Platinum-bismuth alloy catalyst, method for preparing the same, and direct methanol fuel cell

Abstract

The application provides a platinum-bismuth alloy catalyst, a preparation method thereof and a direct methanol fuel cell, and belongs to the technical field of electrochemical catalysts. The method comprises the following steps: mixing carbon black and an acidic aqueous solution, and then sequentially performing acidification treatment and calcination treatment to obtain pretreated carbon black; mixing the pretreated carbon black, Bi2O2CO3, a platinum source, a precipitating agent, a pH adjusting agent, a first dispersing agent and water, and then performing a double decomposition reaction to obtain a suspension; mixing a reducing agent, a second dispersing agent and water to obtain a mixed solution; adding the suspension into the mixed solution to perform a reduction reaction, and then a catalyst precursor is obtained; and performing calcination treatment on the catalyst precursor under a first protective gas to obtain the platinum-bismuth alloy catalyst. The prepared platinum-bismuth alloy catalyst has excellent electrocatalytic performance, shows high catalytic activity and cycle stability, and can be applied to a cathode oxygen reduction reaction in a direct methanol fuel cell.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalyst technology, and more specifically, to a platinum-bismuth alloy catalyst, its preparation method, and a direct methanol fuel cell. Background Technology

[0002] Direct methanol fuel cells (DMFCs) have broad application prospects in portable power sources and vehicle power sources due to their compact structure, convenient refueling, and excellent energy density. However, DMFC development faces a core bottleneck: the "methanol penetration effect." Methanol passes through the electrolyte membrane from the anode to the cathode, where it undergoes both oxidation-reduction (ORR) and methanol oxidation (MOR) reactions simultaneously on the surface of a traditional Pt / C catalyst, creating a mixed potential and leading to a significant decrease in battery output power. Therefore, developing a cathode oxygen reduction catalyst that combines methanol tolerance, high catalytic activity, and long-term stability is crucial to overcoming the technological bottleneck of DMFCs.

[0003] Platinum-based catalysts currently represent the most efficient system for oxygen reduction reactions, but they face several challenges in practical applications: First, during the reaction, the active component (Pt particles) is prone to migration, aggregation, and leaching, leading to the loss of active sites. Second, the Pt surface is easily adsorbed by reaction intermediates (such as CO) or poisoned by methanol oxidation products, reducing catalytic selectivity. Third, the interaction between the support (such as carbon black) and the active component is weak, and long-term reactions are prone to corrosion and collapse of the porous structure, exacerbating catalyst deactivation. Fourth, the insufficient reduction efficiency of Pt ions and low utilization of precious metals result in high catalyst costs. To address these issues, researchers have developed Pt-Ni and Pt-Fe-Ir multi-component alloy catalysts by using alloying strategies (introducing transition metals or main group metals) to regulate the electronic structure and surface adsorption characteristics of Pt. However, existing preparation techniques still have many limitations that need to be addressed, hindering their industrial application and performance improvement.

[0004] Chinese patent application CN116706106B discloses a platinum-nickel alloy catalyst and its preparation method. This method constructs the alloy structure through a two-step heating process of "nickel nanoparticle prefabrication + platinum source surface reduction." Specifically, nickel nanoparticles are obtained by first mixing a nickel source, reducing agent, organic surfactant, and solvent with a solvent and heating; then, a platinum source aqueous solution is added for a second high-temperature heating treatment, reducing the platinum source on the surface of the nickel nanoparticles; finally, the catalyst is obtained by mixing with a support and calcining. However, in this technical solution, the two high-temperature heating treatments easily induce agglomeration effects between nanoparticles. Chinese patent application CN113611877A discloses a method for preparing a multi-element alloy catalyst. Its technical route involves mixing carbon materials with a platinum source and other metal raw materials to form a suspension, adding additives, reacting at 80-180℃, and then calcining and surface platinum enrichment treatment to obtain a platinum multi-element alloy catalyst. This method has a lengthy process and requires a high amount of Pt, which not only increases operational complexity but also fails to achieve efficient utilization of precious metal resources. Chinese patent application publication number CN115241472B discloses an oxygen reduction catalyst with a platinum-bismuth alloy shell. It uses ethylene glycol as both a solvent and a reducing agent to prepare carbon black-supported platinum alloy solid solution nanoparticles, followed by acidification and heat treatment to obtain a catalyst with a "platinum alloy core-platinum-bismuth alloy shell" structure. However, this technology suffers from poor Bi dispersion uniformity, easily forming localized enrichment regions that disrupt the uniformity of the shell structure, and it does not address the efficient utilization of bismuth resources. Chinese patent application publication number CN115084544B provides a method for preparing an alloy catalyst. It involves mixing and dispersing a platinum-carbon mixed source, a transition metal source, and a dispersant, then stirring at a constant temperature until a viscous state is reached. After drying, the mixture is calcined under a protective atmosphere to obtain a Pt-M / C alloy catalyst. Chinese patent application publication number CN114792816B discloses a platinum-based alloy catalyst with ordered platinum-iron-iridium alloy nanowires as the active component, uniformly dispersed on the surface of a carbon black support, focusing on improving structural stability and oxygen reduction catalytic performance. However, neither of the aforementioned technical solutions addresses the key synergistic issue in the catalytic system: the synergistic matching among the uniformity of the active component's dispersion, the strength of the interaction between the active component and the support, and the optimized design of the support's pore structure. This synergistic effect directly impacts the stability of active sites and the mass transfer efficiency between reactants and products; existing technologies have failed to achieve effective synergy. Furthermore, the white smoke dust (industrial solid waste) generated by the copper smelting industry contains 1-15 wt% bismuth, representing a rich bismuth resource. However, current technologies have not yet enabled its high-value utilization in high-performance catalysts, leading to resource waste and environmental pressure.

[0005] In summary, existing platinum-based alloy catalyst preparation technologies still have significant limitations in terms of controlling the dispersion of active components, the efficiency of precious metal resource utilization, process simplification, and synergistic optimization of the catalytic system. Furthermore, they have failed to achieve efficient recovery and high-value utilization of bismuth resources from copper smelting white dust. Therefore, it is urgent to develop a new preparation method that can simultaneously overcome the above-mentioned technical challenges and take into account both resource recycling and catalytic performance improvement. Summary of the Invention

[0006] The main objective of this invention is to provide a platinum-bismuth alloy catalyst, its preparation method, and a direct methanol fuel cell, in order to solve the problem of low catalytic activity and stability of platinum-based catalysts in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a platinum-bismuth alloy catalyst is provided, comprising: step S1, mixing raw materials including carbon black and an acidic aqueous solution and then subjecting them to acidification and calcination treatments sequentially to obtain pretreated carbon black; step S2, mixing raw materials including pretreated carbon black, Bi2O2CO3, platinum source, precipitant, pH adjuster, first dispersant and first water and then subjecting them to a metathesis reaction to obtain a suspension; step S3, mixing raw materials including a reducing agent, a second dispersant and second water to obtain a mixed solution; step S4, adding the suspension dropwise to the mixed solution to carry out a reduction reaction to obtain a catalyst precursor; and step S5, calcining the catalyst precursor under a first protective gas to obtain a platinum-bismuth alloy catalyst.

[0008] Further, in step S1, the mass ratio of carbon black to the volume of the acidic aqueous solution is (5~15g):(100~300mL), the concentration of the acidic aqueous solution is 0.3~0.7mol / L; and / or, the acidification treatment temperature is 110~130℃; and / or, the acidification treatment time is 4~6h; and / or, the specific surface area of ​​the carbon black is 200~400m². 2 / g, pore size 3~10nm, pore volume 0.5~1.2cm³ 3 / g; and / or, the calcination temperature is 200~350℃; and / or, the calcination is carried out in a second protective gas at a heating rate of 3~7℃ / min; and / or, the calcination time is 2~4h.

[0009] Further, in step S2, the mass ratio of pretreated carbon black, Bi2O2CO3, and platinum source is (5~20):(1~15):(0.1~2); and / or, the mass ratio of platinum source, precipitant, and pH adjuster is (0.1~2):(0.1~0.5):(0.01~0.03); and / or, the mass ratio of platinum source, the mass of the first dispersant, and the volume of the first water is (0.1~2g):(40~70g):(140~160mL); and / or, the temperature of the metathesis reaction is 5~15℃; and / or, the time of the metathesis reaction is 20~40min; and / or, the metathesis reaction is carried out under stirring at a stirring rate of 300~350r / min.

[0010] Further, in step S3, the ratio of the mass of the reducing agent, the mass of the second dispersant, to the volume of the second water is (1.5~2.0g):(0.1~0.3g):(50~150mL); and / or, the mixing in step S3 is stirring, with a stirring rate of 200~300r / min; and / or, in step S4, the rate at which the suspension is added is 1mL / min~30mL / min; and / or, the volume ratio of the suspension to the mixed solution is 1:(0.3~0.7); and / or, the temperature of the reduction reaction is 5~15℃; and / Or, the reduction reaction time is calculated from the time the suspension is first added dropwise to the mixed solution, and the reduction reaction time is 50~70 min; and / or, in step S5, the first protective gas is selected from any one or more of nitrogen, helium and argon, and the flow rate of the first protective gas is 50~100 mL / min; and / or, the heating rate of the calcination treatment is 3~7℃ / min; and / or, the temperature of the calcination treatment is 300~900℃; and / or, the calcination treatment time is 0.5~1.5 h; and / or, the calcination treatment is naturally cooled to 20~30℃.

