An oxygen reduction catalyst based on Nb-oxygen fluorine cluster confinement and pulse-induced ordering and a preparation method and application thereof

Abstract

This invention discloses an oxygen reduction catalyst based on Nb-oxyfluorine cluster confinement and pulse-induced ordering, its preparation method, and its application. The preparation method of the platinum-based multi-element alloy catalyst of this invention includes the following steps: S1, adding ammonium niobium fluoride and hydrogen peroxide to a dispersion containing a carbon support to introduce Nb-oxyfluorine clusters in situ onto the surface of the carbon support; S2, adding a platinum source, a cobalt source, and a nickel source to the product obtained in step S1, followed by the addition of ascorbic acid and sodium borohydride to obtain Nb-oxyfluorine cluster-confined Pt–Co-Ni alloy particles; S3, subjecting the product obtained in step S2 to pulse Joule heating treatment to transform the alloy from a disordered structure to an ordered L12 phase, thereby obtaining the platinum-based multi-element alloy catalyst. The catalyst of this invention exhibits excellent oxygen reduction reaction activity and long-term stability in proton exchange membrane fuel cell cathode applications.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy materials technology, specifically relating to a platinum-based multi-element alloy electrocatalyst and its preparation method, particularly to an oxygen reduction reaction catalyst that achieves structural ordering through confined regulation and pulse treatment. Background Technology

[0002] Fuel cells are clean energy conversion devices that efficiently and directly convert the chemical energy of fuel into electrical energy, holding significant strategic importance in the construction of a green and low-carbon energy system. Proton exchange membrane fuel cells (PEMFCs), in particular, exhibit broad application prospects in transportation, stationary power generation, and portable power supplies due to their low operating temperature, high energy conversion efficiency, fast response speed, and compact structure. However, the large-scale industrialization of fuel cells remains limited by key materials, with the slow kinetics of the oxygen reduction reaction (ORR) at the cathode being the most significant bottleneck. Developing electrocatalysts that simultaneously possess high activity and high stability is one of the core challenges driving the advancement of fuel cell technology.

[0003] Currently, platinum and its alloys remain the most effective oxygen reduction catalysts, and carbon-supported platinum nanoparticles are commonly used as cathode catalysts in commercial fuel cells. However, single-metal platinum in acidic media suffers from problems such as high precious metal content, limited specific activity, and susceptibility to dissolution and aggregation during long-term operation. These drawbacks not only lead to a significant increase in platinum resource consumption but also make it difficult for fuel cells to meet the durability requirements of commercial applications during long-term operation. To overcome these problems, researchers have proposed various improvement strategies.

[0004] A common approach is to introduce transition metal elements into the platinum lattice through alloying to modulate the electronic structure and surface adsorption properties of platinum, thereby optimizing the reaction pathway of the oxygen reduction reaction. Elements such as nickel, cobalt, iron, copper, and chromium are widely used in alloying research and can improve catalyst activity and utilization to some extent. However, traditional alloy catalysts often face serious stability problems under actual fuel cell operating conditions. The base metal is prone to dissolution in acidic electrolytes, causing the loss of active sites. Simultaneously, particles may sinter or agglomerate at high potentials, significantly reducing the long-term stability of the catalyst.

[0005] Another development direction is single-atom catalysts. By dispersing metal atoms in single-atom form on a carbon support or doped substrate, the atom utilization rate can be significantly improved, achieving almost 100% exposure of active sites. These materials theoretically possess excellent mass activity and lower noble metal requirements, exhibiting certain advantages in oxygen reduction reactions. However, single-atom catalysts still have shortcomings in practical applications. Their structure is often unstable in complex electrochemical environments, prone to migration and aggregation, causing single atoms to gradually evolve into small clusters or nanoparticles, thus reducing long-term performance. Furthermore, the synthesis methods of single-atom catalysts are demanding, typically requiring special defect sites or coordination structures to stabilize the single atoms, making it difficult to guarantee process controllability and the feasibility of large-scale production.

[0006] Another approach is to increase the loading of noble metals on the carbon support, thereby enhancing the apparent activity of the catalyst by increasing the overall platinum content. In this strategy, various wet chemical methods are typically used to uniformly deposit the noble metals onto the carbon support surface, and particle size and distribution are controlled by optimizing reaction conditions. While high-loading catalysts can improve initial activity to some extent, the reduced interparticle spacing easily leads to agglomeration and Oswald ripening, resulting in a decrease in the catalyst's specific surface area and ultimately reducing the utilization rate of the noble metals. Furthermore, these methods often require complex pretreatment steps and long synthesis cycles, presenting certain limitations in terms of process technology.

[0007] Current research on oxygen reduction catalysts mainly focuses on three directions: alloying, single-atom formation, and high loading. While these methods have made some progress in improving activity or reducing costs, they generally suffer from the inability to simultaneously achieve high activity and high stability. This is particularly true in acidic electrolyte environments, where the dissolution of alloy components, particle sintering, and structural evolution remain unavoidable. Furthermore, some process routes suffer from stringent conditions, high energy consumption, and poor scalability, limiting their widespread application in practical fuel cells. Therefore, how to further improve the long-term stability of catalysts while maintaining high catalytic activity, and how to explore more efficient, simple, and controllable preparation methods, remain key scientific and technological problems that urgently need to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to address the problems of insufficient activity, poor durability, and complex preparation methods of existing platinum-based catalysts in the oxygen reduction reaction, and to propose a new solution. This invention provides an oxygen reduction catalyst (such as Pt3Co) based on in-situ confinement and microsecond pulse ordering of Nb-oxyfluorine clusters. 0.8 Ni 0.1 Nb 0.1 / C) and its preparation method. By constructing a special confined structure and adopting a rapid pulse-induced process, this invention can effectively solve the technical problems of severe metal component loss, inevitable particle agglomeration, and insufficient structural stability of existing alloyed catalysts in acidic environments, thereby obtaining an advanced electrocatalyst with both high activity and high stability.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a platinum-based multi-element alloy catalyst, comprising the following steps: S1. Niobium ammonium fluoride and hydrogen peroxide are added to a dispersion containing a carbon support to react and introduce Nb-oxyfluorine clusters in situ on the surface of the carbon support. S2. Platinum source, cobalt source and nickel source are added to the product obtained in step S1, and then ascorbic acid and sodium borohydride are added to react and obtain Nb-oxyfluorine cluster confined Pt-Co-Ni alloy particles. S3. The product obtained in step S2 is subjected to pulse Joule heating treatment to transform the alloy from a disordered structure to an ordered L12 phase, thereby obtaining the platinum-based multi-element alloy catalyst.

