] The average particle size of the composite hygroscopic agent is 50~300nm; The specific surface area of ​​the zeolite imidazole organic framework material is 1000 m². 2 / g or more, the zeolite imidazole organic framework material includes ZIF-8.

[0007] Optionally, the membrane electrode comprises a proton exchange membrane and a catalyst layer stacked sequentially, and along the direction away from the proton exchange membrane, the catalyst layer comprises a bottom catalyst layer, an intermediate catalyst layer and a top catalyst layer in sequence; The weight content of the composite hygroscopic agent in the bottom catalyst layer is 2~6wt%; the weight content of the composite hygroscopic agent in the middle catalyst layer is 2~15wt%; and the weight content of the composite hygroscopic agent in the top catalyst layer is 2~15wt%.

[0008] Optionally, the total weight content of ionomers in the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is the same, the weight content of the first perfluorosulfonic acid ionomer decreases sequentially, the weight content of the second perfluorosulfonic acid ionomer increases sequentially, and the weight content difference of the first perfluorosulfonic acid ionomer between adjacent catalyst layers is more than 1%. The EW value of the first perfluorosulfonic acid ionomer is 700~900, and the EW value of the second perfluorosulfonic acid ionomer is 1000~1100.

[0009] Optionally, the weight content of the first perfluorosulfonic acid ionomer in the bottom catalyst layer is 15-30 wt%; and / or, The intermediate catalyst layer contains 10-25 wt% of the first perfluorosulfonic acid ionomer and 2-15 wt% of the second perfluorosulfonic acid ionomer; and / or, The weight content of the first perfluorosulfonic acid ionomer in the top catalyst layer is 0~10wt%, and the weight content of the second perfluorosulfonic acid ionomer is 5~30wt%.

[0010] Optionally, the intermediate catalyst layer includes multiple intermediate catalyst sublayers. Along the direction from the bottom catalyst layer to the top catalyst layer, the weight content of the first perfluorosulfonic acid ionomer in each intermediate catalyst sublayer decreases sequentially, the weight content of the second perfluorosulfonic acid ionomer increases sequentially, and the weight content difference of the first perfluorosulfonic acid ionomer in adjacent intermediate catalyst sublayers is greater than 1%. Each of the intermediate catalyst sublayers has the same thickness, and the mass ratio of the first perfluorosulfonic acid ionomer to the second perfluorosulfonic acid ionomer in the intermediate catalyst sublayer is 1:(0.2~1.5).

[0011] Optionally, the thickness ratio of the bottom catalyst layer, the intermediate catalyst layer and the top catalyst layer is (1~2):(0.5~1):1.

[0012] A second aspect of this disclosure provides a method for preparing the membrane electrode described in the first aspect of this disclosure, the method comprising: A slurry containing a composite hygroscopic agent is coated onto a proton exchange membrane to form a catalytic layer.

[0013] Optionally, the catalyst is mixed with a solvent to obtain a first suspension; the composite hygroscopic agent, the solvent, and different contents of the first perfluorosulfonic acid ionomer and the second perfluorosulfonic acid ionomer are respectively mixed to obtain a second suspension; the first suspension is then mixed with the second suspensions of the first perfluorosulfonic acid ionomer and the second perfluorosulfonic acid ionomer with different contents to obtain slurries with different contents of the first perfluorosulfonic acid ionomer and the second perfluorosulfonic acid ionomer. The slurry is coated and pre-hydrated in a direction away from the proton exchange membrane, with the content of the first perfluorosulfonic acid ionomer decreasing sequentially. The prehydration conditions include: 100% humidity, a temperature of 70-90°C, and a time of 5-15 minutes; After the prehydration treatment, the water content of each catalyst layer is above 10%; The coating conditions include: a coating speed of 1~3 m / min, a temperature of 90~150℃, and a coating thickness of 8~12 μm.

[0014] A third aspect of this disclosure provides a proton exchange membrane fuel cell, including the membrane electrode described in the first aspect of this disclosure.

[0015] Through the above technical solution, this disclosure adds a composite hygroscopic agent to the catalyst layer. This composite hygroscopic agent comprises a microcrystalline cellulose core and a shell of zeolite imidazole organic framework material. The composite hygroscopic agent has a certain moisture regulation capability. Within the range of 20-100℃, the microcrystalline cellulose provides hydrophilic groups such as hydroxyl groups to capture gaseous water through hydrogen bonds. The zeolite imidazole organic framework material (ZIF-8) has a high specific surface area and a certain microporous adsorption capacity, selectively adsorbing water molecules through micropores, thereby increasing the moisture absorption capacity of the composite hygroscopic agent. Furthermore, the moisture release temperature window (60-80℃) of the composite hygroscopic agent is more matched with the operating temperature of the fuel cell, realizing an intelligent water cycle of "release during operation and capture during standby". This reduces the dependence of the ionomers in the catalyst layer on humidity, enabling the membrane electrode to operate stably for a long time under dry conditions, and giving the proton exchange membrane fuel cell excellent durability.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this disclosure.

