Intermetallic compound nano-catalyst, preparation method and application thereof

Abstract

The application provides an intermetallic compound nano-catalyst, a preparation method and application thereof, and belongs to the technical field of electrochemistry. The intermetallic compound nanoparticles comprise intermetallic compound nanoparticles formed by a transition metal compound and graphene loaded with elemental platinum through redox reaction and then annealing treatment, the transition metal compound comprises one or more of zinc acetylacetonate, iron nitrate nonahydrate, cobalt chloride and nickel acetylacetonate, and the particle size of the intermetallic compound nanoparticles is 2nm-20nm. The catalyst provided by the application can reduce the use amount of platinum, reduce the cost of the catalyst, and meanwhile, the catalyst has higher catalytic activity compared with traditional catalysts.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an intermetallic compound nanocatalyst, its preparation method, and its application. Background Technology

[0002] Today, one of the greatest challenges the world faces in addressing climate change is the ever-increasing demand for green and safe energy. Fuel cells, as a novel green energy power system, offer advantages such as high energy conversion efficiency, low noise, and zero emissions, effectively solving energy problems. Among them, proton exchange membrane fuel cells (PEMFCs) have attracted widespread attention from researchers due to their ability to start up quickly and operate stably at low temperatures. In PEMFCs, the oxygen reduction reaction (ORR) at the cathode is particularly important. Due to its inherent low efficiency and sluggish reaction kinetics, researchers use precious metal catalysts to accelerate the ORR reaction. Platinum (Pt) is the most suitable catalyst for the ORR reaction in traditional technologies, but the scarcity and high cost of platinum significantly limit the large-scale commercialization of fuel cells. Summary of the Invention

[0003] Therefore, it is necessary to provide an intermetallic compound nanocatalyst that can reduce the amount of platinum used and lower the cost of the catalyst, as well as its preparation method and application, while the catalyst has higher catalytic activity compared with traditional catalysts.

[0004] A first aspect of this application provides an intermetallic compound nanocatalyst, comprising graphene and intermetallic compound nanoparticles supported on the graphene.

[0005] The intermetallic compound nanoparticles include those formed by a redox reaction between a transition metal compound and graphene loaded with elemental platinum, followed by annealing. The transition metal compound includes one or more of zinc acetylacetonate, ferric nitrate nonahydrate, cobalt chloride, and nickel acetylacetonate. The particle size of the intermetallic compound nanoparticles is 2 nm to 20 nm.

[0006] In some embodiments, the platinum content in the intermetallic compound nanocatalyst is 10% to 40% by mass.

[0007] In some more specific embodiments, the platinum content in the intermetallic compound nanocatalyst is 10% to 20% by mass.

[0008] In some embodiments, the annealing process conditions include: annealing temperature of 500℃~800℃ and annealing time of 1h~3h.

[0009] In some embodiments, the graphene loaded with elemental platinum is further loaded with a template agent, the template agent including tetraethoxysilane.

[0010] A second aspect of this application provides a method for preparing the above-mentioned intermetallic compound nanocatalyst, comprising the following steps:

[0011] The graphene and platinum source are dispersed in a solvent to form a mixed solution. The pH of the mixed solution is adjusted to alkaline. A first heating treatment is performed in a protective atmosphere to cause the platinum source to undergo a redox reaction with the solvent. The elemental platinum generated by the reaction is loaded on the graphene.

[0012] The surfactant, template agent, and the resulting mixed solution were mixed, washed, and dried to obtain the first intermediate.

[0013] The first intermediate, the transition metal compound, and the capping agent are mixed and subjected to a second heat treatment in a protective atmosphere to cause the first intermediate to undergo a redox reaction with the transition metal compound. After cooling, washing, and drying, the second intermediate is obtained.

[0014] The second intermediate is subjected to the annealing treatment in a protective atmosphere to form the intermetallic compound nanoparticles.

