A supported intermetallic compound catalyst with improved stability and a method for preparing and using the same

Abstract

The application relates to the field of nanomaterials and catalysts, in particular to a supported intermetallic compound catalyst with improved stability and a preparation method and application thereof. The supported intermetallic compound catalyst is an M1-M2 intermetallic compound uniformly dispersed in a nanocrystalline form on a carrier, the metal M1 is at least one selected from platinum, iridium, ruthenium, palladium and rhodium, the metal M2 is at least one selected from chromium, manganese, iron, cobalt, nickel, copper and zinc, the average particle size of the intermetallic compound is 3-5 nm, and the span of the particle size is 0.4-0.7. The supported catalyst prepared by the preparation method has high loading, small size and narrow particle size dispersion, and has excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and catalysts, specifically to a supported intermetallic compound catalyst with improved stability, its preparation method, and its application. Background Technology

[0002] With the rapid development of human production and life, the exploitation and consumption of non-renewable fossil energy has increased rapidly, urgently requiring the development of sustainable energy and new energy conversion devices. Hydrogen energy, as a renewable energy source, has the characteristics of high energy density and low environmental pollution, and has broad application prospects. Fuel cells can convert hydrogen energy into electrical energy. Compared with traditional internal combustion engines and thermal power generation devices, they have advantages such as high energy conversion efficiency, high power density, non-toxic and harmless byproducts, and environmental friendliness, making them a key link in the development of hydrogen energy. Proton exchange membrane fuel cells (PEMFCs) can start at low temperatures, have strong membrane durability, and high energy density, making them a widely studied type of fuel cell with promising applications in transportation, energy storage, and other fields. Currently, the main limiting factor for the large-scale application of fuel cells is the slow electrode reaction kinetics, requiring large amounts of expensive platinum-based catalysts. Furthermore, the activity and stability of commercial platinum-based catalysts are insufficient to meet application requirements. Therefore, there is an urgent need to develop new, highly active, and highly stable platinum-based catalysts for the oxygen reduction reaction at the fuel cell cathode.

[0003] When non-precious metals are alloyed with platinum, the d-band center position of platinum is adjusted due to ligand and strain effects, thereby optimizing the adsorption energy of platinum with electrocatalytic reaction intermediates and accelerating reaction kinetics. Platinum-based intermetallic compounds, as a special type of ordered alloy, exhibit a strong interaction between non-precious metals and platinum atoms due to their ordered arrangement, resulting in significantly improved activity and stability. However, the transformation from a disordered alloy to an intermetallic compound requires overcoming a significant kinetic barrier, thus the synthesis of platinum-based intermetallic compounds typically requires a high-temperature environment (generally above 500°C). High temperatures can cause catalyst particle agglomeration during preparation, reducing the active surface area and consequently decreasing catalytic activity. Reducing the platinum loading can alleviate catalyst agglomeration, but a low loading reduces the active site density. To achieve high power density, more catalyst needs to be coated, increasing the catalyst layer thickness and affecting mass transfer, making it difficult to further improve battery power density. Therefore, developing a high-loading, small-size method for synthesizing platinum-based intermetallic compounds is of great significance for promoting the large-scale application of fuel cells and the development of hydrogen energy.

[0004] Existing technologies disclose some high-loading, small-size platinum-based intermetallic compound catalysts and related synthesis methods, but some shortcomings remain in fuel cell applications. For example, Reference 1 (A sequential hydrogen-adsorption-assisted bond-weakening strategy for preparing sub-2-nm ordered Ptalloy nanocrystals, Matter. 2022, 5, 1-14) reports a strategy that utilizes single-atom MNCs (M=Fe, Ni) as supports, inducing platinum-platinum bond energy weakening through a hydrogen atmosphere to enhance the migration rate of non-noble metal single atoms, thereby achieving the synthesis of intermetallic compounds at lower temperatures and suppressing particle aggregation. However, the types of intermetallic compounds applicable to this method are limited by the species of the substrate single atom, making it difficult to prepare multi-element intermetallic compounds, thus limiting further improvement in the activity of platinum-based intermetallic compounds in fuel cells. Reference 2 (Sulfur-anchoring synthesis of platinum intermetallic nanoparticle catalysts for fuel cells, Science. 2021, 374, 459-464) reports a strategy for preparing platinum-based intermetallic compounds supported on sulfur-doped mesoporous carbon. By using sulfur species to enhance the interaction between the substrate and platinum, platinum-based intermetallic compounds with dimensions less than 5 nm can be prepared, exhibiting high mass activity in oxygen reduction tests. However, the introduction of sulfur during the preparation process leads to poor cycle stability of the catalyst in fuel cells.