[0011] Based on the above technical solutions, the method of this invention adopts a synergistic strategy of "in-situ confinement of Nb-oxyfluorine clusters + dual reduction rate control + pulse ordering + selective acid washing" to solve the problems of uncontrollable particle size, uneven composition distribution, and poor structural stability in the preparation of traditional multi-metal alloy catalysts. The key innovation of this invention lies in the combination of the introduction of Nb-oxyfluorine clusters and microsecond pulse ordering. During the reaction, Nb-oxyfluorine clusters not only act as physical confinement centers to inhibit excessive particle growth, but also regulate the electronic structure of the alloy through the Nb–O–F coordination environment, thereby optimizing the adsorption energy of the oxygen reduction reaction intermediate and improving reaction kinetics. On the other hand, microsecond pulse-induced ordering can significantly improve the lattice stability of the alloy, enhance the resistance of transition metal elements to dissolution in acidic environments, and reduce the degradation rate of the catalyst during long-term operation. The synergistic effect of these two factors makes the catalyst prepared by this invention superior to Pt-based catalysts obtained by traditional methods in terms of both activity and stability.

[0012] In the above preparation method, optionally, the carbon support includes one or more of carbon black, N-doped graphene, carbon nanotubes, and graphene oxide. Further, the carbon support is carbon black, and the method further includes the following pretreatment step for the carbon black: treating the carbon black at 700–900℃ (e.g., 800℃, 850℃, 750℃, 900℃, 700℃) under an inert atmosphere for 1–2 hours (e.g., 1 hour, 2 hours), then ultrasonically dispersing it in 0.05–0.2M (e.g., 0.2M, 0.1M, 0.05M) nitric acid solution and refluxing at 70–100℃ (e.g., 70℃, 80℃, 90℃, 85℃) for 2–4 hours (e.g., 3 hours, 4 hours, 2 hours). The purpose of the pretreatment is to improve the surface structure of the carbon support, enhance its interaction with the metal precursor, and provide more active sites. This process helps to improve the dispersibility and stability of the catalyst, ensures that the metal particles are uniformly distributed on the surface of the carbon support, thereby avoiding metal particle agglomeration and improving the electrochemical activity of the catalyst.

[0013] In the above preparation method, the mass ratio of the carbon support to the niobium ammonium fluoride is further 2:(0.3-0.6), such as 2:0.3, 2:0.5, 2:0.4, or 2:0.6. If the mass ratio of niobium ammonium fluoride is too high, it may lead to excessive formation of niobium-oxyfluorine clusters, affecting the uniform distribution of metal particles and resulting in excessively large catalyst particles. This may, in turn, affect the number of surface active sites on the catalyst, reducing its electrochemical activity. If the mass ratio of niobium ammonium fluoride is too low, it will lead to insufficient Nb-oxyfluorine clusters, easily causing metal particle aggregation and sintering, reducing the stability and durability of the catalyst. This method introduces Nb-oxyfluorine clusters in situ onto the surface of a pretreated carbon support, forming a stable structural unit with spatial confinement and electronic regulation effects. Specifically, this is achieved by introducing a niobium precursor onto the surface of the carbon support, and generating Nb-oxyfluorine clusters in situ under the synergistic effect of a fluorinating agent and an oxidizing agent. This cluster can serve as a spatial confinement center, effectively regulating the subsequent nucleation and growth process of alloy particles.

[0014] Further, 5-10 mL of a 30% (w / w) aqueous solution of hydrogen peroxide (e.g., 10 mL, 5 mL, 8 mL, 9 mL) is added to every 2 g of carbon support. In this invention, hydrogen peroxide acts as an oxidant, oxidizing the niobium source and promoting the dissolution of ammonium fluoride. Excessive amounts of hydrogen peroxide can lead to over-generation of functional groups on the carbon support surface, making the surface overly active, resulting in excessive loading or uneven distribution of the metal precursor. Conversely, insufficient amounts of hydrogen peroxide cannot adequately oxidize the carbon support surface, leading to an insufficient number of oxidized functional groups, limiting the effective loading of the metal precursor, and reducing the number of active sites on the catalyst.

[0015] Furthermore, in step S1, the reaction temperature is 50–80°C and the reaction time is 1–3 h, such as 2 h, 2.5 h, 3 h or 1.5 h at 50°C, 55°C, 60°C, 65°C or 70°C.

[0016] In the above preparation method, further, the molar ratio of the platinum source, the cobalt source and the nickel source, based on metals, is 1:(0.2-0.3):(0.05-0.3), including but not limited to 1:0.25:0.05, 1:0.24:0.08, 1:0.22:0.08, 1:0.27:0.09, and 1:0.25:0.075. An increased Ni ratio reduces the catalyst's stability, especially after prolonged electrochemical cycling. An increased Co ratio leads to particle agglomeration after long-term operation, resulting in decreased activity.