[0011] Further, the carbon black is selected from any one or more of Ketjen black, Vulcan XC-72R carbon black, and acetylene black; and / or, the acid in the acidic aqueous solution is selected from any one or more of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, and hypochlorous acid; and / or, the platinum source is selected from any one or more of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, [Pt(acac)2], diammonium dinitrite platinum, and [Pt(CH3NH2)4][PtCl4]; and / or, the precipitant is selected from any one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium oxalate, ammonium acetate, ammonium chloride, and ammonia water; and / or, The pH adjuster is selected from any one or more of oxalic acid, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, ammonium carbonate, sodium carbonate, and sodium bicarbonate; and / or, the first dispersant is selected from any one or more of ethylene glycol, propylene glycol, polyethylene glycol, polyvinylpyrrolidone, and citric acid; and / or, the reducing agent is selected from any one or more of ascorbic acid, glucose, sodium borohydride, hydrazine hydrate, glutathione, sodium bisulfite, and sodium hypophosphite; and / or, the second dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, and sodium polyacrylate.

[0012] Furthermore, the preparation method of Bi2O2CO3 includes: mixing the white smoke dust generated during copper smelting with an inorganic acid aqueous solution and then performing acid leaching treatment to obtain acid leaching residue; mixing the acid leaching residue with a chloride salt aqueous solution and then performing chlorination treatment to obtain bismuth chloride; mixing bismuth chloride with tertiary water and then performing a hydrolysis reaction to obtain BiOCl suspension; mixing the BiOCl suspension with carbonate and then performing a precipitation reaction to obtain Bi2O2CO3.

[0013] Further, the bismuth content in the white dust is 1-15% by mass; and / or, the mass ratio of white dust to inorganic acid aqueous solution is 1:(2-5), and the concentration of inorganic acid in the inorganic acid aqueous solution is 0.3-0.7 mol / L; and / or, the acid leaching temperature is 30-90℃; and / or, the acid leaching time is 1-4 h; and / or, the acid leaching is carried out under stirring at a stirring rate of 200-400 r / min; and / or, the mass ratio of acid leaching residue to chloride aqueous solution is 1:(1-3), the chloride aqueous solution includes water, acid and chloride, and the concentration of acid in the chloride aqueous solution is 1-3 mol / L and the concentration of chloride ions is 1-3.5 mol / L; And / or, the chlorination treatment temperature is 50~70℃; and / or, the chlorination treatment time is 2~4h; and / or, the molar ratio of bismuth chloride to third water is 2:(1~1.2); and / or, the hydrolysis reaction temperature is 30~40℃; and / or, the hydrolysis reaction time is 20~40min; and / or, the molar ratio of BiOCl to carbonate in the BiOCl suspension is 2:(1~1.2); and / or, the carbonate is selected from any one or more of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and potassium bicarbonate; and / or, the precipitation reaction temperature is 30~40℃; and / or, the precipitation reaction time is 50~70min.

[0014] According to another aspect of the present invention, a platinum-bismuth alloy catalyst is provided, which is prepared by the aforementioned method for preparing platinum-bismuth alloy catalysts.

[0015] Furthermore, the bismuth content in the platinum-bismuth alloy catalyst is 30-39 wt%, and the platinum content is 1-10 wt%; and / or, the specific surface area of ​​the platinum-bismuth alloy catalyst is 300-700 m². 2 / g, pore size 5~15nm, pore volume 2~10cm³ 3 / g; and / or, the average particle size of the platinum-bismuth alloy in the platinum-bismuth alloy catalyst is 2~5nm; and / or, the half-wave potential of the platinum-bismuth alloy catalyst is 895~935mV; and / or, the oxygen reduction initiation potential of the platinum-bismuth alloy catalyst is 1010~1050mV.

[0016] According to another aspect of the invention, a direct methanol fuel cell is provided, comprising an anode, a proton exchange membrane, and a cathode, the cathode containing the aforementioned platinum-bismuth alloy catalyst.

[0017] Applying the technical solution of this invention, in step S1, the surface properties of carbon black are improved through acidification treatment, increasing the number of oxygen-containing functional groups on the surface. These functional groups are beneficial for promoting the interaction between the metal and the support, thereby improving the stability and activity of the catalyst. Calcination treatment helps to adjust the pore structure of the carbon black, forming a more suitable pore size distribution, thereby increasing the diffusion efficiency of reactants and improving the utilization efficiency of the catalyst. In step S2, the platinum source undergoes a metathesis reaction under the action of a precipitant and a pH adjuster, depositing platinum compounds on the surface of the pretreated carbon black. The presence of the first dispersant helps to improve the uniformity of the dispersion of platinum compounds and Bi₂O₂CO₃ on the surface of the pretreated carbon black, and refines the particle size of the platinum compounds. Using Bi₂O₂CO₃ as the bismuth source helps to form a platinum-bismuth alloy at a lower calcination temperature during subsequent calcination treatment, reducing the impact of temperature on the pore structure of carbon black compared to existing high-temperature treatment processes, thereby helping to improve the catalytic activity and stability of the catalyst. In steps S3 and S4, a reducing agent is used to reduce platinum ions to metallic platinum. The presence of a second dispersant helps to further reduce the particle size of metallic platinum and prevent particle agglomeration, thereby contributing to further improving the catalytic activity of the catalyst. In step S5, the catalyst precursor undergoes calcination treatment, resulting in the decomposition of Bi2O2CO3 and its co-formation with metallic platinum to form a platinum-bismuth alloy. The calcination treatment also promotes strong interactions between the metal and the carbon black support, removes residual organic matter and moisture, and thus helps to further improve the stability of the platinum-bismuth alloy catalyst. Therefore, the platinum-bismuth alloy catalyst prepared by the method of this application exhibits excellent electrocatalytic performance, demonstrating high catalytic activity and cycle stability. It possesses a good pore structure and a high specific surface area, which is beneficial for improving catalytic reaction efficiency. The preparation of Bi2O2CO3 from copper smelting white dust achieves high-value utilization of bismuth resources, effectively solving the problem of resource waste compared to existing technologies. Furthermore, this platinum-bismuth alloy catalyst can be widely used in the oxygen reduction reaction at the cathode of a direct methanol fuel cell. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A TEM image of the platinum-bismuth alloy catalyst in Example 1 of this application is shown;

[0020] Figure 2 The XRD pattern of the platinum-bismuth alloy catalyst in Example 1 of this application is shown;

[0021] Figure 3The diagram shows a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalyst in Example 1 and Comparative Example 1 before and after 5000 cycles of accelerated cyclic voltammetry aging. Figure 3 3a in the figure is a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalysts in Example 1 and Comparative Example 1 before 5000 cycles of accelerated cyclic voltammetry aging. Figure 3 3b in the figure is a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalysts in Example 1 and Comparative Example 1 after 5000 cycles of accelerated cyclic voltammetry aging.

[0022] Figure 4 The CV curves of the platinum-bismuth alloy catalysts in Examples 1, 2, and Comparative Example 1 of this application are shown. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] As analyzed in the background section of this application, platinum-based catalysts in the prior art have low catalytic activity and stability. To solve the above problems, this application provides a platinum-bismuth alloy catalyst, its preparation method, and a direct methanol fuel cell.

[0025] In a typical embodiment of this application, a method for preparing a platinum-bismuth alloy catalyst is provided, comprising: step S1, mixing raw materials including carbon black and an acidic aqueous solution and then subjecting them to acidification and calcination treatments sequentially to obtain pretreated carbon black; step S2, mixing raw materials including pretreated carbon black, Bi2O2CO3, platinum source, precipitant, pH adjuster, first dispersant and first water and then subjecting them to a metathesis reaction to obtain a suspension; step S3, mixing raw materials including a reducing agent, a second dispersant and second water to obtain a mixed solution; step S4, adding the suspension dropwise to the mixed solution to carry out a reduction reaction to obtain a catalyst precursor; and step S5, calcining the catalyst precursor under a first protective gas to obtain a platinum-bismuth alloy catalyst.

