A chromium group metal doped platinum alloy catalyst and its preparation method and application

Abstract

A chromium group metal-doped platinum alloy catalyst, its preparation method and application, which relates to a platinum alloy catalyst, its preparation method and application. It is to solve the technical problem of poor catalytic activity and durability of the existing alloy catalyst formed by Pt and transition metals. The catalyst is PtM alloy nanoparticles doped with a chromium group element X uniformly supported on a carbon carrier; in the PtM alloy doped with the chromium group element X, X exists in a simple form, and the mass percentage of X is 5% to 10%; it is recorded as X‑PtM / C, wherein X is Cr, Mo or W; M is Fe, Co or Ni. Preparation method: Pt / C is used as a precursor for secondary reduction and high-temperature heat treatment to obtain a catalyst. The mass activities of Cr‑PtNi / C, Mo‑PtNi / C and Cr‑PtCo / C are 0.419, 0.254 and 0.314 A / mg, respectively. Pt , 5.0 to 8.1 times that of Pt / C. Cr-PtNi / C showed no potential decay after 30,000 cycles of aging. It can be used in the fuel cell field.

Description

Technical Field

[0001] The present invention relates to a platinum alloy catalyst and a preparation method and application thereof, belonging to the field of new energy materials. Background Art

[0002] Currently, proton exchange membrane fuel cells (PEMFCs) require improvement in performance, cost, and mass production. Commercial Pt / C catalysts effectively accelerate electrochemical reaction rates, but the fuel cell operating environment is harsh. Pt / C catalysts are susceptible to degradation under high potential and strongly acidic conditions, resulting in weakened performance and decreased stability after cycling. Therefore, the key to addressing these issues is to prepare highly active and durable electrocatalysts while reducing cost. Research has shown that alloying Pt with transition metals (such as Fe, Co, and Ni, transition metals from the fourth period) not only reduces the amount of precious Pt required but also enhances ORR activity and stability by adjusting the electronic structure and geometry to alter the binding strength between Pt and oxygen intermediates. Among all PtM catalysts, PtNi and PtCo alloy catalysts have attracted considerable attention due to their superior performance. However, because transition metals such as Ni are more soluble under PEMFC operating conditions, leaching of non-Pt elements leads to significant structural degradation, weakening the strain effect and reducing the catalytic activity and durability of the catalyst. Summary of the Invention

[0003] The present invention addresses the technical issues of insufficient catalytic activity and durability in existing alloy catalysts formed by platinum (Pt) and a transition metal (M) (Fe, Co, or Ni). The invention provides a chromium-group metal-doped platinum alloy catalyst, its preparation method, and its application. The present invention utilizes PtC as a precursor, undergoes secondary reduction and high-temperature heat treatment to produce an X-PtM / C alloy catalyst (X is Cr, Mo, or W, and M is Fe, Co, or Ni). The resulting catalyst exhibits significantly improved Pt activity and durability.

[0004] The chromium group metal-doped platinum alloy catalyst of the present invention comprises PtM alloy nanoparticles doped with a chromium group element X uniformly supported on a carbon carrier. In the PtM alloy doped with the chromium group element X, X exists in a simple substance form, and the mass percentage of the chromium group element X is 5% to 10%. The catalyst is denoted as X-PtM / C, where X is Cr, Mo or W, and M is Fe, Co or Ni.

[0005] The preparation method of the chromium group metal-doped platinum alloy catalyst is carried out according to the following steps:

[0006] 1. Preparation of Pt / C by polyol reduction method: A carbon support is added to a mixed solution of ethylene glycol and isopropanol, and the carbon powder is evenly dispersed by ultrasonic and magnetic stirring to obtain a carbon dispersion; an ethylene glycol solution of chloroplatinic acid is then added to the carbon dispersion and stirred evenly to obtain a slurry; the pH of the slurry is then adjusted to alkaline; microwave heating is performed under inert gas protection to reduce Pt to Pt nanoparticles; the pH of the slurry is then adjusted to acidic to load the Pt nanoparticles on the carbon support; the slurry is filtered, washed, vacuum-dried, and ground evenly to obtain Pt / C particles;

[0007] 2. Sodium borohydride reduction: Pt / C particles are dissolved in ultrapure water and uniformly dispersed by ultrasonic and magnetic stirring. A metal salt solution of a chromium group element X and a metal salt solution of M are added and stirred to obtain a mixed solution. An aqueous sodium borohydride solution is added dropwise to the mixed solution in an ice-water bath and stirred for 2 to 3 hours after the addition is complete. The mixture is then filtered, washed, vacuum-dried, and ground to obtain XM-Pt / C powder.

