Catalyst of high-temperature proton exchange membrane fuel cell as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for a high-temperature proton exchange membrane fuel cell as well as a preparation method and application of the catalyst. The catalyst of the high-temperature proton exchange membrane fuel cell comprises a carbon carrier and Pt nano-particles loaded on the carbon carrier, and at least part of the surface of the Pt nano-particles is coated with manganese dioxide. According to the catalyst of the high-temperature proton exchange membrane fuel cell, the Pt nano-particles are coated with the manganese dioxide, catalytic active sites of the catalyst can be protected after coating, the poisoning effect of phosphoric acid on the catalyst at high temperature is relieved, and the performance of the high-temperature proton fuel cell is improved. In addition, manganese dioxide not only can be used as a protective layer, but also can form a new proton conductor with phosphoric acid, so that a proton transmission channel of the membrane electrode under a high-temperature working condition is improved, and the performance of the high-temperature proton fuel cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a catalyst for a high-temperature proton exchange membrane fuel cell, a preparation method thereof, and an application thereof. Background Art

[0002] As a clean energy conversion device, a proton exchange membrane fuel cell can effectively convert chemical energy into electrical energy and, to a certain extent, reduce air pollution caused by fossil fuels. Proton exchange membrane fuel cells are mainly divided into low-temperature proton exchange membrane fuel cells (LT-PEMFCs) and high-temperature proton exchange membrane fuel cells (HT-PEMFCs). The low-temperature proton exchange membrane fuel cell (LT-PEMFC) generally relies on water to conduct protons, and the operating temperature of the fuel cell is generally 60 - 95°C. The water management and heat management during operation are relatively complex; moreover, due to its low operating temperature, it has very high requirements for the purity of the fuel (especially the content of CO in the fuel), and it is extremely prone to carbon monoxide poisoning. The high-temperature proton exchange membrane fuel cell (HT-PEMFC) generally uses H3PO4 as a proton conductor, and the operating temperature of the fuel cell is generally above 120°C. Since humidification is not required, the water management of the fuel cell system is simplified, and due to its relatively high operating temperature, the requirements for fuel purity are also reduced, and the probability of carbon monoxide poisoning is also greatly reduced.

[0003] In existing high-temperature proton exchange membrane fuel cells, the catalysts in the cathode and anode are mostly commercial Pt / C catalysts. Although the Pt / C catalyst has good oxygen reduction reaction activity and hydrogen oxidation reaction activity, its acid resistance is not ideal. In practical applications, the H3PO4 proton conductor will poison the active sites of the Pt-based catalyst, resulting in a significant reduction in the catalytic activity of the catalyst, and the adsorption of phosphoric acid on the catalyst surface will also hinder the proton transport ability of the HT-PEMFC. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a catalyst for a high-temperature proton exchange membrane fuel cell and a preparation method thereof.

[0005] In a first aspect, the present invention provides a catalyst for a high-temperature proton exchange membrane fuel cell, including a carbon carrier and Pt nanoparticles supported on the carbon carrier, and at least part of the surface of the Pt nanoparticles is coated with manganese dioxide.

[0006] Preferably, the mass of the manganese dioxide is 1 - 40% of the total mass of the Pt nanoparticles and the carbon carrier.

[0007] In a second aspect, the present invention provides a preparation method for a catalyst for a high-temperature proton exchange membrane fuel cell, including the following steps: Disperse the carbon catalyst loaded with Pt nanoparticles in water to obtain a dispersion; after adding a potassium permanganate solution and ethanol to the dispersion, carry out a reflux reaction to obtain a catalyst for a high-temperature proton exchange membrane fuel cell.

[0008] Preferably, the carbon catalyst loaded with Pt nanoparticles is a Pt / C catalyst.

[0009] More preferably, the Pt / C catalyst is one of a commercial Johnson Matthey (JM) Pt / C catalyst, a Heshen Pt / C catalyst, a Japanese Tanaka (TANAKA) Pt / C catalyst, a self-made Pt / C, and a PtCo / C catalyst.

[0010] Preferably, the concentration of the carbon catalyst loaded with Pt nanoparticles in the dispersion is 0.5 - 10.0 mg / mL.

[0011] Preferably, the mass ratio of the carbon catalyst loaded with Pt nanoparticles to potassium permanganate is 10:(1 - 3).