[0017] Furthermore, the ratio of the carbon support to the platinum element in the platinum source is 2g:(0.1~0.3)mmol, such as 2g:0.2mmol, 2g:0.18mmol, 2g:0.25mmol; Optionally, the platinum source is selected from one or more of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, and ammonium chloroplatinate; the cobalt source is selected from one or more of cobalt chloride, chlorocobaltic acid, and sodium chlorocobaltate; and the nickel source is selected from nickel nitrate, nickel chloride, and sodium chloronickelate.

[0018] In the above preparation method, the ascorbic acid is further added in the form of an aqueous solution, and the ratio of the platinum source to the ascorbic acid solution is 0.1 mmol: 5–30 mL (e.g., 0.1 mmol: 10 mL, 0.1 mmol: 5.6 mL, 0.1 mmol: 9.1 mL, 0.1 mmol: 7.5 mL), and the concentration of the ascorbic acid solution is 0.05 M–0.5 M (e.g., 0.1 M). Excessive addition of ascorbic acid leads to a rapid reduction reaction rate, causing rapid nucleation and aggregation of metal particles, which in turn affects the uniformity and stability of the catalyst. Conversely, insufficient addition of ascorbic acid results in incomplete reduction of the metal source, potentially leading to unreduced platinum source in the catalyst and reduced catalyst activity.

[0019] In the above preparation method, the sodium borohydride is further added in the form of an aqueous solution, wherein the ratio of the platinum source to the sodium borohydride solution is 0.1 mmol: 4–15 mL (e.g., 0.1 mmol: 5 mL, 0.1 mmol: 6 mL, 0.1 mmol: 5.6 mL, 0.1 mmol: 4.6 mL, 0.1 mmol: 4 mL), and the concentration of the sodium borohydride solution is 0.02 M–0.1 M (e.g., 0.05 M). Excessive addition of sodium borohydride will lead to over-reduction of the metal particles, resulting in uneven platinum particles and aggregation of over-reduced metal particles, affecting the stability and activity of the catalyst. Insufficient addition of sodium borohydride will result in incomplete reduction of the metal precursor, with some platinum source not being fully reduced, leading to insufficient active sites on the catalyst and reducing its overall performance.

[0020] In step S2, a precursor solution of platinum, cobalt, and nickel is used, and preliminary alloy nanoparticles are formed under the confinement of a cluster through the combined reduction of ascorbic acid and sodium borohydride. A dual-aid system of mild reduction with ascorbic acid and rapid reduction with NaBH4 is employed. Ascorbic acid is used for slow-release reduction, while NaBH4 is used for rapid nucleation. This combined reduction enables the gradual nucleation and alloying of multiple metal ions, significantly inhibiting particle agglomeration and segregation.

[0021] In the above preparation method, further, in the pulse Joule heating treatment step, the pulse width is 100-500 microseconds (e.g., 200 μs, 100 μs, 300 μs, 150 μs, 400 μs), the pulse current is 5-15A (e.g., 10 A, 8 A, 12 A, 9 A, 11 A), the temperature is 850-950 ℃ (e.g., 900 ℃, 880 ℃, 930 ℃, 940 ℃), and the heating time is 1ms-1.5ms (e.g., 1 ms, 1.2 ms, 1.5 ms, 1.4 ms, 1.3 ms).

[0022] In step S3, the material is treated using microsecond-level pulsed Joule heating to induce high-temperature transformation of the alloy from a disordered structure to an ordered L12 phase in an extremely short time. Because pulsed heating allows for rapid heating and instantaneous cooling, this method not only avoids particle agglomeration caused by prolonged annealing but also promotes the formation of an ordered structure, thereby endowing the catalyst with excellent stability and durability. Specifically, precisely controlled microsecond-level pulsed Joule heating not only induces L12 ordering in the Pt3Co main phase but also promotes surface Pt enrichment and interface energy optimization. The treated catalyst has a surface Pt-enriched layer.

[0023] In the above preparation method, further, after step S3, the method includes the following step: acid washing or electrochemical cycling treatment of the product obtained in step S3, to remove impurities, unreacted precursors, and other unstable components from the catalyst surface, ensuring the exposure of the active sites of the catalyst. Specifically, the acid washing step can use 0.2 M sulfuric acid solution or a mixture thereof with dilute perchloric acid. In step S3, unstable components are selectively removed under a mild acidic environment through moderate acid washing or electrochemical cycling treatment, further optimizing the surface electronic structure and enhancing the exposure of active sites. Specifically, the electrochemical cycling conditions are as follows: potential range of 0.2–1.5 V vs. RHE, scan rate of 50 mV / s, activation 100–200 cycles, such as 200 cycles.

[0024] Secondly, the present invention provides a platinum-based multi-element alloy catalyst prepared by the method described in any of the preceding claims. As an example, the catalyst is Pt3Co. 0.8 Ni 0.1 Nb 0.1 / C electrocatalyst. The catalyst has a particle size of 1.5–5 nm, and features uniform composition distribution, L12 ordered structure, and surface Pt enrichment. It is homogeneous in composition and stable in structure.

[0025] Thirdly, this invention provides the application of the platinum-based multi-element alloy catalyst in catalytic oxygen reduction reactions. Specifically, the catalytic oxygen reduction reaction can be a redox reaction in various electrochemical energy systems such as proton exchange membrane fuel cells, metal-air batteries, and alkaline fuel cells.

