A fuel cell membrane electrode operable across temperature regimes

Abstract

The application belongs to the field of fuel cells, and particularly relates to a fuel cell membrane electrode capable of operating across temperature zones. From the direction of a proton exchange membrane to a gas diffusion layer, the catalytic layer comprises an inner layer catalytic layer, an intermediate layer catalytic layer and an outer layer catalytic layer in sequence; the inner layer catalytic layer is composed of a 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 layer 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); and the outer layer 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). Through the structural design of the catalytic layer and the diffusion layer, the application reduces the resistance of liquid water removal, and further achieves the purpose of water retention in the membrane electrode.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, and specifically relates to a fuel cell membrane electrode assembly that can operate across temperature zones. Background Technology

[0002] A cross-temperature-range membrane electrode assembly (MEA) refers to a membrane electrode assembly that can operate stably under single-phase flow conditions above 105°C, improving catalyst activity and MEA power density to support high-power fuel cell applications, while also maintaining battery performance under two-phase flow conditions at room temperature. However, traditional MEA technology suffers from decreased conductivity and poisoning due to rapid water loss at temperatures above 95°C, further impacting battery performance. Summary of the Invention

[0003] The purpose of this invention is to provide a fuel cell membrane electrode assembly (MEA) capable of operating across temperature zones, aiming to improve the battery performance of the MEA within a wide temperature range. By optimizing the composition and structure of the catalyst layers, water-retaining particles are added to the inner catalyst layer, which is made of perfluorosulfonic acid resin with a short side-chain molecular structure. The middle catalyst layer is a mixture of perfluorosulfonic acid resins with short and long side-chain molecular structures, while the outer catalyst layer is made of perfluorosulfonic acid resin with a long side-chain molecular structure. Simultaneously, a hydrophobic gradient design is implemented in the diffusion layer to reduce resistance to liquid water removal, thereby achieving the goal of water retention within the MEA.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] The present invention provides a fuel cell membrane electrode that can operate across temperature zones. The membrane electrode includes a proton exchange membrane, a catalyst layer and a gas diffusion layer. From the proton exchange membrane to the gas diffusion layer, the catalyst layer sequentially includes an inner catalyst layer, a middle catalyst layer and an outer catalyst layer.

[0006] The inner catalyst layer is composed of a catalyst, sulfonated SiO2 particles, PVA, and short-side-chain perfluorosulfonic acid resin, with a mass ratio of 15:1:1:(3-5).

[0007] The intermediate catalyst layer is composed of a catalyst, PVA, short-side-chain perfluorosulfonic acid resin, and long-side-chain perfluorosulfonic acid resin, with a mass ratio of 15:1:(1.5-2.5):(1.5-2.5).

[0008] The outer catalytic layer is composed of a catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin, with a mass ratio of 15:1:(3-5).

[0009] In the above technical solution, the gas diffusion layer further includes a microporous layer and a support layer; the microporous layer is composed of an inner hydrophobic microporous layer near the support layer and an outer hydrophobic microporous layer near the catalyst layer.

[0010] In the above technical solution, the inner hydrophobic layer is further composed of graphite powder and PTFE, wherein the PTFE content is 40-50 wt.%.

[0011] The outer hydrophobic layer is composed of acetylene black and PTFE, wherein the PTFE content is 20-35 wt.%.

[0012] In the above technical solution, 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.

[0013] In the above technical solution, the catalyst is further selected from Pt / C, PtCo / C, and PtPdAu / C.

[0014] In the above technical solution, the preparation method of the membrane electrode further includes one of spraying, transfer printing, coating, and electrospinning. The catalyst layer is prepared sequentially onto the surface of the proton exchange membrane in the order of inner catalyst layer, middle catalyst layer, and outer catalyst layer, or sequentially onto the surface of the gas diffusion layer in the order of outer catalyst layer, middle catalyst layer, and inner catalyst layer.

[0015] In the above technical solution, the operating temperature of the membrane electrode is further defined as 65-110℃.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) The present invention designs a three-layer structure for the catalyst layer. In the vertical area direction, a gradient of sulfonate concentration and hydrophilicity / hydrophobicity can be formed simultaneously. When the temperature increases, the silica and PVA in the inner catalyst layer play a hydrophilic role at the same time. Combined with short side chain perfluorosulfonic acid resin, it can maintain high conductivity and battery performance. The concentration of sulfonate in the middle catalyst layer and the outer catalyst layer decreases. The reduction of sulfonate is beneficial to reduce the hydrophilicity of the catalyst layer. The middle catalyst layer has no silica and only PVA. The outer catalyst layer has no silica and PVA, but adds PTFE, which further makes the catalyst layer form a hydrophobic gradient. At high temperature, the rapid removal of water is reduced, which can effectively improve the battery performance decline caused by the absence of membrane electrode when the membrane electrode is running above 95°C.