[0005] Therefore, in order to improve the activity and stability of platinum-based intermetallic compound catalysts in fuel cells, it is of great significance to develop a synthesis method for high-density, small-size platinum-based intermetallic compounds that does not depend on metal or support components for their application in fuel cells.

[0006] The inventor's previous patent CN118048538A discloses a method for preparing a medium-to-low ordered nanoscale intermetallic compound, wherein the chemical formula of the intermetallic compound is M1. xM2, M1 = Pt, Pd, Ru, Ir; M2 = Cr, Mn, Fe, Co, Ni, Cu, Zn; x = 1~3; By controlling the cooling rate and media selection, a nanoscale intermetallic compound catalyst with medium to low order was prepared at a high annealing temperature, solving the problems of large catalyst size, low loading, and insufficient stability in existing technologies. However, this patent requires the use of a specific cooling medium to inhibit particle agglomeration. However, it requires a large amount of solvent, and the resulting intermetallic compound particles are still relatively large in size with a wide particle size dispersion. The Pt loading of this patented catalyst is also low, and the order is not high; its catalytic performance in oxygen reduction catalysis needs further improvement.

[0007] Reference 3 (Direct access to aggregation-free and small intermetallic nanoparticles in ordered, large-pore mesoporous carbon for anelectrocatalyst, RSC Adv., 2016, 6, 88255–88264) discloses a strategy of constructing mesoporous carbon by self-assembling block copolymers into positive micelles for the preparation of intermetallic compounds, such as Pt3Co. However, this method essentially utilizes high specific surface area mesoporous carbon to disperse metal precursors, so the loading of the resulting material is still limited by the metal loading per unit volume, ultimately resulting in a loaded intermetallic compound with a loading of less than 20 wt%, low active site density, and poor performance in catalytic reactions. Summary of the Invention

[0008] The intermetallic compound catalyst provided by this invention exhibits significantly superior oxygen reduction catalytic performance compared to commercial platinum-carbon catalysts, and its stability is higher than that of most reported intermetallic compound catalysts. In fuel cell devices, dye-coated cells using the catalyst of this invention can achieve peak discharge power exceeding 2 W·cm⁻¹. -2 This catalyst outperforms most reported platinum-based catalysts; it exhibits excellent cycle stability, maintaining over 95% of its power density after 30,000 voltage cycles. The catalyst provided by this invention is a highly efficient and stable intermetallic compound catalyst that can promote the large-scale development of fuel cells.

[0009] To achieve the above objectives, the present invention provides a supported intermetallic compound catalyst with improved stability, wherein intermetallic compounds M1-M2 are uniformly dispersed in nanocrystal form on a support, wherein metal M1 is selected from at least one of platinum, iridium, ruthenium, palladium, and rhodium; metal M2 is selected from at least one of chromium, manganese, iron, cobalt, nickel, copper, and zinc; the average particle size of the intermetallic compounds is 3-5 nm, and the particle size span (SPAN) is 0.4-0.7.

[0010] The span (SPAN) is calculated using the following formula:

[0011] The lower the SPAN value, the narrower the particle size distribution.

[0012] Furthermore, the support is selected from at least one of carbon substrates (such as porous carbon, Ketjen carbon, Vulcan carbon, carbon nanotubes), carbide substrates (such as MXene), silica substrates, and metal oxide substrates (such as CeO2, Nb2O5).

[0013] Furthermore, the molar ratio of M1 to M2 is 1-3:1, for example 1:1, or 3:1.

[0014] Furthermore, in the intermetallic compound catalyst, the loading of metal M1 is 20-65%. Using the method of this invention, the loading of noble metal M1 in the obtained supported intermetallic compound catalyst is significantly increased. The loading of M1 varies depending on the support. For example, for carbon substrates, the loading of noble metal M1 can reach 30-65%; for metal oxide substrates, the loading of noble metal can reach 20-40%.

