An oxide-modified carbon-supported platinum catalyst for fuel cells and a method for preparing the same

Abstract

The present application relates to a kind of oxide modified carbon-supported platinum catalyst for fuel cell and its preparation method.The present application is directed to the problem that high potential of proton exchange membrane fuel cell leads to serious corrosion of catalyst carrier, by surface oxide modification of catalyst carbon carrier, then in situ load platinum nanoparticles.The prepared platinum nanoparticles are uniformly dispersed, and the particle size is 2-5nm.The modification of carbon carrier surface oxide avoids the direct exposure of carbon material under high potential, due to the presence of oxide, at the same time, the anchoring effect of carrier to platinum is enhanced, the dispersity of catalyst is improved, the activity of catalyst is improved, the high potential stability of catalyst is improved, and the service life of catalyst is improved.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and fuel cell technology, specifically to an oxide-modified carbon-supported platinum catalyst for fuel cells and its preparation method. Background Technology

[0002] In recent years, with the increasing prominence of energy and environmental issues, the research and development of new energy vehicles has become a global hot topic. Fuel cell vehicles (FCVs), powered by proton exchange membrane fuel cells (PEMFCs), are considered ideal tools for future road transportation due to their numerous advantages, including fast start-up, high energy conversion efficiency, long driving range, and zero emissions. However, their further large-scale commercialization still faces three major technological bottlenecks: cost, performance, and durability.

[0003] A significant challenge for carbon materials used as catalyst supports in fuel cells is corrosion resistance. Prolonged start-up / shutdown cycles, potentiodynamic cycling, and high-potential operation accelerate the corrosion of carbon catalyst supports. This corrosion leads to the agglomeration and growth of noble metal particles, reducing the active sites for electrochemical reactions. Furthermore, changes in the membrane electrode structure caused by carbon corrosion affect proton, electron, and water vapor transport, resulting in irreversible performance losses. Therefore, the research and development of catalyst supports resistant to high-potential corrosion has been a crucial focus for researchers in this field.

[0004] To improve the durability of platinum-based catalyst supports, amorphous carbon is typically subjected to high-temperature graphitization to enhance its resistance to high-potential corrosion. However, graphitization leads to a sharp decrease in the specific surface area of ​​the carbon material and collapse of the pore volume, affecting the uniformity of the Pt-based nanoparticle loading and thus impacting the catalyst's catalytic activity. Alternatively, metal oxides have been used as supports for platinum-based catalysts, achieving better high-potential stability. However, the poor conductivity of metal oxides results in high electronic resistance and low catalyst activity, making them unsuitable for commercial applications. Chinese invention patent application CN202110710978.7 discloses a graphitized carbon support for hydrogen fuel cells, its preparation method, and a battery catalyst. The catalyst support is graphitized carbon, the catalyst preparation system is an ethylene glycol system, and the catalyst is heated by microwave heating, which differs from the water system used in this invention. Furthermore, the ethylene glycol on the surface of the synthesized particles is difficult to clean thoroughly. Chinese invention patent application number CN201710903746.7 proposes a core-shell structure oxide-supported Pt catalyst, its preparation method and application; the catalyst support is a core-shell structure SiO2 / TiO2, and its Pt content is only 0.5% to 1%; on the one hand, a completely oxide support is difficult to meet the requirements of electron conduction in fuel cells, and on the other hand, the too low platinum content is difficult to meet the requirements of catalytic reaction. Summary of the Invention

[0005] To address the problem of high electrochemical corrosion resistance in existing catalyst supports, the present invention aims to provide a simple preparation method for an oxide-modified carbon-supported platinum catalyst for fuel cells, which exhibits high activity and resistance to high electrochemical corrosion, as well as its preparation method.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention relates to an oxide-modified carbon-supported platinum catalyst for fuel cells, wherein the catalyst uses oxide-modified carbon black as a support and has monodisperse Pt nanoparticles uniformly dispersed on the surface of the support; wherein the oxide is an acid-resistant oxide nanoparticle uniformly dispersed on the surface of the carbon black.