[0018] (2) By optimizing the composition and structure of the gas diffusion layer microporous layer, the present invention forms a hydrophobic gradient distribution in the vertical area direction. The outer hydrophobic microporous layer uses acetylene black and a low proportion of PTFE, while the inner hydrophobic microporous layer uses graphite powder and a high proportion of PTFE. The graphitization of carbon materials improves the hydrophobicity of the powder. Combined with the change in PTFE content, a hydrophobic gradient is formed in the microporous layer. When the temperature rises and liquid water is lost, the change in hydrophobicity can inhibit the removal of liquid water.

[0019] (3) In this invention, the gradient catalytic layer structure and the gradient diffusion layer structure are applied to the membrane electrode. When the temperature is raised to above 90°C, the water in the catalytic layer changes from liquid to gas and enters the gradient microporous layer, which is beneficial to the re-liquefaction of gaseous water in the micropores, thereby effectively improving the water management of the membrane electrode when it is running at above 95°C. Attached Figure Description

[0020] Figure 1 The performance of the film electrodes of Example 1 and Comparative Examples 1 and 2 across the temperature range;

[0021] Figure 2 The temperature range performance of the film electrodes in Examples 2, 3 and Comparative Example 3 is shown. Detailed Implementation

[0022] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0023] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0024] Example 1

[0025] Sulfonated SiO2 was prepared by the following method: nano-SiO2 (20nm, from Zhoushan, Zhejiang) in a mass ratio of 1:1:10, 1,3-propyl sulfonyl lactone, and toluene were reacted at 110℃ for 36h; after the reaction was completed, the mixture was repeatedly washed with toluene three times and dried to obtain sulfonated SiO2.

[0026] A Gore M775.15 proton exchange membrane was selected, and catalyst layers were sprayed onto both sides of the membrane. First, a catalyst slurry consisting of PtCo / C catalyst, sulfonated SiO2, PVA, and short-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed onto both sides of the membrane in a mass ratio of 15:1:1:4, resulting in a Pt carrying capacity of 0.1 mg / cm³. 2The inner catalyst layer is dried; after drying, a catalyst slurry consisting of PtCo / C catalyst, PVA, short-chain perfluorosulfonic acid resin (EW value 850 g / mol), and long-chain perfluorosulfonic acid resin (EW value 1100 g / mol) is sprayed on, with a mass ratio of 15:1:2:2, forming a Pt carrying capacity of 0.2 mg / cm³. 2 The intermediate catalyst layer is dried; after drying, a catalyst slurry consisting of PtCo / C catalyst, PTFE, and long-chain perfluorosulfonic acid resin (EW value 1100 g / mol) is sprayed on, with a mass ratio of 15:1:4, forming a Pt carrying capacity of 0.1 mg / cm³. 2 The outer catalytic layer;

[0027] Carbon paper with a thickness of 170 micrometers was selected and impregnated in PTFE emulsion before calcination to achieve hydrophobic treatment. Following this treatment, an inner hydrophobic microporous layer was coated onto its surface. This inner hydrophobic microporous layer consisted of graphite powder and PTFE, with a PTFE content of 40 wt.% and a graphite powder loading of 0.8 mg / cm³. 2 After drying, an outer hydrophobic microporous layer is coated. This outer hydrophobic microporous layer is composed of acetylene black and PTFE, with a PTFE content of 30 wt.% and an acetylene black loading of 0.8 mg / cm³. 2 .

[0028] The CCM and gas diffusion layer prepared in Example 1 were hot-pressed to form a film electrode, and a battery was assembled for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 1 As shown.