[0008] 3. High-temperature annealing: The XM-Pt / C powder is placed in a high-temperature furnace and heated to 700-1100°C in a reducing or inert atmosphere for 0.5-4 hours for annealing. After cooling, the powder is ground uniformly to obtain a primary product. During the high-temperature annealing process, PtM alloy nanoparticles doped with the chromium group element X are formed, and the particles are supported on the carbon support.

[0009] 4. Acid washing treatment of heteroatoms on the catalyst surface: The initial product of step 1 was acid washed in a dilute sulfuric acid solution, then filtered and washed with ultrapure water until neutral, and vacuum dried to obtain a chromium group metal-doped platinum alloy catalyst, which was recorded as X-PtM / C.

[0010] Furthermore, the carbon support in step 1 is ECP-600JD, ECP-300JD or XC-72.

[0011] Furthermore, the volume ratio of ethylene glycol to isopropyl alcohol in the mixed solution of ethylene glycol and isopropyl alcohol described in step 1 is (2-3):1.

[0012] Furthermore, in step 1, adjusting the pH of the slurry to be alkaline is to adjust the pH value to 9-13; adjusting the pH of the slurry to be acidic is to adjust the pH value to 0.5-4.

[0013] Furthermore, the concentration of chloroplatinic acid in the ethylene glycol solution of chloroplatinic acid in step 1 is 0.03M to 0.05M;

[0014] Furthermore, the ratio of chloroplatinic acid to carbon support in step 1 is (0.2-0.6):1.

[0015] Furthermore, the metal salt of the chromium group element X in step 2 is chromium chloride, chromium nitrate, molybdenum chloride, molybdenum nitrate, tungsten chloride or tungsten nitrate.

[0016] Furthermore, the metal salt of M in step 2 is nickel chloride, nickel nitrate, cobalt chloride, cobalt nitrate, ferric chloride or ferric nitrate.

[0017] Furthermore, the ratio of the metal salt of the chromium group element X, the metal salt of M and the metal in the Pt / C particles in step 2 is (0.1-0.3):(0.5-1):1.

[0018] Furthermore, the concentration of the sodium borohydride aqueous solution in step 2 is 0.05-0.1M.

[0019] Furthermore, the concentration of the dilute sulfuric acid solution in step 4 is 0.05-0.1 M, and the pickling time is 2-6 hours.

[0020] Furthermore, the inert atmosphere in steps 1 and 4 is Ar or N 2；

[0021] Furthermore, the reducing atmosphere in step 4 is a H2 / Ar mixed gas, wherein H2 accounts for 5% to 10% of the volume of the mixed gas.

[0022] The application of the chromium group metal doped platinum alloy catalyst is to use the catalyst in the cathode oxygen reduction reaction (ORR) of a fuel cell.

[0023] The beneficial effects of the present invention compared to the prior art are:

[0024] (1) The present invention can load Pt nanoparticles and transition metal M onto a carbon support in steps by a chemical reduction method to obtain XM-Pt / C, and then form an X-PtM alloy with X and M present as elemental substances in XM-Pt / C and Pt nanoparticles through high-temperature annealing to obtain an X-PtM / C alloy catalyst. The X-PtM structure can effectively regulate the adsorption capacity of Pt nanoparticles for reaction intermediates, thereby improving the catalyst activity.

[0025] (2) The present invention first reduces Pt nanoparticles to prepare Pt / C as a precursor, providing deposition sites for transition metals M and X to form a stable X-PtM / C, which is beneficial to the uniform dispersion of Pt or PtM nanoparticles on the support surface.