[0008] The Pt nanoparticles have a particle size of 1.5-5 nm;

[0009] The catalyst contains 30% to 70% carbon black by mass.

[0010] In oxide-modified carbon black, the size of the oxide nanoparticles is 5-20 nm, and the oxide accounts for 5% to 30% of the mass of the carbon black.

[0011] In some embodiments, the Pt nanoparticles are selected to have a particle size of 2.5-4.0 nm. The carbon black content in the catalyst is selected to be 40 wt% to 60 wt%. The oxide nanoparticles are selected to have a size of 10-15 nm. The oxide accounts for 10 wt% to 20 wt% of the carbon black by mass.

[0012] Secondly, the present invention also relates to a method for preparing an oxide-modified carbon-supported platinum catalyst for fuel cells, the method comprising the following steps:

[0013] a1. Disperse toner in a solvent using ultrasound and stir at room temperature to form mixture A;

[0014] a2. A transition metal chloride is dissolved in a solvent to obtain solution B; solution B is added dropwise to the mixture A at a uniform rate. After the addition is complete, the pH is adjusted to 12-14, and the reaction continues at room temperature; after sedimentation, the supernatant is removed, the reaction product is filtered and washed, dried under vacuum at 80°C for 8-12 hours, and ground into powder to obtain oxide-modified carbon support C.

[0015] a3. The oxide-modified carbon support C is ultrasonically stirred and uniformly dispersed in deionized water to form a mixture D;

[0016] a4. Platinum salt is dissolved in deionized water to obtain a solution E containing Pt salt; and this solution is added to the mixture D under stirring to adjust the pH of the mixture to 11-13.

[0017] a5. Stir at room temperature, add reducing agent, then purge with an inert atmosphere, then heat to a certain temperature and maintain the temperature to continue the reaction for a period of time; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain the oxide-modified carbon-supported platinum catalyst.

[0018] As one implementation, the toner in step a1 is one or a mixture of several selected from acetylene black, EC300J, EC600J, Vulcan XC-72, black pearls, carbon nanotubes, graphitized carbon powder, and graphene. More preferably, the conductive toner is one or a mixture of several selected from acetylene black, EC300J, EC600J, Vulcan XC-72, and graphitized carbon powder.

[0019] As one embodiment, the solvent in step a1 is selected from one or a mixture of several of deionized water, anhydrous ethanol, isopropanol, n-propanol, and n-butanol. More preferably, the solvent in step a1 is deionized water and anhydrous ethanol, and even more preferably, deionized water.

[0020] As one embodiment, the solid content in mixture A is 10 mg / mL to 80 mg / mL. Preferably, the solid content in mixture A is 20 mg / mL to 50 mg / mL. A solid content in mixture A below 10 mg / mL is not conducive to the batch preparation of the catalyst.

[0021] As one implementation scheme, the ultrasonic dispersion power in step a1 is 100-500W and the time is 10-60min.

[0022] As one implementation method, in step a1, the mixture is stirred at room temperature for 50-70 minutes.

[0023] In one embodiment, the transition metal chloride in step a2 is selected from at least one of MoCl5, NbCl5, MnCl2, WCl6, TiCl4, and TaCl5. More preferably, it is one or more of MoCl5, NbCl5, MnCl2, and TiCl4. Most preferably, it is NbCl5 or MnCl2.

[0024] As one embodiment, the solvent in step a2 is selected from at least one or a mixture of several of anhydrous ethanol, isopropanol, and n-propanol. Anhydrous ethanol is more preferred.

[0025] As one implementation scheme, in step a2, the pH value is adjusted using an ammonia solution of 0.5-2.0 mol / L.

[0026] As one implementation scheme, in step a2, the reaction continues for 120–240 min.

[0027] As one implementation scheme, in step a2, the filter cleaning is performed by repeatedly filtering and cleaning with deionized water 3-5 times.