[0026] In step S1 of this application, acidification treatment improves the surface properties of carbon black, increasing the number of oxygen-containing functional groups on the surface. These functional groups facilitate the interaction between the metal and the support, enhancing the stability and activity of the catalyst. Calcination treatment helps adjust the pore structure of the carbon black, forming a more suitable pore size distribution, thereby increasing the diffusion efficiency of reactants and improving the utilization efficiency of the catalyst. In step S2, the platinum source undergoes a metathesis reaction under the action of a precipitant and a pH adjuster, depositing platinum compounds on the surface of the pretreated carbon black. The presence of the first dispersant helps improve the uniformity of the dispersion of platinum compounds and Bi₂O₂CO₃ on the surface of the pretreated carbon black, and refines the particle size of the platinum compounds. Using Bi₂O₂CO₃ as the bismuth source helps form a platinum-bismuth alloy at a lower calcination temperature during subsequent calcination treatment, reducing the influence of temperature on the pore structure of the carbon black, thereby contributing to improved catalytic activity and stability. In steps S3 and S4, a reducing agent is used to reduce platinum ions to metallic platinum. The presence of a second dispersant helps to further reduce the particle size of metallic platinum and prevent particle agglomeration, thereby contributing to further improvement of the catalyst's catalytic activity. In step S5, the catalyst precursor undergoes calcination treatment, causing Bi2O2CO3 to decompose and co-form a platinum-bismuth alloy with metallic platinum. The calcination treatment also promotes strong interactions between the metal and the carbon black support, removes residual organic matter and moisture, and thus helps to further improve the stability of the platinum-bismuth alloy catalyst. Therefore, the platinum-bismuth alloy catalyst prepared by the method of this application exhibits excellent electrocatalytic performance, demonstrating high catalytic activity and cycle stability. It possesses a good pore structure and a high specific surface area, which is beneficial for improving catalytic reaction efficiency. This platinum-bismuth alloy catalyst can be widely used in the oxygen reduction reaction at the cathode of a direct methanol fuel cell.

[0027] In some embodiments of this application, in step S1, the mass ratio of carbon black to the volume of the acidic aqueous solution is (5~15g):(100~300mL), the concentration of the acidic aqueous solution is 0.3~0.7mol / L; and / or, the acidification temperature is 110~130℃; and / or, the acidification time is 4~6h; and / or, the specific surface area of ​​the carbon black is 200~400m². 2 / g, pore size 3~10nm, pore volume 0.5~1.2cm³ 3 / g; and / or, the calcination temperature is 200~350℃; and / or, the calcination is carried out in a second protective gas at a heating rate of 3~7℃ / min; and / or, the calcination time is 2~4h.

[0028] Controlling the volume ratio of carbon black to acidic aqueous solutions (e.g., H2SO4, HNO3), the concentration of the acidic aqueous solution, and the temperature and time of acidification treatment within the aforementioned ranges helps optimize the number of oxygen-containing functional groups (carboxyl, hydroxyl, carbonyl, etc.) on the carbon black surface through oxidative etching, reducing inert carbon sites on the surface. This helps enhance the interaction between carbon black and metal. The oxygen-containing functional groups act as anchoring sites for the platinum source, the catalyst's active metal precursor, inhibiting the migration and aggregation of metal particles during the loading / reduction process through coordination, electrostatic adsorption, and hydrogen bonding, thus improving metal dispersion and ultimately enhancing the catalyst's cycle stability. Acidification etching forms micropores / mesopores on the carbon black surface, appropriately enlarging the pore size, increasing pore volume and specific surface area, and providing more active sites for metal deposition. Furthermore, acidification treatment improves the wettability of the support surface and enhances the impregnation efficiency of the precursor. This is because the surface of untreated carbon black is hydrophobic, making it difficult for acidic aqueous solutions to spread, resulting in uneven impregnation of the metal precursor. The polar functional groups introduced after acidification significantly enhance the hydrophilicity of the carbon black surface, allowing the acidic impregnation solution to fully wet the support and ensuring that the metal precursor is evenly distributed on the carbon black surface and within the pores, avoiding excessively high local metal concentrations that could lead to particle agglomeration. Controlling the specific surface area of ​​the carbon black within the aforementioned range helps provide more active sites for metal deposition, thereby contributing to improved catalytic activity. Controlling the pore size and pore volume of the carbon black within the aforementioned range facilitates sufficient contact between reactants and active sites during mass transfer, reducing mass transfer resistance and improving both catalytic efficiency and reaction rate. Controlling the temperature and time of calcination within the above range helps stabilize the microstructure of carbon black, enhance its thermal stability, avoid structural collapse or decomposition of surface functional groups during subsequent heat treatment, adjust the pore structure of carbon black to form a more suitable pore size distribution, remove residual acid and other organic matter from the surface of carbon black, purify the carrier surface, and avoid impurities interfering with the adsorption and catalytic reaction of metal precursors.

[0029] Including but not limited to, the second protective gas is selected from any one or more of nitrogen, argon and helium.

[0030] In some embodiments of this application, in step S2, the mass ratio of pretreated carbon black, Bi2O2CO3, and platinum source is (5~20):(1~15):(0.1~2); and / or, the mass ratio of platinum source, precipitant, and pH adjuster is (0.1~2):(0.1~0.5):(0.01~0.03); and / or, the mass ratio of platinum source, the mass of the first dispersant, and the volume of the first water is (0.1~2g):(40~70g):(140~160mL); and / or, the temperature of the metathesis reaction is 5~15℃; and / or, the time of the metathesis reaction is 20~40min; and / or, the metathesis reaction is carried out under stirring at a stirring rate of 300~350r / min.

[0031] Controlling the mass ratio of pretreated carbon black, Bi₂O₂CO₃, and platinum source within the aforementioned range helps to control the mass content of platinum and bismuth in the platinum-bismuth alloy catalyst within a suitable range. On one hand, during heat treatment, Bi₂O₂CO₃ thermally decomposes into bismuth oxide, which, with the aid of suitable carbon black, facilitates carbothermic reduction: Bi₂O₃ + 3C = 2Bi + 3CO, Bi₂O₃ + 3CO = 2Bi + 3CO₂, at a temperature ≥700℃. In a closed / flowing inert atmosphere, this facilitates the formation of an alloy between bismuth and platinum. Furthermore, at the platinum-bismuth bimetallic interface, electron transfer occurs (electrons from bismuth shift towards platinum), altering the d-band center position of platinum. This weakens the adsorption strength of reaction intermediates (such as oxygen-containing intermediates) on the Pt surface, preventing the active sites from being poisoned or covered, and simultaneously lowering the activation energy, thereby improving catalytic activity and selectivity (alcohol oxidation reaction). Simultaneously, Bi can regulate the electron density of Pt, inhibiting the oxidation of Pt nanoparticles and maintaining the metallic active centers of Pt, especially in acidic electrolytes. Furthermore, the Bi component (its carbonate precursor) can serve as isolation and anchoring sites for Pt particles, hindering their migration and aggregation during the loading / reduction / calcination / catalytic cycles, maintaining small particle size and high dispersion, and improving the catalyst's cycle stability and lifespan. Simultaneously, the Bi carbonate on the carbon black surface provides more active sites for Pt deposition, further improving Pt utilization and reducing the amount of Pt required.

[0032] Controlling the mass ratio of platinum source, precipitant, and pH adjuster within the above range helps improve the purity and quality of the product; this is because the platinum source (such as H₂PtCl₆) in aqueous solution is in the form of [PtCl₆]. 2-The degree of hydrolysis of platinum ions exists in the form of complex ions, and its degree is related to the pH value of the solution. When the pH is too low, the complex ions are highly stable and difficult to react with the precipitant, resulting in Pt residue. When the pH is too high, the Pt complex ions will undergo excessive hydrolysis to generate impurities such as hydroxyl Pt complexes and platinum hydroxide, or even undergo peptization, failing to form the target crystalline phase. Controlling the mass of the platinum source, the mass ratio of the first dispersant to the volume of the first water within the above range helps to improve the uniformity of the platinum compound deposition distribution and control the particle size of the platinum compound within a suitable range, thereby helping to improve the catalytic activity of the catalyst. The dispersant undergoes specific adsorption on the surface of the platinum compound particles through polar groups (such as carbonyl and carboxyl groups), forming a dense adsorption layer, generating steric hindrance, and simultaneously regulating the zeta potential of the particle surface, significantly weakening the van der Waals attraction between particles and inhibiting agglomeration. When the dispersant concentration is too low, the adsorption is insufficient, the steric hindrance is insufficient, and the particles are prone to collision and agglomeration. When the concentration is too high, the dispersant is prone to forming micelles, encapsulating particles or occupying active sites, affecting subsequent reactions. The volume of water determines the system concentration: too high a concentration increases particle collision frequency and the risk of agglomeration; too low a concentration results in low reaction efficiency and uneven particle size distribution. Therefore, precise control of the ratio of these three factors allows for synergistic optimization of the dispersant adsorption density and system concentration, thereby precisely regulating the nucleation and growth process of platinum compound particles and ensuring uniform deposition distribution and particle size within a suitable range. Controlling the temperature and time of the metathesis reaction within the above range helps to further refine the size of platinum compound particles, thus further improving the catalytic activity of the catalyst. Temperature determines the Pt ion diffusion rate: at a suitable temperature, the metathesis reaction rate is moderate, which is conducive to uniform nucleation of Pt atoms; if the temperature is too low, Pt ion diffusion is slow, the reaction is incomplete, and the particle size is uneven; if the temperature is too high, the crystal growth rate is much greater than the nucleation rate, easily forming large particles. In addition, if the time is too short, the metathesis reaction is incomplete, resulting in small and uneven particle size; if the time is too long, Ostwald ripening is likely to occur (small particles have higher solubility than large particles, small particles dissolve and deposit on the surface of large particles), leading to a wider particle size distribution and a decrease in specific surface area. Therefore, by controlling the temperature and time of the metathesis reaction within the above-mentioned range, the reaction kinetics rate and crystal nucleation-growth process can be synergistically regulated, Ostwald ripening can be suppressed, the particle size of platinum compounds can be further refined and the particle size distribution can be narrowed, thereby improving the catalytic activity of the catalyst.