[0015] In some embodiments, the platinum source includes one or more of chloroplatinic acid hexahydrate and platinum tetrachloride, and the solvent includes one or more of ethylene glycol and deionized water.

[0016] In some embodiments, the mass ratio of the graphene, the solvent, and the platinum source is 27:27:(8-48), and the mass ratio of the platinum source and the transition metal compound is 2:(1-4).

[0017] In some embodiments, the surfactant comprises hexadecyltrimethylammonium bromide, the template agent comprises tetraethoxysilane, and the capping agent comprises oleylamine and oleic acid.

[0018] In some embodiments, the mass ratio of the platinum source to the surfactant is 1:(1-5), and the mass ratio of the platinum source to the template agent is 1:(8-40).

[0019] In some embodiments, the pH of the solution is adjusted to 11-14.

[0020] In some embodiments, the process conditions for the first heat treatment include: a heating temperature of 80°C to 200°C and a holding time of 1 hour to 4 hours.

[0021] In some embodiments, the process conditions for the second heat treatment include: a heating temperature of 200°C to 350°C and a holding time of 0.5h to 3h.

[0022] In some embodiments, the annealing temperature is 500°C to 800°C, and the annealing time is 1 hour to 3 hours.

[0023] A third aspect of this application provides the application of the above-described intermetallic compound nanocatalyst or the intermetallic compound nanocatalyst prepared by the above-described preparation method in the preparation of fuel cells.

[0024] Compared with traditional technologies, the above-mentioned intermetallic compound nanocatalysts, their preparation methods, and applications have at least the following advantages:

[0025] The catalyst described above utilizes a redox reaction between transition metal compounds and graphene supported on elemental platinum, followed by annealing to form intermetallic compound nanoparticles. This introduces one or more transition metals from zinc, iron, cobalt, and nickel, effectively reducing the amount of platinum used. The platinum and transition metal elements in the intermetallic compound nanoparticles exhibit synergistic catalytic effects. Furthermore, the intermetallic compound nanoparticles formed by the reaction of the transition metal compounds with elemental platinum supported on graphene show minimal agglomeration, resulting in nanoparticles with small particle sizes. Consequently, the catalytic performance of this catalyst surpasses that of commercial platinum-carbon catalysts (pure platinum), significantly reducing catalyst costs. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the catalyst prepared in Example 1 of this application.

[0027] Figure 2 This is a transmission electron microscope image of the catalyst prepared in Example 1 of this application.

[0028] Figure 3 This is a linear sweep voltammetry curve of the catalyst prepared in Example 1 of this application.

[0029] Figure 4 This is a comparison chart of the durability tests of the catalysts in Example 1 and Comparative Example 1 of this application.

[0030] Figure 5 This is a comparison chart of the durability tests of the catalysts in Example 2 and Comparative Example 1 of this application. Detailed Implementation

[0031] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0032] In this application, unless otherwise defined, all technical terms and jargon not explicitly stated have the same meaning as commonly understood by those skilled in the art and are common knowledge to those skilled in the art. Methods not explicitly stated are all conventional methods known to those skilled in the art. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0034] In this application, the use of numerical ranges represented by endpoints includes all numbers within that range as well as any range within that range. For example, 1 to 6 can include 1, 1.2, 1.5, 1.7, 2, 2.6, 3, 3.8, 4, 4.4, 5 or 6, etc., or it can include 1 to 1.2, 1 to 1.7, 2 to 4.4, 3.8 to 5, 4 to 5.5, 5 to 6, etc.

[0035] Catalysts significantly influence the performance of proton exchange membrane fuel cells. To address the high cost and scarcity of platinum catalysts in traditional technologies, researchers have invested considerable time and effort in studying how to reduce the platinum content in catalysts, or even eliminate platinum altogether. Traditional solutions include the following three:

[0036] One approach is to improve the catalytic performance of platinum by controlling its surface and crystal structures; however, pure platinum catalysts can suffer from platinum poisoning and decreased catalytic performance after prolonged use.