[0026] Compared with the prior art, the present invention has the following advantages and positive effects: (1) The Nb-oxyfluorine clusters introduced during the preparation process effectively solved the problems of agglomeration and uneven distribution of high-load alloy nanoparticles, so that the particle size was controlled within a reasonable range and the distribution was uniform. (2) The microsecond-level pulse-induced ordered structure greatly improves the structural stability and electrochemical durability of the catalyst, avoiding metal dissolution and grain coarsening caused by long-term annealing; (3) The process of this invention is simple and efficient. From the introduction of the precursor to the final catalyst, the overall preparation cycle is significantly shortened and the energy consumption is lower, making it suitable for large-scale preparation and industrial application. (4) The catalyst of the present invention exhibits excellent oxygen reduction reaction activity and long-term stability in the application of proton exchange membrane fuel cell cathode. Its mass activity is higher than that of commercial Pt / C catalyst, and its potential decay in lifetime test is much lower than that of control sample, showing good application prospects. Attached Figure Description

[0027] Figure 1 The Pt3Co prepared in Example 1 of this invention 0.8 Ni 0.1 Nb 0.1 STEM image and elemental distribution map of the / C catalyst.

[0028] Figure 2 The Pt3Co prepared in Example 1 of this invention 0.8 Ni 0.1 Nb 0.1 XRD pattern of / C catalyst.

[0029] Figure 3 The Pt3Co prepared in Example 1 of this invention 0.8 Ni 0.1 Nb 0.1HAADF-STEM aberration-corrected plot of / C catalyst.

[0030] Figure 4 The Pt3Co prepared in Example 2 of this invention 0.8 Ni 0.1 Nb 0.1 TEM image of the / C catalyst.

[0031] Figure 5 The Pt3Co prepared in Example 2 of this invention 0.8 Ni 0.1 Nb 0.1 XRD pattern of / C catalyst.

[0032] Figure 6 The Pt3Co prepared in Example 3 of this invention 0.8 Ni 0.1 Nb 0.1 TEM image of the / C catalyst.

[0033] Figure 7 The Pt3Co prepared in Example 3 of this invention 0.8 Ni 0.1 Nb 0.1 XRD pattern of / C catalyst.

[0034] Figure 8 The Pt3Co prepared in Comparative Example 1 of this invention 0.8 Ni 0.1 Nb 0.1 TEM image of the / C catalyst.

[0035] Figure 9 The Pt3Co prepared in Comparative Example 2 of this invention 0.8 Ni 0.1 Nb 0.1 TEM image of the / C catalyst.

[0036] Figure 10 The Pt3Co prepared in Comparative Example 2 of this invention 0.8 Ni 0.1 Nb 0.1 XRD pattern of / C catalyst.

[0037] Figure 11 The Pt3Co prepared in Example 1 of this invention 0.8 Ni 0.1 Nb 0.1 Electrochemical cyclic voltammetry (CV) curves of the / C catalyst.

[0038] Figure 12 The Pt3Co prepared in Example 1 of this invention0.8 Ni 0.1 Nb 0.1 Electrochemical cyclic voltammetry (LSV) plot of the / C catalyst. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0040] Unless otherwise specified, the methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0041] Example 1 This embodiment provides a Pt3Co based on Nb-oxyfluorine cluster confinement and pulse-induced ordering. 0.8 Ni 0.1 Nb 0.1 / C oxygen reduction catalyst.

[0042] The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of carbon black (Vulcan XC-72), place it in an argon atmosphere at 800 ℃ for 1 h, cool it and then ultrasonically disperse it in 0.1 M nitric acid solution. Reflux it at 80 ℃ for 3 h, filter and wash it until neutral, and dry it for later use.

[0043] (2) Generation of Nb-oxyfluorine clusters: The pretreated carbon support was dispersed in 200 mL of deionized water, and 0.5 g of ammonium niobium fluoride (NH4NbF6) and 10 mL of 30% hydrogen peroxide solution were added. The mixture was stirred at 60 °C for 2 h.

[0044] (3) Introduction and reduction of metal precursor: 20 mL of 10 mM chloroplatinic acid solution (Pt 0.2 mmol), 10 mL of 5 mM cobalt chloride solution (Co 0.05 mmol) and 2 mL of 5 mM nickel nitrate solution (Ni 0.01 mmol) were added to the above dispersion in sequence. After stirring evenly, 20 mL of 0.1 M ascorbic acid solution was added dropwise for slow reduction. Then, 10 mL of 0.05 M sodium borohydride solution was added for rapid reduction. Stirring was continued for 1 h. After washing and drying, particles formed under the confinement of Nb-oxyfluorine clusters were obtained.

[0045] (4) Pulse ordering treatment: The sample is placed in a pulse Joule heating device with a pulse width of 200 μs and a pulse current of 10 A to heat the material to about 900 °C and cool it rapidly. The heating time is completed within 1 ms, which induces the alloy to transform from a disordered phase to an ordered L12 structure.

[0046] (5) Post-treatment: The obtained material was electrochemically cycled in 0.05 M HClO4 solution at a potential range of 0.2–1.2 V vs. RHE and a scan rate of 50 mV / s for 200 cycles to remove unstable components on the surface, finally yielding Pt3Co. 0.8 Ni 0.1 Nb 0.1 / C catalyst.

[0047] like Figure 1-3 As shown, transmission electron microscopy characterization revealed particle sizes of 2.5–3.5 nm, and XRD testing confirmed that the alloy possesses an L12 ordered structure.

[0048] Example 2 This embodiment provides a Pt3Co based on Nb-oxyfluorine cluster confinement and pulse-induced ordering. 0.8 Ni 0.1 Nb 0.1 / C Oxygen reduction catalyst.