[0015] Furthermore, the intermetallic compound has an average particle size of 3-4 nm and a span (SPAN) of 0.4-0.6.

[0016] The supported intermetallic compound catalyst obtained in this invention not only features small intermetallic compound particle size but also narrow particle size dispersion and low span of polarity (SPAN). Small particle size leads to better catalytic activity, but small particles, especially nanoscale particles, are prone to agglomeration, causing catalyst activity degradation. Narrow particle size dispersion reduces the chemical potential difference between different nanoparticles, mitigating Oswald ripening and ensuring the structural stability of the material during catalytic reactions. The structure and performance of active sites also tend to be more consistent, resulting in more stable and predictable overall catalyst performance, which is crucial for designing efficient fuel cell membrane electrode assemblies.

[0017] A second objective of this invention is to provide a method for preparing the above-mentioned high-loading, small-size intermetallic compound catalyst, comprising the following steps:

[0018] (S1) The complexes of metal M1 and metal M2 are dissolved in an organic solvent, and a carrier and block polymer are added and dispersed evenly to obtain a dispersion; the block copolymer has hydrophilic blocks and hydrophobic blocks, and the block copolymer has functional groups that have coordination interactions with metal ions.

[0019] (S2) The powder obtained after drying the dispersion is treated at high temperature under an inert atmosphere and then cooled to room temperature to obtain a high-loading, small-sized intermetallic compound catalyst.

[0020] Further, in step S1, the block copolymer polymer includes, but is not limited to: polystyrene-ethylene oxide block copolymer (PS-b-PEO), polystyrene-polyacrylic acid block copolymer (PS-b-PAA), polystyrene-b-polystyrene sulfonic acid (PS-b-PSSA), polyacrylonitrile-b-polyacrylic acid (PAN-b-PAA), polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP), etc., preferably PS-b-PEO block copolymer. The number average molecular weight of the block copolymer is 10,000-30,000 g / mol.

[0021] Unlike previous strategies that used block copolymers to assemble hydrophilic micelles with outward-facing hydrophilic ends to adsorb metal precursors and synthesize mesoporous intermetallic compounds, this invention utilizes block copolymers to form inverted micelles with inward-facing hydrophilic ends in a hydrophobic solvent. This confines metal ions within a micelle reactor, and a carbon layer is generated during subsequent pyrolysis, protecting the nanoparticles from sintering. By adjusting the ratio of block polymer to metal precursor, the size and dispersion of the inverted micelles can be controlled, ultimately achieving the synthesis of small-sized, highly ordered intermetallic compound nanoparticles with narrow particle size distribution and high loading capacity.

[0022] Taking polystyrene-ethylene oxide block copolymer (PS-b-PEO) as an example, during the synthesis of PS-b-PEO, inverse micelles are formed with PEO ends pointing inward and PS ends pointing outward. The hydrophilic PEO segments form crown ether-like cavities within the micelles, which can capture various metal ions through multidentate chelate configurations formed by ether-oxygen bonds. Simultaneously, the outer hydrophobic PS shell imparts structural rigidity to the micelles, preventing premature collapse during thermal annealing. When the metal precursor decomposes to form metal clusters during thermal annealing, PS-b-PEO decomposes to form a carbon layer, further providing confinement protection, resulting in small, uniformly distributed, and highly loaded nanoparticles.

[0023] Further, in step S1, the ligand in the complex is selected from at least one of acetylacetone, acetate, ethylenediaminetetraacetic acid, and triphenylphosphine ligand. The amounts of the complex of metal M1 and the complex of metal M2 satisfy a molar ratio of metal M1 to metal M2 of 1-3:1. The organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloromethane, and chloroform, and the amount of solvent used results in a block copolymer concentration of 5 mg / mL-10 mg / mL.

[0024] Furthermore, in step S1, the amount of block polymer used is 2-5 times, preferably 2-3 times, the total mass of the complexes of metal M1 and metal M2.