[0026] (3) The PtM alloy catalyst doped with chromium group element X of the present invention, the chromium group element X doping plays an electronic buffering role on the alloy particles. Specifically, these elements have weak electron affinity and strong ionization tendency, and can act as electron acceptors or donors, thereby promoting the transmission of electrons in the metal alloy. This effect helps to evenly distribute the electron density, reduce local charge imbalance and polarization, and thus effectively improve the activity and stability of the alloy catalyst. Compared with existing commercial platinum carbon catalysts, its catalytic activity and stability are greatly improved, among which the mass activity (MA) of Cr-PtNi / C is 0.419mA / μg Pt , about 8.1 times that of Pt / C and about 3.9 times that of PtNi / C. The mass activity (MA) of Mo-PtNi / C is 0.254A / mg Pt , which is about 5.0 times that of Pt / C. The mass activity (MA) of Cr-PtCo / C is 0.314A / mg Pt , about 6.1 times that of Pt / C and about 1.2 times that of PtCo / C. The potential of Cr-PtNi / C showed no decay after 30,000 cycles of aging, and its stability was superior to that of PtNi / C and Pt / C, making it suitable for use in the fuel cell field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a preparation flow chart of the present invention;

[0028] Figure 2 1 is an XRD pattern of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, and PtNi / C prepared in Comparative Example 2;

[0029] Figure 3 is a TEM image of Cr-PtNi / C prepared in Example 1;

[0030] Figure 4 is a TEM image of Cr-PtNi / C prepared in Example 1;

[0031] Figure 5 ORR polarization diagrams of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, PtNi / C prepared in Comparative Example 2, and Mo-PtNi / C prepared in Example 3;

[0032] Figure 6 is a mass specific activity diagram of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, PtNi / C prepared in Comparative Example 2, and Mo-PtNi / C prepared in Example 3;

[0033] Figure 7ORR polarization diagrams of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, and PtNi / C prepared in Comparative Example 2 before and after aging;

[0034] Figure 8 ORR polarization diagram of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, and PtNi / C prepared in Comparative Example 2 under hydrogen and oxygen conditions in MEA;

[0035] Figure 9 ORR polarization diagrams of Cr-PtNi / C prepared in Example 1, Pt / C prepared in Comparative Example 1, and PtNi / C prepared in Comparative Example 2 under hydrogen-air conditions in MEA;

[0036] Figure 10 2 are ORR polarization diagrams of Cr-PtCo / C prepared in Example 2, Pt / C prepared in Comparative Example 1, and PtCo / C prepared in Comparative Example 3;

[0037] Figure 11 3 is a mass specific activity diagram of Cr-PtCo / C prepared in Example 2, Pt / C prepared in Comparative Example 1, and PtCo / C prepared in Comparative Example 3. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0039] Example 1: The preparation method of the chromium group metal-doped platinum alloy catalyst Cr-PtNi / C of this embodiment is carried out according to the following steps:

[0040] 1. Preparation of Pt / C by polyol reduction method: weigh 48 mg ECP-600JD carbon powder was placed in a beaker, and 40 ml of a mixed solution of ethylene glycol and isopropanol was added; wherein the volume ratio of ethylene glycol to isopropanol in the mixed solution of ethylene glycol and isopropanol was 5:2; ultrasonic stirring was performed for 120 min to obtain a carbon dispersion; 0.800 ml of a 0.0385 mol / L chloroplatinic acid ethylene glycol solution was added to the carbon dispersion, and ultrasonic stirring was continued for 30 min to fully mix it to obtain a slurry; the pH of the slurry was then adjusted to 12 using a 1 mol / L NaOH ethylene glycol solution, and nitrogen was introduced into the slurry to remove dissolved air in the solution to protect the solution; the slurry was then placed in a microwave oven and microwave-heated for 100 s; after cooling, the pH of the slurry was adjusted to 2 using a nitric acid ethylene glycol solution, and stirring was continued for 12 hours; the slurry was then filtered and washed three times, the filter residue was taken out, and vacuum dried in a vacuum drying oven at 80°C for 8 hours; and the mixture was evenly ground to obtain Pt / C particles;

[0041] Preparation of CrNi-Pt / C by sodium borohydride reduction: 40 mg of Pt / C was dissolved in ultrapure water, and the carbon powder was evenly dispersed by ultrasonic and magnetic stirring. Then, 4 ml of a 10 mmol / L nickel nitrate solution and 2.5 ml of a 5 mmol / L chromium nitrate solution were added and stirred to obtain a mixed solution. Then, 10 ml of a 0.025 mol / L sodium borohydride aqueous solution was added dropwise to the mixed solution in an ice-water bath. After the addition was completed, stirring was continued for 2 hours. The slurry was filtered and washed three times. The filter residue was removed and dried in a vacuum drying oven at 80°C for 8 hours. The mixture was ground to obtain CrNi-Pt / C powder.

