A platinum-carbon catalyst and its preparation method, membrane electrode and fuel cell

Abstract

This invention discloses a platinum-carbon catalyst, its preparation method, a membrane electrode assembly (MEA), and a fuel cell. The preparation method of the platinum-carbon catalyst includes the following steps: (1) ball milling and mixing a carbon support and a platinum precursor to obtain a composite precursor; (2) calcining the composite precursor; and (3) heat-treating the calcined composite precursor in step (2) under an ammonia atmosphere to obtain a surface-functionalized amine-based platinum-carbon catalyst. The amine groups in the platinum-carbon catalyst prepared by this invention form hydrogen bonds with the ionomer, which self-assemble into highly permeable channels within the MEA, improving platinum utilization, reducing platinum loading, lowering system impedance, increasing power density, and enabling high-performance output and industrial application of the fuel cell.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, and more specifically, to a platinum-carbon catalyst, its preparation method, a membrane electrode assembly, and a fuel cell. Background Technology

[0002] Fuel cells are power generation devices that convert chemical energy into electrical energy using fuel and oxidant as raw materials. They are characterized by high energy conversion efficiency, fast start-up, and environmentally friendly byproducts, and are used in various fields such as fuel cell vehicles, heavy-duty trucks, drones, and stationary power stations. The membrane electrode assembly (CCM), a three-in-one structure consisting of an anode catalyst layer, a proton exchange membrane, and a cathode catalyst layer, is a key component of proton exchange membrane fuel cells, playing a crucial role in their cost and performance. Currently, the catalysts used in proton exchange membrane fuel cells are mainly platinum-carbon catalysts, with the active slurry consisting of the platinum-carbon catalyst, ion-crosslinked polymer (ionomer), and solvent. However, the membrane electrode assembly prepared from the active slurry has a disordered structure, and the utilization rate of the ion-crosslinked polymer and catalyst is low, leading to significant electrochemical polarization, ohmic polarization, and mass transfer polarization problems. Therefore, there is a need to develop a method for preparing fuel cell membrane electrodes with high platinum utilization and high power density suitable for continuous industrial production. Summary of the Invention

[0003] This invention is based on the inventors' discoveries and understanding of the following facts and problems: Membrane electrodes prepared from active slurries have a disordered structure, resulting in long transport paths for water, gas, protons, and electrons, and low utilization rates of ion-crosslinked polymers and catalysts, leading to significant electrochemical polarization, ohmic polarization, and mass transfer polarization problems. Therefore, there is a need to develop highly permeable, ordered membrane electrodes suitable for continuous industrial production, shortening electron / proton transport paths, improving platinum utilization, and thus enhancing fuel cell performance.

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a platinum-carbon catalyst and its preparation method. In the platinum-carbon catalyst, hydrogen bonds are formed between the amine groups and ionomers, resulting in highly permeable channels within the membrane electrode assembly (MEA) through self-assembly. This improves platinum utilization, reduces platinum loading, lowers system impedance, and increases power density, thereby preparing a low-platinum-loading, high-power-density fuel cell MEA, enabling high-performance fuel cell output and industrial applications.

[0005] A method for preparing a platinum-carbon catalyst according to an embodiment of the present invention includes the following steps:

[0006] (1) The carbon support and platinum precursor were ball-milled and mixed to obtain a composite precursor;

[0007] (2) The composite precursor is subjected to calcination treatment;

[0008] (3) The composite precursor that has been calcined in step (2) is heat-treated in an ammonia atmosphere to obtain a platinum carbon catalyst with surface amine functionalization.