[0012] Preferably, the concentration of the potassium permanganate solution is 0.5 - 5 mg / mL.

[0013] Preferably, the volume ratio of ethanol to the dispersion is 1:(0.1 - 5).

[0014] Preferably, the reflux reaction temperature is 65 - 150 °C, and the reaction time is 0.1 - 3.0 h.

[0015] Preferably, after the reflux reaction, filtration, washing, and drying are further included.

[0016] In a third aspect, the present invention provides a membrane electrode, including the catalyst for the high-temperature proton exchange membrane fuel cell described above.

[0017] In a fourth aspect, the present invention provides a method for preparing a membrane electrode, including the following steps: Step (1): Disperse the catalyst for the high-temperature proton exchange membrane fuel cell and a binder in a solvent to obtain a catalyst slurry; Step (2): Coat the catalyst slurry on a cathode diffusion layer and an anode diffusion layer respectively to obtain a cathode and an anode; laminate the anode, a proton exchange membrane, and the cathode in sequence to obtain a membrane electrode.

[0018] Preferably, in the step (1), the solvent is a mixed solvent composed of water and isopropanol, and the volume ratio of water to isopropanol is 1:(4 - 12).

[0019] Preferably, in the step (1), the binder is one or more of polytetrafluoroethylene (PTFE), polybenzimidazole (PBI), and polybenzimidazole derivatives; the mass ratio of the catalyst to the binder in the high-temperature proton exchange membrane fuel cell is (2-5):1; the solid content of the catalyst slurry is 20-25 wt%.

[0020] Preferably, in the step (2), when coating, the loading of the catalyst in the high-temperature proton exchange membrane fuel cell is controlled to be 0.2-1.1 mg / cm 2 .

[0021] In a fifth aspect, the present invention provides a high-temperature proton exchange membrane fuel cell, including the aforementioned membrane electrode.

[0022] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) In the present invention, the catalyst of the high-temperature proton exchange membrane fuel cell uses manganese dioxide to coat Pt nanoparticles. After coating, the catalytic active sites of the catalyst can be protected, the poisoning effect of phosphoric acid on the catalyst at high temperature can be alleviated, and the performance of the high-temperature proton fuel cell can be improved. In addition, manganese dioxide can not only serve as a protective layer, but also form a new proton conductor with phosphoric acid, improving the proton transport channels of the membrane electrode under high-temperature conditions and improving the performance of the high-temperature proton fuel cell.

[0023] (2) In the present invention, the catalyst of the high-temperature proton exchange membrane fuel cell uses manganese dioxide to coat and protect Pt nanoparticles, which can increase the operating temperature of the high-temperature proton exchange membrane fuel cell, and the highest operating temperature can reach 230 °C.

[0024] (3) In the present invention, after manganese dioxide coats Pt nanoparticles, the agglomeration of Pt catalyst particles under the conditions of the high-temperature proton fuel cell can be alleviated.

[0025] (4) The preparation method of the catalyst of the high-temperature proton exchange membrane fuel cell in the present invention is simple and easy to realize industrial production. Description of the Drawings

[0026] Figure 1 It is a STEM diagram of a commercial JM 40% Pt / C catalyst.

[0027] Figure 2 It is a STEM diagram of the catalyst of the high-temperature proton exchange membrane fuel cell in Example 1.

[0028] Figure 3 It is an EDS analysis diagram of the catalyst of the high-temperature proton exchange membrane fuel cell in Example 1.

[0029] Figure 4STEM image of the catalyst for the high-temperature proton exchange membrane fuel cell in Example 2.

[0030] Figure 5 EDS analysis diagram of the catalyst for the high-temperature proton exchange membrane fuel cell in Example 2.

[0031] Figure 6 Polarization curve test performance diagram of the membrane electrode in Example 6.

[0032] Figure 7 Polarization curve test performance diagram of the membrane electrode in Example 7.

[0033] Figure 8 Polarization curve test performance diagram of the membrane electrode in Example 8.

[0034] Figure 9 Polarization curve test performance diagram of the membrane electrode in Comparative Example 2.

[0035] Figure 10 Polarization curve test performance diagram of the membrane electrode in Comparative Example 3.