[0042] 3. High-temperature annealing: CrNi-Pt / C powder is placed in a corundum magnetic boat, which is then placed in a tube furnace. The temperature is raised to 900°C at a rate of 5°C / min in a H2 / Ar atmosphere and maintained for 120 minutes for annealing. The temperature is then naturally cooled to room temperature and ground uniformly to obtain a primary product. During the high-temperature annealing process, Cr-doped PtNi alloy nanoparticles are formed, and the particles are supported on the carbon support.

[0043] 4. Acid washing treatment of heteroatoms on the catalyst surface: The initial product of the step was placed in a dilute sulfuric acid solution with a concentration of 0.05 mol / L and acid washed at 80°C for 120 minutes, then filtered and washed with ultrapure water until neutral, and the filtered residue was placed in a vacuum drying oven at 80°C for 8 hours to obtain a chromium group metal doped platinum alloy catalyst, recorded as Cr-PtNi / C.

[0044] Comparative Example 1: In this comparative example, a catalyst PtNi / C not doped with chromium group metal elements was prepared. The difference between this comparative example and Example 1 is that the chromium nitrate solution in step 2 is omitted. The other steps and parameters are the same as those in Example 1. The obtained catalyst not doped with chromium group metal elements is recorded as PtNi / C.

[0045] Example 2: The preparation method of the chromium group metal-doped platinum alloy catalyst Mo-PtNi / C of this embodiment is carried out according to the following steps:

[0046] 1. Preparation of Pt / C: This step is the same as step 1 of Example 1 to obtain Pt / C particles;

[0047] 2. Preparation of MoNi-Pt / C: 40 mg of Pt / C was dissolved in ultrapure water, and the carbon powder was evenly dispersed by ultrasonic and magnetic stirring. Then, 4 ml of 10 mmol / L nickel nitrate solution and 2.5 ml of 5 mmol / L molybdenum nitrate were added and stirred to make the slurry uniform. Then, 10 ml of 0.025 mol / L sodium borohydride aqueous solution was added dropwise in an ice-water bath. After stirring for 2 h, the slurry was filtered, washed, and vacuum-dried to obtain the MoNi-Pt / C catalyst, which was ground uniformly for later use.

[0048] 2. Take 40mg of Pt / C and dissolve it in ultrapure water. Disperse the carbon powder evenly by ultrasonic and magnetic stirring. Then add 4ml of 10mmol / L nickel nitrate solution and 2.5ml of 5mmol / L molybdenum nitrate solution and stir evenly to obtain a mixed solution. Then, add 10ml of 0.025mol / L sodium borohydride aqueous solution to the mixed solution under ice-water bath conditions. After the addition is completed, continue stirring for 2h. Then, filter and wash the slurry 3 times. Take out the filter residue and place it in a vacuum drying oven at a temperature of 80°C for 8h. Grind it evenly to obtain MoNi-Pt / C powder.

[0049] 3. High-temperature annealing: MoNi-Pt / C powder is placed in a corundum magnetic boat, which is then placed in a tube furnace and heated to 900°C at a rate of 5°C / min in a H2 / Ar atmosphere and held for 120 minutes for annealing. The temperature is then naturally cooled to room temperature and ground uniformly to obtain a primary product. During the high-temperature annealing process, Mo-doped PtNi alloy nanoparticles are formed, and the particles are supported on the carbon support.

[0050] 4. Acid washing treatment of heteroatoms on the catalyst surface: The initial product of the step was placed in a dilute sulfuric acid solution with a concentration of 0.05 mol / L and acid washed at a temperature of 80°C for 120 minutes, then filtered and washed with ultrapure water until neutral, and the filtered residue was placed in a vacuum drying oven at a temperature of 80°C and vacuum dried for 8 hours to obtain a chromium group metal doped platinum alloy catalyst, recorded as Mo-PtNi / C.

[0051] The XRD spectra of the Pt / C particles prepared in step 1 of Example 1, the Cr-PtNi / C catalyst prepared in step 4, and the PtNi / C catalyst prepared in comparative example 1 are as follows: Figure 2 As shown, from Figure 2 It can be seen that the doping of metal Cr and Ni causes the Pt lattice to compress, resulting in a significant right shift of the characteristic peak, indicating that the catalyst is an alloy particle.