[0033] In some embodiments of this application, in step S3, the ratio of the mass of the reducing agent, the mass of the second dispersant, and the volume of the second water is (1.5~2.0g):(0.1~0.3g):(50~150mL); and / or, the mixing in step S3 is stirring mixing at a stirring rate of 200~300r / min; and / or, in step S4, the rate at which the suspension is added is 1mL / min~30mL / min; and / or, the volume ratio of the suspension to the mixed solution is 1:(0.3~0.7); and / or, the temperature of the reduction reaction is 5~15℃; and / or, The reduction reaction time is calculated from the time the suspension is first added dropwise to the mixed solution, and the reduction reaction time is 50-70 min; and / or, in step S5, the first protective gas is selected from any one or more of nitrogen, helium, and argon, and the flow rate of the first protective gas is 50-100 mL / min; and / or, the heating rate of the calcination treatment is 3-7 °C / min; and / or, the calcination treatment temperature is 300-900 °C, preferably 300-400 °C; and / or, the calcination treatment time is 0.5-1.5 h; and / or, the calcination treatment is followed by natural cooling to 20-30 °C.

[0034] Controlling the mass of the reducing agent, the mass ratio of the second dispersant to the volume of the second water, the dropwise addition rate of the suspension, the volume ratio of the suspension to the mixed solution, and the temperature and time of the reduction reaction within the aforementioned ranges helps to improve the uniformity of the platinum particle distribution and reduce the size of the platinum particles, thereby contributing to improved catalytic activity. Controlling the heating rate, temperature, and time of the calcination treatment within the aforementioned ranges helps to promote the interaction between the metal and the carbon black support, forming a platinum-bismuth alloy, while simultaneously reducing the impact of the calcination treatment on the pore structure of the carbon black support.

[0035] When the suspension is added dropwise to the mixed solution (reducing agent), the reducing agent is in excess and is in the bulk phase (continuous phase). The precursor salt (chloroplatinic acid) enters slowly and dispersedly in droplet form. The system is always in a quasi-steady state with excess reducing agent and locally low precursor concentration. This is beneficial for controlling the nucleation-growth balance of Pt nanocrystals (the precursor droplets slowly enter the excess reducing agent, the local precursor concentration is low, the nucleation rate is uniform and controllable, and the explosive nucleation caused by oversaturation is avoided; the growth of newly formed nanocrystal nuclei is limited under the action of excess reducing agent and dispersant, resulting in smaller particle size and narrower particle size distribution), and inhibiting instantaneous mass nucleation and particle agglomeration. In contrast, with reverse addition (reducing agent added to the precursor): reverse addition is prone to local excess reducing agent, excessive instantaneous nucleation, uneven particle size and easy agglomeration; at the same time, the concentration gradient of the bulk precursor phase is large, resulting in uneven reduction. Meanwhile, the dispersant can be fully adsorbed on the surface of the newly formed particles, exerting the steric hindrance effect (DLVO theory). Furthermore, uniform and fine metal particles facilitate uniform solid-state diffusion during subsequent calcination, forming a platinum-bismuth alloy phase. (Slow heating reduces the temperature gradient, preventing localized overheating that could lead to carbon black support ablation or pore collapse; simultaneously, slow heating provides sufficient time for the solid-state diffusion of platinum and bismuth atoms, promoting uniform alloying; rapid heating can easily lead to uneven local alloying, or even the formation of elemental bismuth or platinum-bismuth oxide impurities. The temperature needs to be higher than the thermodynamic critical temperature for platinum-bismuth alloying to drive atomic diffusion and form the alloy phase; but lower than the graphitization / ablation temperature of the carbon black support (usually <800℃); in addition, if the time is too short, atomic diffusion will be insufficient and alloying will be incomplete; if the time is too long, particle sintering and support pore shrinkage are likely to occur.) At the same time, uniformly distributed particles can better interact with the support, increasing the loading strength, reducing particle shedding, and extending the catalyst's lifespan.

[0036] To further improve the catalytic activity and stability of the platinum-bismuth alloy catalyst, in some embodiments of this application, the carbon black is selected from any one or more of Ketjen black, Vulcan XC-72R carbon black, and acetylene black; and / or, the acid in the acidic aqueous solution is selected from any one or more of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, and hypochlorous acid; and / or, the platinum source is selected from any one or more of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, [Pt(acac)2], diammonium dinitrite platinum, and [Pt(CH3NH2)4][PtCl4]; and / or, the precipitant is selected from any one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium oxalate, ammonium acetate, ammonium chloride, and ammonia water; and / or, The pH adjuster is selected from any one or more of oxalic acid, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, ammonium carbonate, sodium carbonate, and sodium bicarbonate; and / or, the first dispersant is selected from any one or more of ethylene glycol, propylene glycol, polyethylene glycol, polyvinylpyrrolidone, and citric acid; and / or, the reducing agent is selected from any one or more of ascorbic acid, glucose, sodium borohydride, hydrazine hydrate, glutathione, sodium bisulfite, and sodium hypophosphite; and / or, the second dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, and sodium polyacrylate.

[0037] In some embodiments of this application, the second dispersant is a polymer dispersant with a number-average molecular weight of 10,000 to 25,000 g / mol.

[0038] Due to the characteristics of their molecular chains, polymer dispersants can form a protective film on the surface of metal particles, preventing particle aggregation through steric hindrance. Controlling the number-average molecular weight of the polymer dispersant within the aforementioned range helps to improve the dispersibility of platinum metal without affecting its activity, and also helps to control the particle size of platinum metal within a suitable range, thereby further enhancing the catalytic activity of the catalyst.

[0039] Through the combined effects of electrostatic repulsion and steric hindrance in its molecular structure, Pt nanoparticles achieve uniform nucleation, inhibit aggregation, and are stably dispersed in the liquid phase. Polyacrylic acid (PAA) is a water-soluble polyelectrolyte. In a reducing agent system, its carboxyl functional group dissociates: -COOH=-COO - +H + After dissociation, the PAA molecular chain carries a high density of negative charge, and the chain stretches due to electrostatic repulsion; low to medium molecular weight PAA will not become entangled due to excessive chain length; this is because of the carboxyl group (-COO) of PAA. -The PAA (particulate organic ether) can bind to the surface of newly formed Pt nanocrystal nuclei through coordination / electrostatic interactions. The Pt nanocrystal surface is positively charged in solution (or has a localized positive potential region), forming a strong adsorption with the negative charge of PAA. The PAA molecular chains adsorb onto the particle surface in a "ring-tail" manner, forming a dense charged polymer adsorption layer, achieving monolayer adsorption and avoiding steric hindrance failure caused by multilayer adsorption. After PAA adsorption, the platinum particle surface changes from weakly positive to strongly negatively charged, forming a diffused double layer (Stern layer + diffusion layer) on the platinum particle surface. That is, when two negatively charged particles approach each other, the double layers overlap, generating a strong electrostatic repulsion force, counteracting the van der Waals attraction between platinum particles and preventing collisional aggregation. Under the synergistic effect of this dual stabilizing mechanism, the second dispersant can inhibit the explosive nucleation and Ostwald ripening of platinum nanocrystal nuclei, thereby achieving uniform nucleation, particle size refinement, and narrow distribution of the platinum nanoparticles without interfering with the reduction reaction process.

[0040] In some embodiments of this application, the preparation method of Bi2O2CO3 includes: mixing white smoke dust generated during copper smelting with an inorganic acid aqueous solution and then performing acid leaching treatment to obtain acid leaching residue; mixing the acid leaching residue with a chloride salt aqueous solution and then performing chlorination treatment to obtain bismuth chloride; mixing bismuth chloride with third water and then performing a hydrolysis reaction to obtain BiOCl suspension; mixing the BiOCl suspension with carbonate and then performing a precipitation reaction to obtain Bi2O2CO3.