[0037] Secondly, alloys of platinum and other non-precious metals are prepared as catalysts. Alloy catalysts with lower platinum content can not only increase the specific surface area of ​​the catalyst and facilitate the exposure of platinum active sites, thus improving the catalyst activity, but when platinum and other non-precious metals form alloy catalysts, the resulting alloy catalysts are prone to agglomeration, resulting in larger particle sizes and unsatisfactory catalytic performance.

[0038] Third, platinum-free catalysts are prepared using transition metal chalcogenides, transition metal alloys (copper-nickel alloys, lead-cobalt alloys, etc.), transition metal nitrides, and transition metal oxides as catalysts to improve the kinetic rate of the ORR reaction. However, the catalytic activity of non-platinum alloys is much lower than that of platinum, and they also have problems such as complicated preparation, instability in electrolytes, and lack of practicality.

[0039] In view of this, this application provides an intermetallic compound nanocatalyst, its preparation method and application, which can reduce the cost of the catalyst while enabling the catalyst to have high catalytic activity.

[0040] One embodiment of this application provides an intermetallic compound nanocatalyst, comprising graphene and intermetallic compound nanoparticles supported on graphene.

[0041] Intermetallic compound nanoparticles include those formed by a redox reaction between a transition metal compound and graphene loaded with elemental platinum, followed by annealing. The transition metal compound includes one or more of zinc acetylacetonate, ferric nitrate nonahydrate, cobalt chloride, and nickel acetylacetonate. The particle size of the intermetallic compound nanoparticles is 2 nm to 20 nm.

[0042] The catalyst described above utilizes a redox reaction between a transition metal compound and graphene supported on elemental platinum. The transition metal in the compound is reduced to its elemental form. During annealing, the transition metal reacts with the elemental platinum supported on the graphene to form intermetallic compound nanoparticles, thereby introducing one or more transition metals from zinc, iron, cobalt, and nickel. This effectively reduces the amount of platinum used. Furthermore, the catalytic performance of this catalyst is superior to that of commercial platinum-carbon catalysts (pure platinum), significantly reducing catalyst costs. For example, in the catalyst with an intermetallic compound nanoparticle mass percentage of 40% and a platinum mass percentage of 20%, the catalyst of this application exhibits better catalytic performance compared to a commercial platinum-carbon catalyst (pure platinum) with a platinum mass percentage of 40%. This may be due to the synergistic catalytic effect of platinum and transition metal elements in the intermetallic compound nanoparticles, and the fact that the intermetallic compound nanoparticles formed by the reaction of the transition metal compound with elemental platinum supported on graphene show minimal agglomeration, resulting in nanoparticles with a small particle size. It is understandable that the particle size of intermetallic compound nanoparticles can be any value between 2nm and 20nm, such as: 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm or 20nm, etc.

[0043] In some embodiments, the platinum content in the intermetallic compound nanocatalyst is 10% to 40% by mass. It should be noted that commercial platinum-carbon catalysts (pure platinum) contain 20% to 60% platinum by mass, while the catalyst of this application can contain 10% to 40% platinum by mass. This catalyst can use less platinum and achieve the same or even better catalytic effect as commercial platinum-carbon catalysts. Therefore, the catalyst of this application effectively reduces the platinum content in the catalyst, significantly reducing the cost. It is understood that the platinum content in the intermetallic compound nanocatalyst can be, for example, 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0044] In some more specific embodiments, the platinum content in the intermetallic compound nanocatalyst is 10% to 20% by mass. It is understood that the platinum content in the intermetallic compound nanocatalyst can be, for example, 10%, 12%, 14%, 16%, 18%, or 20%.

[0045] In some embodiments, the annealing process conditions include: an annealing temperature of 500℃ to 800℃ and an annealing time of 1h to 3h. It is understood that the annealing temperature can be, for example, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃, and the annealing time can be, for example, 1h, 1.5h, 2h, 2.5h, or 3h.