[0052] Example 1 The TEM images of the Cr-PtNi / C catalyst prepared in step 4 are as follows: Figure 3 and Figure 4 shown; from Figure 3 It can be seen that the alloy catalyst obtained by step-by-step reduction is evenly distributed on the carbon support; Figure 4 It can be seen that the lattice spacing of the catalyst particles is smaller than that of pure Pt, which further indicates that the metal atoms form an alloy.

[0053] Figure 5 The ORR polarization diagrams of the Pt / C particles prepared in step 1 of Example 1, the Cr-PtNi / C catalyst prepared in step 4, the PtNi / C prepared in comparative example 1, and the Mo-PtNi / C prepared in example 2 are shown in FIG. Figure 6 As shown, the ORR polarization diagram was measured by staircase voltammetry (LSV) in an oxygen-saturated 0.1 M HClO4 electrolyte with a potential range of 0.05-1.2 V and a rotation speed of 1600 rpm. Figure 6 shown; from Figure 5 and Figure 6 It can be seen that the mass activity (MA) of Pt / C is 0.0516 mA / μg Pt The mass activity (MA) of Cr-PtNi / C prepared in Example 1 is 0.419 mA / μg Pt , which is about 8.1 times that of Pt / C and about 3.9 times that of PtNi / C prepared in Comparative Example 1. The mass activity (MA) of Mo-PtNi / C prepared in Example 2 is 0.254 A / mg Pt , which is about 5.0 times that of Pt / C and about 2.4 times that of PtNi / C prepared in Comparative Example 1.

[0054] Figure 7 The ORR polarization diagrams of the Pt / C particles prepared in step 1 of Example 1, the Cr-PtNi / C catalyst prepared in step 4, and the PtNi / C prepared in comparative example 1 before and after aging for 30,000 cycles are shown. The aging test was conducted by conducting potential cycling in an oxygen-saturated 0.1M HClO4 electrolyte to study the stability of the catalyst. The scan rate was 1, the scan range was 0.6 to 1.0V, and the stability of the catalyst was studied. Figure 7It can be seen that the potential of Cr-PtNi / C prepared in Example 1 has no decay after aging for 30,000 cycles, the potential of PtNi / C decays by 10 mV after aging for 30,000 cycles, and the potential of Pt / C decays by 18 mV after aging for 30,000 cycles. It can be seen from the comparison that the stability of Cr-PtNi / C is much better than that of Pt / C.

[0055] The ORR polarization tests of the Pt / C particles prepared in step 1 of Example 1, the Cr-PtNi / C catalyst prepared in step 4, and the PtNi / C prepared in comparative example 1 under different atmospheres in MEA are as follows: Figure 8 and Figure 9 As shown, Figure 8 The catalyst was measured in an 850e fuel cell test system at a temperature of 80°C, a relative humidity of 100%, hydrogen and oxygen flowing into the anode and cathode respectively, and a back pressure of 100kPa. Figure 9 The catalyst was tested in an 850e fuel cell test system at a temperature of 80°C, a relative humidity of 100%, with hydrogen and air flowing into the anode and cathode respectively, and a back pressure of 200kPa. The maximum power density of the Cr-PtNi / C catalyst prepared in Example 1 in a hydrogen and oxygen atmosphere reached 2.9W / cm 2 , which is about 1.6 times that of Pt / C and about 1.2 times that of PtNi / C prepared in Comparative Example 1. The maximum power density of the Cr-PtNi / C catalyst prepared in Example 1 under hydrogen-air atmosphere reaches 1.9W / cm 2 , which is about 1.2 times that of Pt / C and about 1.1 times that of PtNi / C prepared in Comparative Example 1.

[0056] Example 3: The preparation method of the chromium group metal-doped platinum alloy catalyst Cr-PtCo / C of this embodiment is carried out according to the following steps:

[0057] 1. Preparation of Pt / C: This step is the same as step 1 of Example 1; Pt / C particles are obtained;

[0058] Preparation of CrCo-Pt / C by sodium borohydride reduction: 40 mg of Pt / C was dissolved in ultrapure water, and the carbon powder was evenly dispersed by ultrasonic and magnetic stirring. Then, 4 ml of a 10 mmol / L cobalt nitrate solution and 2.5 ml of a 5 mmol / L chromium nitrate solution were added and stirred to obtain a mixed solution. Then, 10 ml of a 0.025 mol / L sodium borohydride aqueous solution was added dropwise to the mixed solution in an ice-water bath. After the addition was completed, stirring was continued for 2 hours. The slurry was filtered and washed three times. The filter residue was removed and dried in a vacuum drying oven at 80°C for 8 hours. The mixture was then ground to obtain CrCo-Pt / C powder.