[0025] Further, in step S2, drying is performed by centrifugation, and the resulting solid phase is dried to constant weight at 60-90℃; the inert atmosphere is nitrogen and / or argon, and the high-temperature treatment involves heating to 850-1100℃ and holding at that temperature for 1-5 hours. There is no particular limitation on the heating rate, for example, 5-20℃ / min.

[0026] A third objective of this invention is to provide the application of the above-mentioned high-loading, small-size intermetallic compound catalyst as a cathode catalyst for fuel cells.

[0027] The high-load, small-size platinum-based intermetallic compound catalyst of this invention features high metal loading, small particle size, and uniform distribution. Its preparation method is simple, low-cost, and suitable for large-scale production. When applied to devices such as fuel cells, its performance is significantly superior to commercial platinum-carbon catalysts, and it has the potential to replace commercial catalysts in large-scale applications. The preparation method of this invention mainly utilizes the confinement effect provided by the copolymer. Under high-temperature treatment, the polymer decomposes into a porous carbon network and in-situ reduces the metal precursor into small, uniformly distributed metal particles. During subsequent cooling, a carbon layer is formed to coat the platinum-based intermetallic compound nanoparticles.

[0028] Compared with other existing technologies, the present invention has the following characteristics:

[0029] 1. The raw materials used in this invention are all commercially available materials, the synthesis method is simple, and it can be carried out on a large scale for industrial production.

[0030] 2. In this invention, a high molecular polymer is used to provide confinement. Compared with traditional methods that use adsorbed metal salts as metal sources, the pyrolysis process is more controllable, and the prepared particles are small in size, uniformly distributed, and have a high loading capacity.

[0031] 3. The intermetallic compound particles obtained by high-temperature treatment in this invention have strong interaction with the support and high degree of order, which can effectively prevent particle detachment and non-precious metal dissolution during the catalytic reaction. Compared with the traditional adsorption impregnation followed by heat treatment method, this method not only prevents particle agglomeration during heat treatment but also significantly improves stability in fuel cell applications. Attached Figure Description

[0032] Figure 1 The image shows the X-ray powder diffraction pattern of the Pt3Co intermetallic compound catalyst obtained in Example 1.

[0033] Figure 2 The image shows a transmission electron microscope image of the Pt3Co intermetallic compound catalyst obtained in Example 1, with the inset showing particle size distribution.

[0034] Figure 3 The oxygen reduction experimental polarization curve of the Pt3Co intermetallic compound catalyst obtained in Example 1 is shown.

[0035] Figure 4 The power density and polarization curves of the Pt3Co intermetallic compound catalyst obtained in Example 1 and the commercial platinum carbon fuel cell are compared.

[0036] Figure 5 The comparison shows the power density and polarization curves of the fuel cell before and after accelerated degradation tests of the Pt3Co intermetallic compound catalyst obtained in Example 1 and commercial platinum carbon.

[0037] Figure 6 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 3.

[0038] Figure 7 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 4.

[0039] Figure 8 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 5.

[0040] Figure 9 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 6.

[0041] Figure 10 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 7.

[0042] Figure 11 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 8.

[0043] Figure 12 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 9.

[0044] Figure 13 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 10.

[0045] Figure 14 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 11.

[0046] Figure 15 The images show the TEM image, particle size distribution, and XRD pattern of the supported catalyst obtained in Comparative Example 1. Detailed Implementation

[0047] To further understand the present invention, specific embodiments are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and the present invention and the limitations of the claims thereof are not limited thereto.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0049] For polystyrene-polyethylene oxide block copolymers, the degree of polymerization of PEO blocks is about 120, and that of PS blocks is about 70.

[0050] Example 1

[0051] (S1) 20.0 mg of platinum acetylacetonate and 4.4 mg of cobalt acetylacetonate (Pt to Co molar ratio of 3:1) were dissolved in 10 mL of tetrahydrofuran and stirred until homogeneous. Then, 50 mg of polystyrene-polyethylene oxide block copolymer was added, and the mixture was stirred thoroughly to obtain a clear and transparent solution. Subsequently, 30 mg of commercial Ketjen Black (KB-600) carbon support was added to the above solution, and the mixture was stirred further to obtain a dispersion without obvious precipitation. The dispersion was then centrifuged and dried in an oven at 80 °C to constant weight to obtain the polymer-coated precursor.