[0028] In one embodiment, the concentration of solution B in step a2 is 20 mg / mL to 100 mg / mL; the uniform dropping rate is 0.5 mL / min to 5 mL / min. More preferably, the concentration of solution B is 20 mg / mL to 60 mg / mL; the dropping rate of the constant liquid funnel is 1 mL / min.

[0029] In step a2, the drying conditions must be vacuum drying at 80℃ for 8–12 hours. Using high-temperature treatment (e.g., 200–600℃) will have the following adverse effects: 1) Since the metal oxide has already been deposited on the carbon support during the reaction process, high-temperature treatment will lead to the growth of oxide particles, which is detrimental to the uniform loading of the oxide; 2) High-temperature treatment will cause changes in the oxide crystal structure, affecting the uniformity of the subsequent loading of Pt nanoparticles; 3) It will further complicate the preparation process and increase costs.

[0030] In some embodiments, in step a2, solution B is added dropwise to the mixture A at a constant liquid level using a constant liquid funnel. After the addition is complete, the pH of the mixture is adjusted to 12 using a 1.0 mol / L ammonia solution, and the reaction continues for 120 min at room temperature. Then, after sedimentation, the supernatant is removed, and the reaction product is repeatedly filtered and washed 3-5 times with deionized water. It is then vacuum dried at 80°C for 12 h, ground into powder, and the oxide-modified carbon support C is obtained. In the prior art, carbon powder is directly ultrasonically dispersed in a metal salt solution and then separated by filtration. The amount of oxide loaded on the surface cannot be precisely controlled; moreover, it is only loaded in areas with pitted pores, failing to protect the unloaded carbon from corrosion. In contrast, the oxide prepared in this invention is deposited by uniformly adding the metal salt solution to a pre-dispersed carbon support dispersion while stirring. This facilitates uniform loading of the oxide onto the carbon support surface, allowing for better control of the amount and uniformity of the oxide load, thus providing good protection for the carbon support during subsequent operation.

[0031] As one implementation scheme, in step a3, the toner is dispersed by ultrasonic stirring with an ultrasonic power of 100-500W, an ultrasonic time of 30±5min, and a stirring time of 60±10min.

[0032] In one embodiment, the solid content of mixture D in step a3 is 20 mg / mL to 80 mg / mL. More preferably, it is 40-60 mg / mL.

[0033] As one implementation, the Pt salt mentioned in step a4 is selected from at least one of H₂PtCl₆·6H₂O, K₂PtCl₆, Na₂PtCl₆, Na₂PtCl₄, K₂PtCl₄, Pt(NH₃)₄Cl₂, Pt(NH₃)₂(NO₂)₂, and Pt(NO₃)₂. The concentration of the Pt salt in solution E is 5 wt% to 30 wt%. More preferably, the Pt salt is selected from at least one of H₂PtCl₆·6H₂O, K₂PtCl₆, Na₂PtCl₆, and Pt(NH₃)₂(NO₂)₂, with H₂PtCl₆·6H₂O being the most preferred, and the concentration of the Pt salt is 20 wt%.

[0034] As one implementation scheme, in step a4, the pH value is adjusted using a 0.5–2.0 mol / L NaOH solution.

[0035] As one implementation, the pH of the mixture is adjusted to 12 using the alkaline solution described in step a4.

[0036] As one implementation, the reducing agent in step a5 is selected from at least one of formaldehyde, formic acid, sodium formate, ethylene glycol, sodium borohydride, potassium borohydride, hydrogen, carbon monoxide, ascorbic acid, and glucose. More preferably, the reducing agent is at least one of formic acid, sodium formate, hydrogen, carbon monoxide, ascorbic acid, and glucose.

[0037] As one implementation scheme, the specific temperature mentioned in step a5 is 75-120℃, and the reaction time is 1-6 hours. More preferably, the temperature is 80-110℃, and the reaction time is 2-4 hours.

[0038] As one implementation, the oxide-modified carbon-supported platinum catalyst prepared in step a5 has an oxide content of 5% to 30% of the carbon black by mass and a Pt content of 20% to 60% of the total catalyst by mass.