[0049] The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of carbon black (Vulcan XC-72), treat it at 850 ℃ for 1 h under argon atmosphere, cool it and disperse it in 0.2 M nitric acid solution, reflux it at 70 ℃ for 4 h, wash it until neutral, and dry it for later use.

[0050] (2) Generation of Nb-oxyfluorine clusters: The treated carbon support was dispersed in 200 mL of deionized water, and 0.3 g of NH4NbF6 and 5 mL of 30% H2O2 solution were added. The reaction was carried out at 50 °C for 3 h to obtain a carbon support with Nb-oxyfluorine clusters on the surface.

[0051] (3) Introduction and reduction of metal precursors: 10 mM H2PtCl6 (Pt 0.25 mmol), 5 mM CoCl2 (0.06 mmol Co), and 5 mM Ni(NO3)2 solution (0.02 mmol Ni) were added sequentially. After stirring evenly, 25 mL of 0.1 M ascorbic acid solution was added dropwise, followed by 15 mL of 0.05 M NaBH4 solution for rapid reduction. The reaction was carried out for 1 h.

[0052] (4) Pulse ordering treatment: The sample is placed in a pulse device with a pulse width of 100 μs, a current of 8 A, a maximum temperature of about 880 ℃, and a heating time of 1.2 ms. Rapid cooling induces partial ordering of the alloy.

[0053] (5) Post-processing: The obtained material was subjected to electrochemical cycling in 0.05 M HClO4 solution at a potential range of 0.2–1.2 V vs. RHE, a scan rate of 50 mV / s, for 200 cycles to obtain Pt3Co. 0.8 Ni 0.1 Nb 0.1 / C catalyst.

[0054] like Figure 4-5 As shown, TEM revealed a particle size of 3.0–3.8 nm, and XRD showed a slightly lower degree of ordering than in Example 1.

[0055] Example 3 This embodiment provides a Pt3Co based on Nb-oxyfluorine cluster confinement and pulse-induced ordering. 0.8 Ni 0.1 Nb 0.1 / C Oxygen reduction catalyst.

[0056] The specific steps are as follows: (1) Carbon support pretreatment: Take 2g of N-doped graphene, treat it at 750℃ for 2h under nitrogen atmosphere, cool it and disperse it in 0.05 M nitric acid solution, reflux at 90℃ for 2h, wash it until neutral, and dry it for later use.

[0057] (2) Generation of Nb-oxyfluorine clusters: Pretreated graphene was dispersed in 150 mL of deionized water, and 0.4 g of NH4NbF6 and 8 mL of 30% H2O2 solution were added. The reaction was carried out at 70 °C for 1.5 h to obtain a carbon support with Nb-oxyfluorine clusters on the surface.

[0058] (3) Introduction and reduction of metal precursors: 10 mM H2PtCl6 (Pt 0.18 mmol), 5 mM CoCl2 (Co 0.04 mmol), and 5 mM Ni(NO3)2 (Ni 0.015 mmol) were added sequentially. After stirring evenly, 10 mL of 0.1 M ascorbic acid was added dropwise, followed by 10 mL of 0.05 M NaBH4 solution for reduction. The reaction was carried out for 1 h to obtain alloy particles.

[0059] (4) Pulse ordering process: The sample was placed in a pulse Joule heating device with a pulse width of 300 μs, a current of 12 A, a maximum temperature of about 930 °C, and a heating time of 1.5 ms. Rapid cooling induced the formation of a highly ordered L12 structure.

[0060] (5) Post-processing: The sample was electrochemically cycled in 0.05 M HClO4 solution at a potential range of 0.2–1.2 V vs. RHE, a scan rate of 50 mV / s, for 200 cycles to obtain Pt3Co. 0.8 Ni 0.1 Nb 0.1 / NG catalyst.

[0061] like Figure 6-7 As shown, TEM revealed a particle size of 2.8–3.6 nm, and XRD showed a slightly lower degree of ordering than in Example 1.

[0062] Example 4 This embodiment provides a Pt3Co based on Nb-oxyfluorine cluster confinement and pulse-induced ordering. 0.8 Ni 0.1 Nb 0.1 / C Oxygen reduction catalyst.

[0063] The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of carbon nanotubes (CNTs), treat them at 900 °C for 1 h under an argon atmosphere, cool them and disperse them in 0.2 M nitric acid solution, reflux them at 85 °C for 3 h, wash them until neutral and dry them for later use.

[0064] (2) Generation of Nb-oxyfluorine clusters: The carbon nanotubes treated above were dispersed in 200 mL of deionized water, and 0.6 g of NH4NbF6 and 9 mL of 30% H2O2 solution were added. The reaction was carried out at 65 °C for 2 h. After washing and drying, surface confined clusters were obtained.

[0065] (3) Introduction and reduction of metal precursors: 10 mM H2PtCl6 (0.22 mmol Pt), 5 mM CoCl2 (0.06 mmol Co) and 5 mM Ni(NO3)2 solution (0.02 mmol Ni) were added to the above dispersion system in sequence. After stirring evenly, 20 mL of 0.1 M ascorbic acid solution was added dropwise for slow reduction, and then 10 mL of 0.05 M NaBH4 solution was added for rapid reduction. The reaction was carried out for 1 h.

[0066] (4) Pulse ordering treatment: The product is placed in a pulse Joule heating device with a pulse width of 150 μs, a current of 9 A, a maximum temperature of about 880 ℃, and a heating time of 1.4 ms. The product is then rapidly cooled to form an ordered phase.

[0067] (5) Post-processing: The sample was electrochemically cycled in 0.05 M HClO4 solution at a potential range of 0.2–1.2 V vs. RHE, a scan rate of 50 mV / s, for 200 cycles to obtain Pt3Co. 0.8 Ni 0.1 Nb 0.1 / CNT catalyst.