[0052] (S2) The polymer-coated precursor was transferred to a corundum ceramic boat and placed in a tube furnace. The furnace was purged with argon for approximately half an hour, then heated to 450°C at a rate of 10°C / min under an argon atmosphere and held for 1 hour. The temperature was then increased to 1000°C at a rate of 10°C / min and held for 1 hour. Afterward, the furnace was allowed to cool naturally to room temperature, yielding a high-density, small-sized Pt3Co intermetallic compound particle catalyst.

[0053] The X-ray powder diffraction curves of the obtained intermetallic compound catalysts are as follows: Figure 1 As shown, the catalyst corresponds well with the standard diffraction card of the Pt3Co intermetallic compound, indicating that the obtained intermetallic compound is Pt3Co.

[0054] Figure 2 The image shows a transmission electron microscope (TEM) image of the obtained catalyst. The obtained platinum-based intermetallic compound nanoparticles are densely distributed on the carbon substrate. Particle size analysis indicates that the metal particles are of very uniform size and distribution, with a size of approximately 3.9 ± 0.7 nm and a SPAN of 0.51. Inductively coupled plasma mass spectrometry (ICP-MS) analysis shows that the obtained catalyst has a platinum loading of 40%.

[0055] In summary, we can confirm that the catalyst is a highly loaded, small-sized Pt3Co intermetallic compound catalyst particle uniformly distributed on a carbon support, exhibiting high order and uniform size.

[0056] The oxygen reduction experimental curves of the obtained catalyst and the commercially used platinum-carbon catalyst are shown below. Figure 3As shown. The specific experimental method was as follows: the oxygen reduction curve was measured using a rotating disk electrode coated with catalyst ink in a 0.1 mol / L oxygen-saturated perchloric acid solution, with a catalyst loading of 11 μg Pt·cm⁻¹. -2 The rotating disk electrode was rotated at 1600 rpm, and the curve scan rate was 10 mV / s. The control platinum-carbon catalyst was purchased from Alfa Aesar (Tianjin) Catalyst Co., Ltd.

[0057] Comparing the two curves, it can be seen that the supported Pt3Co intermetallic compound catalyst prepared in Example 1 exhibits better performance than the commercial platinum-carbon catalyst, with a half-wave potential of 0.91 V, which is significantly better than the platinum-carbon catalyst.

[0058] The catalyst was further used at the cathode of a practical fuel cell. The resulting performance was as follows: Figure 4 As shown. The specific experimental method is as follows: 6 mg of catalyst was mixed with 73 μL of 5 wt% naphthol solution and dispersed in 2 mL of ethanol, then ultrasonically homogenized to obtain cathode catalyst ink. The cathode catalyst ink was sprayed onto a proton exchange membrane to obtain a proton exchange membrane loaded with cathode catalyst. Next, 2.5 mg of commercial platinum-carbon catalyst was dispersed with 30 μL of 5 wt% naphthol solution and dispersed in 1 mg of ethanol, then ultrasonically homogenized to obtain anolyte catalyst ink. The anolyte catalyst ink was sprayed onto the other side of the above proton exchange membrane, and then two 5 cm sheets were used. 2 Square pieces of carbon paper were placed on proton exchange membranes coated with catalyst inks for both electrodes and then hot-pressed at 120°C and 0.5 MPa to obtain a membrane electrode assembly (MEA). The MEA was then installed in a fuel cell test mold for testing, with a test curve scan rate of 20 mV / s. The control platinum-carbon catalyst was purchased from Alfa Aesar (Tianjin) Catalyst Co., Ltd.

[0059] Depend on Figure 4 It is evident that the catalyst exhibits superior performance compared to commercial platinum-carbon catalysts during discharge. Particularly in the high-current range, the catalyst demonstrates excellent activity, with a maximum discharge current reaching approximately 5605 mA·cm⁻¹. -2 Multiplying the current and voltage of the discharge curve yields the corresponding power curve. The highest power density measured for the catalyst is 2.75 W·cm⁻¹. -2 This is significantly higher than the 1.29 W·cm⁻¹ of commercially available platinum-carbon catalyst-assembled fuel cells. -2 .