[0039] In one implementation scheme, the evacuation time in step a5 is 30–90 min. The stirring time in step a5 is 60–180 min.

[0040] Thirdly, the present invention also relates to the application of an oxide-modified carbon platinum catalyst for fuel cells in the oxygen reduction reaction at the cathode of a fuel cell and in the preparation of the catalyst layer.

[0041] During fuel cell operation, the degradation of platinum-based catalysts can be attributed to 1) the particle growth mechanism caused by Oswald ripening and / or the migration and aggregation of catalyst nanoparticles on the carbon support surface; 2) the degradation caused by Pt 2+ The Pt mass loss process caused by the loss of Pt nanoparticles; 3) The Pt mass loss process caused by the corrosion of carbon carrier materials leading to the detachment of Pt nanoparticles from the carbon surface.

[0042] Traditionally, Pt nanoparticle catalysts are directly loaded onto the surface of a carbon support. Pt and the carbon support are usually adsorbed through electrostatic interactions. Under high temperature, high humidity, and voltage cycling, the particles are prone to migration. Long-term high potential will cause oxidation and corrosion of the carbon support. Furthermore, the direct contact between Pt and the carbon support can also accelerate the high-potential corrosion of the carbon support, making it difficult to meet the application requirements for long life.

[0043] This invention designs an oxide-modified carbon-supported platinum catalyst by pre-loading a metal oxide onto the surface of a carbon support, followed by loading Pt nanoparticles. On one hand, the oxide modification of the carbon support surface enhances the bonding strength between the Pt nanoparticles and the support, reducing Oswald ripening of the Pt particles during fuel cell operation and improving catalyst durability. On the other hand, a certain degree of metallic bonding forms between Pt and the oxide, which is stronger than the electrostatic adsorption between Pt and the carbon support, regulating the electronic structure of Pt and resulting in higher catalyst activity and better stability. Furthermore, the preparation method designed in this patent is a liquid-phase method, which is simple and flexible to operate; and the pre-loading of the metal oxide also optimizes the overall hydrophilicity / hydrophobicity of the catalyst.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. Oxide-modified carbon supports do not corrode at high potentials, inhibiting the aggregation and growth of Pt nanoparticles on the surface, and thus the catalyst activity is more easily preserved.

[0046] 2. After modifying the carbon support with oxides, Pt nanoparticles are then loaded. Pt and metal oxides will form certain metal bonds, which improves the surface electronic structure of Pt and enhances the catalytic activity of the catalyst. At the same time, the bonding between Pt and oxides will further anchor the Pt nanoparticles on the catalyst surface, reduce Pt migration, and improve the stability of the catalyst.

[0047] 3. After modifying the carbon support with oxides, the hydrophilicity and hydrophobicity of the catalyst surface can be further controlled. For example, the surface of graphitized carbon support is highly hydrophobic. Appropriate loading of oxides will improve the hydrophilicity of the carbon support, which is conducive to the uniform loading of Pt particles. At the same time, it is also conducive to the coverage of ionomers in the subsequent slurry preparation process, thereby optimizing the catalyst layer structure. Attached Figure Description

[0048] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0049] Figure 1 A schematic diagram of the preparation process of oxide-modified carbon-supported platinum catalyst;

[0050] Figure 2 The schematic diagram shows the initial and cyclic voltammetry (electrochemically active surface area ECSA) curves of the catalyst prepared in Example 2 of the present invention after 30,000 cycles of 0.6-0.95V durability.

[0051] Figure 3This is a schematic diagram of the initial and cyclic voltammetry (electrochemically active surface area ECSA) curves of the catalyst prepared in Comparative Example 3 of the present invention after 30,000 cycles of 0.6-0.95V durability.