[0009] The advantages and technical effects of the preparation method of the platinum-carbon catalyst according to embodiments of the present invention are as follows: In the embodiments of the present invention, a solid-phase method is used to synthesize the platinum-carbon catalyst. The carbon support and platinum precursor are mechanically ball-milled to obtain a composite precursor powder. Ball milling can fully disperse the composite precursor powder, and the forced force during the ball milling process introduces a large amount of strain and defects. The composite precursor powder is then calcined to remove volatile components, giving the catalyst support a certain strength and making it easier to expose the crystal faces of Pt, thereby improving the activity of the catalyst. After calcination, a black powder platinum-carbon catalyst is obtained. The solid-phase method for synthesizing platinum-carbon catalysts is simple, the platinum-carbon catalyst has uniform particle size, high yield, is easy to industrialize, and produces less pollution. At the same time, it can avoid or reduce the hard agglomeration phenomenon that easily occurs in the liquid-phase method for synthesizing platinum-carbon catalysts. Then, the platinum-carbon catalyst is heat-treated in an ammonia atmosphere. The ammonia reacts with the acidic oxygen groups on the surface of platinum-carbon at high temperature to generate amide, imide, and lactam groups, thus obtaining a surface amine-functionalized platinum-carbon catalyst. In this embodiment of the invention, the amine groups on the surface of the prepared platinum-carbon catalyst can form hydrogen bonds with Ionomers, and through self-assembly, form highly permeable channels inside the membrane electrode, shortening the electron / proton transport path, improving platinum utilization, and reducing the total platinum loading to 0.3-0.35 mg / cm³. 2 This method reduces system impedance, improves catalyst efficiency, lowers the overall cost of the fuel cell stack, and increases power density by more than 30%. It also enables the fabrication of membrane electrodes for low-platinum-loaded, high-power-density proton exchange membrane fuel cells, achieving high-performance output and industrial application of fuel cells.

[0010] In some embodiments, in step (3), the flow rate of ammonia is 50-100 sccm; the temperature of the heat treatment is 400-600℃; the time of the heat treatment is 0.5-2h; and the heating rate of the heat treatment is 2-5℃ / min.

[0011] In some embodiments, in step (1), the carbon support is at least one of carbon black, carbon nanotubes, carbon fibers or graphene; and the platinum precursor is at least one of chloroplatinic acid, tetraammineplatinum chloride, ammonium chloroplatinate, tetraammineplatinum nitrate and platinum acetylacetonate.

[0012] In some embodiments, in step (1), the mass ratio of the carbon support to the platinum element in the platinum precursor is 120:1-120:60; in the ball milling, the mass ratio of the milling beads to the sum of the mass of the carbon support and the platinum precursor is 50:1-75:1; the rotation speed of the ball mill is 600-1000 rpm; and the milling time is 12h-24h.

[0013] In some embodiments, in step (2), the calcination temperature is 900-1200℃; the calcination time is 5-8h; and the calcination atmosphere is at least one of nitrogen and argon.

[0014] In some embodiments, in step (2), the calcination process adopts a segmented temperature rise, with the temperature rising to 400-500℃ at a rate of 5-10℃ / min and held at a constant temperature for 1-3 hours, and then rising to 900-1200℃ at a rate of 2-4℃ / min and calcined at a constant temperature for 5-8 hours.

[0015] A platinum-carbon catalyst according to an embodiment of the present invention is prepared using the preparation method of the present invention. In this embodiment, the amine groups on the surface of the prepared platinum-carbon catalyst can form hydrogen bonds with ionomers, forming highly permeable channels inside the membrane electrode through self-assembly, thereby improving the utilization rate of platinum, reducing the platinum loading, reducing the system impedance, improving the catalyst utilization efficiency, reducing the overall cost of the stack, and increasing the power density by more than 30%.

[0016] An embodiment of the present invention provides a membrane electrode catalyst layer comprising the platinum-carbon catalyst described in this embodiment. In this embodiment, a highly permeable channel is constructed in the proton exchange membrane fuel cell catalyst layer to improve platinum utilization and reduce system impedance.