[0029] Example 2

[0030] A Gore M775.15 proton exchange membrane was selected, and catalyst layers were sprayed onto both sides of the membrane. First, a catalyst slurry consisting of Pt / C catalyst, sulfonated SiO2 (same as in Example 1), PVA, and short-chain perfluorosulfonic acid resin (EW value 800 g / mol) was sprayed onto both sides of the membrane in a mass ratio of 15:1:1:3, resulting in a Pt carrying capacity of 0.1 mg / cm³. 2 The inner catalyst layer is then dried; after drying, a catalyst slurry consisting of Pt / C catalyst, PVA, short-chain perfluorosulfonic acid resin (EW value 800 g / mol), and long-chain perfluorosulfonic acid resin (EW value 1000 g / mol) is sprayed on, with a mass ratio of 15:1:1.5:1.5, resulting in a Pt carrying capacity of 0.2 mg / cm³. 2The intermediate catalyst layer is dried; after drying, a catalyst slurry consisting of Pt / C catalyst, PTFE, and long-chain perfluorosulfonic acid resin (EW value 1000 g / mol) is sprayed on, with a mass ratio of 15:1:3, forming a Pt carrying capacity of 0.1 mg / cm³. 2 The outer catalytic layer;

[0031] Carbon paper with a thickness of 190 micrometers was selected and impregnated in PTFE emulsion before calcination to achieve hydrophobic treatment. Following this treatment, an inner hydrophobic microporous layer was coated onto its surface. This inner hydrophobic microporous layer consisted of graphite powder and PTFE, with a PTFE content of 45 wt.% and a graphite powder loading of 0.8 mg / cm³. 2 After drying, an outer hydrophobic microporous layer is coated. This outer hydrophobic microporous layer is composed of acetylene black and PTFE, with a PTFE content of 25 wt.% and an acetylene black loading of 0.8 mg / cm³. 2 .

[0032] The CCM and gas diffusion layer prepared in Example 2 were hot-pressed to form a film electrode, which was then assembled into a battery for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 2 As shown.

[0033] Example 3

[0034] A Gore M775.15 proton exchange membrane was selected, and catalyst layers were sprayed onto both sides of the membrane. First, a catalyst slurry consisting of PtPdAu / C catalyst, sulfonated SiO2 (same as in Example 1), PVA, and short-chain perfluorosulfonic acid resin (EW value 750 g / mol) was sprayed onto both sides of the membrane. The mass ratio of the four components was 15:1:1:5, resulting in a Pt carrying capacity of 0.1 mg / cm³. 2 The inner catalyst layer is then dried; after drying, a catalyst slurry consisting of PtPdAu / C catalyst, PVA, short-chain perfluorosulfonic acid resin (EW value 750 g / mol), and long-chain perfluorosulfonic acid resin (EW value 950 g / mol) is sprayed on, with a mass ratio of 15:1:2.5:2.5, resulting in a Pt carrying capacity of 0.2 mg / cm³. 2 The intermediate catalyst layer is dried; after drying, a catalyst slurry consisting of PtPdAu / C catalyst, PTFE, and long-chain perfluorosulfonic acid resin (EW value 950 g / mol) is sprayed on, with a mass ratio of 15:1:5, forming a Pt carrying capacity of 0.1 mg / cm³. 2 The outer catalytic layer;

[0035] Carbon paper with a thickness of 190 micrometers was selected and impregnated in PTFE emulsion, followed by calcination to achieve hydrophobic treatment. After hydrophobic treatment, an inner hydrophobic microporous layer was coated on its surface. The inner hydrophobic microporous layer was composed of graphite powder and PTFE, with a PTFE content of 50 wt.% and a graphite powder loading of 0.8 mg / cm³. 2 After drying, an outer hydrophobic microporous layer is coated. This outer hydrophobic microporous layer is composed of acetylene black and PTFE, with a PTFE content of 35 wt.% and an acetylene black loading of 0.8 mg / cm³. 2 .

[0036] The CCM and gas diffusion layer prepared in Example 3 were hot-pressed to form a film electrode, and a battery was assembled for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 2 As shown.

[0037] Comparative Example 1

[0038] A Gore M775.15 proton exchange membrane was selected. Catalytic layers were sprayed onto both sides of the membrane. A catalyst slurry consisting of PtCo / C catalyst, sulfonated SiO2 (same as in Example 1), PVA, and short-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed onto both sides of the membrane in a mass ratio of 15:1:1:4. The resulting Pt loading was 0.4 mg / cm³. 2 Catalytic layer;

[0039] The preparation of the gas diffusion layer is the same as in Example 1.

[0040] The CCM and gas diffusion layer prepared in Comparative Example 1 were hot-pressed to form a film electrode, and a battery was assembled for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 1 As shown.