[0059] 3. High-temperature annealing: CrCo-Pt / C powder is placed in a corundum boat, which is then placed in a tube furnace. The temperature is raised to 900°C at a rate of 5°C / min in a H2 / Ar atmosphere and held for 120 minutes for annealing. The temperature is then naturally cooled to room temperature and ground uniformly to obtain a primary product. During the high-temperature annealing process, Cr-doped PtCo alloy nanoparticles are formed, and the particles are supported on the carbon support.

[0060] 4. Acid washing treatment of heteroatoms on the catalyst surface: The initial product of the step was placed in a dilute sulfuric acid solution with a concentration of 0.05 mol / L and acid washed at 80°C for 120 minutes, then filtered and washed with ultrapure water until neutral, and the filtered residue was placed in a vacuum drying oven at a temperature of 80°C and vacuum dried for 8 hours to obtain a chromium group metal-doped platinum alloy catalyst, recorded as Cr-PtCo / C.

[0061] Comparative Example 2: In this comparative example, a catalyst PtCo / C not doped with a chromium group metal element was prepared. This comparative example differs from Example 3 in that the chromium nitrate solution in step 2 is omitted. The other steps and parameters are the same as those in Example 3. The resulting catalyst not doped with a chromium group metal element is denoted as PtCo / C.

[0062] The ORR polarization test and mass activity of the Pt / C catalyst prepared in step 1 of Example 3, the Cr-PtCo / C catalyst prepared in step 4, and the PtCo / C catalyst prepared in comparative example 2 are shown in FIG. Figure 10 and Figure 11 As shown, from Figure 10 and 11 It can be seen that the mass activity (MA) of Cr-PtCo / C is 0.314 A / mg Pt , which is about 6.1 times that of Pt / C and about 1.2 times that of the PtCo / C catalyst prepared in Comparative Example 2.

[0063] The chromium-group element-doped PtM alloy catalyst of the present invention utilizes a chemical reduction method to sequentially reduce Pt and a transition metal element (M) onto a carbon support. The initially reduced Pt provides initial growth sites for the transition metal (M), facilitating uniform distribution and growth of the alloy under high-temperature conditions. The PtM structure effectively regulates the adsorption capacity of Pt nanoparticles for reaction intermediates, thereby modulating catalyst activity. Furthermore, the chromium-group metal doping acts as an electron buffer for the alloy catalyst, resulting in higher oxygen reduction activity and stability than PtM alloys, and is therefore suitable for fuel cell catalysis.

Claims

1. A chromium group metal-doped platinum alloy catalyst, characterized in that The catalyst is a PtM alloy nanoparticle doped with a chromium group element X uniformly supported on a carbon carrier; in the PtM alloy doped with the chromium group element X, X exists in a simple form, and the mass percentage of the chromium group element X is 5% to 10%; it is denoted as X-PtM / C, wherein X is Cr, Mo or W; and M is Fe, Co or Ni. The preparation method of the catalyst is carried out according to the following steps:

1. Preparation of Pt / C by polyol reduction method: The carbon support is added to a mixed solution of ethylene glycol and isopropanol, and the carbon powder is evenly dispersed by ultrasonication and magnetic stirring to obtain a carbon dispersion. Then, an ethylene glycol solution of chloroplatinic acid is added to the carbon dispersion and stirred evenly to obtain a slurry. The pH of the slurry is then adjusted to alkaline. The Pt nanoparticles are reduced to Pt nanoparticles by microwave heating under inert gas protection; the pH of the slurry is then adjusted to acidic to load the Pt nanoparticles on the carbon support; the slurry is filtered, washed, vacuum-dried, and ground uniformly to obtain Pt / C particles; 2. Sodium borohydride reduction: Pt / C particles are dissolved in ultrapure water and uniformly dispersed by ultrasonic and magnetic stirring. A metal salt solution of a chromium group element X and a metal salt solution of M are added and stirred to obtain a mixed solution. An aqueous sodium borohydride solution is added dropwise to the mixed solution in an ice-water bath and stirred for 2-3 hours after the addition is complete. The mixture is then filtered, washed, vacuum-dried, and ground to obtain XM-Pt / C powder.