[0017] An embodiment of the present invention provides a membrane electrode, comprising the membrane electrode catalytic layer described in this embodiment as a cathode catalytic layer and / or an anode catalytic layer. In this embodiment, hydrogen bonds are formed between the amine groups and ionomers in the platinum-carbon catalyst, and highly permeable channels can be formed inside the CCM through self-assembly to improve platinum utilization, reduce the platinum loading of the membrane electrode, and improve the catalyst utilization efficiency.

[0018] A fuel cell according to an embodiment of the present invention includes a membrane electrode assembly (MEA). In this embodiment, the power density of the fuel cell is significantly improved, reaching up to 0.65V@1.62W / cm². 2Highly permeable membrane electrodes can shorten the proton transport path and improve conductivity, thereby reducing contact resistance and mass transfer resistance. They also help improve the utilization rate of platinum in the catalyst layer, thus improving battery performance and reducing the overall cost of the stack. They are suitable for low humidification conditions in vehicles and are beneficial for the construction of proton exchange membrane fuel cell vehicle power systems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the self-assembled molecules of the platinum-carbon catalyst and perfluorosulfonic acid resin of the present invention.

[0020] Figure 2 These are battery performance comparison curves for Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] A method for preparing a platinum-carbon catalyst according to an embodiment of the present invention includes the following steps:

[0023] (1) The carbon support and platinum precursor were ball-milled and mixed to obtain a composite precursor;

[0024] (2) The composite precursor is subjected to calcination treatment;

[0025] (3) The composite precursor that has been calcined in step (2) is heat-treated in an ammonia atmosphere to obtain a platinum carbon catalyst with surface amine functionalization.

[0026] The preparation method of the platinum-carbon catalyst in this invention employs a solid-phase synthesis method. A carbon support and a platinum precursor are mechanically ball-milled to obtain a composite precursor powder. Ball milling effectively disperses the composite precursor powder, and the forced force during the milling process introduces significant strain and defects. The composite precursor powder is then calcined to remove volatile components, giving the catalyst support a certain strength and making it easier to expose the Pt crystal faces, thereby improving the catalyst activity. After calcination, a black powdered platinum-carbon catalyst is obtained. The solid-phase synthesis of the platinum-carbon catalyst is simple, produces uniform particle size, has a high yield, is easily industrialized, and generates less pollution. It also avoids or reduces the hard agglomeration phenomenon that easily occurs in the liquid-phase synthesis of platinum-carbon catalysts. The platinum-carbon catalyst is then heat-treated in an ammonia atmosphere. The ammonia reacts with acidic oxygen groups on the surface of the platinum-carbon at high temperature to generate amide, imide, and lactam groups, thus obtaining a surface-amine-functionalized platinum-carbon catalyst. In this embodiment of the invention, the amine groups on the surface of the prepared platinum-carbon catalyst can form hydrogen bonds with Ionomers, and through self-assembly, form highly permeable channels inside the membrane electrode, shortening the electron / proton transport path, improving platinum utilization, and reducing the platinum loading to 0.3-0.35 mg / cm³. 2 This method reduces system impedance, improves catalyst efficiency, lowers the overall cost of the fuel cell stack, and increases power density by more than 30%. It also enables the fabrication of membrane electrodes for low-platinum-loaded, high-power-density proton exchange membrane fuel cells, achieving high-performance output and industrial application of fuel cells.

[0027] In some embodiments, in step (3), the flow rate of ammonia gas is 50-100 sccm, optionally 60 sccm, 70 sccm, 80 sccm, or 90 sccm; the temperature of the heat treatment is 400-600℃, optionally 450℃, 500℃, or 550℃; the heat treatment time is 0.5-2h, optionally 1h or 1.5h; the heating rate of the heat treatment is 2-5℃ / min, optionally 3℃ / min or 4℃ / min; and the heat treatment is followed by natural cooling to room temperature. In this embodiment of the invention, the heat treatment temperature is 400-600℃. When the temperature is too low, the binding force of the amine groups is insufficient, which makes it easier for the amine groups to decrease during mechanical processes such as ball milling.

