Fuel cell membrane electrode capable of operating across temperature zones

Abstract

The invention belongs to the field of fuel cells, and particularly relates to a fuel cell membrane electrode capable of operating across temperature zones. In the direction from the proton exchange membrane to the gas diffusion layer, the catalyst layer sequentially comprises an inner catalyst layer, a middle catalyst layer and an outer catalyst layer; the inner catalyst layer is composed of a catalyst, sulfonated SiO2 particles, PVA and short-side-chain perfluorinated sulfonic acid resin in a mass ratio of 15: 1: 1: (3-5); the middle catalyst layer is prepared from a catalyst, PVA, short-side-chain perfluorinated sulfonic acid resin and long-side-chain perfluorinated sulfonic acid resin according to the mass ratio of 15 to 1 to (1.5 to 2.5) to (1.5 to 2.5); the outer catalyst layer is composed of a catalyst, PTFE and long-side-chain perfluorinated sulfonic acid resin, and the mass ratio of the catalyst to the PTFE to the long-side-chain perfluorinated sulfonic acid resin is 15: 1: (3-5). Through the structural design of the catalyst layer and the diffusion layer, the resistance of liquid water removal is reduced, and the purpose of water retention in the membrane electrode is further achieved.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells, and particularly relates to a fuel cell membrane electrode capable of operating across temperature ranges. Background Art

[0002] High-power proton exchange membrane fuel cells have shown obvious advantages in fields such as heavy trucks and long-distance logistics vehicles due to their long cruising range, low-temperature resistance, and fast fuel refueling. Many countries and regions have introduced policies to support the application of PEMFCs in heavy vehicles to promote the achievement of global carbon emission reduction goals. For example, the US Environmental Protection Agency (EPA) announced that starting from 2027, more stringent carbon dioxide emission standards will be implemented for heavy vehicles.

[0003] In 2023, the New Energy and Industrial Technology Development Organization of Japan (NEDO) released the latest "FCV·HDV Fuel Cell Technology Development Roadmap", which proposed the development plan for future fuel cells. It plans to increase the fuel cell operating temperature to 105°C by 2030 and to 120°C by 2040. At the same time, corresponding plans have also been made in terms of platinum usage, polarization performance, durability, etc., which sets higher development goals for global fuel cell technology. In order to enable China's fuel cell membrane electrode technology to lead the international advanced level in the next 10-20 years, it is urgent to develop the next generation of high-performance, ultra-low platinum membrane electrodes that can operate across temperature ranges and complete the exploration of core mechanisms and the tackling of key technologies.

[0004] A membrane electrode across temperature ranges refers to one that can stably operate under single-phase flow conditions above 105°C, improving the catalyst activity and the power density of the membrane electrode to support the application of high-power fuel cells, and can also take into account the battery performance during two-phase flow operation at room temperature. However, in the traditional membrane electrode technology system, when the temperature is above 95°C, there are problems such as a decrease in conductivity and poisoning of the membrane electrode due to rapid water loss, which further affects the performance of the battery. Summary of the Invention

[0005] The purpose of the present invention is to provide a fuel cell membrane electrode capable of operating across temperature ranges, aiming to improve the battery performance of the membrane electrode within the temperature range. By optimizing the composition and structure of the catalytic layer, water-retaining particles are added to the inner catalytic layer of the catalytic layer, and a perfluorosulfonic acid resin with a short side-chain molecular structure is selected. The middle catalytic layer is a mixture of perfluorosulfonic acid resins with short and long side-chain molecular structures, and the outer catalytic layer is a perfluorosulfonic acid resin with a long side-chain molecular structure. At the same time, a hydrophobic gradient design is carried out on the diffusion layer to reduce the resistance to the removal of liquid water, thereby achieving the purpose of retaining water inside the membrane electrode.

[0006] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0007] The present invention provides a fuel cell membrane electrode capable of operating across temperature zones. The membrane electrode includes a proton exchange membrane, a catalytic layer, and a gas diffusion layer. From the proton exchange membrane to the gas diffusion layer, the catalytic layer sequentially includes an inner catalytic layer, an intermediate catalytic layer, and an outer catalytic layer.