[0046] In some embodiments, the graphene loaded with elemental platinum is further loaded with a template agent, including tetraethoxysilane. It should be noted that the template agent provides a silica template; during annealing, the silica template is removed, and the transition metal in the transition metal compound replaces the silica template at the desired position, forming intermetallic compound nanoparticles with the elemental platinum loaded on the graphene.

[0047] Another embodiment of this application provides a method for preparing the above-mentioned intermetallic compound nanocatalyst, comprising the following steps:

[0048] Graphene and platinum source are dispersed in a solvent to form a mixed solution. The pH of the mixed solution is adjusted to alkaline. The first heating treatment is carried out in a protective atmosphere to cause the platinum source and solvent to undergo a redox reaction. The elemental platinum generated by the reaction is loaded onto the graphene.

[0049] The surfactant, template agent, and the resulting mixed solution were mixed, washed, and dried to obtain the first intermediate.

[0050] The first intermediate, the transition metal compound, and the capping agent are mixed and subjected to a second heat treatment in a protective atmosphere to cause the first intermediate to undergo a redox reaction with the transition metal compound. After cooling, washing, and drying, the second intermediate is obtained.

[0051] The second intermediate was annealed in a protective atmosphere to form intermetallic compound nanoparticles.

[0052] In this embodiment, adjusting the pH to alkaline helps the platinum source react with the solvent to generate elemental platinum. As the reaction occurs, the generated elemental platinum is gradually and relatively uniformly loaded onto the graphene to prepare graphene loaded with elemental platinum. The added surfactant and template agent can form a silica template on the graphene loaded with elemental platinum. When the first intermediate undergoes a redox reaction with the transition metal compound, the graphene in the first intermediate reacts with the transition metal compound to generate elemental transition metal. The capping agent can prevent the redox reaction from being too vigorous, thereby preventing the generated product from being too large. When the second intermediate is annealed, the elemental platinum reacts with the elemental transition metal to form intermetallic compound nanoparticles. At the same time, the annealing process can remove the capping agent and silica template. Furthermore, the silica template can prevent the generated intermetallic compound nanoparticles from agglomerating during the annealing process, thereby resulting in a smaller particle size of the intermetallic compound nanoparticles in the obtained catalyst, which is 2 nm to 20 nm. The catalyst described above utilizes a redox reaction between transition metal compounds and graphene loaded with elemental platinum, followed by annealing to form intermetallic compound nanoparticles. This introduces one or more transition metals from zinc, iron, cobalt, and nickel, effectively reducing the amount of platinum used. Furthermore, the catalytic performance of this catalyst is superior to that of commercial platinum-carbon catalysts (pure platinum), significantly reducing the cost of the catalyst.

[0053] In some embodiments, the platinum source includes one or more of chloroplatinic acid hexahydrate and platinum tetrachloride, and the solvent includes one or more of ethylene glycol and deionized water.

[0054] In some embodiments, the mass ratio of graphene, solvent, and platinum source is 27:27:(8-48), and the mass ratio of platinum source to transition metal compound is 2:(1-4). It is understood that the mass ratio of graphene, solvent, and platinum source can be, for example, 27:27:8, 27:27:12, 27:27:16, 27:27:20, 27:27:25, 27:27:30, 27:27:35, 27:27:40, 27:27:45, or 27:27:48; and the mass ratio of platinum source to transition metal compound can be, for example, 2:1, 2:2, 2:3, or 2:4.

[0055] In some embodiments, the surfactant includes hexadecyltrimethylammonium bromide, the template agent includes tetraethoxysilane, and the capping agent includes oleylamine and oleic acid. It is understood that hexadecyltrimethylammonium bromide (CTAB) and tetraethoxysilane (TEOS) can form a silica template, and oleylamine and oleic acid, as capping agents, can prevent the graphene in the first intermediate from undergoing an excessively vigorous redox reaction with the transition metal compound.