[0028] In some embodiments, in step (1), the carbon support is at least one of carbon black, carbon nanotubes, carbon fibers or graphene, preferably, the carbon black is XC-72; the platinum precursor is at least one of chloroplatinic acid, tetraammineplatinum chloride, ammonium chloroplatinate, tetraammineplatinum nitrate and platinum acetylacetonate.

[0029] In some embodiments, in step (1), the mass ratio of the carbon support to the platinum element in the platinum precursor is 120:1-120:60, optionally 120:5, 120:10, 120:15, 120:20, 120:24, 120:30, 120:40, or 120:50; in the ball milling, the mass ratio of the milling beads to the sum of the mass of the carbon support and the platinum precursor is 50:1-75:1, optionally 55:1, 60:1, or 70:1; the ball milling speed is 600-1000 rpm, optionally 700 rpm, 800 rpm, or 900 rpm; the ball milling time is 12h-24h, optionally 15h, 18h, or 20h; and the ball milling atmosphere is nitrogen. After ball milling, the composite precursor powder is sieved and removed. In this embodiment of the invention, by optimizing the ball milling conditions, the ball milling can fully disperse the composite precursor powder. The forced force during the ball milling process will introduce a large amount of strain and defects, which can break chemical bonds and build new surfaces.

[0030] In some embodiments, in step (2), the calcination temperature is 900-1200℃, optionally 1000℃ or 1100℃; the calcination time is 5-8h, optionally 6h or 7h; and the calcination atmosphere is at least one of nitrogen and argon. In some embodiments, the calcination process employs a segmented temperature program, heating at a rate of 5-10℃ / min to 400-500℃, optionally 450℃, holding at that temperature for 1-3h, optionally 2h, and then heating at a rate of 2-4℃ / min to 900-1200℃, optionally 1000℃ or 1100℃, and calcining at that temperature for 5-8h, optionally 6h or 7h; and the calcination atmosphere is at least one of nitrogen and argon. In this embodiment of the invention, calcination can give the catalyst support a certain strength, provide the catalyst with stable active centers, and remove volatile components while retaining a certain chemical composition; it also makes it easier to expose the crystal faces of the catalyst. If the calcination temperature is too high, the carbon support structure is prone to collapse; if the calcination temperature is too low, the graphitization of the carbon support is insufficient, resulting in a large catalyst impedance. The calcination treatment can be further improved by using segmented programmed heating, which can further enhance the proportion and effect of the precursor converting into stable intermediate substances, which is beneficial for the formation of effective components. This is because, compared to segmented programmed heating, if the temperature is directly raised to a high temperature, the stable intermediate substances are prone to rapid decomposition.

[0031] This invention discloses a platinum-carbon catalyst prepared using the method described in this invention. In this embodiment, the surface amine groups of the prepared platinum-carbon catalyst can form hydrogen bonds with iodine, such as perfluorosulfonic acid resin. Through self-assembly, it forms highly permeable channels within the membrane electrode, improving platinum utilization, reducing platinum loading, lowering system impedance, increasing catalyst efficiency, reducing the overall cost of the fuel cell stack, and increasing power density by more than 30%.

[0032] An embodiment of the present invention provides a membrane electrode catalyst layer comprising the platinum-carbon catalyst described in this embodiment. In this embodiment, a highly permeable channel is constructed in the proton exchange membrane fuel cell catalyst layer to improve platinum utilization and reduce system impedance.

[0033] In some embodiments, the membrane electrode catalytic layer is a cathode catalytic layer with a loading of 0.26-0.29 mg Pt / cm³. 2 Optionally, 0.28 mg Pt / cm 2 The membrane electrode catalytic layer is an anode catalytic layer with a loading of 0.04-0.06 mg Pt / cm³. 2 Optionally, 0.05 mg Pt / cm 2 In this embodiment of the invention, the total platinum loading of the cathode and anode catalyst layers is 0.3-0.35 mg / cm³. 2 .