[0041] Inorganic acids are used to leach white dust, achieving preliminary separation of soluble elements such as Zn, Cd, Cu, and Fe. Simultaneously, bismuth is enriched in the leaching residue (i.e., selective enrichment of bismuth), which mainly exists in the form of bismuth oxide. The bismuth oxide in the leaching residue reacts with chloride ions in the chloride solution to generate bismuth chloride (i.e., Bi₂O₃ reacts with Cl⁻ in the chloride solution). - A coordination reaction occurs (Bi₂O₃ + 6HCl = 2BiCl₃ + 3H₂O), producing soluble BiCl₃ or the complex [BiCl₄]. - This process converts bismuth oxide to bismuth chloride, providing a soluble precursor for subsequent hydrolysis. Bismuth chloride then undergoes hydrolysis and precipitation (BiCl3 + H2O = BiOCl(s) + 2HCl, with BiOCl as an intermediate product; its layered structure facilitates the uniform release of Bi atoms during subsequent heat treatment, thus avoiding uneven alloy phases caused by excessively high local Bi concentrations; in the carbonate system, it reacts with CO3... 2- Precipitation transformation occurs: 2BiOCl + CO3 2- =Bi₂O₂CO₃ + 2Cl -Bi2O2CO3 is generated. This application proposes a multi-stage coupled separation-conversion process using copper smelting white dust (industrial solid waste) as a bismuth source, and applies the prepared Bi2O2CO3 to the preparation of a precursor for a platinum-bismuth alloy catalyst, realizing the high-value utilization of bismuth resources in copper smelting white dust and improving the comprehensive utilization rate of bismuth resources.

[0042] Furthermore, the layered metal precursor salt Bi₂O₂CO₃, in the preparation of platinum-bismuth alloy catalysts, achieves uniform dispersion of the active metal components, precise particle size control, and uniform formation of the alloy phase through the confinement effect, controllable release, and interface regulation of the layered structure, while simultaneously improving the stability and activity of the catalyst. This is because the layered structure forms a physical confinement barrier for the active metal platinum particles in the catalyst, limiting the migration distance of metal Pt atoms / Pt nuclei during reduction and calcination, and preventing particle collision and agglomeration. At the same time, the uniformly distributed metal species between the layers can directly form uniformly distributed nanoparticles in subsequent conversions without the need for additional dispersion processes. That is, during the reduction / calcination process, the layered precursor undergoes stepwise dissociation of the interlayer structure and release of metal species. The released Bi atoms and the simultaneously reduced Pt atoms undergo uniform solid-phase diffusion within the confined space, avoiding the formation of heterogeneous alloy phases or impurity phases caused by excessively high local Bi concentrations.

[0043] In addition, the surface of the lamellar precursor usually has a high density of active sites (such as oxygen vacancies and hydroxyl groups), which can form strong interfacial interactions (such as hydrogen bonds and coordination bonds) with the functional groups (such as carboxyl groups and hydroxyl groups) on the surface of the support (such as carbon black). At the same time, the spread of the lamellar structure on the surface of the support can form a uniform "precursor-support" composite interface, avoiding particle detachment caused by the weak interaction between metal particles and the surface of the support.

[0044] Including but not limited to, the inorganic acid in the above-mentioned inorganic acid aqueous solution is selected from any one or more of sulfuric acid, hydrochloric acid, perchloric acid and hypochlorous acid.

[0045] To improve the purity and yield of Bi2O2CO3, in some embodiments of this application, the bismuth content in the white dust is 1-15% by mass; and / or, the mass ratio of white dust to inorganic acid aqueous solution is 1:(2-5), and the concentration of inorganic acid in the inorganic acid aqueous solution is 0.3-0.7 mol / L; and / or, the acid leaching temperature is 30-90℃; and / or, the acid leaching time is 1-4 h; and / or, the acid leaching is carried out under stirring at a stirring rate of 200-400 r / min; and / or, the mass ratio of acid leaching residue to chloride aqueous solution is 1:(1-3), the chloride aqueous solution includes water, acid, and chloride, the concentration of acid in the chloride aqueous solution is 1-3 mol / L, and the concentration of chloride ions is... The concentration is 1~3.5 mol / L; and / or, the chlorination temperature is 50~70℃; and / or, the chlorination time is 2~4h; and / or, the molar ratio of bismuth chloride to third water is 2:(1~1.2); and / or, the hydrolysis temperature is 30~40℃; and / or, the hydrolysis time is 20~40min; and / or, the molar ratio of BiOCl to carbonate in the BiOCl suspension is 2:(1~1.2); and / or, the carbonate is selected from any one or more of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and potassium bicarbonate; and / or, the precipitation temperature is 30~40℃; and / or, the precipitation time is 50~70min.

[0046] Including but not limited to, the acids mentioned above are selected from any one or more of sulfuric acid, hydrochloric acid, perchloric acid, and hypochlorous acid; the chloride salts are selected from any one or more of sodium chloride, potassium chloride, and ammonium chloride.

[0047] In another typical embodiment of this application, a platinum-bismuth alloy catalyst is provided, which is prepared by the aforementioned method for preparing platinum-bismuth alloy catalysts.

[0048] Since the above-mentioned platinum-bismuth alloy catalyst is prepared using the preparation method of this application, the active metal in the catalyst has good uniformity of dispersion, suitable pore structure, high electrocatalytic activity and strong cycle stability.

[0049] In some embodiments of this application, the bismuth content in the platinum-bismuth alloy catalyst is 30-39 wt%, and the platinum content is 1-10 wt%; and / or, the specific surface area of ​​the platinum-bismuth alloy catalyst is 300-700 m². 2 / g, pore size 5~15nm, pore volume 2~10cm³ 3 / g; and / or, the average particle size of the platinum-bismuth alloy in the platinum-bismuth alloy catalyst is 2~5nm; and / or, the half-wave potential of the platinum-bismuth alloy catalyst is 895~935mV; and / or, the oxygen reduction initiation potential of the platinum-bismuth alloy catalyst is 1010~1050mV.

[0050] Platinum-bismuth alloy catalysts with the above parameters have higher catalytic activity and cycle stability, making them more suitable for the oxygen reduction reaction at the cathode of direct methanol fuel cells.

[0051] In another typical embodiment of this application, a direct methanol fuel cell is provided, comprising an anode, a proton exchange membrane, and a cathode, the cathode containing the aforementioned platinum-bismuth alloy catalyst.

[0052] Because the cathode of the aforementioned direct methanol fuel cell contains the platinum-bismuth alloy catalyst of this application, the direct methanol fuel cell has a long service life.

[0053] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0054] Example 1

[0055] Preparation of Bi₂O₂CO₃: 50g of white smoke dust generated during copper smelting, with a bismuth content of 12wt%, was acid-leached with a 0.5mol / L sulfuric acid aqueous solution at a stirring rate of 300r / min, a temperature of 60℃, and a time of 3h. The mass ratio of white smoke dust to sulfuric acid aqueous solution was 1:4, yielding acid-leached residue. Sulfuric acid, sodium chloride, and water were mixed to obtain a chloride salt aqueous solution with a sulfuric acid concentration of 2mol / L and a chloride ion concentration of 2.5mol / L. This chloride salt aqueous solution was used to chlorinate the acid-leached residue at a temperature of 60℃ for 2h, with a mass ratio of acid-leached residue to chloride salt aqueous solution of 1:2, yielding bismuth chloride. Bismuth chloride and water were mixed at a molar ratio of 2:1 and hydrolyzed at 35°C and 200 r / min for 30 min to obtain a BiOCl suspension. The BiOCl suspension was then mixed with (NH4)2CO3 at a molar ratio of 2:1 and hydrolyzed at 35°C and 200 r / min for 60 min. (NH4)2CO3 was added in multiple portions to control the pH of the system within the range of 1.5 to 2.5 until no bubbles or yellow precipitate were formed, reaching the endpoint. After solid-liquid separation, Bi2O2CO3 was obtained.

[0056] Step S1: Pretreatment of carbon black. Vulcan XC-72R carbon black was selected as the carrier material, with a specific surface area of ​​240 m². 2 / g, pore size 3.5nm, pore volume 0.85cm³ 3 / g. Mix 10g of carbon black with 100mL of 0.5mol / L sulfuric acid aqueous solution and place in a distillation flask. Acidify the mixture in an oil bath at 120℃, refluxing at 800rpm for 5h. Filter and wash with deionized water. During acidification, the surface properties of the carbon black are improved, increasing the number of oxygen-containing functional groups. These functional groups promote the interaction between the metal and the support, improving the stability and activity of the catalyst. After acidification, calcine the dried carbon black in a tube furnace under nitrogen atmosphere at 300℃ (5℃ / min) for 3h, then allow it to cool naturally to room temperature to obtain pretreated carbon black. Calcination helps adjust the pore structure of the carbon black, forming a more suitable pore size distribution, thereby increasing the diffusion efficiency of reactants and improving the utilization efficiency of the catalyst. It also removes residual acid and other organic matter from the carbon black surface and purifies the support surface.