[0056] In some embodiments, the mass ratio of platinum source to surfactant is 1:(1-5), and the mass ratio of platinum source to template agent is 1:(8-40). It is understood that the mass ratio of platinum source to surfactant can be, for example, 1:1, 1:2, 1:3, 1:4, or 1:5, and the mass ratio of platinum source to template agent can be, for example, 1:8, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, or 1:40.

[0057] In some implementations, the pH of the solution is adjusted to 11-14. It is understood that the pH of the solution can be adjusted to any value between 11 and 14, such as 11, 11.5, 12, 12.5, 13, 13.5, or 14.

[0058] In some embodiments, the process conditions for the first heat treatment include: a heating temperature of 80°C to 200°C and a holding time of 1 hour to 4 hours. It is understood that the heating temperature can be any value between 80°C and 200°C, such as 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, or 200°C, and the holding time can be, for example, 1 hour, 2 hours, 3 hours, or 4 hours, or other values ​​between 1 hour and 4 hours.

[0059] In some embodiments, the process conditions for the second heat treatment include: a heating temperature of 200℃ to 350℃ and a holding time of 0.5h to 3h. It is understood that the heating temperature can be 200℃, 230℃, 250℃, 270℃, 300℃, 330℃, or 350℃, and can also be other values ​​between 200℃ and 350℃. The holding time can be, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h, etc.

[0060] In some implementations, the protective atmosphere includes one or more of nitrogen, argon, and neon.

[0061] Another embodiment of this application provides the application of the above-described intermetallic compound nanocatalyst or the intermetallic compound nanocatalyst prepared by the above-described preparation method in the preparation of fuel cells.

[0062] The present application will be further illustrated below through examples and comparative examples.

[0063] Example 1

[0064] Intermetallic compound nanocatalysts were prepared using the following method:

[0065] S1. Take 38 mg of graphene and 38 mg of ethylene glycol and mix them evenly in a 1:1 mass ratio. Sonicate for 30 min. Then add the solution to 100 mL of ethylene glycol solution containing 0.0012 M chloroplatinic acid hexahydrate (the concentration of platinum is 0.0012 M) to form a mixed solution. Adjust the pH of the mixed solution to 13.

[0066] S2. The mixed solution was purged with nitrogen as a protective atmosphere and stirred at 160°C for 1 hour (first heat treatment) to allow the elemental platinum generated from the reaction of chloroplatinic acid hexahydrate and ethylene glycol to be gradually loaded onto the graphene, and then cooled to room temperature.

[0067] S3. Add 320 mg cetyltrimethylammonium bromide (CTAB) and 2 mL tetraethoxysilane (TEOS) to the cooled mixed solution, continue stirring at room temperature for 6 h, collect the obtained product by filtration, wash with ethanol, and dry under vacuum at 60 °C to obtain the first intermediate;

[0068] S4. The first intermediate was mixed with 31.6 mg of zinc acetylacetonate powder (the molar ratio of platinum in chloroplatinic acid hexahydrate to zinc in zinc acetylacetonate was 1:1), and then dispersed in a mixed solution of 30 mL of oleylamine and 5 mL of oleic acid. The solution was heated to 330 °C and kept at that temperature for 1 h under an argon atmosphere (second heat treatment) to allow the first intermediate to undergo a redox reaction with zinc acetylacetonate. After cooling to room temperature, the product was collected by centrifugation and washed 5 times with hexane. The product was then dried under vacuum at 60 °C to obtain the second intermediate.

[0069] S5. The second intermediate was annealed at 600°C for 2 hours under an argon atmosphere to form platinum-zinc intermetallic compound nanoparticles. After cooling to room temperature, graphene-based platinum-zinc intermetallic compound nanocatalysts were obtained.