3. High-temperature annealing: The XM-Pt / C powder is placed in a high-temperature furnace and heated to 700-1100°C in a reducing or inert atmosphere for 0.5-4 hours for annealing. After cooling, the powder is ground uniformly to obtain a primary product. During the high-temperature annealing process, PtM alloy nanoparticles doped with the chromium group element X are formed, and the particles are supported on the carbon support.

4. Acid washing treatment of heteroatoms on the catalyst surface: The primary product was acid washed in a dilute sulfuric acid solution, then filtered and washed with ultrapure water until neutral, and vacuum dried to obtain a chromium group metal-doped platinum alloy catalyst, which was recorded as X-PtM / C.

2. The method for preparing the chromium group metal-doped platinum alloy catalyst according to claim 1, characterized in that: The method proceeds as follows:

1. Preparation of Pt / C by polyol reduction method: The carbon support is added to a mixed solution of ethylene glycol and isopropanol, and the carbon powder is evenly dispersed by ultrasonication and magnetic stirring to obtain a carbon dispersion. Then, an ethylene glycol solution of chloroplatinic acid is added to the carbon dispersion and stirred evenly to obtain a slurry. The pH of the slurry is then adjusted to alkaline. The Pt nanoparticles are reduced to Pt nanoparticles by microwave heating under inert gas protection; the pH of the slurry is then adjusted to acidic to load the Pt nanoparticles on the carbon support; the slurry is filtered, washed, vacuum-dried, and ground uniformly to obtain Pt / C particles; 2. Sodium borohydride reduction: Pt / C particles are dissolved in ultrapure water and uniformly dispersed by ultrasonic and magnetic stirring. A metal salt solution of a chromium group element X and a metal salt solution of M are added and stirred to obtain a mixed solution. An aqueous sodium borohydride solution is added dropwise to the mixed solution in an ice-water bath and stirred for 2-3 hours after the addition is complete. The mixture is then filtered, washed, vacuum-dried, and ground to obtain XM-Pt / C powder.

3. High-temperature annealing: The XM-Pt / C powder is placed in a high-temperature furnace and heated to 700-1100°C in a reducing or inert atmosphere for 0.5-4 hours for annealing. After cooling, the powder is ground uniformly to obtain a primary product. During the high-temperature annealing process, PtM alloy nanoparticles doped with the chromium group element X are formed, and the particles are supported on the carbon support.

4. Acid washing treatment of heteroatoms on the catalyst surface: The primary product was acid washed in a dilute sulfuric acid solution, then filtered and washed with ultrapure water until neutral, and vacuum dried to obtain a chromium group metal-doped platinum alloy catalyst, which was recorded as X-PtM / C.

3. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2, characterized in that: The carbon support described in step 1 is ECP-600JD, ECP-300JD or XC-72.

4. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The volume ratio of ethylene glycol to isopropyl alcohol in the mixed solution of ethylene glycol and isopropyl alcohol described in step 1 is (2-3):

1.

5. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The ratio of chloroplatinic acid to carbon support described in step 1 is (0.2~0.6):

1.

6. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The metal salt of the chromium group element X in step 2 is chromium chloride, chromium nitrate, molybdenum chloride, molybdenum nitrate, tungsten chloride or tungsten nitrate.

7. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The metal salt of M in step 2 is nickel chloride, nickel nitrate, cobalt chloride, cobalt nitrate, ferric chloride or ferric nitrate.

8. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The ratio of the metal salt of the chromium group element X, the metal salt of M and the metal in the Pt / C particles described in step 2 is (0.1-0.3):(0.5-1):

1.

9. The method for preparing a chromium group metal-doped platinum alloy catalyst according to claim 2 or 3, characterized in that: The concentration of the dilute sulfuric acid solution described in step 4 is 0.05~0.1M, and the pickling time is 2~6 hours.

10. The use of a chromium group metal-doped platinum alloy catalyst according to claim 1, characterized in that The application is to use chromium group metal-doped platinum alloy catalysts in the oxygen reduction reaction at the cathode of fuel cells.

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