[0068] Example 5 This embodiment provides a Pt3Co based on Nb-oxyfluorine cluster confinement and pulse-induced ordering. 0.8 Ni 0.1 Nb 0.1 / C Oxygen reduction catalyst.

[0069] The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of graphene oxide (GO) and treat it at 700 °C for 2 h under nitrogen atmosphere to partially reduce it. After cooling, disperse it in 0.05 M nitric acid solution, reflux at 70 °C for 2 h, wash until neutral and dry.

[0070] (2) Generation of Nb-oxyfluorine clusters: The above graphene was dispersed in 150 mL of deionized water, and 0.4 g of NH4NbF6 and 5 mL of 30% H2O2 solution were added. The reaction was carried out at 55 °C for 2.5 h. After washing and drying, graphene with Nb-oxyfluorine clusters on the surface was obtained.

[0071] (3) Introduction and reduction of metal precursor: 10 mM H2PtCl6 (0.2 mmol Pt), 5 mM CoCl2 (0.05 mmol Co), and 5 mM Ni(NO3)2 solution (0.015 mmol Ni) were added sequentially. After stirring evenly, 15 mL of 0.1 M ascorbic acid solution was added dropwise, followed by 8 mL of 0.05 M NaBH4 solution for rapid reduction. The reaction was carried out for 1 h to obtain alloy precursor particles.

[0072] (4) Pulse ordering process: The obtained material is placed in a pulse Joule heating device with a pulse width of 400 μs, a current of 11 A, a maximum temperature of about 940 °C, and a heating time of 1.3 ms. The material is heated and cooled instantaneously to induce the formation of a highly ordered structure.

[0073] (5) Post-processing: The sample was treated with 0.05 M HClO4 solution, and the electrochemical cycling potential range was 0.2–1.5 V vs. RHE, the scan rate was 50 mV / s, and the activation was performed for 200 cycles to obtain Pt3Co. 0.8 Ni 0.1 Nb 0.1 / Graphene catalyst.

[0074] Comparative Example 1 The difference from Example 1 is that the Nb-oxyfluorine cluster generation step is omitted. The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of carbon black (Vulcan XC-72), treat it at 800 ℃ for 1 h under argon atmosphere, cool it and disperse it in 0.1 M nitric acid solution, reflux it at 80 ℃ for 3 h, filter and wash it until neutral, and dry it for later use.

[0075] (2) Nb-oxyfluorine cluster generation: This step is omitted, and the pretreated carbon support is used directly.

[0076] (3) Introduction and reduction of metal precursors: 10 mM H2PtCl6 (0.2 mmol Pt), 5 mM CoCl2 (0.05 mmol Co), and 5 mM Ni(NO3)2 (0.01 mmol Ni) solutions were added sequentially. After stirring evenly, 20 mL of 0.1 M ascorbic acid solution was added dropwise, followed by 10 mL of 0.05 M NaBH4 solution for reduction. Stirring was continued for 1 h. After washing and drying, Pt-Co-Ni alloy particles were obtained.

[0077] (4) Pulse ordering treatment: The obtained sample is placed in a pulse heating device with a pulse width of 200 μs and a current of 10 A to instantly heat the material to about 900 °C and then cool it rapidly for 1 ms. Rapid cooling induces the ordering of the alloy part.

[0078] (5) Post-treatment: The obtained material was activated for 200 cycles in 0.05 M HClO4 solution with an electrochemical cycling potential range of 0.2–1.2 V vs. RHE and a scan rate of 50 mV / s to obtain the catalyst.

[0079] like Figure 8 As shown, compared with Example 1, the catalyst prepared in Comparative Example 1 exhibits obvious particle agglomeration and a wider particle size distribution range (3.0–8.0 nm). Due to the lack of confinement effect of Nb-oxyfluorine clusters, the metal precursor is prone to migration and aggregation during reduction, resulting in excessively large particle sizes in some regions.

[0080] Comparative Example 2 The difference from Example 1 is that the pulse ordering process is omitted. The specific steps are as follows: (1) Carbon support pretreatment: Take 2 g of carbon black (Vulcan XC-72), treat it at 800 ℃ for 1 h under argon atmosphere, cool it and disperse it in 0.1 M nitric acid solution, reflux it at 80 ℃ for 3 h, filter and wash it until neutral, and dry it for later use.

[0081] (2) Nb-oxyfluorine cluster formation: The pretreated carbon support was dispersed in 200 mL of deionized water, and 0.5 g of NH4NbF6 and 10 mL of 30% H2O2 solution were added. The mixture was stirred at 60 °C for 2 h.

[0082] (3) Introduction and reduction of metal precursor: 0.2 mmol Pt 10 mM H2PtCl6 (Pt 0.2 mmol), 0.05 mmol Co 5 mM CoCl2 (Co 0.05 mmol), and 0.01 mmol Ni 5 mM Ni(NO3)2 solution (Ni 0.01 mmol) were added sequentially. After stirring evenly, 20 mL of 0.1 M ascorbic acid solution was added dropwise for slow reduction. Then, 10 mL of 0.05 M NaBH4 solution was added for further reduction. Stirring was continued for 1 h. After washing and drying, the confined alloy precursor was obtained.

[0083] (4) Pulse ordering process: This step is omitted. The sample is dried at 300 °C for 2 h without pulse heating.

[0084] (5) Post-processing and performance results: The sample was activated by electrochemical cycling in 0.05 M HClO4 solution with a potential range of 0.2–1.2 V vs. RHE and a scan rate of 50 mV / s for 200 cycles to obtain the catalyst.

[0085] like Figure 9-10 As shown, although the catalyst particles of Comparative Example 2 are small in size (about 2.5 nm), no characteristic peaks of the L12 superlattice were observed in the XRD pattern.