[0034] An embodiment of the present invention provides a membrane electrode, comprising the membrane electrode catalytic layer described in this embodiment as a cathode catalytic layer and / or an anode catalytic layer. In this embodiment, hydrogen bonds are formed between the amine groups and ionomers in the platinum-carbon catalyst, and highly permeable channels can be formed inside the CCM through self-assembly to improve platinum utilization, obtain a low-platinum, high-performance CCM, reduce the platinum loading of the membrane electrode, and improve the catalyst utilization efficiency.

[0035] A fuel cell according to an embodiment of the present invention includes a membrane electrode assembly (MEA). In this embodiment, the power density of the fuel cell is significantly improved, reaching up to 0.65V@1.62W / cm². 2 Highly permeable membrane electrodes can shorten the proton transport path and improve conductivity, thereby reducing contact resistance and mass transfer resistance. They also help improve the utilization rate of platinum in the catalyst layer, thus improving battery performance and reducing the overall cost of the stack. They are suitable for low humidification conditions in vehicles and are beneficial for the construction of proton exchange membrane fuel cell vehicle power systems.

[0036] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0037] Example 1

[0038] 1. Preparation of surface-amine-functionalized platinum-carbon catalysts, including the following steps:

[0039] (1) Carbon black XC-72 and chloroplatinic acid were mixed. The mass ratio of carrier carbon black XC-72 to metal element platinum was 3:1. Chloroplatinic acid and carrier carbon black XC-72 were compounded by ball milling. The mass ratio of ball milling beads to raw materials was 60:1. The ball milling speed was 800 rpm and the ball milling time was 18 h. The ball milling atmosphere was nitrogen. Then the black composite precursor powder after ball milling was sieved and taken out.

[0040] (2) The black composite precursor powder after ball milling and sieving was placed in the center of a tube furnace for calcination under nitrogen atmosphere. The calcination was carried out by segmented temperature program. The temperature was increased to 500℃ at a rate of 5℃ / min and then held at the temperature for 2 hours. Then the temperature was increased to 1000℃ at a rate of 4℃ / min and held at the temperature for 8 hours to obtain the calcined powder.

[0041] (3) The calcined powder is amination in an ammonia atmosphere with an ammonia flow rate of 100 sccm. The amination temperature is increased to 500℃ at a rate of 5℃ / min and kept at a constant temperature for 1.5h. Then it is naturally cooled to room temperature and ground to obtain a platinum carbon catalyst with surface amine functionalization.

[0042] 2. Fabrication and testing of membrane electrodes:

[0043] (1) Preparation of catalytic layer slurry for anode and cathode: Weigh 2.5g of platinum carbon catalyst on an analytical balance and put it into a ball mill jar. Add 5g of deionized water to fully wet the catalyst and stir evenly. Then add 15g of n-propanol and 150g of ZrO2 particles in sequence. After sealing the ball mill jar, put it into a ball mill and ball mill at a speed of 300r / min for 2.5h.

[0044] Then, remove the ball mill jar, add 7.3g of Ionomer (15wt%) to the slurry, seal it, and continue ball milling at 400r / min for 12h. Finally, stop the machine, remove the ball mill jar, filter out the ball milling beads, then remove bubbles under vacuum, and finally stir for 15min. Use a dropper to take a small amount of slurry and place it on a clean PTFE film. Place a suitable coating rod on the automatic coating instrument to automatically complete the coating of catalyst layers of different thicknesses. Place the coated catalyst layer in a vacuum drying oven, evacuate the vacuum, dry at 80℃ for 6h, and then take it out and place it in a constant temperature and humidity oven for later use.