[0057] Step S2: Preparation of suspension via metathesis reaction. Pretreated carbon black, Bi₂O₂CO₃, and platinum source were weighed in a ratio of 5.75:2.53:0.42. Chloroplatinic acid was chosen as the platinum source, ammonium chloride as the precipitant, ammonium carbonate as the pH adjuster, and ethylene glycol as the primary dispersant. 0.42 g of chloroplatinic acid, 0.3 g of ammonium chloride, 0.02 g of ammonium carbonate, 55 g of ethylene glycol, and 150 mL of water were mixed. Then, pretreated carbon black and Bi₂O₂CO₃ were added, and the mixture was subjected to a metathesis reaction at 10°C and a stirring rate of 300 r / min for 30 min to obtain a suspension. Under the action of the precipitant and pH adjuster, the platinum source undergoes a metathesis reaction, depositing platinum compounds on the surface of the pretreated carbon black. The presence of the primary dispersant helps to improve the uniformity of the dispersion of platinum compounds and Bi₂O₂CO₃ on the surface of the pretreated carbon black, and also refines the particle size of the platinum compounds. Using Bi2O2CO3 as the bismuth source helps to form a platinum-bismuth alloy at a lower calcination temperature during subsequent calcination, thus reducing the impact of temperature on the pore structure of carbon black.

[0058] Step S3: Prepare the mixed solution. Mix 1.8g ascorbic acid as a reducing agent, 0.2g polyacrylic acid (number average molecular weight of 10000g / mol) as a second dispersant with 100mL of second water, and stir at a stirring rate of 200~300r / min to obtain the mixed solution.

[0059] Step S4: Preparation of the catalyst precursor by reduction reaction. At 10°C, the suspension prepared in step S2 was added dropwise to the mixed solution prepared in step S3 at a rate of 15 mL / min, with a volume ratio of suspension to mixed solution of 1:0.5. Timing was maintained from the start of the dropwise addition of the suspension for 60 min. After the reaction was complete, the precursor was obtained by centrifugation, washing three times with anhydrous ethanol, and freeze-drying at -50°C for 12 h. During the reduction reaction, the reducing agent reduced platinum ions to metallic platinum. The presence of the second dispersant helps to further reduce the particle size of the metallic platinum and prevents particle aggregation, thereby contributing to further improvement of the catalyst's catalytic activity.

[0060] Step S5: Preparation of platinum-bismuth alloy catalyst by calcination. The catalyst precursor was heated from room temperature to 850℃ at a rate of 5℃ / min under a nitrogen protective gas atmosphere (nitrogen flow rate of 70 mL / min), held at this temperature for 1 h, and then cooled to room temperature in the furnace to obtain the platinum-bismuth alloy catalyst. The bismuth content was 37.25 wt%, the platinum content was 2.75 wt%, and the specific surface area was 569 m². 2 / g, pore size 7.9nm, pore volume 6.2cm³ 3 / g, the average particle size of the platinum-bismuth alloy is 3.5nm. During the calcination process, Bi2O2CO3 decomposes and co-forms with metallic platinum to form a platinum-bismuth alloy. Furthermore, the calcination process helps to promote strong interactions between the metal and the carbon black support, remove residual organic matter and moisture, thereby contributing to further improvement in the stability of the platinum-bismuth alloy catalyst.

[0061] Example 2

[0062] The difference from Example 1 is that the acidification temperature was 110°C and the acidification time was 6 hours, ultimately yielding a platinum-bismuth alloy catalyst.

[0063] Example 3

[0064] The difference from Example 1 is that the acidification temperature was 130°C and the acidification time was 4 hours, ultimately yielding a platinum-bismuth alloy catalyst.

[0065] Example 4

[0066] The difference from Example 1 is that the acidification temperature was 140°C and the acidification time was 3 hours, ultimately yielding a platinum-bismuth alloy catalyst.

[0067] Example 5

[0068] The difference from Example 1 is that the calcination temperature was 200°C and the calcination time was 4 hours, ultimately yielding a platinum-bismuth alloy catalyst.

[0069] Example 6

[0070] The difference from Example 1 is that the calcination temperature was 350°C and the calcination time was 2 hours, ultimately yielding a platinum-bismuth alloy catalyst.

[0071] Example 7

[0072] The difference from Example 1 is that the calcination temperature was 400°C and the calcination time was 1 hour, ultimately yielding a platinum-bismuth alloy catalyst.

[0073] Example 8

[0074] The difference from Example 1 is that the mass of carbon black after pretreatment is 5.75g, the mass of Bi2O2CO3 is 1.17g, the mass of chloroplatinic acid is 1.53g, and the final product is a platinum-bismuth alloy catalyst with a bismuth content of 25wt% and a platinum content of 15wt%.

[0075] Example 9

[0076] The difference from Example 1 is that the mass of carbon black after pretreatment is 5.75g, the mass of Bi2O2CO3 is 1.824g, the mass of chloroplatinic acid is 0.102g, and the final product is a platinum-bismuth alloy catalyst with a bismuth content of 39wt% and a platinum content of 1wt%.

[0077] Example 10

[0078] The difference from Example 1 is that the mass of carbon black after pretreatment is 5.75g, the mass of Bi2O2CO3 is 1.41g, the mass of chloroplatinic acid is 1.02g, and the final product is a platinum-bismuth alloy catalyst with a bismuth content of 30wt% and a platinum content of 10wt%.

[0079] Example 11

[0080] The difference from Example 1 is that the calcination temperature was 300°C and the calcination time was 1.5 hours, ultimately yielding a platinum-bismuth alloy catalyst with a specific surface area of ​​351 m². 2 / g, pore size 10.8nm, pore volume 3.4cm³ 3 / g.

[0081] Example 12

[0082] The difference from Example 1 is that the calcination temperature was 400°C and the calcination time was 0.5 h, ultimately yielding a platinum-bismuth alloy catalyst with a specific surface area of ​​367 m². 2 / g, pore size 9.7nm, pore volume 3.9cm³ 3 / g.

[0083] Example 13

[0084] The difference from Example 1 is that the calcination temperature was 500°C and the calcination time was 0.3 h, ultimately yielding a platinum-bismuth alloy catalyst with a specific surface area of ​​426 m². 2 / g, pore size 9.2nm, pore volume 4.5cm³ 3 / g.

[0085] Example 14

[0086] The difference from Example 1 lies in the preparation of Bi₂O₂CO₃: 50g of white smoke dust generated during copper smelting, with a bismuth content of 15wt%, was subjected to acid leaching with a 0.7mol / L sulfuric acid aqueous solution at 30°C for 4 hours, with a mass ratio of white smoke dust to sulfuric acid aqueous solution of 1:5, yielding acid-leached residue. Sulfuric acid, sodium chloride, and water were mixed to obtain a chloride salt aqueous solution with a sulfuric acid concentration of 1mol / L and a chloride ion concentration of 3.5mol / L. This chloride salt aqueous solution was used to chlorinate the acid-leached residue at 50°C for 4 hours, with a mass ratio of acid-leached residue to chloride salt aqueous solution of 1:1, yielding bismuth chloride. Bismuth chloride and water were mixed at a molar ratio of 2:1.2 and hydrolyzed at 30°C and 200 r / min for 40 min to obtain a BiOCl suspension. The BiOCl suspension was then mixed with (NH4)2CO3 at a molar ratio of 2:1.1 and hydrolyzed at 40°C and 200 r / min for 50 min. (NH4)2CO3 was added in multiple portions to control the pH of the system within the range of 1.5 to 2.5 until no bubbles or yellow precipitate formed, reaching the endpoint. After solid-liquid separation, Bi2O2CO3 was obtained.

[0087] Carbon black pretreatment: 6g of Vulcan XC-72R carbon black (specific surface area 240m²) was used. 2 / g, pore size 3.5nm, pore volume 0.85cm³ 3 The carbon black was prepared by placing 100 mL of 0.3 mol / L sulfuric acid aqueous solution (g) and 100 mL of 0.3 mol / L sulfuric acid aqueous solution in a distillation flask and acidifying it in an oil bath at 120 °C. After reflux at 800 r / min for 5 h, it was washed with deionized water, dried, and then calcined in a tube furnace at 300 °C for 3 h under nitrogen. After natural cooling to room temperature, the pretreated carbon black was obtained.

[0088] Preparation of catalyst precursor: 5.75 g of pretreated carbon black, 1.64 g of Bi₂O₂CO₃, 0.51 g of chloroplatinic acid, 0.3 g of ammonium chloride, 0.03 g of ammonium carbonate, 44.5 g of ethylene glycol, and 160 mL of water were mixed and subjected to a metathesis reaction at 15 °C for 20 min to obtain a 200 mL suspension. 1.76 g of ascorbic acid, 0.3 g of polyacrylic acid (number average molecular weight of 25000 g / mol), and 100 mL of water were mixed to obtain a 100 mL mixed solution. Under stirring at 300 rpm, 200 mL of the above suspension was added dropwise to 100 mL of the above mixed solution at a rate of 10 mL / min. A reduction reaction was carried out at 15 °C for 50 min. The reduction reaction time was calculated from the time the suspension was added dropwise to the mixed solution. The mixture was then centrifuged, washed three times with anhydrous ethanol, and freeze-dried at -50 °C for 12 h to obtain the catalyst precursor.

[0089] Catalyst preparation: The catalyst precursor obtained above was transferred to a tube furnace, nitrogen gas was introduced, and the temperature was increased from 25℃ to 800℃ at a heating rate of 5℃ / min for calcination. The temperature was held for 1 hour, and after natural cooling to room temperature, a platinum-bismuth alloy catalyst was obtained. The bismuth content was 35wt%, the platinum content was 5wt%, and the specific surface area was 528 m². 2 / g, pore size 6.2nm, pore volume 5.9cm³ 3 / g, the average particle size of the platinum-bismuth alloy is 3.8nm.