[0036] Figure 11 Comparison diagram of the peak power density of the membrane electrode in Examples 6 - 10 and Comparative Examples 2 - 3 at different temperatures. Detailed implementation manners

[0037] As described above, in a first aspect, the present invention provides a catalyst for a high-temperature proton exchange membrane fuel cell, comprising a carbon support, Pt nanoparticles supported on the carbon support, and manganese dioxide coated on at least a part of the surface of the Pt nanoparticles.

[0038] In the catalyst for the high-temperature proton exchange membrane fuel cell of the present invention, manganese dioxide is coated on the surface of the Pt nanoparticles. The coating of manganese dioxide can adsorb phosphoric acid at high temperatures, which can play a role in protecting the catalytic sites of the Pt nanoparticles, thereby reducing the poisoning of the catalyst by phosphoric acid at high temperatures; in addition, manganese dioxide reacts with phosphoric acid at high temperatures to generate manganese phosphate or manganese dihydrogen phosphate or acid manganese phosphate, etc., which can provide new proton conductors and dredge the proton transport channels of the membrane electrode under high-temperature conditions; secondly, the coating of manganese dioxide reduces the agglomeration of Pt nanoparticles at high temperatures.

[0039] Preferably, the mass of the manganese dioxide is 1 - 40% of the total mass of the carbon support and the Pt nanoparticles, including but not limited to 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0040] By controlling the coating amount of manganese dioxide, the present invention can ensure the improvement of the high-temperature performance of the catalyst while avoiding excessive coverage of the catalytic active sites of the Pt nanoparticles by manganese dioxide, which may affect the activity of the catalyst.

[0041] In the second aspect, the present invention provides a method for preparing a catalyst for a high-temperature proton exchange membrane fuel cell, comprising the following steps: Disperse the carbon catalyst loaded with Pt nanoparticles in water to obtain a dispersion; add potassium permanganate solution and ethanol to the dispersion, and then carry out a reflux reaction to obtain the catalyst for the high-temperature proton exchange membrane fuel cell.

[0042] Since the carbon catalyst loaded with Pt nanoparticles in the present invention contains Pt nanoparticles, during the decomposition process of the reaction between potassium permanganate and ethanol, the Pt nanoparticles will guide the deposition of manganese dioxide on the surface of the Pt nanoparticles, realizing the coating of the Pt nanoparticles with manganese dioxide.

[0043] Preferably, the carbon catalyst loaded with Pt nanoparticles is a Pt / C catalyst, including but not limited to one of commercial Johnson Matthey (JM) 40% Pt / C catalyst, Hosen 40% Pt / C catalyst, Japanese Tanaka 50% Pt / C catalyst, self-made Pt / C catalyst, PtCo / C catalyst.

[0044] Preferably, the concentration of the carbon catalyst loaded with Pt nanoparticles in the dispersion is 0.5 - 10.0 mg / mL, including but not limited to 0.5 mg / mL, 1.0 mg / mL, 2.0 mg / mL, 3.0 mg / mL, 4.0 mg / mL, 5.0 mg / mL, 6.0 mg / mL, 7.0 mg / mL, 8.0 mg / mL, 9.0 mg / mL, 10.0 mg / mL, etc.

[0045] Preferably, the mass ratio of the carbon catalyst loaded with Pt nanoparticles to potassium permanganate is 10:(1 - 3), including but not limited to 10:1, 10:1.5, 10:2, 10:2.5, 10:3, etc.

[0046] Preferably, the concentration of the potassium permanganate solution is 0.5 - 5 mg / mL, including but not limited to 0.5 mg / mL, 0.8 mg / mL, 1.0 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2.0 mg / mL, 2.5 mg / mL, 2.8 mg / mL, 3.0 mg / mL, 3.5 mg / mL, 4.0 mg / mL, 4.5 mg / mL, 5.0 mg / mL, etc.

[0047] Preferably, the volume ratio of the ethanol to the dispersion is 1:(0.1 - 5), including but not limited to 1:0.1, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0048] Preferably, the reflux reaction temperature is 65~150°C, including but not limited to 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.

[0049] Preferably, the reflux reaction time is 0.1~3.0 h, including but not limited to 0.1 h, 0.3 h, 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, etc.