[0008] The inner catalytic layer is composed of a catalyst, sulfonated SiO 2 particles, PVA, and short-side-chain perfluorosulfonic acid resin, and the mass ratio of the four is 15:1:1:(3 - 5);

[0009] The intermediate catalytic layer is composed of a catalyst, PVA, short-side-chain perfluorosulfonic acid resin, and long-side-chain perfluorosulfonic acid resin, and the mass ratio of the four is 15:1:(1.5 - 2.5):(1.5 - 2.5);

[0010] The outer catalytic layer is composed of a catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin, and the mass ratio of the three is 15:1:(3 - 5).

[0011] In the above technical solution, further, the gas diffusion layer includes a microporous layer and a support layer; the microporous layer is composed of an inner hydrophobic microporous layer close to the support layer and an outer hydrophobic microporous layer close to the catalytic layer.

[0012] In the above technical solution, further, the inner hydrophobic layer is composed of graphite powder and PTFE, and the PTFE content is 40 - 50 wt.%;

[0013] The outer sub-hydrophobic layer is composed of acetylene black and PTFE, and the PTFE content is 20 - 35 wt.%.

[0014] In the above technical solution, further, the ion exchange equivalent of the short-side-chain perfluorosulfonic acid resin is 750 - 900 g / mol, and the ion exchange equivalent of the long-side-chain perfluorosulfonic acid resin is 910 - 1100 g / mol.

[0015] In the above technical solution, further, the catalyst is one of Pt / C, PtCo / C, and PtPdAu / C.

[0016] In the above technical solution, further, the preparation method of the membrane electrode includes one of spraying, transfer printing, coating, and electrospinning. The catalytic layer is prepared on the surface of the proton exchange membrane in the order of the inner catalytic layer, the intermediate catalytic layer, and the outer catalytic layer, or is prepared on the surface of the gas diffusion layer in the order of the outer catalytic layer, the intermediate catalytic layer, and the inner catalytic layer.

[0017] In the above technical solution, further, the operating temperature of the membrane electrode is 65 - 110 °C.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention designs a three-layer structure for the catalyst layer, which can simultaneously form a gradient of sulfonate concentration and hydrophilicity in the vertical area direction. When the temperature increases, the silica and PVA in the inner catalyst layer play a hydrophilic role at the same time, and can maintain a high conductivity and battery performance in combination with the short side chain perfluorosulfonic acid resin, while the sulfonate concentration in the middle catalyst layer and the outer catalyst layer decreases. The reduction of sulfonate is beneficial to reducing the hydrophilicity of the catalyst layer. The middle catalyst layer does not contain silica but only PVA, and the outer catalyst layer does not contain silica and PVA, but adds PTFE, which further forms a hydrophobicity gradient in the catalyst layer, reduces the rapid removal of water at high temperature, and can effectively improve the battery performance degradation caused by the loss of the membrane electrode when it is operated above 95°C.

[0020] (2) The present invention optimizes the composition and structure of the gas diffusion layer microporous layer to form a hydrophobic gradient distribution in the vertical area direction, wherein the outer hydrophobic microporous layer is made of acetylene black and a low proportion of PTFE, and the inner hydrophobic microporous layer is made of graphite powder and a high proportion of PTFE. The graphitization of the carbon material will improve the hydrophobicity of the powder, and combined with the change in PTFE content, a hydrophobic gradient of the microporous layer is formed. When the temperature rises and the liquid water is lost, the change in hydrophobicity can inhibit the removal of liquid water.

[0021] (3) The gradient catalytic layer structure and the gradient diffusion layer structure of the present invention are simultaneously applied to the membrane electrode. When the temperature is raised to above 90°C, the water in the catalytic layer changes from liquid phase to gas phase and enters the gradient microporous layer, which is beneficial to the reliquefaction of gaseous water in the micropores, thereby effectively improving the water management of the membrane electrode when operating above 95°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The performance of the membrane electrode in the cross-temperature range is shown in Example 1 and Comparative Example 1 and Comparative Example 2;

[0023] Figure 2 The cross-temperature performance of the membrane electrode of Example 2, Example 3 and Comparative Example 3. DETAILED DESCRIPTION

[0024] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0025] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0026] Example 1

[0027] Sulfonated SiO 2It is prepared by the following method: nano-SiO with a mass ratio of 1:1:10 2 (20 nm, Zhoushan, Zhejiang), 1,3-propane sultone, toluene, are reacted at 110 °C for 36 h; after the reaction is completed, it is washed repeatedly with toluene 3 times and dried to obtain sulfonated SiO 2 .