[0018] The first aspect of this disclosure provides a proton exchange membrane electrode, including a catalyst layer comprising a composite hygroscopic agent comprising a core and a shell, the core comprising microcrystalline cellulose and the shell comprising a zeolite imidazole organic framework material.

[0019] This disclosure introduces a composite hygroscopic agent added to the catalyst layer. This composite hygroscopic agent comprises a microcrystalline cellulose core and a shell of zeolite imidazole organic framework material. The composite hygroscopic agent has a certain moisture regulation capability. Within the temperature range of 20-100℃, the microcrystalline cellulose provides hydrophilic groups such as hydroxyl groups to capture gaseous water through hydrogen bonds. The zeolite imidazole organic framework material (ZIF-8) has a high specific surface area and a certain microporous adsorption capacity, selectively adsorbing water molecules through micropores, thereby increasing the moisture absorption capacity of the composite hygroscopic agent. Furthermore, the moisture release temperature window (60-80℃) of the composite hygroscopic agent is more matched with the operating temperature of the fuel cell, realizing an intelligent water cycle of "release during operation and capture during standby". This reduces the dependence of the ionomers in the catalyst layer on humidity, enabling the membrane electrode to operate stably for a long time under dry conditions, and giving the proton exchange membrane fuel cell excellent durability.

[0020] According to one embodiment of this disclosure, the mass ratio of the core to the shell in the composite desiccant is (1~3):1, for example, it can be any value within a range of 1:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1, 2.5:1, 2.7:1, 2.9:1, 3:1, or any two of these values. In the above embodiment, using a suitable composite desiccant is beneficial for achieving wide-temperature-range moisture control and reducing the dependence of the ionomer on humidity.

[0021] According to one embodiment of this disclosure, the average particle size of the composite desiccant is 50-300 nm, for example, it can be any value within the range of 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any two of these values. In the above embodiment, using a suitable composite desiccant is beneficial for achieving wide-temperature-range moisture regulation and reducing the dependence of ionomers on humidity.

[0022] According to one embodiment of this disclosure, the zeolite imidazole organic framework material has a specific surface area of ​​1000 m². 2 / g or higher, for example, 1000~2000m 2 / g, wherein the zeolite imidazole organic framework material includes ZIF-8. In the above embodiments, the zeolite imidazole organic framework material (ZIF-8) has a high specific surface area and a certain microporous adsorption capacity. By selectively adsorbing water molecules through micropores, it increases the moisture absorption of the composite desiccant, and achieves wide-temperature-range moisture regulation through the gradient design of the first perfluorosulfonic acid ionomer in the synergistic catalyst layer.

[0023] According to one embodiment of this disclosure, the membrane electrode includes a proton exchange membrane and a catalyst layer stacked sequentially. Along the direction away from the proton exchange membrane, the catalyst layer sequentially includes a bottom catalyst layer, an intermediate catalyst layer, and a top catalyst layer. The weight content of the composite hygroscopic agent in the bottom catalyst layer is 2-6 wt%, for example, it can be any value within the range of 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or any two of these values. The weight content of the composite hygroscopic agent in the intermediate catalyst layer is 2-15 wt%, for example, it can be any value within the range of 2 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 13 wt%, 15 wt%, or any two of these values. The weight content of the composite hygroscopic agent in the top catalyst layer is 2-15 wt%, for example, it can be any value within the range of 2 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 13 wt%, 15 wt%, or any two of these values. In the above embodiments, an appropriate amount of composite hygroscopic agent is added to the bottom catalyst layer, the middle catalyst layer and the top catalyst layer to reduce the dependence of the ionomer on humidity, thereby enabling the membrane electrode to operate stably for a long time under dry conditions.

[0024] According to one embodiment of this disclosure, the total weight content of ionomers in the bottom catalyst layer, the intermediate catalyst layer, and the top catalyst layer is the same. The weight content of the first perfluorosulfonic acid ionomer decreases sequentially, and the weight content of the second perfluorosulfonic acid ionomer increases sequentially. Furthermore, the weight difference of the first perfluorosulfonic acid ionomer between adjacent catalyst layers is greater than 1%. The EW value of the first perfluorosulfonic acid ionomer is 700-900, and the EW value of the second perfluorosulfonic acid ionomer is 1000-1100. Further, the first perfluorosulfonic acid ionomer is a perfluorosulfonic acid resin ionomer, and the second perfluorosulfonic acid ionomer is also a perfluorosulfonic acid resin ionomer. In this disclosure, the EW value refers to the dry weight of the ionomer containing 1 mole of sulfonic acid groups (-SO3H). In the above embodiments, adding a large amount of low-EW perfluorosulfonic acid ionomers with highly flexible molecular chains to the bottom catalyst layer near the proton exchange membrane facilitates the formation of a continuous proton conduction network. Adding a large amount of high-EW perfluorosulfonic acid ionomers to the top catalyst layer away from the proton exchange membrane reduces the density of sulfonate groups, allowing the ionomers to pre-crosslink the carbon particles of the catalyst rather than directly coating the Pt of the catalyst, forming "ionomer bridges" that connect the Pt / C aggregates of the catalyst, reducing oxygen mass transfer resistance and further improving battery performance. The gradient design of the content of the first and second perfluorosulfonic acid ionomers from the bottom to the top catalyst layer helps balance the contradiction between proton conduction and gas transport, ensuring efficient proton conduction, reducing gas diffusion obstacles, and reducing interfacial contact resistance, further enabling the membrane electrode to achieve long-term stable operation under dry conditions.