[0050] Preferably, after the reflux reaction, filtration, washing and drying are further included.

[0051] In a third aspect, the present invention provides a membrane electrode, including the catalyst of the high-temperature proton exchange membrane fuel cell described above.

[0052] In a fourth aspect, the present invention provides a preparation method of a membrane electrode, including the following steps: Step (1): Disperse the catalyst and binder of the high-temperature proton exchange membrane fuel cell in a solvent to obtain a catalyst slurry; Step (2): Coat the catalyst slurry on the cathode diffusion layer and the anode diffusion layer respectively to obtain a cathode and an anode; laminate the anode, the proton exchange membrane and the cathode in sequence to obtain a membrane electrode.

[0053] Preferably, in the step (1), the solvent is a mixed solvent composed of water and isopropyl alcohol.

[0054] Preferably, the volume ratio of water to isopropyl alcohol is 1:(4~12), including but not limited to 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, etc.

[0055] Preferably, in the step (1), the binder is one or more of polytetrafluoroethylene (PTFE), polybenzimidazole (PBI), and polybenzimidazole derivatives; including but not limited to, the combination of polytetrafluoroethylene (PTFE) and polybenzimidazole (PBI), the combination of polytetrafluoroethylene (PTFE) and polybenzimidazole derivatives, etc.

[0056] Preferably, in the step (1), the mass ratio of the catalyst and binder of the high-temperature proton exchange membrane fuel cell is (2~5):1, including but not limited to 2:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc.; Preferably, in the step (1), the solid content of the catalyst slurry is 0.2~0.25, including but not limited to 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, etc.

[0057] Preferably, in the step (2), the catalyst loading of the high-temperature proton exchange membrane fuel cell during coating is controlled to be 0.2 - 1.1 mg / cm 2 , including but not limited to 0.2 mg / cm 2 , 0.3 mg / cm 2 , 0.4 mg / cm 2 , 0.5 mg / cm 2 , 0.6 mg / cm 2 , 0.7 mg / cm 2 , 0.8 mg / cm 2 , 0.9 mg / cm 2 , 1.0 mg / cm 2 , 1.1 mg / cm 2 and so on.

[0058] In a fifth aspect, the present invention provides a high-temperature proton exchange membrane fuel cell, including the aforementioned membrane electrode.

[0059] For ease of understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0060] The Pt / C catalyst in the embodiments of the present invention is the commercially available JM 40% Pt / C catalyst from Johnson Matthey.

[0061] Example 1 In this example, the catalyst of the high-temperature proton exchange membrane fuel cell includes a Pt / C catalyst and manganese dioxide coated on the surface of Pt nanoparticles in the Pt / C catalyst, where: the Pt / C catalyst is composed of a carbon support and Pt nanoparticles supported on the carbon support.

[0062] The specific preparation method is as follows: (1) Ultrasonically disperse 50 mg of the commercially available JM 40% Pt / C catalyst in 40 mL of deionized water to obtain a dispersion; (2) Add 10 mL of a 1 mg / mL KMnO4 aqueous solution to the dispersion, stir and mix well, then continue to add 40 mL of an ethanol solution, stir and mix well to obtain a mixed solution; reflux the mixed solution in an 80°C oil bath for 2.0 h, and after the reaction solution is filtered, washed, and dried, the catalyst of the high-temperature proton exchange membrane fuel cell is obtained.

[0063] Figure 1 is the STEM diagram of the commercially available JM 40% Pt / C catalyst, and it can be seen that the Pt / C catalyst is composed of a carbon support and Pt nanoparticles supported on the carbon support.

[0064] The STEM image of the microscopic morphology of the catalyst for preparing a high-temperature proton exchange membrane fuel cell in this example is as shown in Figure 2 . It can be seen that there are many nanoparticles dispersed on the carbon support. Further, EDS elemental analysis was performed on the catalyst, and the results are as shown in Figure 3 . It can be seen that the Mn element and the O element are mainly distributed adhering to the Pt element, indicating that the MnO2 in the present invention is mainly coated on the surface of the Pt nanoparticles.

[0065] Comparative Example 1 50 mg of commercial JM 40% Pt / C catalyst was ultrasonically dispersed in 40 mL of deionized water to obtain a dispersion; 5.56 mg of nano-manganese dioxide was added to the dispersion and stirred thoroughly until evenly mixed to obtain a mixed slurry; after filtering and drying the mixed slurry, a catalyst for a high-temperature proton exchange membrane fuel cell was obtained.