[0086] Comparative Example 3 The difference from Example 1 lies in adjusting the molar ratio of the metal precursors, so that the cobalt content exceeds the range defined in this invention, and the elemental molar ratio of the platinum source, the cobalt source, and the nickel source is 1:(0.2-0.3):(0.05-0.3). The specific steps are as follows: (1) Carbon carrier pretreatment: Same as in Example 1.

[0087] (2) Generation of Nb-oxyfluorine clusters: Same as in Example 1.

[0088] (3) Add 20 mL of 10 mM chloroplatinic acid solution (containing 0.2 mmol Pt), 20 mL of 5 mM cobalt chloride solution (containing 0.1 mmol Co), and 2 mL of 5 mM nickel nitrate solution (containing 0.01 mmol Ni) to the above dispersion in sequence. After stirring evenly, add 20 mL of 0.1 M ascorbic acid solution dropwise for slow reduction, and then add 10 mL of 0.05 M sodium borohydride solution for rapid reduction. Continue stirring for 1 h.

[0089] (4) Pulse ordering process: Same as in Example 1.

[0090] (5) Post-processing: Same as in Example 1. The final product is a Co-excess Pt-Co-Ni-Nb / C catalyst.

[0091] Comparative Example 4 The difference from Example 1 lies in adjusting the molar ratio of the metal precursors, so that the nickel content exceeds the range defined in this invention, and the elemental molar ratio of the platinum source, the cobalt source, and the nickel source is 1:(0.2-0.3):(0.05-0.3). The specific steps are as follows: (1) Carbon carrier pretreatment: Same as in Example 1.

[0092] (2) Generation of Nb-oxyfluorine clusters: Same as in Example 1.

[0093] (3) Introduction and reduction of metal precursors: 20 mL of 10 mM chloroplatinic acid solution (containing 0.2 mmol of Pt), 10 mL of 5 mM cobalt chloride solution (containing 0.05 mmol of Co) and 20 mL of 5 mM nickel nitrate solution (containing 0.1 mmol of Ni) were added to the above dispersion in sequence. After stirring evenly, 20 mL of 0.1 M ascorbic acid solution was added dropwise for slow reduction, and then 10 mL of 0.05 M sodium borohydride solution was added for rapid reduction. Stirring was continued for 1 h.

[0094] (4) Pulse ordering process: Same as in Example 1.

[0095] (5) Post-processing: Same as in Example 1.

[0096] The Ni-excess Pt-Co-Ni-Nb / C catalyst was finally obtained.

[0097] Electrochemical performance test examples Electrochemical performance tests were performed on the catalysts prepared in the above examples and comparative examples, as well as on commercial Pt / C. All electrochemical tests were conducted in ammonium chloride (0.1 M HClO4) solution as an acidic medium. The experimental methods are as follows: the working electrode was a glassy carbon electrode, and the catalyst loading was 0.2 mg / cm³. 2 The potential scan range was 0.2–1.2 V vs. RHE, and the scan rate was 50 mV / s. In the accelerated lifetime test, all catalysts underwent 5000 electrochemical cycles to observe their electrochemical stability during long-term reactions.

[0098] Wherein, the initial electrochemical active area = ,in It is the hydrogen desorption charge. Platinum loading on the electrode; mass activity = in The test current is at 0.9V. The limiting diffusion current; electrochemical active area retention rate = 100%.

[0099] The experimental results are shown in Table 1. Among them, the Pt3Co prepared in Example 1... 0.8 Ni 0.1 Nb 0.1 The electrochemical cyclic voltammograms (CV and LSV plots) of the / C catalyst are shown below. Figure 11-12 .

[0100] Table 1 Electrochemical active area and mass activity

[0101] As shown in Table 1, the catalyst prepared in Example 1 exhibits the best overall performance, with a mass activity as high as 1.3 A / mgPt, which is 5.2 times that of commercial Pt / C (0.25 A / mgPt). This is mainly attributed to the small particle size and high dispersion resulting from the confinement of Nb-oxyfluorine clusters and the optimization of the electronic structure by Ni / Co co-doping. Furthermore, its ECSA retention rate after 5000 cycles is as high as 92%, far superior to Comparative Example 2 (50%) and commercial Pt / C (65%), demonstrating that the pulse-induced L12 ordered structure significantly improves the alloy's resistance to dissolution and sintering under acidic conditions. Examples 3 and 5 show that although changing the carbon support slightly affects the performance, the overall performance remains high, demonstrating the universality of this method.

[0102] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 omits the Nb-oxyfluorine cluster generation step. As can be seen from the comparison results between Example 1 and Comparative Example 1 in Table 1, the initial electrochemical active area, mass activity, and electrochemical active area retention rate of the catalyst synthesized by omitting this step are all significantly reduced, especially the initial electrochemical active area and mass activity. This is because the Nb-oxyfluorine cluster not only acts as a physical confinement center to inhibit the excessive growth of particles during the reaction, but also regulates the electronic structure of the alloy through the Nb–O–F coordination environment, thereby optimizing the adsorption energy of the oxygen reduction reaction intermediate and greatly improving the oxygen reduction reaction activity of the catalyst.

[0103] The difference between Comparative Example 2 and Example 1 is that Comparative Example 1 omits the pulse ordering treatment step. As can be seen from the comparison results between Example 1 and Comparative Example 2 in Table 1, the initial electrochemical active area, mass activity and electrochemical active area retention rate of the catalyst synthesized by omitting this step are all significantly reduced, especially the electrochemical active area retention rate. This is because microsecond pulse-induced ordering can significantly improve the lattice stability of the alloy, enhance the anti-dissolution ability of transition metal elements in acidic environments, and reduce the decay rate of the catalyst during long-term operation.