[0052] Figure 4 This is a schematic diagram comparing the hydrophilicity and stability of Example 2 and Comparative Example 3 (dispersed and left to stand for 3 days). Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment relates to a method for preparing an oxide-modified carbon-supported platinum catalyst for fuel cells; Figure 1 This is a schematic diagram of the preparation process, by Figure 1 It is known that the catalyst preparation process involves adding a metal salt solution to a pre-mixed carbon support dispersion, adjusting the pH of the system with ammonia water to convert the metal salt ions into metal hydroxides loaded onto the surface of the carbon support, forming an oxide-modified carbon support after heat treatment, and then further reducing platinum onto the support to obtain an oxide-modified carbon-supported platinum catalyst.

[0056] Specifically, the preparation of NbO2-modified carbon black Vulcan XC-72 supported platinum catalyst (50% Pt / NbO2 / XC-72) includes the following steps:

[0057] a1) Weigh 4.6g of Vulcan XC-72, disperse it in 50mL of deionized water by ultrasonication at a power of 300W for 30min, and stir at room temperature for 60min to form a homogeneous mixture A.

[0058] a2) Weigh 1.0 g of NbCl5 and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and continue the reaction at room temperature for 120 min. Then, after sedimentation, remove the supernatant, wash the reaction product with deionized water repeatedly by filtration four times, dry it under vacuum at 80 °C for 12 h, grind it into powder, and obtain NbO2 modified carbon support C (NbO2 / Vulcan XC-72), wherein NbO2 accounts for 10 wt% of carbon black.

[0059] a3) The NbO2 / Vulcan XC-72 solid powder C obtained above was ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0060] a4) Weigh 13.5g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 54g of deionized water to obtain a solution E with a Pt salt content of 20wt%; add it to the above mixture D under stirring, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0061] a5) Stir at room temperature for 60 min, then add sodium formate (Pt:sodium formate molar ratio of 1:6) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain oxide-modified carbon-supported platinum catalyst F (50% Pt / NbO2 / XC-72), in which the Pt content is 50 wt%.

[0062] Example 2

[0063] The preparation of NbO2-modified EC300J supported platinum catalyst (50% Pt / NbO2 / EC300J) includes the following steps:

[0064] a1) Weigh 4.6g of EC300J, disperse it in 50mL of deionized water by ultrasonication at a power of 300W for 30min, and stir at room temperature for 60min to form a homogeneous mixture A.

[0065] a2) Weigh 1.0 g of NbCl5 and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and continue the reaction at room temperature for 120 min. Then, after sedimentation, remove the supernatant, wash the reaction product repeatedly with deionized water by filtration 3-5 times, dry it under vacuum at 80℃ for 12 h, grind it into powder, and obtain NbO2 modified carbon support C (NbO2 / Vulcan XC-72), wherein NbO2 accounts for 10 wt% of carbon black.

[0066] a3) The NbO2 / EC300J solid powder C obtained above is ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0067] a4) Weigh 13.5g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 54g of deionized water to obtain a solution E with a Pt salt content of 20wt%; add it to the above mixture D under stirring, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0068] a5) Stir at room temperature for 60 min, then add sodium formate (Pt:sodium formate molar ratio of 1:6) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain oxide-modified carbon-supported platinum catalyst F (50% Pt / NbO2 / EC300J), in which the Pt content is 50 wt%.

[0069] Figure 2 This is a schematic diagram of the initial and cyclic voltammetry (electrochemically active surface area, ECSA) curves of the catalyst prepared in this embodiment after 30,000 cycles at 0.6–0.95 V. Figure 2 It can be seen that after 30,000 cycles of durability testing, the cyclic voltammetry curve of the catalyst remained basically consistent with the initial value, and the ECSA decay rate was less than 5%, indicating that the loading of oxides can significantly improve the durability of the catalyst.

[0070] Figure 4 For the comparison of hydrophilicity and stability between this embodiment and Comparative Example 3 (dispersion and standing for 3 days), by Figure 4 It can be seen that in this embodiment, after standing in deionized water for 3 days, the slurry is in a dispersed state without precipitation; for Comparative Example 3, it can be found that the catalyst is deposited at the bottom of the beaker, indicating that the catalyst has poor hydrophilicity, which is not conducive to stable dispersion.