[0028] Select a proton exchange membrane of Gore's model M775.15, and spray a catalytic layer on both of its surfaces. First, spray a catalyst slurry 1 composed of PtCo / C catalyst, sulfonated SiO 2 , PVA, and short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol) on both sides of the membrane. The mass ratio of the four components is 15:1:1:4, and the sprayed inner catalytic layer has a Pt loading of 0.1 mg / cm 2 ; after drying, continue to spray a catalyst slurry 2 composed of PtCo / C catalyst, PVA, short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol), and long-side-chain perfluorosulfonic acid resin (EW value 1100 g / mol). The mass ratio of the four is 15:1:2:2, and the sprayed middle catalytic layer has a Pt loading of 0.2 mg / cm 2 ; after drying, continue to spray a catalyst slurry 3 composed of PtCo / C catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin (EW value 1100 g / mol). The mass ratio of the three is 15:1:4, and the sprayed outer catalytic layer has a Pt loading of 0.1 mg / cm 2 .

[0029] Select a carbon paper with a thickness of 170 microns, impregnate it in a PTFE emulsion and then calcine it to achieve hydrophobic treatment. After the hydrophobic treatment, coat an inner hydrophobic microporous layer on its surface. The inner hydrophobic microporous layer is composed of graphite powder and PTFE, and the PTFE content is 40 wt.%, and the loading of graphite powder in the formed inner hydrophobic microporous layer is 0.8 mg / cm 2 ; after drying, continue to coat an outer hydrophobic microporous layer. The outer hydrophobic microporous layer is composed of acetylene black and PTFE, and the PTFE content is 30 wt.%, and the loading of acetylene black in the formed outer hydrophobic microporous layer is 0.8 mg / cm 2 .

[0030] The CCM prepared in Example 1 and the gas diffusion layer are hot-pressed to form a membrane electrode, and the battery is assembled for performance testing. The test conditions are: the battery operating temperature is 65 - 110 °C, the operating pressure is 1 bar, and the stoichiometric ratios of hydrogen and air are 1.5 and 2.5 respectively. The test results are as Figure 1 shown.

[0031] Example 2

[0032] Select a proton exchange membrane of Gore's model M775.15, and spray a catalytic layer on each of its two side surfaces. First, spray catalyst slurry I composed of Pt / C catalyst, sulfonated SiO 2 (same as Example 1), PVA, and short-side-chain perfluorosulfonic acid resin (EW value 800 g / mol) on both sides of the membrane. The mass ratio of the four components is 15:1:1:3, and spray to form an inner catalytic layer with a Pt loading of 0.1 mg / cm 2 . After drying, continue to spray catalyst slurry II composed of Pt / C catalyst, PVA, short-side-chain perfluorosulfonic acid resin (EW value 800 g / mol), and long-side-chain perfluorosulfonic acid resin (EW value 1000 g / mol). The mass ratio of the four is 15:1:1.5:1.5, and spray to form an intermediate catalytic layer with a Pt loading of 0.2 mg / cm 2 . After drying, continue to spray catalyst slurry III composed of Pt / C catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin (EW value 1000 g / mol). The mass ratio of the three is 15:1:3, and spray to form an outer catalytic layer with a Pt loading of 0.1 mg / cm 2 .

[0033] Select carbon paper with a thickness of 190 microns, impregnate it in PTFE emulsion and then calcine it to achieve hydrophobic treatment. After hydrophobic treatment, coat an inner hydrophobic microporous layer on its surface. The inner hydrophobic microporous layer is composed of graphite powder and PTFE, and the PTFE content is 45 wt.%, and the loading of graphite powder in the formed inner hydrophobic microporous layer is 0.8 mg / cm 2 ; After drying, continue to coat an outer hydrophobic microporous layer. The outer hydrophobic microporous layer is composed of acetylene black and PTFE, and the PTFE content is 25 wt.%, and the loading of acetylene black in the formed outer hydrophobic microporous layer is 0.8 mg / cm 2 .

[0034] Thermally press the CCM and gas diffusion layer prepared in Example 2 to form a membrane electrode, and assemble the battery for performance testing. The testing conditions are: the battery operating temperature is 65 - 110 °C, the operating pressure is 1 bar, and the stoichiometric ratios of hydrogen and air are 1.5 and 2.5 respectively. The test results are as Figure 2 shown.