[0025] According to one embodiment of this disclosure, the weight content of the first perfluorosulfonic acid ionomer in the bottom catalyst layer is 15-30 wt%, for example, it can be any value within the range of 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, or any two of these values. This disclosure does not limit the weight content of the catalyst in the bottom catalyst layer; it can be a conventional content in the art. For example, the weight content of the catalyst in the bottom catalyst layer can be 30-60 wt%, for example, it can be any value within the range of 30 wt%, 35 wt%, 37 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt%, 50 wt%, 53 wt%, 55 wt%, 57 wt%, 60 wt%, or any two of these values. In the above embodiment, adding an appropriate amount of low EW value perfluorosulfonic acid ionomer to the bottom catalyst layer is beneficial for ensuring efficient proton conduction.

[0026] According to one embodiment of this disclosure, the weight content of the first perfluorosulfonic acid ionomer in the intermediate catalyst layer is 10-25 wt%, for example, it can be any value within the range of 10 wt%, 13 wt%, 15 wt%, 17 wt%, 19 wt%, 20 wt%, 23 wt%, 25 wt%, or any two of these values; the weight content of the second perfluorosulfonic acid ionomer is 2-15 wt%, for example, it can be any value within the range of 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, or any two of these values. This disclosure does not limit the weight content of the catalyst in the intermediate catalyst layer, for example, it can be 30-60 wt%, for example, it can be 30 wt%, 35 wt%, 37 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt%, 50 wt%, 53 wt%, 55 wt%, 57 wt%, 60 wt%, or any two of these values. The above implementation method helps to balance the contradiction between proton conduction and gas transport, ensures efficient proton conduction, reduces gas diffusion resistance, reduces interfacial contact resistance, and further helps the membrane electrode to achieve long-term stable operation under dry conditions.

[0027] According to one embodiment of this disclosure, the weight content of the first perfluorosulfonic acid ionomer in the top catalyst layer is 0-10 wt%, for example, it can be any value within the range of 0, 3 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any two of these values; the weight content of the second perfluorosulfonic acid ionomer is 5-30 wt%, for example, it can be any value within the range of 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any two of these values. This disclosure does not limit the weight content of the catalyst in the top catalyst layer; for example, it can be 30-60 wt%, for example, it can be any value within the range of 30 wt%, 35 wt%, 37 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt%, 50 wt%, 53 wt%, 55 wt%, 57 wt%, 60 wt%, or any two of these values. The above embodiment is beneficial for reducing gas diffusion resistance, and further beneficial for the membrane electrode to achieve long-term stable operation under dry conditions.

[0028] According to one embodiment of the present disclosure, the intermediate catalyst layer includes a plurality of intermediate catalyst sublayers. Along the direction from the bottom catalyst layer to the top catalyst layer, the weight content of the first perfluorosulfonic acid ionomer in each intermediate catalyst sublayer decreases sequentially, the weight content of the second perfluorosulfonic acid ionomer increases sequentially, and the weight content difference of the first perfluorosulfonic acid ionomer in adjacent intermediate catalyst sublayers is more than 1%, preferably 1 to 5%. Compared to a single intermediate catalyst layer, the above-described implementation can better reduce oxygen mass transfer resistance and improve oxygen supply efficiency at high current densities; it increases the contact area with the proton exchange membrane, improves proton conduction efficiency, and reduces interfacial polarization; the multilayer intermediate catalyst sublayer can better achieve gradient conduction matching of oxygen, protons, and electrons, better match the spatial requirements of oxygen gas transport, proton conduction, and electron conduction, solve the "mass transfer-reaction" contradiction of traditional single-layer catalyst layers, reduce overall electrode polarization loss, better alleviate the problems of electrode flooding and uneven thermal stress, reduce the risk of catalyst layer cracking and detachment, improve the durability of membrane electrode in long-term operation, achieve comprehensive optimization of membrane electrode power performance, durability, and cost, and further enable the membrane electrode to operate stably for a long time under dry conditions.