[0060] We also compared the accelerated stress stability of the described catalyst and a commercial platinum catalyst in fuel cells. The anode and cathode atmospheres were high-purity hydrogen and high-purity nitrogen, respectively. The test program consisted of square wave cycling at 0.6V and 0.95V, with each potential held for 3 seconds, for a total of 30,000 cycles. After cycling, the cell discharge curve was repeatedly tested. The polarization curves after cycling are shown below. Figure 5 As shown, the catalyst maintained excellent stability after 30,000 cycles, and its discharge power density still reached 2.67 W·cm⁻¹. -2 The catalyst exhibits a retention rate of 97.1%, while commercial platinum-carbon assembled fuel cells have shown significant degradation, with a retention rate of only 47.6%. The excellent stability of this catalyst stems from its ultra-high orderliness, which inhibits the dissolution of non-precious metals during electrochemical processes, and the enhanced interaction between the support and particles after high-temperature pyrolysis, thus slowing down particle dissolution and detachment. These superior activity and stability indicate that this catalyst has strong application potential in fuel cells and related electrocatalytic applications.

[0061] Example 2

[0062] Other conditions and procedures were the same as in Example 1, except that the molar ratio of platinum acetylacetonate to cobalt acetylacetonate was 1:1. A supported PtCo intermetallic compound catalyst was obtained.

[0063] Example 3

[0064] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetone was replaced with an equimolar amount of chromium acetylacetone. A supported Pt3Cr intermetallic compound catalyst was obtained. Figure 6 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 3.

[0065] Example 4

[0066] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetone was replaced with an equimolar amount of manganese acetylacetone. A supported Pt3Mn intermetallic compound catalyst was obtained. Figure 7 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 4.

[0067] Example 5

[0068] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetone was replaced with an equimolar amount of iron acetylacetone. A supported Pt3Fe intermetallic compound catalyst was obtained. Figure 8 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 5.

[0069] Example 6

[0070] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetone was replaced with an equimolar amount of zinc acetylacetone. A supported Pt3Zn intermetallic compound catalyst was obtained. Figure 9 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 6.

[0071] Example 7

[0072] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetone was replaced with chromium acetylacetone and manganese acetylacetone (Pt:Cr:Mn molar ratio of 3:1:1). A supported Pt3(CrMn) intermetallic compound catalyst was obtained. Figure 10 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 7.

[0073] Example 8

[0074] Other conditions and operations were the same as in Example 1, except that cobalt acetylacetonate was replaced with a mixed precursor of manganese acetylacetonate, iron acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, and copper acetylacetonate (the molar ratio of Pt:Mn:Fe:Co:Ni:Cu was 5:1:1:1:1:1). A supported Pt5MnFeCoNiCu intermetallic compound catalyst was obtained. Figure 11 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 8. (Note: Since there is currently no standard XRD card for the composition of Pt5MnFeCoNiCu, the Pt4Fe2CuNi card, which has the closest composition, was used as a reference.)

[0075] Example 9

[0076] The other conditions and operations are the same as in Example 1, except that in step S1, the metal complex is iridium acetylacetone and manganese acetylacetone in a molar ratio of 1:1. This yields a supported IrMn intermetallic compound catalyst. Figure 12 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 9.

[0077] Example 10

[0078] Other conditions and operations were the same as in Example 1, except that the support was replaced with an equal mass of CeO2. A CeO2-supported Pt3Co intermetallic compound catalyst was obtained. Figure 13 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 10.

[0079] Example 11

[0080] The other conditions and operations are the same as in Example 1, except that the polystyrene-ethylene oxide block copolymer is replaced with an equal mass of polystyrene-acrylic acid block copolymer (PS-b-PAA). Figure 14 These are TEM images, particle size distribution diagrams, and XRD patterns of the supported catalyst obtained in Example 11.

[0081] Comparative Example 1

[0082] The other conditions and procedures are the same as in Example 1, except that polystyrene-polyethylene oxide block copolymer is not added. Figure 15 The images show the TEM image, particle size distribution, and XRD pattern of the supported catalyst obtained in Comparative Example 1.