[0066] Example 2 It is basically the same as Example 1, except that in step (2), the added volume of the KMnO4 aqueous solution is 5 mL.

[0067] The STEM image of the microscopic morphology of the catalyst for preparing a high-temperature proton exchange membrane fuel cell in this example is as shown in Figure 4 . It can be seen that there are many nanoparticles dispersed on the carbon support. Further, EDS elemental analysis was performed on the catalyst, and the results are as shown in Figure 5 . It can be seen that the Mn element and the O element are mainly distributed adhering to the Pt element, indicating that the MnO2 in the present invention is mainly coated on the surface of the Pt nanoparticles.

[0068] Example 3 It is basically the same as Example 1, except that in step (2), the added volume of the KMnO4 aqueous solution is 15 mL.

[0069] Example 4 The catalyst for the high-temperature proton exchange membrane fuel cell in this example includes a Pt / C catalyst and manganese dioxide coated on the surface of the Pt nanoparticles in the Pt / C catalyst, wherein: the Pt / C catalyst is composed of a carbon support and Pt nanoparticles supported on the carbon support.

[0070] The specific preparation method is as follows: (1) 60 mg of commercial JM 40% Pt / C catalyst was ultrasonically dispersed in 40 mL of deionized water to obtain a dispersion; (2) Add 5 mL of an aqueous KMnO₄ solution with a concentration of 3 mg / mL to the dispersion liquid. After stirring and mixing evenly, continue to add 50 mL of ethanol solution. After stirring and mixing evenly, a mixed liquid is obtained. The mixed liquid is subjected to a reflux reaction in an oil bath at 90 °C for 3 h. After the reaction liquid is filtered by suction, washed, and dried, a catalyst for a high-temperature proton exchange membrane fuel cell is obtained.

[0071] Example 5 In this example, the catalyst for the high-temperature proton exchange membrane fuel cell includes a Pt / C catalyst and manganese dioxide coated on the surface of Pt nanoparticles in the Pt / C catalyst, where: the Pt / C catalyst is composed of a carbon carrier and Pt nanoparticles supported on the carbon carrier.

[0072] The specific preparation method is as follows: (1) Ultrasonically disperse 40 mg of a commercial JM 40% Pt / C catalyst in 40 mL of deionized water to obtain a dispersion liquid; (2) Add 16 mL of an aqueous KMnO₄ solution with a concentration of 0.5 mg / mL to the dispersion liquid. After stirring and mixing evenly, continue to add 30 mL of ethanol solution. After stirring and mixing evenly, a mixed liquid is obtained. The mixed liquid is refluxed in an oil bath at 70 °C for 45 min. After the reaction liquid is filtered by suction, washed, and dried, a catalyst for a high-temperature proton exchange membrane fuel cell is obtained.

[0073] Example 6 Preparation of membrane electrode: S1: Add 40 mg of the catalyst for the high-temperature proton exchange membrane fuel cell prepared in Example 1 to 2 mL of deionized water and stir to moisten it; then add 16 mL of isopropanol to disperse it into a slurry. Then add 203 mg of a 5 wt% PBI DMSO solution to the slurry; after stirring and mixing, a catalyst slurry is obtained, and the solid content of the catalyst slurry is 20 - 25 wt%.

[0074] S2: Coat the catalyst slurry on the cathode diffusion layer and the anode diffusion layer by ultrasonic spraying respectively. After drying, the anode and cathode are obtained respectively. When spraying, control the catalyst loading to be about 0.9 mg / cm 2 .

[0075] S3: Assemble the anode, cathode, and n-PBI-10% POSS / H₃PO₄ composite membrane into a fuel cell membrane electrode, where: the n-PBI-10% POSS / H₃PO₄ composite membrane is obtained by soaking the n-PBI membrane in 85 wt% phosphoric acid at 60 °C for 48 h.

[0076] The membrane electrode of the fuel cell is subjected to HT - PEMFC testing; the specific operating conditions are as follows: the working temperature of the single cell is 160 °C to 230 °C, the anode is fed with pure hydrogen, and the cathode is fed with pure oxygen; the anode gas flow rate is 350 sccm / min, and the cathode gas flow rate is 350 sccm / min.