[0045] (2) The catalyst layer coated on the PTFE film was cut into 5cm×5cm pieces with a loading of 0.28 / 0.05mg Pt / cm. 2As cathode / anode catalyst layers, the anode and cathode catalyst layers were transferred to the Gore 12 proton exchange membrane on a hot press at a temperature of 165°C and a pressure of 30 kgf / cm². 2 The hot pressing time is 85 seconds. After the hot pressing is completed, the PTFE film is quickly peeled off to obtain the No. 1 membrane electrode.

[0046] (3) The prepared membrane electrode No. 1 was directly clamped between the two gas diffusion layers and tested using a fuel cell test fixture with a serpentine flow field. The cell temperature was 80℃, the humidification was 10% / 35% (anode / cathode), the initial flow rates on the H2 side and nitrogen side were set to 300 / 700 sccm, the excess coefficient was 1.5 / 2.0, and the back pressure was 100kPa / 100kPa. The test results are shown in Table 1.

[0047] Example 2

[0048] 1. Preparation of surface-functionalized amine-based platinum-carbon catalysts:

[0049] The preparation method of the surface amine functionalized platinum carbon catalyst in Example 1 is exactly the same, except that the calcination treatment in step (2) does not involve programmed temperature rise. That is, step (2) is: the black composite precursor powder after ball milling and sieving is placed in the center of a tube furnace for calcination treatment under nitrogen atmosphere, and the temperature is raised from room temperature to 1000℃ at a rate of 4℃ / min, and calcined at a constant temperature for 8h to obtain calcined powder.

[0050] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 2 was obtained. The test results are shown in Table 1.

[0051] Comparative Example 1

[0052] 1. Preparation of surface-functionalized amine-based platinum-carbon catalysts:

[0053] (1) The carrier carbon black XC-72 was amination in an ammonia atmosphere with an ammonia flow rate of 100 sccm. The amination temperature was increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 1.5h. Then it was naturally cooled to room temperature to obtain carbon black XC-72 with surface amino functionalization.

[0054] (2) The surface amino functionalized carbon black XC-72 and chloroplatinic acid were mixed. The mass ratio of the surface amino functionalized carrier carbon black XC-72 to the metal element platinum was 3:1. The chloroplatinic acid and carbon black were composited by ball milling. The mass ratio of the ball milling beads to the raw material was 60:1. The ball milling speed was 800 rpm and the ball milling time was 18 h. The ball milling atmosphere was nitrogen. The black composite precursor powder after ball milling was then sieved and removed.

[0055] (3) The black composite precursor powder after ball milling and sieving was placed in the center of a tube furnace for calcination under nitrogen atmosphere. The calcination was carried out by segmented temperature program. The temperature was increased to 500℃ at a rate of 5℃ / min and then held at the temperature for 2 hours. Then the temperature was increased to 1000℃ at a rate of 4℃ / min and calcined at the temperature for 8 hours to obtain calcined powder. After grinding, a platinum carbon catalyst with surface amine functionalization was obtained.

[0056] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 3 was obtained. The test results are shown in Table 1.

[0057] Comparative Example 2

[0058] 1. Preparation of platinum-carbon catalysts:

[0059] The preparation method is exactly the same as that of the platinum-carbon catalyst in Example 1, except that step (3) is omitted, that is, the amination step of heat treatment under an ammonia atmosphere is not performed.

[0060] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 4 was obtained. The test results are shown in Table 1.

[0061] Comparative Example 3

[0062] 1. Preparation of surface-functionalized amine-based platinum-carbon catalysts:

[0063] The preparation method of the surface amine functionalized platinum carbon catalyst in Example 1 is exactly the same as that in Example 1. The difference is that steps (1) and (2) in Example 1 are omitted. The platinum carbon catalyst is prepared first by liquid phase method and then step (3) is performed.