[0035] Example 3

[0036] Select a proton exchange membrane of Gore's model M775.15, and spray a catalytic layer on each of its two side surfaces. First, spray catalyst slurry I composed of PtPdAu / C catalyst, sulfonated SiO 2 (same as Example 1), PVA, and short-side-chain perfluorosulfonic acid resin (EW value 750 g / mol) on both sides of the membrane. The mass ratio of the four components is 15:1:1:5, and spray to form a Pt loading of 0.1 mg / cm2 The inner catalytic layer; after drying, continue to spray catalyst slurry II composed of PtPdAu / C catalyst, PVA, short-side-chain perfluorosulfonic acid resin (EW value 750 g / mol), and long-side-chain perfluorosulfonic acid resin (EW value 950 g / mol). The mass ratio of the four is 15:1:2.5:2.5, and spraying forms a Pt loading of 0.2 mg / cm 2 The intermediate catalytic layer; after drying, continue to spray catalyst slurry III composed of PtPdAu / C catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin (EW value 950 g / mol). The mass ratio of the three is 15:1:5, and spraying forms a Pt loading of 0.1 mg / cm 2 The outer catalytic layer;

[0037] Select carbon paper with a thickness of 190 microns, impregnate it in PTFE emulsion and then calcine it for hydrophobic treatment. After hydrophobic treatment, coat the inner hydrophobic microporous layer on its surface. The inner hydrophobic microporous layer is composed of graphite powder and PTFE, and the PTFE content is 50 wt.%. The loading of graphite powder in the formed inner hydrophobic microporous layer is 0.8 mg / cm 2 ; after drying, continue to coat the outer hydrophobic microporous layer. The outer hydrophobic microporous layer is composed of acetylene black and PTFE, and the PTFE content is 35 wt.%. The loading of acetylene black in the formed outer hydrophobic microporous layer is 0.8 mg / cm 2 .

[0038] Thermally press the CCM and gas diffusion layer prepared in Example 3 to form a membrane electrode, and assemble the battery for performance testing. The testing conditions are: the battery operating temperature is 65 - 110 °C, the operating pressure is 1 bar, and the stoichiometric ratios of hydrogen and air are 1.5 and 2.5 respectively. The test results are as Figure 2 shown.

[0039] Comparative Example 1

[0040] Select a proton exchange membrane of Gore's model M775.15, spray catalytic layers on both of its surface sides, and spray catalyst slurry composed of PtCo / C catalyst, sulfonated SiO 2 (same as Example 1), PVA, and short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol) on both sides of the membrane. The mass ratio of the four components is 15:1:1:4, and spraying forms a Pt loading of 0.4 mg / cm 2 of the catalytic layer;

[0041] The preparation of the gas diffusion layer is the same as that in Example 1.

[0042] The CCM prepared in Comparative Example 1 and the gas diffusion layer were hot-pressed to form a membrane electrode, and the battery was assembled for performance testing. The test conditions were as follows: the battery operating temperature was 65 - 110 °C, the operating pressure was 1 bar, and the stoichiometric ratios of hydrogen and air were 1.5 and 2.5, respectively. The test results are as Figure 1 shown.

[0043] Comparative Example 2

[0044] A proton exchange membrane of Gore's model M775.15 was selected, and a catalytic layer was sprayed on both of its surfaces. First, a catalyst slurry composed of Pt / C catalyst, sulfonated SiO 2 , PVA, and short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed on both sides of the membrane. The mass ratio of the four components was 15:1:1:4, and the Pt loading in the catalytic layer formed by spraying was 0.1 mg / cm 2 ; after drying, a second catalyst slurry composed of Pt / C catalyst, PVA, and short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed. The mass ratio of the three components was 15:1:4, and the Pt loading in the catalytic layer formed by spraying was 0.2 mg / cm 2 ; after drying, a third catalyst slurry composed of Pt / C catalyst, PTFE, and short-side-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed. The mass ratio of the three components was 15:1:4, and the Pt loading in the catalytic layer formed by spraying was 0.1 mg / cm 2 ;

[0045] The preparation method of the gas diffusion layer was the same as that in Example 1.

[0046] The CCM prepared in Comparative Example 2 and the diffusion layer were hot-pressed to form a membrane electrode, and the battery was assembled for performance testing. The test conditions were as follows: the battery operating temperature was 65 - 110 °C, the operating pressure was 1 bar, and the stoichiometric ratios of hydrogen and air were 1.5 and 2.5, respectively. The test results are as Figure 1 shown.