[0077] Example 7 It is basically the same as Example 6, except that the catalyst used is the catalyst of the high - temperature proton exchange membrane fuel cell in Example 2.

[0078] Example 8 It is basically the same as Example 6, except that the catalyst used is the catalyst of the high - temperature proton exchange membrane fuel cell in Example 3.

[0079] Comparative Example 2 It is basically the same as Example 6, except that the catalyst used is the commercial JM 40% Pt / C catalyst.

[0080] Comparative Example 3 It is basically the same as Example 6, except that the catalyst used is the catalyst of the high - temperature proton exchange membrane fuel cell in Comparative Example 1.

[0081] Example 9 Preparation of the membrane electrode: S1: Add 40 mg of the catalyst of the high - temperature proton exchange membrane fuel cell prepared in Example 4 to 4 mL of deionized water and stir to moisten it; then add 16 mL of isopropanol to disperse it into a slurry, and then add 260 mg of a 5 wt% PBI DMSO solution to the slurry; after stirring and mixing, a catalyst slurry is obtained, and the solid content of the catalyst slurry is 20 - 25 wt%.

[0082] S2: Spray - coat the catalyst slurry on the cathode diffusion layer and the anode diffusion layer by ultrasonic spraying respectively. After drying, the anode and the cathode are obtained respectively. When spraying, control the catalyst loading to be about 0.7 mg / cm 2 .

[0083] S3: Assemble the anode, the cathode and the n - PBI - 10% POSS / H3PO4 composite membrane into a fuel cell membrane electrode, where: the n - PBI - 10% POSS / H3PO4 composite membrane is obtained by soaking the n - PBI membrane in 85 wt% phosphoric acid at 60 °C for 48 h.

[0084] The membrane electrode of the fuel cell was tested by HT - PEMFC. The specific operating conditions were as follows: the operating temperature of the single cell was 160°C - 230°C, the anode was fed with pure hydrogen, and the cathode was fed with pure oxygen; the anode gas flow rate was 350 sccm / min, and the anode gas flow rate was 350 sccm / min.

[0085] Example 10 Preparation of the membrane electrode: S1: 40 mg of the catalyst of the high - temperature proton exchange membrane fuel cell prepared in Example 4 was added to 4 mL of deionized water and stirred to make it wet; then 12 mL of isopropanol was added to disperse it into a slurry, and then 170 mg of a 5 wt% PBI DMSO solution was added to the slurry; after stirring and mixing, a catalyst slurry was obtained, and the solid content of the catalyst slurry was 20 - 25 wt%.

[0086] S2: The catalyst slurry was coated on the cathode diffusion layer and the anode diffusion layer by ultrasonic spraying respectively. After drying, the anode and the cathode were obtained respectively. When spraying, the catalyst loading was controlled at about 1.1 mg / cm 2 .

[0087] S3: The anode, the cathode and the n - PBI - 10% POSS / H3PO4 composite membrane were assembled into a fuel cell membrane electrode. Among them, the n - PBI - 10% POSS / H3PO4 composite membrane was obtained by immersing the n - PBI membrane in 85 wt% phosphoric acid at 60°C for 48 h.

[0088] The membrane electrode of the fuel cell was tested by HT - PEMFC; the specific operating conditions were as follows: the operating temperature of the single cell was 160°C - 230°C, the anode was fed with pure hydrogen, and the cathode was fed with pure oxygen; the anode gas flow rate was 350 sccm / min, and the anode gas flow rate was 350 sccm / min.