[0083] Comparative Example 2

[0084] The other conditions and operations are the same as in Example 1, except that the solvent is replaced with a mixture of equal volumes of tetrahydrofuran and water in a volume ratio of 5:1.

[0085] The characterization and performance test results of the supported catalysts obtained in the above examples and comparative examples are shown in Table 1.

[0086] Table 1 Test results of supported catalysts

[0087]

[0088] It can be seen that the supported catalyst prepared according to the method of the present invention has high loading, small size and narrow particle size dispersion, and has excellent electrochemical performance.

Claims

1. A supported intermetallic compound catalyst with improved stability, characterized in that, The intermetallic compounds M1-M2 are uniformly dispersed on a support in the form of nanocrystals. Metal M1 is selected from at least one of platinum, iridium, ruthenium, palladium, and rhodium; metal M2 is selected from at least one of chromium, manganese, iron, cobalt, nickel, copper, and zinc; the intermetallic compound can have 2-8 elements; the average particle size of the intermetallic compound is 3-5 nm, and the particle size span (SPAN) is 0.4-0.

7.

2. The supported intermetallic compound catalyst according to claim 1, characterized in that, The carrier is selected from at least one of the following: carbon substrate (such as porous carbon, Ketjen carbon, Vulcan carbon, carbon nanotubes), carbide substrate (such as MXene), silica substrate, and metal oxide substrate (such as CeO2, Nb2O5).

3. The supported intermetallic compound catalyst according to claim 1, characterized in that, The molar ratio of M1 to M2 is 1-3:

1.

4. The supported intermetallic compound catalyst according to claim 1, characterized in that, The intermetallic compound catalyst has a metal M1 loading of 20-65%; further, for a carbon substrate, the noble metal M1 loading is 40-65%; for a metal oxide substrate, the noble metal loading is 20-40%.

5. The supported intermetallic compound catalyst according to claim 1, characterized in that, The intermetallic compound has an average particle size of 3-4 nm and a span (SPAN) of 0.4-0.

6.

6. A method for preparing the supported intermetallic compound catalyst according to any one of claims 1-5, characterized in that, Includes the following steps: (S1) The complexes of metal M1 and metal M2 are dissolved in an organic solvent, and a carrier and block polymer are added and dispersed evenly to obtain a dispersion; the block copolymer has hydrophilic blocks and hydrophobic blocks, and the block copolymer has functional groups that have coordination interactions with metal ions. (S2) The powder obtained after drying the dispersion is treated at high temperature under an inert atmosphere and then cooled to room temperature to obtain a high-loading, small-sized intermetallic compound catalyst.

7. The preparation method according to claim 6, characterized in that, In step S1, the block copolymer polymers include, but are not limited to: polystyrene-ethylene oxide block copolymer (PS-b-PEO), polystyrene-polyacrylic acid block copolymer (PS-b-PAA), polystyrene-b-polystyrene sulfonic acid (PS-b-PSSA), polyacrylonitrile-b-polyacrylic acid (PAN-b-PAA), polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP), etc., preferably PS-b-PEO block copolymers; further, the number average molecular weight of the block copolymers is 10,000-30,000 g / mol.

8. The preparation method according to claim 6, characterized in that, In step S1, the ligand in the complex is selected from at least one of acetylacetone, acetate, ethylenediaminetetraacetic acid, and triphenylphosphine ligand; the amounts of the complex of metal M1 and the complex of metal M2 satisfy the molar ratio of metal M1 to metal M2 as 1-3:1; the organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloromethane, and chloroform, and the amount of solvent used is such that the concentration of the block copolymer is between 5 mg / mL and 10 mg / mL.

9. The preparation method according to claim 6, characterized in that, In step S1, the amount of block polymer used is 2-5 times the total mass of the complexes of metal M1 and metal M2, preferably 2-3 times. Further, in step S2, drying is performed by centrifugation, and the resulting solid phase is dried to constant weight at 60-90℃; the inert atmosphere is nitrogen and / or argon, and the high-temperature treatment is to heat to 850-1100℃ and hold for 1-5 hours; there is no particular limitation on the heating rate, such as 5-20℃ / min.

10. The use of the supported intermetallic compound catalyst according to any one of claims 1-5 as a cathode catalyst for a fuel cell.

Images