[0104] Analysis of Comparative Examples 3 and 4 with Example 1: As shown in Table 1, when the alloy composition exceeded the molar ratio range defined in this invention, the catalyst performance significantly decreased. Specifically, although Comparative Example 3 exhibited acceptable mass activity (0.75 A / mgPt) in the initial stage, its ECSA retention rate was only 60%, significantly lower than that of Example 1 (92%). This is because excess cobalt readily dissolves in an acidic electrolyte environment, leading to alloy lattice collapse and the formation of a loose porous structure within the particles, thereby causing particle agglomeration and loss of active sites. Comparative Example 4 showed poor mass activity (0.45 A / mgPt) and stability (68%). This is mainly because excess nickel easily segregates on the catalyst surface, forming inactive nickel oxide species, which not only occupy platinum active sites and hinder oxygen molecule adsorption but also accelerate metal dissolution and loss during long-term cycling.

[0105] In summary, this invention, by constructing a special confined structure and employing a rapid pulse-induced process, effectively solves the technical challenges of severe metal component loss, inevitable particle agglomeration, and insufficient structural stability in existing alloyed catalysts under acidic environments, thereby obtaining an advanced electrocatalyst with both high activity and high stability. The synergistic effect of these two methods results in the catalyst prepared by this invention exhibiting superior activity and stability compared to Pt-based catalysts obtained by conventional methods and the samples in Comparative Examples 1-2. Furthermore, as shown in Example 1 and Comparative Examples 3-4, the molar ratio of platinum, cobalt, and nickel also affects the activity and stability of the catalyst.

[0106] This invention is not limited to the specific embodiments described above. For those skilled in the art, various substitutions or adjustments can be made to the selection of raw materials, process steps, processing conditions, and structural parameters without departing from the core concept of this invention; all such equivalent changes should be considered within the scope of protection of this invention. The technical solutions involved in this invention are not only applicable to proton exchange membrane fuel cells, but can also be extended to various electrochemical energy systems such as metal-air batteries and alkaline fuel cells; their application scope should be interpreted accordingly. Therefore, all modifications, alterations, and improvements made based on the principles of this invention should be covered within the scope of protection claimed in this application.

Claims

1. A method for preparing a platinum-based multi-element alloy catalyst, characterized in that, Includes the following steps: S1. Niobium ammonium fluoride and hydrogen peroxide are added to a dispersion containing a carbon support to react and introduce Nb-oxyfluorine clusters in situ on the surface of the carbon support. The mass ratio of the carbon support to the ammonium niobium fluoride is 2:(0.3-0.6); Add 5-10 mL of a 30% hydrogen peroxide aqueous solution to every 2 g of carbon support; S2. Platinum source, cobalt source and nickel source are added to the product obtained in step S1, and then ascorbic acid and sodium borohydride are added to react and obtain Nb-oxyfluorine cluster confined Pt-Co-Ni alloy particles. The molar ratio of the platinum source, the cobalt source, and the nickel source, calculated in terms of metals, is 1:(0.2–0.3):(0.05–0.3). The ratio of the carbon support to the platinum element in the platinum source is 2g:(0.1~0.3)mmol; S3. The product obtained in step S2 is subjected to pulse Joule heating treatment to transform the alloy from a disordered structure to an ordered L12 phase, thereby obtaining the platinum-based multi-element alloy catalyst.

2. The preparation method according to claim 1, characterized in that: The carbon support includes one or more of carbon black, N-doped graphene, carbon nanotubes, and graphene oxide.

3. The preparation method according to claim 2, characterized in that: The carbon support is carbon black, and the method further includes the following steps for pretreating the carbon black: treating the carbon black at 700-900℃ for 1-2 hours under an inert atmosphere, cooling it, and then ultrasonically dispersing it in a 0.05-0.2M nitric acid solution and refluxing it at 70-100℃ for 2-4 hours.

4. The preparation method according to any one of claims 1-3, characterized in that: In step S1, the reaction temperature is 50–80°C and the reaction time is 1–3 h.

5. The preparation method according to any one of claims 1-3, characterized in that: The platinum source is selected from one or more of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, and ammonium chloroplatinate. And / or, the cobalt source is selected from one or more of cobalt chloride, cobalt chloride, and sodium cobalt chloride; And / or, the nickel source is selected from nickel nitrate, nickel chloride, or sodium nickel chloride.

6. The preparation method according to claim 5, characterized in that: The ascorbic acid is added in the form of an aqueous solution, the ratio of the platinum source to the ascorbic acid solution is 0.1 mmol: 5-30 mL, and the concentration of the ascorbic acid solution is 0.05 M to 0.5 M.

7. The preparation method according to claim 5, characterized in that: The sodium borohydride is added in the form of an aqueous solution, and the ratio of the platinum source to the sodium borohydride solution is 0.1 mmol: 4-15 mL, and the concentration of the sodium borohydride solution is 0.02 M-0.1 M.

8. The preparation method according to any one of claims 1-3, characterized in that: In the pulsed Joule heating process, the pulse width is 100–500 microseconds, the pulse current is 5–15A, the heating time is 1–1.5 milliseconds, and the temperature is 850–950 °C.

9. The preparation method according to any one of claims 1-3, characterized in that: The method further includes the following steps after step S3: acid washing the product obtained in step S3 or electrochemical cycling treatment in an acidic solution.

10. The platinum-based multi-element alloy catalyst prepared by the method of any one of claims 1-9.

11. The application of the platinum-based multi-element alloy catalyst according to claim 10 in the catalytic oxygen reduction reaction.

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