[0071] Example 3

[0072] The preparation of Mn3O4-modified carbon black EC300J supported platinum catalyst (50% Pt / Mn3O4 / EC300J) includes the following steps:

[0073] a1) Weigh 5g of EC300J and disperse it in 50mL of deionized water by ultrasonication. The ultrasonic power is 300W and the ultrasonication time is 30min. Stir at room temperature for 60min to form a homogeneous mixture A.

[0074] a2) Weigh 1.45 g of MnCl2˙4H2O and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and react at 70℃ for 240 min. Then, after sedimentation, remove the supernatant, wash the reaction product repeatedly with deionized water by filtration 3-5 times, dry it under vacuum at 80℃ for 12 h, and grind it into powder to obtain Mn3O4 modified carbon support C (Mn3O4 / EC300J), in which Mn3O4 accounts for 10 wt% of the carbon black mass.

[0075] a3) The Mn3O4 / EC300J solid powder C obtained above is ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0076] a4) Weigh 14.83g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 59.32g of deionized water to obtain a solution E with a Pt salt content of 20wt%; add it to the above mixture D under stirring, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0077] a5) Stir at room temperature for 60 min, then add sodium formate (Pt:sodium formate molar ratio of 1:6) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain oxide-modified carbon-supported platinum catalyst F (50% Pt / Mn3O4 / EC300J), in which the Pt content is 50 wt%.

[0078] Example 4

[0079] The preparation of NbO2-modified carbon black Vulcan XC-72 supported platinum catalyst (30% Pt / NbO2 / XC-72) includes the following steps:

[0080] a1) Weigh 4.6g of Vulcan XC-72, disperse it in 50mL of deionized water by ultrasonication at a power of 300W for 30min, and stir at room temperature for 60min to form a homogeneous mixture A.

[0081] a2) Weigh 1.0 g of NbCl5 and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and continue the reaction at room temperature for 120 min. Then, after sedimentation, remove the supernatant, wash the reaction product repeatedly with deionized water by filtration 3-5 times, dry it under vacuum at 80℃ for 12 h, grind it into powder, and obtain NbO2 modified carbon support C (NbO2 / Vulcan XC-72), wherein NbO2 accounts for 10 wt% of carbon black.

[0082] a3) The NbO2 / Vulcan XC-72 solid powder C obtained above was ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0083] a4) Weigh 4.1g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 16.4g of deionized water to obtain a solution E with a Pt salt content of 20wt%; add it to the above mixture D under stirring, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0084] a5) Stir at room temperature for 60 min, then add sodium formate (Pt:sodium formate molar ratio of 1:6) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to prepare oxide-modified carbon-supported platinum catalyst F (30% Pt / NbO2 / XC-72), in which the Pt content is 30 wt%.

[0085] Example 5

[0086] The preparation of NbO2-modified carbon black EC300J supported platinum catalyst (30% Pt / NbO2 / EC300J) includes the following steps:

[0087] a1) Weigh 4.6g of EC300J, disperse it in 50mL of deionized water by ultrasonication at a power of 300W for 30min, and stir at room temperature for 60min to form a homogeneous mixture A.

[0088] a2) Weigh 1.0 g of NbCl5 and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and continue the reaction at room temperature for 120 min. Then, after sedimentation, remove the supernatant, wash the reaction product repeatedly with deionized water by filtration 3-5 times, dry it under vacuum at 80℃ for 12 h, and grind it into powder to obtain NbO2-modified carbon support C (NbO2 / EC300J), in which NbO2 accounts for 10 wt% of carbon black.

[0089] a3) The NbO2 / Vulcan XC-72 solid powder C obtained above was ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0090] a4) Weigh 4.1g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 16.4g of deionized water to obtain a solution E with a Pt salt content of 20wt%; add it to the above mixture D under stirring, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0091] a5) Stir at room temperature for 60 min, then add ascorbic acid (Pt:ascorbic acid molar ratio of 1:10) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to prepare oxide-modified carbon-supported platinum catalyst F (30% Pt / NbO2 / EC300J), in which the Pt content is 30 wt%.