[0070] Example 2

[0071] Intermetallic compound nanocatalysts were prepared using the following method:

[0072] S1. Take 780mg of graphene and 780mg of ethylene glycol and mix them evenly in a 1:1 mass ratio. Sonicate for 30min. Then add the solution to 100mL of ethylene glycol solution containing 0.01M chloroplatinic acid hexahydrate (the concentration of platinum is 0.01M) to form a mixed solution. Adjust the pH of the mixed solution to 14.

[0073] S2. The mixed solution was purged with nitrogen as a protective atmosphere and stirred at 160°C for 2 hours (first heat treatment) to allow the elemental platinum generated from the reaction of chloroplatinic acid hexahydrate and ethylene glycol to be gradually loaded onto the graphene, and then cooled to room temperature.

[0074] S3. Add 520 mg cetyltrimethylammonium bromide (CTAB) and 4 mL tetraethoxysilane (TEOS) to the cooled mixed solution, continue stirring at room temperature for 6 h, collect the obtained product by filtration, wash with ethanol, and dry under vacuum at 60 °C to obtain the first intermediate;

[0075] S4. The first intermediate was mixed with 404 mg of ferric nitrate nonahydrate (the molar ratio of platinum in chloroplatinic acid hexahydrate to iron in ferric nitrate nonahydrate was 1:1), and dispersed in a mixed solution of 30 mL of oleylamine and 5 mL of oleic acid. The solution was heated to 330 °C and kept at that temperature for 1 h under an argon atmosphere (second heating treatment) to allow the first intermediate to undergo a redox reaction with ferric nitrate nonahydrate. After cooling to room temperature, the product was collected by centrifugation and washed 5 times with hexane. The product was then dried under vacuum at 60 °C to obtain the second intermediate.

[0076] S5. The second intermediate was annealed at 700°C for 2 hours under an argon atmosphere to form platinum-iron intermetallic compound nanoparticles. After cooling to room temperature, graphene-based platinum-iron intermetallic compound nanocatalysts were obtained.

[0077] Example 3

[0078] Intermetallic compound nanocatalysts were prepared using the following method:

[0079] S1. Take 1140mg of graphene and 1140mg of ethylene glycol and mix them evenly in a 1:1 mass ratio. Sonicate for 30min. Then add the solution to 100mL of ethylene glycol solution containing 0.005M platinum tetrachloride (platinum concentration is 0.005M) to form a mixed solution. Adjust the pH of the mixed solution to 14.

[0080] S2. The mixed solution was purged with nitrogen as a protective atmosphere and stirred at 80°C for 4 hours (first heat treatment) to allow the elemental platinum generated from the reaction of platinum tetrachloride and ethylene glycol to be gradually loaded onto the graphene. Then the mixture was cooled to room temperature.

[0081] S3. Add 320 mg cetyltrimethylammonium bromide (CTAB) and 2 mL tetraethoxysilane (TEOS) to the cooled mixed solution, continue stirring at room temperature for 6 h, collect the obtained product by filtration, wash with ethanol, and dry under vacuum at 50 °C to obtain the first intermediate;

[0082] S4. The first intermediate was mixed with 119 mg of cobalt chloride (the molar ratio of platinum in platinum tetrachloride to cobalt in cobalt chloride was 1:1) and dispersed in a mixed solution of 30 mL of oleylamine and 5 mL of oleic acid. The solution was heated to 100 °C and kept at that temperature for 4 h under an argon atmosphere (second heat treatment) to allow the first intermediate to undergo a redox reaction with cobalt chloride. After cooling to room temperature, the product was collected by centrifugation and washed 5 times with hexane. The product was then dried under vacuum at 50 °C to obtain the second intermediate.

[0083] S5. The second intermediate was annealed at 800°C for 1 hour under an argon atmosphere to form platinum-cobalt intermetallic compound nanoparticles. After cooling to room temperature, graphene-based platinum-cobalt intermetallic compound nanocatalysts were obtained.