[0090] Example 15

[0091] The difference from Example 1 lies in the preparation of Bi₂O₂CO₃: 50g of white smoke dust generated during copper smelting, with a bismuth content of 1wt%, was subjected to acid leaching with a 0.3mol / L sulfuric acid aqueous solution at 85°C for 1 hour, with a mass ratio of white smoke dust to sulfuric acid aqueous solution of 1:2, yielding acid-leached residue. Sulfuric acid, sodium chloride, and water were mixed to obtain a chloride salt aqueous solution with a sulfuric acid concentration of 3mol / L and a chloride ion concentration of 1mol / L. This chloride salt aqueous solution was used to chlorinate the acid-leached residue at 70°C for 2 hours, with a mass ratio of acid-leached residue to chloride salt aqueous solution of 1:3, yielding bismuth chloride. Bismuth chloride and water were mixed at a molar ratio of 2:1.1 and hydrolyzed at 40°C and 200 r / min for 20 min to obtain a BiOCl suspension. The BiOCl suspension was then mixed with (NH4)2CO3 at a molar ratio of 2:1.2 and hydrolyzed at 30°C and 200 r / min for 70 min. (NH4)2CO3 was added in multiple portions to control the pH of the system within the range of 1.5 to 2.5 until no bubbles or yellow precipitate formed, reaching the endpoint. After solid-liquid separation, Bi2O2CO3 was obtained.

[0092] Carbon black pretreatment: 15g of Vulcan XC-72R carbon black (specific surface area 240m²) was used. 2 / g, pore size 3.5nm, pore volume 0.85cm³ 3 The carbon black was prepared by placing 100 mL of 0.7 mol / L sulfuric acid aqueous solution (g) and 100 mL of 0.7 mol / L sulfuric acid aqueous solution in a distillation flask and acidifying it in an oil bath at 120 °C. After reflux at 800 r / min for 5 h, it was washed with deionized water, dried, and then calcined in a tube furnace at 300 °C for 3 h under nitrogen. After natural cooling to room temperature, the pretreated carbon black was obtained.

[0093] Preparation of catalyst precursor: 5.75 g of pretreated carbon black, 1.31 g of Bi₂O₂CO₃, 1.22 g of chloroplatinic acid, 0.3 g of ammonium chloride, 0.01 g of ammonium carbonate, 66.8 g of ethylene glycol, and 140 mL of water were mixed and subjected to a metathesis reaction at 5 °C for 40 min to obtain a 200 mL suspension. 1.76 g of ascorbic acid, 0.1 g of polyacrylic acid (number average molecular weight of 10000 g / mol), and 100 mL of water were mixed to obtain a 100 mL mixed solution. Under stirring at 300 rpm, 200 mL of the above suspension was added dropwise to 100 mL of the above mixed solution at a rate of 10 mL / min. A reduction reaction was carried out at 5 °C for 70 min. The reduction reaction time was calculated from the time the suspension was added dropwise to the mixed solution. The mixture was then centrifuged, washed three times with anhydrous ethanol, and freeze-dried at -50 °C for 12 h to obtain the catalyst precursor.

[0094] Catalyst preparation: The catalyst precursor obtained above was transferred to a tube furnace, nitrogen gas was introduced, and the temperature was increased from 25℃ to 800℃ at a heating rate of 5℃ / min for calcination. The temperature was held for 1 hour, and after natural cooling to room temperature, a platinum-bismuth alloy catalyst was obtained. The bismuth content was 28wt%, the platinum content was 12wt%, and the specific surface area was 541 m². 2 / g, pore size 6.8nm, pore volume 6.1cm³ 3 / g, the average particle size of the platinum-bismuth alloy is 3.9nm.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the acidification treatment of Vulcan XC-72R carbon black was omitted, and a platinum-bismuth alloy catalyst was finally obtained.

[0097] Comparative Example 2

[0098] The difference from Example 1 is that the calcination treatment of Vulcan XC-72R carbon black was omitted, and a platinum-bismuth alloy catalyst was finally obtained.

[0099] Comparative Example 3

[0100] The difference from Example 1 is that the addition of ethylene glycol and polyacrylic acid was omitted, resulting in a platinum-bismuth alloy catalyst.

[0101] Comparative Example 4

[0102] The difference from Example 1 is that bismuth chloride is used instead of Bi2O2CO3 to finally obtain a platinum-bismuth alloy catalyst.

[0103] Performance testing

[0104] Hole volume: Tested according to GB / T 7702.20-2025.

[0105] Aperture: Tested according to GB / T 20042.4-2025.

[0106] Specific surface area: Tested according to GB / T 20042.4-2025.

[0107] The mass content of bismuth and platinum in the platinum-bismuth alloy catalyst was determined by the methods specified in GB / T 43901-2024 and GB / T 15072.3-2025.

[0108] Electrochemical tests were performed on the platinum-bismuth alloy catalysts prepared in the examples and comparative examples. A rotating ring-disk electrode (RRDE) was used. 5 mg of catalyst sample was weighed and added to a 2 mL centrifuge tube, followed by 500 μL of deionized water, 500 μL of ethanol dispersion, and then 30 μL of 5% (v / v) Nafion solution. The centrifuge tube was placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz for 30 min to ensure thorough dispersion of the catalyst in the mixed solvent, yielding catalyst ink. 20 μL of the catalyst ink was then spin-coated onto the RRDE surface and allowed to air dry to obtain an electrode loaded with the catalyst sample. High-purity oxygen was continuously bubbled into a 0.1 mol / L HClO4 electrolyte for 30 min before testing. The scan rate was 100 mV / s. The half-wave potential, oxygen reduction initiation potential, and activity decay rate after 5000 cycles were measured. The test results are shown in Table 1.

[0109] Table 1

[0110]

[0111] Figure 1 The image shows a TEM image of the platinum-bismuth alloy catalyst in Example 1 of this application. As can be seen from the image, the platinum-bismuth alloy particles prepared by the preparation method of this application are relatively uniformly distributed on the carbon black support, with an average particle size of 3.5 nm and relatively uniform particle size.

[0112] Figure 2 The image shows the XRD pattern of the platinum-bismuth alloy catalyst in Example 1 of this application. As can be seen from the image, the platinum-bismuth alloy prepared by the preparation method of this application in Example 1 exhibits the characteristic diffraction peaks of platinum-bismuth alloy, indicating that the platinum-bismuth alloy phase structure was constructed by the preparation method described in this application.

[0113] Figure 3 This is a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalyst in Example 1 and Comparative Example 1 of this application before and after 5000 cycles of accelerated cyclic voltammetry aging. Figure 33a in the figure is a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalysts in Example 1 and Comparative Example 1 before 5000 cycles of accelerated cyclic voltammetry aging. Figure 3 Figure 3b shows a comparison of the oxygen reduction reaction polarization curves of the platinum-bismuth alloy catalysts in Example 1 and Comparative Example 1 after 5000 cycles of accelerated cyclic voltammetry aging. The comparison results show that the catalyst in Example 1 still maintains high catalytic activity after aging, and the performance degradation is significantly lower than that in Comparative Example 1. This phenomenon can be attributed to two synergistic effects: First, the acid-treated support shows the formation of more active sites, which has a stronger anchoring effect on Pt-based active metal particles compared to the untreated support, effectively inhibiting particle migration and agglomeration; Second, the layered structure of the metal precursor salt Bi₂O₂CO₃ provides a confined growth space for the active metal Pt, significantly improving the structural stability and catalytic durability of Pt nanoparticles, thereby ensuring a higher utilization rate of the catalyst during long-term operation.

[0114] Figure 4 The cyclic voltammetry (CV) test results for the catalysts of Examples 1, 2, and Comparative Example 1 are presented. With the positive sweep peak current as the evaluation index, the mass activities of methanol oxidation for the three catalysts are 1055 mA / mg Pt, 704 mA / mg Pt, and 395 mA / mg Pt, respectively. The data show that the methanol oxidation catalytic activities of the catalysts of Examples 1 and 2 are significantly better than those of Comparative Example 1, which confirms that the preparation strategy adopted in this application (including support modification and layered precursor regulation) can effectively optimize the electronic structure and surface adsorption characteristics of Pt-based active metals and significantly improve their catalytic activity.