[0092] Example 6

[0093] The preparation of NbO2-modified carbon black EC300J supported platinum catalyst (60% Pt / NbO2 / EC300J) includes the following steps:

[0094] a1) Weigh 4.6g of EC300J, disperse it in 50mL of deionized water by ultrasonication at a power of 300W for 30min, and stir at room temperature for 60min to form a homogeneous mixture A.

[0095] a2) Weigh 1.0 g of NbCl5 and dissolve it in 20 mL of anhydrous ethanol to obtain solution B. Add solution B dropwise to the above mixture A at a rate of 1 mL / min through a constant liquid funnel. After the addition is complete, adjust the pH of the mixture to 12 with 1.0 mol / L ammonia solution and continue the reaction at room temperature for 120 min. Then, after sedimentation, remove the supernatant, wash the reaction product repeatedly with deionized water by filtration 3-5 times, dry it under vacuum at 80℃ for 12 h, and grind it into powder to obtain NbO2-modified carbon support C (NbO2 / EC300J), in which NbO2 accounts for 10 wt% of carbon black.

[0096] a3) The NbO2 / EC600J solid powder C obtained above is ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, stirring time of 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0097] a4) Weigh 20g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 80g of deionized water to obtain a solution E with a Pt salt content of 20wt%; and add it to the above mixture D under stirring conditions, and adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution;

[0098] a5) Stir at room temperature for 60 min, then add ascorbic acid (Pt:sodium formate molar ratio of 1:10) to ensure complete reduction of Pt; purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain oxide-modified carbon-supported platinum catalyst F (60% Pt / NbO2 / EC300J), in which the Pt content is 60 wt%.

[0099] Comparative Example 1

[0100] The main preparation steps are the same as in Example 1, except that Vulcan XC-72 is ultrasonically dispersed in solution B; specifically:

[0101] 1.0 g of NbCl5 was dissolved in 20 mL of anhydrous ethanol to obtain solution B. 4.6 g of Vulcan XC-72 was ultrasonically dispersed in solution B at a power of 300 W for 30 min. The pH of the mixture was adjusted to 12 with a 1.0 mol / L ammonia solution, and the reaction was continued at room temperature for 180 min. Subsequent steps were the same as in Example 1.

[0102] Comparative Example 2

[0103] The main preparation steps are the same as in Example 1, except that in step a2, the sample is vacuum dried at 200°C for 5 hours.

[0104] Comparative Example 3

[0105] The main preparation steps are the same as in Example 2, the only difference being that the carrier is only EC300J. Specifically:

[0106] b1) 4.6g EC300J was ultrasonically stirred (ultrasonic power of 300W, ultrasonic time of 30min, and stirred at room temperature for 60min) and uniformly dispersed in 100mL of deionized water to form a uniform mixture D.

[0107] b2) Weigh 13.5g of chloroplatinic acid (H2PtCl6˙6H2O) and dissolve it in 54g of deionized water to obtain a solution E with a Pt salt content of 20wt%; and add it to the above mixture D under stirring. Adjust the pH of the mixture to 12 with 1.0mol / L NaOH solution.

[0108] b3) Stir at room temperature for 60 min, then add sodium formate (Pt:sodium formate molar ratio is 1:6) to ensure that Pt is completely reduced; then purge with an inert atmosphere for 30 min, then heat to 90℃ and maintain this temperature for 3 h; after the reaction is complete, cool to room temperature, and then precipitate, filter, wash, dry and grind the reaction product to obtain oxide-modified carbon-supported platinum catalyst F (50% Pt / EC300J).