[0041] Comparative Example 2

[0042] A Gore M775.15 proton exchange membrane was selected, and catalyst layers were sprayed onto both sides of the membrane. First, a catalyst slurry consisting of Pt / C catalyst, sulfonated SiO2, PVA, and short-chain perfluorosulfonic acid resin (EW value 850 g / mol) was sprayed onto both sides of the membrane in a mass ratio of 15:1:1:4. The Pt carrying capacity in the sprayed catalyst layer was 0.1 mg / cm³. 2After drying, a second layer of catalyst slurry is sprayed, consisting of Pt / C catalyst, PVA, and short-chain perfluorosulfonic acid resin (EW value 850 g / mol). The mass ratio of the three components is 15:1:4, and the Pt content in the sprayed catalyst layer is 0.2 mg / cm³. 2 After drying, a third layer of catalyst slurry is sprayed, consisting of Pt / C catalyst, PTFE, and short-chain perfluorosulfonic acid resin (EW value 850 g / mol). The mass ratio of the three components is 15:1:4. The Pt content in the sprayed catalyst layer is 0.1 mg / cm³. 2 ;

[0043] The preparation method of the gas diffusion layer is the same as that in Example 1.

[0044] The CCM and diffusion layer prepared in Comparative Example 2 were hot-pressed to form a film electrode, and a battery was assembled for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 1 As shown.

[0045] Comparative Example 3

[0046] The preparation of the catalyst layer is the same as in Example 2;

[0047] Carbon paper with a thickness of 190 micrometers was selected and impregnated in PTFE emulsion before calcination to achieve hydrophobic treatment. Following this treatment, a hydrophobic microporous layer was coated onto its surface. This microporous layer consisted of graphite powder and PTFE, with a PTFE content of 45 wt.% and a graphite powder loading of 1.6 mg / cm³. 2 .

[0048] The CCM and gas diffusion layer prepared in Comparative Example 3 were hot-pressed to form a film electrode, and a battery was assembled for performance testing. The test conditions were: battery operating temperature 65-110℃, operating pressure 1 bar, and stoichiometric ratios of hydrogen and air of 1.5 and 2.5, respectively. The test results are as follows: Figure 2 As shown.

[0049] Figure 1 Comparing the effects of Example 1 with Comparative Examples 1 and 2, the catalyst layer in this invention uses SiO2, PVA, and PTFE to adjust the hydrophilicity-hydrophobicity gradient of the catalyst layer, and uses ion polymers with different EW values ​​to adjust the sulfonate concentration gradient, which can improve the battery performance at 90-110℃. Moreover, the hydrophilicity-hydrophobicity gradient and the sulfonate concentration gradient have a synergistic effect, which is better than the simple hydrophilicity gradient.

[0050] Figure 2Comparing the effects of Example 2 and Comparative Example 3, the gradient design of microporous carbon material and PTFE content in this invention is more conducive to improving the performance of the battery in the 90-110℃ range compared to a uniform microporous structure.

[0051] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A membrane electrode assembly (MEA) for a fuel cell capable of operating across temperature zones, the MEA 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 catalyst layer sequentially includes 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 perfluorosulfonic acid resin, with a mass ratio of 15:1:1:(3-5). The intermediate catalyst layer is composed of a catalyst, PVA, short-side-chain perfluorosulfonic acid resin, and long-side-chain perfluorosulfonic acid resin, with a mass ratio of 15:1:(1.5-2.5):(1.5-2.5). The outer catalytic layer is composed of a catalyst, PTFE, and long-side-chain perfluorosulfonic acid resin, with a mass ratio of 15:1:(3-5). The gas diffusion layer includes a microporous layer and a support layer; the microporous layer is composed of an inner hydrophobic microporous layer near the support layer and an outer hydrophobic microporous layer near the catalyst layer. The inner hydrophobic microporous layer is composed of graphite powder and PTFE, wherein the PTFE content is 40-50 wt.%. The outer hydrophobic microporous layer is composed of acetylene black and PTFE, wherein the PTFE content is 20-35 wt.%.

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

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

4. The fuel cell membrane electrode according to claim 1, characterized in that, The preparation method of the membrane electrode includes one of transfer printing, coating, and electrospinning.

5. The fuel cell membrane electrode according to claim 1, characterized in that, The operating temperature of the membrane electrode is 65-110℃.

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