[0029] According to one embodiment of this disclosure, each of the intermediate catalyst sublayers has the same thickness, and the mass ratio of the first perfluorosulfonic acid ionomer to the second perfluorosulfonic acid ionomer in the intermediate catalyst sublayer is 1:(0.2~1.5), for example, it can be any value in the range of 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.3, 1:1.5 or any two of these values. Compared to a single intermediate catalyst layer, the above-described implementation can better reduce oxygen mass transfer resistance and improve oxygen supply efficiency at high current densities; it increases the contact area with the proton exchange membrane, improves proton conduction efficiency, and reduces interfacial polarization; the multilayer intermediate catalyst sublayer can better achieve gradient conduction matching of oxygen, protons, and electrons, better match the spatial requirements of oxygen gas transport, proton conduction, and electron conduction, solve the "mass transfer-reaction" contradiction of traditional single-layer catalyst layers, reduce overall electrode polarization loss, better alleviate the problems of electrode flooding and uneven thermal stress, reduce the risk of catalyst layer cracking and detachment, improve the durability of membrane electrode in long-term operation, achieve comprehensive optimization of membrane electrode power performance, durability, and cost, and further enable the membrane electrode to operate stably for a long time under dry conditions.

[0030] According to one embodiment of this disclosure, the thickness ratio of the bottom catalyst layer, the intermediate catalyst layer, and the top catalyst layer is (1~2):(0.5~1):1. This embodiment facilitates long-term stable operation of the membrane electrode under dry conditions.

[0031] According to one embodiment of this disclosure, the total catalyst loading in the catalyst layer is 0.2~0.4 mg / cm³. 3 The above-described embodiments facilitate the application of appropriate catalyst loading in the membrane electrode, enabling it to operate stably for extended periods under dry conditions.

[0032] The catalyst layer disclosed herein can be applied to both anodic and cathode catalyst layers.

[0033] A second aspect of this disclosure provides a method for preparing the membrane electrode described in the first aspect of this disclosure, the method comprising: A slurry containing a composite hygroscopic agent is coated onto a proton exchange membrane to form a catalytic layer.

[0034] According to one embodiment of this disclosure, the method further includes: mixing a catalyst with a solvent to obtain a first suspension; mixing a composite hygroscopic agent, a solvent, and different contents of a first perfluorosulfonic acid ionomer and a second perfluorosulfonic acid ionomer to obtain a second suspension; mixing the first suspension with the second suspensions of the first perfluorosulfonic acid ionomer and the second perfluorosulfonic acid ionomer with different contents to obtain slurries with different contents of the first perfluorosulfonic acid ionomer and the second perfluorosulfonic acid ionomer; and coating and pre-hydrating the slurries in a direction away from the proton exchange membrane in order of decreasing contents of the first perfluorosulfonic acid ionomer.

[0035] The preparation method disclosed herein solves the problem of phase separation of ionomers through multi-step dispersion slurry and step-by-step coating process, and achieves nanoscale uniform film formation of catalyst layer, which is beneficial to the long-term stable operation of membrane electrode under dry conditions.

[0036] According to one embodiment of this disclosure, the method includes: preparing a bottom layer slurry, an intermediate layer slurry, and a top layer slurry respectively; and sequentially coating and pre-hydrating the bottom layer slurry, intermediate layer slurry, and top layer slurry along a direction away from the proton exchange membrane. This embodiment helps solve the problem of ionomer phase separation, achieves nanoscale uniform film formation of the catalyst layer, and facilitates long-term stable operation of the membrane electrode under dry conditions.

[0037] According to one embodiment of this disclosure, the method further includes adding an alkali metal ion stabilizer to the second suspension. This disclosure does not limit the weight content of the alkali metal ion stabilizer; it can be a conventional content in the art. The above embodiment is beneficial for inhibiting ionomer aggregation and for achieving wide-temperature-range moisture regulation through the synergistic effect of the ionomer and the composite desiccant, reducing the ionomer's dependence on humidity and facilitating long-term stable operation of the membrane electrode under dry conditions.

[0038] According to one embodiment of this disclosure, the pre-hydration conditions include: 100% humidity, a temperature of 70-90°C, and a time of 5-15 minutes. This embodiment facilitates the formation of a moisture reserve, ensuring the proton conduction requirements during the initial dry start-up phase.

[0039] According to one embodiment of this disclosure, after the pre-hydration treatment, the water content of each catalyst layer is above 10%. This embodiment facilitates the formation of a water reserve, ensuring the proton conduction requirements during the initial dry start-up phase.

[0040] According to one embodiment of this disclosure, the coating conditions include: a coating speed of 1~3 m / min, a temperature of 90~150℃ (e.g., any value within the range of 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or any two of these values), and a coating thickness of 8~12 μm (e.g., any value within the range of 8μm, 9μm, 10μm, 11μm, 12μm, or any two of these values). In this disclosure, the coating thickness refers to the overall thickness of the dry catalytic layer film formed after coating. The above embodiment is beneficial for solving the problem of ionomer phase separation, achieving nanoscale uniform film formation of the catalytic layer, and enabling the membrane electrode to operate stably for a long time under dry conditions.

[0041] A third aspect of this disclosure provides a proton exchange membrane fuel cell, including the membrane electrode described in the first aspect of this disclosure.