[0084] Example 4

[0085] Intermetallic compound nanocatalysts were prepared using the following method:

[0086] S1. Take 380mg of graphene and 380mg of ethylene glycol and mix them evenly in a 1:1 mass ratio. Sonicate for 30min. Then add the solution to 100mL of ethylene glycol solution containing 0.01M chloroplatinic acid hexahydrate (the concentration of platinum is 0.01M) to form a mixed solution. Adjust the pH of the mixed solution to 11.

[0087] S2. The mixed solution was purged with nitrogen as a protective atmosphere and stirred at 200°C for 1 hour (first heat treatment) to allow the elemental platinum generated from the reaction of chloroplatinic acid hexahydrate and ethylene glycol to be gradually loaded onto the graphene, and then cooled to room temperature.

[0088] S3. Add 520 mg cetyltrimethylammonium bromide (CTAB) and 4 mL tetraethoxysilane (TEOS) to the cooled mixed solution, continue stirring at room temperature for 6 h, collect the obtained product by filtration, wash with ethanol, and dry under vacuum at 75 °C to obtain the first intermediate;

[0089] S4. The first intermediate was mixed with 257 mg of nickel acetylacetonate (the molar ratio of platinum in chloroplatinic acid hexahydrate to nickel in nickel acetylacetonate was 1:1), and dispersed in a mixed solution of 30 mL of oleylamine and 5 mL of oleic acid. The solution was heated to 120 °C and kept at that temperature for 2 h under an argon atmosphere (second heat treatment) to allow the first intermediate to undergo a redox reaction with nickel acetylacetonate. After cooling to room temperature, the product was collected by centrifugation and washed 5 times with hexane. The product was then dried under vacuum at 75 °C to obtain the second intermediate.

[0090] S5. The second intermediate was annealed at 800°C for 1 hour under an argon atmosphere to form platinum-nickel intermetallic compound nanoparticles. After cooling to room temperature, graphene-based platinum-nickel intermetallic compound nanocatalysts were obtained.

[0091] Comparative Example 1

[0092] Commercial platinum-carbon catalyst (pure platinum) was used.

[0093] Depend on Figures 1-2 It can be seen that the platinum-zinc intermetallic compound nanocatalyst prepared in Example 1 is loaded relatively uniformly on graphene. The particle size of the platinum-zinc intermetallic compound nanocatalyst prepared in Example 1 is 2nm to 20nm, with the particle size mainly around 5nm.

[0094] The catalysts prepared in Examples 2-4 were also subjected to scanning electron microscopy and transmission electron microscopy tests, and the results were similar to those in Example 1. The intermetallic compound nanocatalysts in Examples 2-4 were also relatively uniformly loaded on graphene, and the particle size of the intermetallic compound nanocatalysts in Examples 2-4 was 2 nm to 20 nm.

[0095] TG test method: Under air atmosphere, the catalysts of Examples 1-4 and Comparative Example 1 were tested from room temperature to 1000℃ at a heating rate of 5℃ / min to obtain the metal content in the catalysts. The results are shown in Table 1.

[0096] Table 1

[0097] Group Metal content (%) as determined by TG test Platinum content (%) Transition metal content (%) Example 1 40 20 20 (Zinc) Example 2 40 20 20 (Iron) Example 3 20 10 10 (Cobalt) Example 4 80 40 40 (Nickel) Comparative Example 1 40 40 /

[0098] Linear sweep voltammetry method: A typical three-electrode system was used, with the catalyst attached to a glassy carbon electrode to form the working electrode, Ag / AgCl / KCl as the reference electrode, and a Pt wire as the counter electrode. The voltammetry was performed in an oxygen-saturated sulfuric acid solution at a scan rate of 10 mV / s within the range of 0–1.05 V vs. RHE. The results are as follows: Figure 3 As shown.

[0099] The half-wave potential is calculated as (maximum current density - minimum current density) / 2, which represents the voltage value corresponding to the current density. A larger half-wave potential indicates better catalyst performance. Figure 3 It can be seen that the catalyst prepared in Example 1 has significantly better performance than that in Comparative Example 1.