[0047] Comparative Example 3

[0048] The preparation of the catalytic layer was the same as that in Example 2;

[0049] Carbon paper with a thickness of 190 microns was selected, impregnated in PTFE emulsion and then calcined to achieve hydrophobic treatment. After hydrophobic treatment, a hydrophobic microporous layer was coated on its surface. The hydrophobic microporous layer was composed of graphite powder and PTFE, and the PTFE content was 45 wt.%, and the graphite powder loading in the formed hydrophobic microporous layer was 1.6 mg / cm 2 .

[0050] The CCM and gas diffusion layer prepared in Comparative Example 3 were hot-pressed to form a membrane electrode, and the battery was assembled for performance testing. The test conditions were as follows: the battery operating temperature was 65 - 110 °C, the operating pressure was 1 bar, and the stoichiometric ratios of hydrogen and air were 1.5 and 2.5 respectively. The test results are as Figure 2 shown.

[0051] Figure 1 The effects of Example 1 were compared with those of Comparative Example 1 and Comparative Example 2. In the present invention, SiO 2 , PVA, and PTFE were used to adjust the hydrophilic-hydrophobic gradient of the catalyst layer, and ion polymers with different EW values were used to adjust the sulfonate concentration gradient, which could improve the battery performance at 90 - 110 °C. Moreover, the hydrophilic-hydrophobic gradient and the sulfonate concentration gradient had a synergistic effect, and the effect was better than that of a simple hydrophilic gradient.

[0052] Figure 2 The effects of Example 2 were compared with those of Comparative Example 3. In the present invention, the gradient design of the carbon material and PTFE content in the microporous layer was more conducive to improving the battery performance in the range of 90 - 110 °C compared with the uniform microporous layer structure.

[0053] The above embodiments are only the preferred embodiments of the present invention and do not limit the implementation manner. The protection scope of the present invention should be subject to the scope defined by the claims. Other different forms of changes or modifications can be made on the basis of the above description. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A fuel cell membrane electrode capable of operating across temperature ranges, the membrane electrode comprising a proton exchange membrane, a catalyst layer and a gas diffusion layer, characterized in that: From the proton exchange membrane to the gas diffusion layer, the catalytic layer includes an inner catalytic layer, an intermediate catalytic layer and an outer catalytic layer in sequence; The inner catalytic layer is composed of catalyst, sulfonated SiO2 particles, PVA, and short side chain perfluorosulfonic acid resin, and the mass ratio of the four is 15:1:1:(3-5); The intermediate catalytic layer is composed of a catalyst, PVA, a short side chain perfluorosulfonic acid resin, and a long side chain perfluorosulfonic acid resin, and the mass ratio of the four is 15:1:(1.5-2.5):(1.5-2.5); The outer catalytic layer is composed of a catalyst, PTFE and a long side chain perfluorosulfonic acid resin, and the mass ratio of the three is 15:1:(3-5).

2. The fuel cell membrane electrode according to claim 1, characterized in that: The gas diffusion layer comprises a microporous layer and a support layer; the microporous layer consists of an inner hydrophobic microporous layer close to the support layer and an outer hydrophobic microporous layer close to the catalytic layer.

3. The fuel cell membrane electrode according to claim 2, characterized in that: The inner hydrophobic microporous layer is composed of graphite powder and PTFE, wherein the PTFE content is 40-50wt.%; The outer hydrophobic microporous layer is composed of acetylene black and PTFE, wherein the content of PTFE is 20-35wt.%.

4. The fuel cell membrane electrode according to claim 1, characterized in that: The ion exchange equivalent of the short side chain perfluorosulfonic acid resin is 750-900 g / mol, and the ion exchange equivalent of the long side chain perfluorosulfonic acid resin is 910-1100 g / mol.

5. The fuel cell membrane electrode according to claim 1, characterized in that: The catalyst is one of Pt / C, PtCo / C and PtPdAu / C.

6. The fuel cell membrane electrode according to claim 1, characterized in that: The preparation method of the membrane electrode comprises one of spraying, transfer, coating and electrostatic spinning.

7. The fuel cell membrane electrode according to claim 1, characterized in that: The operating temperature of the membrane electrode is 65-110°C.

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