[0042] The present disclosure is further described in detail below with reference to the embodiments, but is not limited thereto. Unless otherwise specified, all reagents used in this disclosure are commercially available. The anode settings in the following embodiments and comparative examples are conventional methods in the art and will not be described in detail here.

[0043] In this disclosure, the composite hygroscopic agent A core (microcrystalline cellulose) and shell (ZIF-8, with a specific surface area of ​​1000~2000 m²) are used. 2 The mass ratio of (g / g) is 2.4:1, and the average particle size is 150nm; The composite hygroscopic agent used consists of a core (microcrystalline cellulose) and a shell (ZIF-8, with a specific surface area of ​​1000~2000 m²). 2 The mass ratio of g to 0.5:1 is 0.5:1, and the average particle size is 150 nm. The composite hygroscopic agent used consists of a core (microcrystalline cellulose) and a shell (ZIF-8, with a specific surface area of ​​1000~2000 m²). 2 The mass ratio of / g) is 6:1, and the average particle size is 150nm; The first perfluorosulfonic acid ionomer used was a perfluorosulfonic acid resin ionomer (EW value 720) purchased from Solvay, with the trade name D72-25BS; The second perfluorosulfonic acid ionomer used was a perfluorosulfonic acid resin ionomer (EW value 1100) purchased from DuPont, with the trade name D2020; Cellulose nanowires (CNFs) were purchased from Shanghai Maclean Bioreactor Co., Ltd., with trade name 9004-34-6; The catalyst Pt / C was purchased from Tanaka Precious Metals Co., Ltd., with the trade name 10E50TPM.

[0044] Example 1 Example 1 describes the preparation of a fuel cell system for new energy vehicles, which enables the membrane electrode to provide high power output under 0% humidification and 80°C conditions.

[0045] The preparation method of this embodiment includes: (1) The catalyst Pt / C was mixed with a solvent (deionized water / isopropanol, mass ratio 3:7) and ball-milled (using planetary ball milling, conditions 300 rpm, 3 h) to obtain a first suspension. The D90 particle size of the catalyst in the first suspension was less than 5 μm. The first perfluorosulfonic acid resin ionomer, composite hygroscopic agent A, and alkali metal ion stabilizer (Rb) are added. + Stabilizer), cellulose nanowires and solvent (deionized water / isopropanol, mass ratio 3:7) were mixed and ultrasonically broken (40kHz, 30min) to obtain a second dispersion. The D50 particle size of the particles in the second dispersion was 50nm. Add 50% of the second suspension to the first suspension, stir evenly, then add the remaining second dispersion and stir at low speed to obtain the bottom catalyst layer slurry; in the bottom catalyst layer slurry, the weight content of the catalyst is 35wt%, the weight content of the first perfluorosulfonic acid resin ionomer is 25wt%, the weight content of the second perfluorosulfonic acid resin ionomer is 0wt%, the weight content of the alkali metal ion stabilizer is 1.5wt%, the weight content of the composite hygroscopic agent A is 3wt%, the weight content of the cellulose nanofibers is 1wt%, and the balance is solvent; (2) The preparation method of the intermediate catalyst layer slurry is the same as step (1), except that the intermediate catalyst layer also includes a second perfluorosulfonic acid resin ionomer, and the intermediate catalyst layer includes three intermediate catalyst sublayers, and the weight contents of the first perfluorosulfonic acid resin ionomer and the second perfluorosulfonic acid resin ionomer are different. (3) The preparation method of the slurry of the top catalyst layer is the same as that of step (1), except that the contents of the first perfluorosulfonic acid resin ionomer and the second perfluorosulfonic acid resin ionomer are different. Along the direction away from the proton exchange membrane, five layers of ionomer slurry were coated in steps in descending order of the content of the first perfluorosulfonic acid ionomer, followed by pre-hydration treatment. Each layer was dried at 80°C for 1 hour, and finally cured by hot pressing (120°C, 1MPa, 5 min). The coating conditions were: coating speed of 1 m / min, temperature of 110°C, and coating thickness of 8 μm. The formed catalyst layer was placed in a saturated steam environment (80°C, 100%RH) for 10 min to allow the composite hygroscopic agent (MCC / ZIP-8) to pre-bind water molecules, forming a "moisture reservoir". After treatment, the water content of the catalyst layer was more than 10%, forming the cathode catalyst layer with a thickness of 8 μm.

[0046] The cathode of this embodiment of the membrane electrode comprises a proton exchange membrane, a cathode catalyst layer, and a gas diffusion layer stacked sequentially. Along the direction away from the proton exchange membrane, the cathode catalyst layer includes a bottom catalyst layer, an intermediate catalyst layer, and a top catalyst layer. The intermediate catalyst layer comprises three intermediate catalyst sublayers. The contents of ionomers and composite hygroscopic agents in each catalyst layer are shown in Table 1. The total catalyst loading is 0.23 mg / cm³. 3 The thickness ratio of the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is 2:1:1.

[0047] Table 1

[0048] Example 2 This embodiment 2 prepares a low-cost portable power film electrode suitable for outdoor portable power generation equipment.