[0100] Durability testing method: The catalyst was attached to a glassy carbon electrode to form the working electrode, and the electrode was cycled 1000 times in an oxygen-saturated sulfuric acid solution. The current density at 0.45V was compared, and the loss rate was calculated as (current density of the 1000th cycle - current density of the 1st cycle) / current density of the 1st cycle × 100%. Results are as follows: Figures 4-5 As shown in Table 2.

[0101] Table 2

[0102]

[0103]

[0104] From Table 2 and Figures 4-5 As can be seen, after 1000 cycles, comparing the current density at 0.45V, the catalyst loss rate of Example 1 was 5.1%, that of Example 2 was 6.9%, that of Example 3 was 5.5%, that of Example 4 was 5.7%, and that of the commercial platinum-carbon catalyst in Comparative Example 1 was 12.2%, indicating that the catalysts prepared in Examples 1 to 4 of this application have better stability.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing an intermetallic compound nanocatalyst, characterized in that, Includes the following steps: Graphene and platinum source are dispersed in a solvent to form a mixed solution. The pH of the mixed solution is adjusted to alkaline. A first heating treatment is performed in a protective atmosphere to cause the platinum source to undergo a redox reaction with the solvent. The elemental platinum generated by the reaction is loaded on the graphene. The surfactant, template agent, and the resulting mixed solution are mixed, washed, and dried to obtain a first intermediate; the surfactant comprises hexadecyltrimethylammonium bromide, and the template agent comprises tetraethoxysilane; The first intermediate, the transition metal compound, and the capping agent are mixed and subjected to a second heat treatment in a protective atmosphere to cause the first intermediate to undergo a redox reaction with the transition metal compound. After cooling, washing, and drying, the second intermediate is obtained. The capping agent includes oleylamine and oleic acid. The process conditions for the second heat treatment include: heating temperature of 200℃~350℃, and holding time of 0.5h~3h; The second intermediate is annealed in a protective atmosphere to form the intermetallic compound nanoparticles; the intermetallic compound nanocatalyst includes the graphene and the intermetallic compound nanoparticles supported on the graphene. The intermetallic compound nanoparticles are formed by the redox reaction of the transition metal compound with graphene loaded with elemental platinum and a template agent, followed by annealing. The transition metal compound includes one or more of zinc acetylacetonate, ferric nitrate nonahydrate, cobalt chloride, and nickel acetylacetonate. The particle size of the intermetallic compound nanoparticles is 2 nm to 20 nm.

2. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The platinum content in the intermetallic compound nanocatalyst is 10% to 40% by mass.

3. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The annealing process conditions include: annealing temperature of 500℃~800℃ and annealing time of 1h~3h.

4. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The annealing process conditions include: annealing temperature of 600℃~800℃ and annealing time of 1h~3h.

5. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The platinum source includes one or more of chloroplatinic acid hexahydrate and platinum tetrachloride, and the solvent includes one or more of ethylene glycol and deionized water.

6. The method for preparing intermetallic compound nanocatalysts according to claim 1 or 5, characterized in that, The mass ratio of the graphene, the solvent, and the platinum source is 27:27:(8~48), and the mass ratio of the platinum source and the transition metal compound is 2:(1~4).

7. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The platinum content in the intermetallic compound nanocatalyst is 10% to 20% by mass.

8. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The mass ratio of the platinum source to the surfactant is 1:(1~5), and the mass ratio of the platinum source to the template agent is 1:(8~40).

9. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, Adjust the pH of the solution to 11-14.

10. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The process conditions for the first heat treatment include: heating temperature of 80℃~200℃ and holding time of 1h~4h.

11. The method for preparing intermetallic compound nanocatalysts according to claim 1, characterized in that, The protective atmosphere includes one or more of nitrogen, argon, and neon.

12. The application of the intermetallic compound nanocatalyst prepared by the preparation method according to any one of claims 1 to 11 in the preparation of fuel cells.

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