[0109] Figure 3 This is a schematic diagram of the initial and cyclic voltammetry (electrochemically active surface area, ECSA) curves of the catalyst prepared in this comparative example after 30,000 cycles at 0.6–0.95 V. Figure 3 It can be seen that after 30,000 cycles of durability testing, the ECSA decay rate of the catalyst prepared in Comparative Example 3 was more than 50% compared with the initial value.

[0110] The BET specific surface area and average particle size of the catalysts prepared in each embodiment are shown in Table 1:

[0111] Table 1

[0112]

[0113] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An oxide-modified carbon-supported platinum catalyst for fuel cells, characterized in that the catalyst is supported on oxide NbO2-modified carbon black, has monodispersed Pt nanoparticles uniformly dispersed on the surface of the support, the oxide NbO2 is acid-resistant oxide nanoparticles uniformly dispersed on the surface of the carbon black, the particle size of the Pt nanoparticles is 1.5-5 nm, the mass percentage content of the carbon black in the catalyst is 30%-70%, the size of the oxide NbO2 nanoparticles in the oxide NbO2-modified carbon black is 5-20 nm, and the mass percentage of the oxide NbO2 in the carbon black is 5%-30%.

2. The oxide-modified carbon-supported platinum catalyst for fuel cells is prepared by a method comprising the following steps: a1. Ultrasonic dispersion of carbon black in a solvent and stirring at room temperature to form a mixed solution A; a2. Dissolution of NbCl5 in a solvent to obtain a solution B, and dropwise addition of the solution B to the mixed solution A at a constant speed while stirring and depositing, after the dropwise addition is completed, adjustment of the pH value to 12-14, and continuous reaction at room temperature; after sedimentation, removal of the supernatant, filtration and washing of the reaction product, vacuum drying at 80°C for 8-12 h, grinding into powder, and obtaining of an oxide NbO2-modified carbon support C; a3. Ultrasonic stirring of the oxide NbO2-modified carbon support C and uniform dispersion in deionized water to form a mixed solution D; a4. Dissolution of a platinum salt in deionized water to obtain a solution E containing the Pt salt, and addition of the solution E to the mixed solution D under stirring and adjustment of the pH value of the mixed solution to 11-13; a5. Stirring at room temperature, addition of a reducing agent, evacuation by introduction of an inert atmosphere, heating to 75-120°C, maintenance of the temperature and continuous reaction for 1-6 h, cooling to room temperature after the reaction is completed, and sedimentation, filtration and washing of the reaction product, and drying and grinding to obtain the oxide-modified carbon-supported platinum catalyst; the reducing agent is at least one selected from sodium formate and ascorbic acid. In step a1, the carbon black is one or a mixture of several selected from EC300J, EC600J, Vulcan XC-72 and Black pearls; the solvent is one or a mixture of several selected from deionized water, anhydrous ethanol, isopropanol, n-propanol and n-butanol; and the solid content in the mixed solution A is 10-80 mg / mL. In step a2, the solvent is one or a mixture of several selected from anhydrous ethanol, isopropanol and n-propanol. In step a2, the concentration of the solution B is 20-100 mg / mL; and the constant dropwise addition speed is 0.5-5 mL / min. In step a3, the solid content of the mixed solution D is 20-80 mg / mL.

2. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, In step a4, the platinum salt is at least one selected from H2PtCl6·6H2O, K2PtCl6, Na2PtCl6, Na2PtCl4, K2PtCl4, Pt(NH3)4Cl2, Pt(NH3)2(NO2)2 and Pt(NO3)2; and the concentration of the Pt salt in the solution E is 5%-30% by weight.

3. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, ​ 4. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, ​ 5. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, ​ 6. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, ​ 7. The oxide-modified carbon-supported platinum catalyst for fuel cells according to claim 1, characterized by, The oxide NbO2 modified carbon supported platinum catalyst prepared in step a5, wherein the percentage content of Pt in the total mass of the catalyst is 20% to 60%.

8. Use of the oxide modified carbon supported platinum catalyst according to any one of claims 1 to 7 in the oxygen reduction reaction in the cathode of a fuel cell and in the preparation of a catalyst layer.

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