[0089] The performance graphs after testing Examples 6 - 8 and Comparative Examples 2 - 3 can be seen respectively Figures 6 - 10 ; it can be seen from the figure that: Through testing, it was found that the performance of the membrane electrode of Example 6 increased steadily within the temperature range of 160 - 230°C. However, when the operating temperature of the membrane electrode of Comparative Example 2 reached 200°C, the change in battery performance was not obvious, and within the entire temperature range of 160 - 230°C, the performance was significantly lower than that of Example 6. At 220°C, the peak power densities of the corresponding membrane electrodes of Example 6 and Comparative Example 2 of the present invention were measured to be 1.64 W cm -2 , 1.14 W cm -2 ; after optimizing the test conditions, the peak power density of Example 6 at 220°C could reach 2.06 W cm -2。At a voltage of 0.65 V, the current densities of the membrane electrode of Example 6 of the present invention and the membrane electrode of Comparative Example 2 were measured to be 1.31 A cm -2 and 0.659 A cm -2 respectively. Compared with the membrane electrode of Comparative Example 2, the maximum power density of the membrane electrode in Example 6 of the present invention is about 500 mW cm higher than that of the membrane electrode in Comparative Example 2 -2 . Especially in the high-temperature range of 200-230 °C, at the same voltage, the current density of the membrane electrode of Example 6 of the present invention is significantly higher than that of the corresponding membrane electrode in Comparative Example 2, making the overall performance of the battery higher. The main reason for the performance improvement of the membrane electrode in Example 6 is that at high temperatures, manganese dioxide can adsorb a certain amount of phosphoric acid, reducing the poisoning of the active sites of the Pt-based catalyst by phosphoric acid; and at high temperatures, manganese dioxide can react with phosphoric acid to form new proton conductors such as manganese phosphate, manganese dihydrogen phosphate or acid manganese phosphate, dredging the proton conduction channels and contributing to the performance improvement of HT-PEMFC.

[0090] Within the temperature range of 200-230 °C, the membrane electrode performances of Example 7 and Example 8 are also better than those of the membrane electrode of Comparative Example 2. This shows that the commercial JM 40% Pt / C catalyst modified with manganese dioxide is indeed helpful for improving the membrane electrode performance at high temperatures. This is because at temperatures above 200 °C, manganese dioxide will react with phosphoric acid to form new proton conductors; and manganese dioxide will adsorb a certain amount of phosphoric acid to protect the sites of the Pt-based catalyst and reduce the poisoning of the catalyst by phosphoric acid. In addition, there is a situation of phosphoric acid loss in the membrane electrode of Comparative Example 2 under high-temperature working conditions, and the proton conductor does cause its performance to decay. However, in Examples 6-8, manganese dioxide will react with phosphoric acid to form new proton conductors, which has a certain improvement on the operating temperature of the battery. At a high temperature of 220 °C, the peak power densities of the membrane electrodes of Example 7 and Example 8 of the present invention are 1.39 W cm -2 and 1.42 W cm -2 respectively, both lower than that of Example 6, indicating that there is an optimal ratio for the coating amount of manganese dioxide. This may be because when the amount of manganese dioxide is small, the protection of the active sites of the Pt-based catalyst is lacking; while when the amount of manganese dioxide is large, a certain amount of active sites of the Pt-based catalyst will be covered, increasing the proton conduction resistance and thus reducing the performance of the high-temperature fuel cell.

[0091] Through testing, it is found that the performance of the membrane electrode of Example 6 steadily increases within the temperature range of 160-230 °C, but when the operating temperature of the membrane electrode of Comparative Example 3 reaches 200 °C, the battery performance begins to decrease. At 220 °C, the peak power densities of the corresponding membrane electrodes of Example 6 of the present invention and Comparative Example 3 are measured to be 1.64 W cm -2 and 1.29 W cm -2; and at a voltage of 0.65 V, the current densities of the membrane electrode of Example 6 of the present invention and the membrane electrode of Comparative Example 3 were measured to be 1.31 A cm -2 and 0.72 A cm -2 . This shows that the coating of manganese dioxide on the surface of Pt nanoparticles of the Pt / C catalyst in the present invention has obvious advantages compared with directly mixing nano-manganese dioxide in the Pt / C catalyst.

[0092] The comparison chart of the peak power densities of the membrane electrodes of Examples 6 to 10 and Comparative Examples 2 to 3 at different temperatures is as shown in Figure 11 . It can be seen that after 210 °C, the peak power densities of Examples 6 to 10 are significantly higher than those of Comparative Examples 2 to 3.