[0064] The specific steps for preparing platinum-carbon catalysts using the liquid-phase method are as follows:

[0065] Add 6.6g of chloroplatinic acid to 500mL of ethylene glycol and stir at room temperature for 10 minutes. Then add 2.52g of carrier carbon black XC-72, sonicate for 200 minutes, and stir for 20 minutes. Adjust the pH to 12 with 1M sodium hydroxide solution. Transfer the mixed solution to a reaction vessel and treat at 170℃ for 2 hours. After the reaction is complete, cool the reaction vessel to room temperature and remove the slurry. Filter the slurry and wash it with 1M nitric acid solution. Adjust the pH of the slurry filtrate to acidic and wash it with ultrapure water until neutral. Finally, place the washed catalyst in a vacuum drying oven and dry it under vacuum at 70℃ for 12 hours.

[0066] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 5 was obtained. The test results are shown in Table 1.

[0067] Comparative Example 4

[0068] 1. Preparation of surface-functionalized amine-based platinum-carbon catalysts:

[0069] The preparation process of the surface amine functionalized platinum carbon catalyst in Example 1 is exactly the same. The difference is that in step (2), the black powder that has been ball-milled and sieved is placed in the center of a tube furnace for calcination under nitrogen atmosphere. The temperature is increased to 500°C at a rate of 5°C / min and calcined at a constant temperature for 8 hours to obtain calcined powder.

[0070] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 6 was obtained. The test results are shown in Table 1.

[0071] Comparative Example 5

[0072] 1. Preparation of surface-functionalized amine-based platinum-carbon catalysts:

[0073] The preparation process is exactly the same as that of the surface-amine functionalized platinum carbon catalyst in Example 1. The difference is that in step (3), the amination is heated to 200°C at a heating rate of 5°C / min and then heat-treated at a constant temperature for 1.5h.

[0074] 2. The preparation and testing steps of the membrane electrode were exactly the same as in Example 1, and membrane electrode No. 7 was obtained. The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] from Figure 2 As can be seen from the data, compared with Comparative Example 1, the No. 1 film electrode of Example 1 (0.65V@1.62W / cm) 2 It outperforms the No. 3 film electrode (0.65V@1.42W / cm) in battery performance compared to Comparative Example 1. 2 This is because the carbon black in Comparative Example 1 is first surface-aminated, and then the platinum-carbon catalyst is synthesized through steps such as ball milling. During the ball milling process, the shear force and collision force between the balls will reduce the interaction between the amine groups and the carbon, resulting in a reduction of the amine groups loaded on the surface of the platinum-carbon. This leads to a reduction in the high-permeability channels in the membrane electrode, and a decrease in the utilization rate of platinum, which in turn leads to a decrease in battery performance. Therefore, in the high current density region, the battery performance of membrane electrode No. 3 in Comparative Example 1 is worse than that of membrane electrode No. 1 in Example 1.

[0078] Compared to Comparative Example 2, the membrane electrode 1 in Example 1, which has highly permeable channels, has a higher power density than the membrane electrode 4 in Comparative Example 2, which lacks highly permeable channels and has not undergone amine functionalization. The power density of the membrane electrode 1 in Example 1 is 0.65V@1.22W / cm². 2 Increased to 0.65V@1.62W / cm 2The power density has been greatly improved because the high-permeability membrane electrode can shorten the proton transport path, improve conductivity, thereby reducing the overall internal resistance. At the same time, it is beneficial to improve the utilization rate of platinum in the catalyst layer, thereby improving battery performance.

[0079] In Example 1, during the preparation of the platinum-carbon catalyst, the calcination process employed a segmented temperature program with a power density of 0.65V@1.62W / cm³. 2 In Example 2, the calcination process involved direct heating with a power density of 0.65V@1.50W / cm³. 2 The calcination process employs a segmented, programmed heating method, which can further enhance the proportion and effectiveness of the precursor's conversion into a stable intermediate state, thus promoting the formation of effective components and improving battery performance.