[0049] The preparation method of this embodiment includes: (1) The catalyst Pt / C was mixed with a solvent (deionized water / ethanol, mass ratio 2:1) and dispersed by high-speed shear (1500 rpm, 2 h) to obtain a first suspension. The D90 particle size of the catalyst in the first suspension was less than 5 μm. The first perfluorosulfonic acid resin ionomer, composite hygroscopic agent A, and alkali metal ion stabilizer (Rb) are added. + Stabilizer), cellulose nanowires and solvent (deionized water / isopropanol, mass ratio 0.5:1) were mixed and ultrasonically broken (40kHz, 30min) to obtain a second dispersion. The D50 particle size of the particles in the second dispersion was 50nm. Add 50% of the second suspension to the first suspension, stir evenly, then add the remaining second dispersion and stir at low speed to obtain the bottom catalyst layer slurry; in the bottom catalyst layer slurry, the weight content of the catalyst is 30wt%, the weight content of the first perfluorosulfonic acid resin ionomer is 20wt%, the weight content of the second perfluorosulfonic acid resin ionomer is 0wt%, the weight content of the alkali metal ion stabilizer is 1.5wt%, the weight content of the composite hygroscopic agent is 4wt%, the weight content of the cellulose nanofibers is 1wt%, and the balance is solvent; (2) The preparation method of the intermediate catalyst layer slurry is the same as that of step (1), except that the intermediate catalyst layer also includes a second perfluorosulfonic acid resin ionomer, and the contents of the first perfluorosulfonic acid resin ionomer and the second perfluorosulfonic acid resin ionomer are different. (3) The preparation method of the slurry of the top catalyst layer is the same as that of step (1), except that the second perfluorosulfonic acid resin ionomer is used instead of the first perfluorosulfonic acid resin ionomer. Along the direction away from the proton exchange membrane, the slurry was coated stepwise with ionomer slurry and pre-hydrated in order of decreasing content of the first perfluorosulfonic acid ionomer. Each layer was dried at 60°C for 30 min, and finally hot-pressed for curing (120°C, 1 MPa, 5 min). The coating conditions were: coating speed of 1 m / min, temperature of 110°C, and coating thickness of 8 μm. The formed catalyst layer was treated in a saturated steam environment (80°C, 100% RH) for 10 min to allow the composite hygroscopic agent (MCC / ZIP-8) to pre-bind water molecules to form a "moisture reservoir". After treatment, the water content of the catalyst layer was more than 10%, forming the cathode catalyst layer with a thickness of 8 μm.

[0050] The cathode of this embodiment of the membrane electrode comprises a proton exchange membrane, a cathode catalyst layer, and a gas diffusion layer stacked sequentially. Along the direction away from the proton exchange membrane, the cathode catalyst layer includes a bottom catalyst layer, an intermediate catalyst layer, and a top catalyst layer. The contents of ionomers and composite hygroscopic agents in each catalyst layer are shown in Table 2. The total catalyst loading is 0.4 mg / cm³. 3 The thickness ratio of the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is 2:1:1.

[0051] Table 2

[0052] Example 3 Example 3 describes the preparation of a long-life 30,000-hour power membrane electrode (stationary power supply), suitable for distributed power stations. The membrane electrode needs to operate stably for an extended period under 0% humidification conditions.

[0053] The preparation method of this embodiment includes: (1) The catalyst Pt / C was mixed with a solvent (deionized water / isopropanol, mass ratio 1:1) and subjected to ultrasonic and ball milling (planetary ball milling, conditions 300 rpm, 5 h; ultrasonic power 1500 W, time 60 min) to obtain a first suspension. The D90 particle size of the catalyst in the first suspension was less than 5 μm. The first perfluorosulfonic acid resin ionomer, composite hygroscopic agent A, and alkali metal ion stabilizer (Rb) are added. + Stabilizer), cellulose nanowires and solvent (deionized water / isopropanol, mass ratio 1:1) were mixed and ultrasonically broken (40kHz, 30min) to obtain a second dispersion. The D50 particle size of the particles in the second dispersion was 50nm. Add 50% of the second suspension to the first suspension, stir evenly, then add the remaining second dispersion and stir at low speed to obtain the bottom catalyst layer slurry; in the bottom catalyst layer slurry, the weight content of the catalyst is 40wt%, the weight content of the first perfluorosulfonic acid resin ionomer is 30wt%, the weight content of the second perfluorosulfonic acid resin ionomer is 0wt%, the weight content of the alkali metal ion stabilizer is 1.5wt%, the weight content of the composite hygroscopic agent is 2wt%, the weight content of the cellulose nanofibers is 1wt%, and the balance is solvent; (2) The preparation method of the intermediate catalyst layer slurry is the same as step (1), except that the intermediate catalyst layer also includes a second perfluorosulfonic acid resin ionomer, and the intermediate catalyst layer includes two intermediate catalyst sublayers, and the contents of the first perfluorosulfonic acid resin ionomer and the second perfluorosulfonic acid resin ionomer are different. (3) The preparation method of the slurry of the top catalyst layer is the same as that of step (1), except that the contents of the second perfluorosulfonic acid resin ionomer and the first perfluorosulfonic acid resin ionomer are different. Along the direction away from the proton exchange membrane, four layers of ionomer slurry were coated in steps, with the content of the first perfluorosulfonic acid ionomer decreasing sequentially, followed by pre-hydration treatment. Each layer was dried at 80°C for 1 hour, and finally cured by hot pressing (120°C, 1MPa, 5 min). A high-precision coating machine (error ±1μm) was used during coating to ensure the uniformity of the thickness of each ionomer layer. The coating conditions were: coating speed 1 m / min, temperature 110°C, and coating thickness 8 μm. The formed catalyst layer was treated in a saturated steam environment (80°C, 100%RH) for 10 min to allow the composite hygroscopic agent (MCC / ZIP-8) to pre-bind water molecules, forming a "moisture reservoir". After treatment, the water content of the catalyst layer was above 10%, forming the cathode catalyst layer with a thickness of 8 μm.