[0115] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0116] In step S1 of this application, acidification treatment improves the surface properties of carbon black, increasing the number of oxygen-containing functional groups on the surface. These functional groups facilitate the interaction between the metal and the support, enhancing the stability and activity of the catalyst. Calcination treatment helps adjust the pore structure of the carbon black, forming a more suitable pore size distribution, thereby increasing the diffusion efficiency of reactants and improving the utilization efficiency of the catalyst. In step S2, the platinum source undergoes a metathesis reaction under the action of a precipitant and a pH adjuster, depositing platinum compounds on the surface of the pretreated carbon black. The presence of the first dispersant helps improve the uniformity of the dispersion of platinum compounds and Bi₂O₂CO₃ on the surface of the pretreated carbon black, and refines the particle size of the platinum compounds. Using Bi₂O₂CO₃ as the bismuth source helps form a platinum-bismuth alloy at a lower calcination temperature during subsequent calcination treatment, reducing the influence of temperature on the pore structure of the carbon black, thereby contributing to improved catalytic activity and stability. In steps S3 and S4, a reducing agent is used to reduce platinum ions to metallic platinum. The presence of a second dispersant helps to further reduce the particle size of metallic platinum and prevent particle agglomeration, thereby contributing to further improvement of the catalyst's catalytic activity. In step S5, the catalyst precursor undergoes calcination treatment, causing Bi2O2CO3 to decompose and co-form a platinum-bismuth alloy with metallic platinum. The calcination treatment also promotes strong interactions between the metal and the carbon black support, removes residual organic matter and moisture, and thus helps to further improve the stability of the platinum-bismuth alloy catalyst. Therefore, the platinum-bismuth alloy catalyst prepared by the method of this application exhibits excellent electrocatalytic performance, demonstrating high catalytic activity and cycle stability. It possesses a good pore structure and a high specific surface area, which is beneficial for improving catalytic reaction efficiency. This platinum-bismuth alloy catalyst can be widely used in the oxygen reduction reaction at the cathode of a direct methanol fuel cell.

[0117] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a platinum-bismuth alloy catalyst, characterized in that, include: Step S1: The raw materials, including carbon black and acidic aqueous solution, are mixed and then subjected to acidification and calcination treatments in sequence to obtain pretreated carbon black. Step S2 involves mixing the raw materials, including the pretreated carbon black, Bi2O2CO3, platinum source, precipitant, pH adjuster, first dispersant, and first water, and then carrying out a metathesis reaction to obtain a suspension. Step S3: Mix the raw materials including the reducing agent, the second dispersant, and the second water to obtain a mixed solution; Step S4: The suspension is added dropwise to the mixed solution to carry out a reduction reaction, thereby obtaining the catalyst precursor; Step S5: The catalyst precursor is calcined under a first protective gas to obtain a platinum-bismuth alloy catalyst. The mass ratio of the pretreated carbon black, the Bi2O2CO3 and the platinum source is (5~20):(1~15):(0.1~2); the calcination temperature is 200~350℃; and the calcination temperature is 300~900℃.

2. The method for preparing the platinum-bismuth alloy catalyst according to claim 1, characterized in that, In step S1, the mass ratio of the carbon black to the volume of the acidic aqueous solution is (5~15g):(100~300mL), the concentration of the acidic aqueous solution is 0.3~0.7mol / L; and / or, the acidification treatment temperature is 110~130℃; and / or, the acidification treatment time is 4~6h. And / or, the specific surface area of ​​the carbon black is 200~400m². 2 / g, pore size 3~10nm, pore volume 0.5~1.2cm³ 3 / g; And / or, the calcination treatment is carried out in a second protective gas at a heating rate of 3~7℃ / min, and / or, the calcination treatment time is 2~4h.

3. The method for preparing the platinum-bismuth alloy catalyst according to claim 1, characterized in that, In step S2, the mass ratio of the platinum source, the precipitant, and the pH adjuster is (0.1~2):(0.1~0.5):(0.01~0.03); and / or, the mass ratio of the platinum source, the mass of the first dispersant, and the volume of the first water is (0.1~2g):(40~70g):(140~160mL). And / or, the temperature of the metathesis reaction is 5~15℃; and / or, the time of the metathesis reaction is 20~40min; and / or, the metathesis reaction is carried out under stirring at a stirring rate of 300~350r / min.

4. The method for preparing the platinum-bismuth alloy catalyst according to any one of claims 1 to 3, characterized in that, In step S3, the ratio of the mass of the reducing agent, the mass of the second dispersant, and the volume of the second water is (1.5~2.0g):(0.1~0.3g):(50~150mL); and / or, the mixing in step S3 is stirring mixing at a stirring rate of 200~300r / min. And / or, in step S4, the rate at which the suspension is added is 1 mL / min to 30 mL / min; and / or, the volume ratio of the suspension to the mixed solution is 1:(0.3 to 0.7); and / or, the temperature of the reduction reaction is 5 to 15°C; and / or, the time of the reduction reaction is calculated from the start of the addition of the suspension to the mixed solution, and the time of the reduction reaction is 50 to 70 min; And / or, in step S5, the first protective gas is selected from any one or more of nitrogen, helium, and argon, and the flow rate of the first protective gas is 50~100 mL / min; and / or, the heating rate of the calcination treatment is 3~7℃ / min; and / or, the calcination treatment time is 0.5~1.5h; and / or, the calcination treatment is followed by natural cooling to 20~30℃.

5. The method for preparing the platinum-bismuth alloy catalyst according to any one of claims 1 to 3, characterized in that, The carbon black is selected from any one or more of Ketjen black, Vulcan XC-72R carbon black, and acetylene black; and / or, the acid in the acidic aqueous solution is selected from any one or more of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, and hypochlorous acid; and / or, the platinum source is selected from any one or more of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, [Pt(acac)2], diammonium dinitrite platinum, and [Pt(CH3NH2)4][PtCl4]; and / or, the precipitant is selected from any one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium oxalate, ammonium acetate, ammonium chloride, and ammonia water; and / or, the... The pH adjuster is selected from any one or more of oxalic acid, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, ammonium carbonate, sodium carbonate, and sodium bicarbonate; and / or, the first dispersant is selected from any one or more of ethylene glycol, propylene glycol, polyethylene glycol, polyvinylpyrrolidone, and citric acid; and / or, the reducing agent is selected from any one or more of ascorbic acid, glucose, sodium borohydride, hydrazine hydrate, glutathione, sodium bisulfite, and sodium hypophosphite; and / or, the second dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, and sodium polyacrylate.

6. The method for preparing the platinum-bismuth alloy catalyst according to any one of claims 1 to 3, characterized in that, The preparation method of Bi2O2CO3 includes: The white smoke dust generated during copper smelting is mixed with an inorganic acid aqueous solution and then subjected to acid leaching to obtain acid leaching residue. The acid leaching residue is then mixed with a chloride salt aqueous solution and subjected to chlorination to obtain bismuth chloride. The bismuth chloride and third water are mixed and hydrolyzed to obtain a BiOCl suspension. The BiOCl suspension is then mixed with carbonate and precipitated to obtain Bi2O2CO3.

7. The method for preparing the platinum-bismuth alloy catalyst according to claim 6, characterized in that, The bismuth content in the white smoke dust is 1-15% by mass; and / or, the mass ratio of the white smoke dust to the inorganic acid aqueous solution is 1:(2-5), and the concentration of the inorganic acid in the inorganic acid aqueous solution is 0.3-0.7 mol / L; and / or, the temperature of the acid leaching treatment is 30-90℃; and / or, the time of the acid leaching treatment is 1-4 h; and / or, the acid leaching treatment is carried out under stirring at a stirring rate of 200-400 r / min. And / or, the mass ratio of the acid leaching residue to the chloride aqueous solution is 1:(1~3), the chloride aqueous solution comprises water, acid and chloride, the concentration of acid in the chloride aqueous solution is 1~3 mol / L, and the concentration of chloride ions is 1~3.5 mol / L; and / or, the chlorination treatment temperature is 50~70℃; and / or, the chlorination treatment time is 2~4 h; And / or, the molar ratio of bismuth chloride to the third water is 2:(1~1.2); and / or, the temperature of the hydrolysis reaction is 30~40℃; and / or, the time of the hydrolysis reaction is 20~40min; And / or, the molar ratio of BiOCl to carbonate in the BiOCl suspension is 2:(1~1.2); and / or, the carbonate is selected from any one or more of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and potassium bicarbonate; and / or, the precipitation reaction temperature is 30~40℃; and / or, the precipitation reaction time is 50~70min.

8. A platinum-bismuth alloy catalyst, characterized in that, The platinum-bismuth alloy catalyst is prepared by the method for preparing platinum-bismuth alloy catalyst according to any one of claims 1 to 7.

9. The platinum-bismuth alloy catalyst according to claim 8, characterized in that, The platinum-bismuth alloy catalyst contains 30-39 wt% bismuth and 1-10 wt% platinum; and / or, the platinum-bismuth alloy catalyst has a specific surface area of ​​300-700 m². 2 / g, pore size 5~15nm, pore volume 2~10cm³ 3 / g; and / or, the average particle size of the platinum-bismuth alloy in the platinum-bismuth alloy catalyst is 2~5nm; and / or, the half-wave potential of the platinum-bismuth alloy catalyst is 895~935mV; and / or, the oxygen reduction initiation potential of the platinum-bismuth alloy catalyst is 1010~1050mV.

10. A direct methanol fuel cell, comprising an anode, a proton exchange membrane, and a cathode, characterized in that, The cathode contains the platinum-bismuth alloy catalyst as described in claim 8 or 9.

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