[0080] Comparative Example 3 used a liquid-phase method to prepare a platinum-carbon catalyst, followed by surface amination. Compared to membrane electrode 1 in Example 1, membrane electrode 5 in Comparative Example 3 showed a power density of 0.65 V @ 1.62 W / cm². 2 Reduced to 0.65V@1.25W / cm 2 This is because Example 1 uses a solid-phase method to synthesize a platinum-carbon catalyst. The carbon support and platinum precursor are mixed by mechanical ball milling to obtain a composite precursor powder. Ball milling can fully disperse the composite precursor powder, and the forced force during the ball milling process introduces a large amount of strain and defects. The composite precursor powder is then calcined to remove volatile components, giving the catalyst support a certain strength and making it easier to expose the crystal faces of Pt, thereby improving the activity of the catalyst and reducing the hard agglomeration phenomenon that easily occurs in the liquid-phase synthesis of platinum-carbon catalyst in Comparative Example 3.

[0081] In Comparative Example 4, the calcination temperature was 500°C. Compared to membrane electrode 1 in Example 1, membrane electrode 6 in Comparative Example 4 showed a power density of 0.65V@1.62W / cm². 2 Reduced to 0.65V@1.04W / cm 2 This is because the appropriate calcination temperature in Example 1 allows the catalyst support structure to have a certain strength and graphitization degree. In Comparative Example 4, when the calcination temperature is too low, the graphitization degree of the carbon support is insufficient, the catalyst impedance is large, and the fuel cell performance deteriorates.

[0082] In Comparative Example 5, the amination temperature was 200°C. Compared to membrane electrode 1 in Example 1, membrane electrode 7 in Comparative Example 5 showed a power density of 0.65V@1.62W / cm². 2 Reduced to 0.65V@1.28W / cm 2This is because when the temperature is too low, there are fewer amine groups and the binding force is insufficient. This makes it easier for the number of amine groups to decrease during the ball milling process in the subsequent preparation of the membrane electrode, resulting in a reduction in the high-permeability channels in the membrane electrode, a decrease in the utilization rate of platinum, and a decline in battery performance.

[0083] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0084] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that, Includes the following steps: (1) The carbon support and the platinum precursor are ball-milled and mixed to obtain a composite precursor; the carbon support is at least one of carbon black, carbon nanotubes, carbon fibers or graphene; the platinum precursor is at least one of chloroplatinic acid, tetraammineplatinum chloride, ammonium chloroplatinate, and tetraammineplatinum nitrate. (2) The composite precursor is subjected to calcination treatment; the calcination treatment adopts segmented temperature rise, with a heating rate of 5-10℃ / min to 400-500℃, constant temperature for 1-3h, and then heating rate of 2-4℃ / min to 900-1200℃, constant temperature calcination, the constant temperature calcination time is 5-8h; (3) The composite precursor that has been calcined in step (2) is heat-treated in an ammonia atmosphere to obtain a platinum carbon catalyst with surface amine functionalization; the heat treatment temperature is 400-550℃.

2. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step (3), the flow rate of ammonia is 50-100 sccm; the heat treatment time is 0.5-2h; and the heating rate of the heat treatment is 2-5℃ / min.

3. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step (1), the mass ratio of the carbon support to the platinum element in the platinum precursor is 120:1-120:60; in the ball milling, the mass ratio of the milling beads to the carbon support and the platinum precursor is 50:1-75:1; the rotation speed of the ball milling is 600-1000 rpm; and the milling time is 12h-24h.

4. The method for preparing the platinum-carbon catalyst according to claim 1, characterized in that, In step (2), the roasting atmosphere is at least one of nitrogen and argon.

5. A platinum-carbon catalyst, characterized in that, It is prepared by any one of the preparation methods according to claims 1-4.

6. A membrane electrode catalytic layer, characterized in that, Including the platinum-carbon catalyst as described in claim 5.

7. A membrane electrode, characterized in that, It includes the membrane electrode catalytic layer as described in claim 6, wherein the membrane electrode catalytic layer serves as a cathode catalytic layer and / or an anode catalytic layer.

8. A fuel cell, characterized in that, Includes the membrane electrode as described in claim 7.

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