[0054] The cathode of this embodiment of the membrane electrode comprises a proton exchange membrane, a cathode catalyst layer, and a gas diffusion layer stacked sequentially. Along the direction away from the proton exchange membrane, the cathode catalyst layer includes a bottom catalyst layer, an intermediate catalyst layer, and a top catalyst layer. The intermediate catalyst layer includes two intermediate catalyst sublayers. The contents of ionomers and composite hygroscopic agents in each catalyst layer are shown in Table 3. The total catalyst loading is 0.4 mg / cm³. 3 The thickness ratio of the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is 2:1:1.

[0055] Table 3

[0056] Example 4 The method in this embodiment is the same as in embodiment 1, except that composite desiccant B is used instead of composite desiccant A.

[0057] Example 5 The method in this embodiment is the same as in embodiment 1, except that composite desiccant C is used instead of composite desiccant A.

[0058] Comparative Example 1 The method of Comparative Example 1 is the same as that of Example 1, except that none of the catalyst layers in Comparative Example 1 contain a composite hygroscopic agent. The contents of ionomer and composite hygroscopic agent in each catalyst layer are shown in Table 4.

[0059] Table 4

[0060] Comparative Example 2 The method of Comparative Example 2 is the same as that of Example 2, except that none of the catalyst layers in Comparative Example 2 contain a composite hygroscopic agent. The contents of ionomer and composite hygroscopic agent in each catalyst layer are shown in Table 5.

[0061] Table 5

[0062] Comparative Example 3 The method of Comparative Example 3 is the same as that of Example 3, except that none of the catalyst layers in Comparative Example 3 contain a composite hygroscopic agent. The contents of ionomer and composite hygroscopic agent in each catalyst layer are shown in Table 6.

[0063] Table 6

[0064] Test case The membrane electrodes prepared in the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Tables 7, 8 and 9.

[0065] Test method: Refer to GB_T 20042.5-2024 Test method for membrane electrode in proton exchange membrane fuel cell.

[0066] Table 7

[0067] Table 8

[0068] Table 9

[0069] According to the results in Table 7, under the conditions of 0% RH, 80℃, and 0.1MPa, the power density of the membrane electrode in Example 1 reaches 1.2W / cm². 2 1A / cm 2 The voltage decay rate was 8.5% after 1000 hours of constant current operation, indicating that the membrane electrode of this embodiment can operate stably for a long time under dry conditions.

[0070] According to the results in Table 8, under the conditions of 0% RH, 80℃, and 0.1MPa, the power density of the membrane electrode in Example 2 reaches 1.1W / cm². 2 High power density, 1 A / cm³ 2 The voltage decay rate was 15% after 500 hours of constant current operation, indicating that the membrane electrode of this embodiment can operate stably for a long time under dry conditions.

[0071] According to the results in Table 9, under the conditions of 0% RH, 80℃, and 0.1MPa, the power density of the membrane electrode in Example 3 reaches 1W / cm². 2 The voltage decay rate was 9.2% after 100 hours of constant potential operation at 0.6V, indicating that the membrane electrode of this embodiment can operate stably for a long time under dry conditions.

[0072] Based on the results of the above embodiments and comparative examples, it can be seen that the membrane electrode prepared in this disclosure can achieve long-term stable operation under dry conditions, and the proton exchange membrane fuel cell has excellent durability.

[0073] Compared to Comparative Example 1, the composite desiccant in Example 1 can achieve wide-temperature-range moisture regulation, reduce the dependence of ionomers on humidity, and result in higher power density, lower voltage decay rate, and better durability of the membrane electrode.

[0074] Compared to Comparative Example 2, the composite desiccant in Example 2 can achieve wide-temperature-range moisture regulation, reduce the dependence of ionomers on humidity, and achieve higher power density and better durability of the membrane electrode when the voltage decay rate is comparable.