[0093] In the present invention, manganese dioxide was used to coat and modify the Pt nanoparticles in the JM 40% Pt / C catalyst. While improving the performance of the membrane electrode fuel cell, it can also improve the working conditions of the fuel cell at high temperatures and broaden the co-working temperature threshold of the fuel cell. Manganese dioxide can react with phosphoric acid at high temperatures, which helps to form a new proton conductor, and can also improve the poisoning of the active sites of the Pt-based catalyst by phosphoric acid. Even in the absence of water and phosphoric acid, it can play a role in constructing a three-phase interface and promoting proton conduction. In addition, under the working conditions above 200 °C, the commercially available JM 40% Pt / C catalyst modified by coating Pt nanoparticles with manganese dioxide can adsorb a certain amount of phosphoric acid, regulate the distribution of phosphoric acid in the catalyst layer, avoid the attenuation of the fuel cell performance at high temperatures caused by acid flooding, and improve the catalyst utilization rate as well as the performance and lifespan of the battery. The invention of this commercially available JM 40% Pt / C catalyst modified by coating Pt nanoparticles with manganese dioxide constructs a new proton conductor and realizes the further improvement of the working temperature and performance of high-temperature fuel cells.

[0094] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A catalyst for a high temperature proton exchange membrane fuel cell, characterized in that: The invention comprises a carbon carrier and Pt nanoparticles loaded on the carbon carrier, wherein at least a part of the surface of the Pt nanoparticles is coated with manganese dioxide.

2. The catalyst for a high temperature proton exchange membrane fuel cell according to claim 1, characterized in that: The mass of the manganese dioxide is 1-40% of the total mass of the Pt nanoparticles and the carbon carrier.

3. A method for preparing a catalyst for a high temperature proton exchange membrane fuel cell according to claim 1 or 2, characterized in that: The following steps are involved: A carbon catalyst loaded with Pt nanoparticles is dispersed in water to obtain a dispersion; a potassium permanganate solution and ethanol are added to the dispersion, and a reflux reaction is performed to obtain a catalyst for a high-temperature proton exchange membrane fuel cell.

4. The method for preparing a catalyst for a high temperature proton exchange membrane fuel cell according to claim 3, characterized in that: The carbon catalyst loaded with Pt nanoparticles is a Pt / C catalyst.

5. The method for preparing a catalyst for a high temperature proton exchange membrane fuel cell according to claim 3, characterized in that: The concentration of the carbon catalyst loaded with Pt nanoparticles in the dispersion is 0.5-10.0 mg / mL; The mass ratio of the carbon catalyst loaded with Pt nanoparticles to potassium permanganate is 10:(1-3); The concentration of the potassium permanganate solution is 0.5-5 mg / mL; The volume ratio of the ethanol to the dispersion is 1:(0.1-5).

6. The method for preparing a catalyst for a high temperature proton exchange membrane fuel cell according to claim 3, characterized in that: The reflux reaction temperature is 65-150° C., and the reaction time is 0.1-3.0 h.

7. A membrane electrode, characterized in that: The invention comprises the catalyst for a high-temperature proton exchange membrane fuel cell according to claim 1 or 2, or the catalyst for a high-temperature proton exchange membrane fuel cell prepared by the preparation method according to any one of claims 3 to 6.

8. A method for preparing a membrane electrode according to claim 7, characterized in that: The following steps are involved: Step (1): dispersing a catalyst and a binder for a high temperature proton exchange membrane fuel cell in a solvent to obtain a catalyst slurry; Step (2): Coating the catalyst slurry on the cathode diffusion layer and the anode diffusion layer respectively to obtain the cathode and the anode respectively; and sequentially laminating the anode, the proton exchange membrane and the cathode to obtain a membrane electrode.

9. The method for preparing a membrane electrode according to claim 8, characterized in that: In the step (1), the solvent is a mixed solvent composed of water and isopropanol, and the volume ratio of water to isopropanol is 1:(4-12); the binder is one or more of polytetrafluoroethylene, polybenzimidazole, and polybenzimidazole derivatives; the mass ratio of the catalyst of the high-temperature proton exchange membrane fuel cell to the binder is (2-5):1; the solid content of the catalyst slurry is 20-25wt%; In the step (2), the catalyst loading of the high temperature proton exchange membrane fuel cell is controlled to be 0.2-1.1 mg / cm during coating. 2 .

10. A high temperature proton exchange membrane fuel cell, characterized in that: It includes the membrane electrode as described in claim 7, or the membrane electrode prepared by the preparation method as described in any one of claims 8 to 9.

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