[0075] Compared to Comparative Example 3, the composite desiccant in Example 3 can achieve wide-temperature-range moisture regulation, reduce the dependence of ionomers on humidity, and result in higher power density, lower voltage decay rate, and better durability of the membrane electrode.

[0076] By comparing Examples 4, 5 and Example 1, it can be seen that within the mass ratio range of the core and shell of the preferred composite desiccant of this disclosure, the composite desiccant can better achieve wide-temperature-range moisture regulation, reduce the dependence of ionomers on humidity, and achieve higher power density, lower voltage decay rate, and better durability of the membrane electrode.

[0077] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0078] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0079] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A proton exchange membrane electrode, characterized by, It includes a catalyst layer, the catalyst layer comprising a composite hygroscopic agent, the composite hygroscopic agent comprising a core and a shell, the core comprising microcrystalline cellulose, and the shell comprising a zeolite imidazole organic framework material; In the composite hygroscopic agent, the mass ratio of the core to the shell is (1~3):

1.

2. The membrane electrode of claim 1, wherein, The average particle size of the composite hygroscopic agent is 50~300nm; The specific surface area of the zeolitic imidazolate framework material is 1000 m 2 / g or more, the zeolitic imidazolate framework material comprising ZIF-8.

3. The membrane electrode of claim 2, wherein, The membrane electrode comprises a proton exchange membrane and a catalytic layer stacked sequentially. Along the direction away from the proton exchange membrane, the catalytic layer comprises a bottom catalytic layer, an intermediate catalytic layer and a top catalytic layer in sequence. The weight content of the composite hygroscopic agent in the bottom catalyst layer is 2~6wt%; the weight content of the composite hygroscopic agent in the middle catalyst layer is 2~15wt%; and the weight content of the composite hygroscopic agent in the top catalyst layer is 2~15wt%.

4. The membrane electrode of claim 3, wherein, The total weight content of ionomers in the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is the same. The weight content of the first perfluorosulfonic acid ionomer decreases sequentially, and the weight content of the second perfluorosulfonic acid ionomer increases sequentially. The weight content difference of the first perfluorosulfonic acid ionomer between adjacent catalyst layers is more than 1%. The EW value of the first perfluorosulfonic acid ionomer is 700~900, and the EW value of the second perfluorosulfonic acid ionomer is 1000~1100.

5. The membrane electrode of claim 4, wherein, The weight content of the first perfluorosulfonic acid ionomer in the bottom catalyst layer is 15~30wt%; and / or, The intermediate catalyst layer contains 10-25 wt% of the first perfluorosulfonic acid ionomer and 2-15 wt% of the second perfluorosulfonic acid ionomer; and / or, The weight content of the first perfluorosulfonic acid ionomer in the top catalyst layer is 0~10wt%, and the weight content of the second perfluorosulfonic acid ionomer is 5~30wt%.

6. The membrane electrode of claim 4, wherein, The intermediate catalyst layer includes multiple intermediate catalyst sublayers. Along the direction from the bottom catalyst layer to the top catalyst layer, the weight content of the first perfluorosulfonic acid ionomer in each intermediate catalyst sublayer decreases sequentially, while the weight content of the second perfluorosulfonic acid ionomer increases sequentially. The weight content difference of the first perfluorosulfonic acid ionomer in adjacent intermediate catalyst sublayers is greater than 1%. Each of the intermediate catalyst sublayers has the same thickness, and the mass ratio of the first perfluorosulfonic acid ionomer to the second perfluorosulfonic acid ionomer in the intermediate catalyst sublayer is 1:(0.2~1.5).

7. The membrane electrode of claim 3, wherein, The thickness ratio of the bottom catalyst layer, the middle catalyst layer and the top catalyst layer is (1~2):(0.5~1):

1.

8. A method of preparing the membrane electrode according to any one of claims 1 to 7, characterized by, The method includes: A slurry containing a composite hygroscopic agent is coated onto a proton exchange membrane to form a catalytic layer.

9. The method of claim 8, wherein, A first suspension is obtained by mixing a catalyst with a solvent; a second suspension is obtained by mixing a composite hygroscopic agent, a solvent, and different contents of a first perfluorosulfonic acid ionomer and a second perfluorosulfonic acid ionomer; the first suspension is then mixed with the second suspensions of the first and second perfluorosulfonic acid ionomers of different contents to obtain slurries with different contents of the first and second perfluorosulfonic acid ionomers. The slurry is coated and pre-hydrated in a direction away from the proton exchange membrane, with the content of the first perfluorosulfonic acid ionomer decreasing sequentially. The prehydration conditions include: 100% humidity, a temperature of 70-90°C, and a time of 5-15 minutes; After the prehydration treatment, the water content of each catalyst layer is above 10%; The coating conditions include: a coating speed of 1~3 m / min, a temperature of 90~150℃, and a coating thickness of 8~12 μm.

10. A proton exchange membrane fuel cell characterized by, Includes the membrane electrode as described in any one of claims 1 to 7.

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