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CN-122025680-A - Method for rapidly converting platinum oxidation state-high metal state of hafnium-doped platinum catalyst

CN122025680ACN 122025680 ACN122025680 ACN 122025680ACN-122025680-A

Abstract

The application provides a method for rapidly converting a platinum oxidation state-high metal state of a hafnium-doped platinum catalyst, belonging to the technical field of new energy catalytic materials. According to the method, commercial carbon-supported platinum catalyst, hafnium salt and super-hydride are mixed in a high-boiling point solvent, the high reduction potential of hafnium is overcome by utilizing the strong reduction environment and chemical energy released by the severe decomposition of the super-hydride, high-valence platinum is reduced to a metal state, and simultaneously reduced hafnium atoms are inlaid on the surface or subsurface layer of platinum nano particles. According to the application, through the synergistic effect of the super-hydride and the hafnium salt, the rapid and efficient removal of the oxidation state of the platinum surface is realized, the d-band center of the platinum is optimized by utilizing the electronic effect and the geometric effect of the hafnium, and the oxygen reduction reaction activity and the stability of the catalyst are obviously improved. The method is simple to operate, low in cost and suitable for large-scale production, and the prepared catalyst has excellent performance and good application prospect in the hydrogen fuel cell.

Inventors

  • FU JINGBO
  • XING ZHIJUN

Assignees

  • 长春黄金研究院有限公司

Dates

Publication Date
20260512
Application Date
20260414

Claims (10)

  1. 1. A method for rapid conversion of platinum oxidation state to highly metallic state of a hafnium-doped platinum catalyst, comprising the steps of: s1, presoaking a carbon-supported platinum catalyst to be treated in dilute acid for 10-30 minutes, and then centrifugally cleaning to be neutral; S2, dispersing the carbon-supported platinum catalyst pretreated in the step S1 in a high boiling point solvent, and performing ultrasonic dispersion to form uniform dispersion; s3, heating the dispersion liquid to 200-350 ℃ in an oil bath under the protection of turbulent stirring and inert gas, adding mixed powder of hafnium salt and super-hydride into the reaction system, and stopping stirring and heating after heat preservation for 5-30 min; S4, after the product obtained in the step S3 is cooled, carrying out solid-liquid separation, washing, drying and grinding to obtain the catalyst of the platinum with high metal state on the surface; S5, dispersing the catalyst obtained in the step S4 in an ethanol solution containing benzotriazole for surface passivation treatment, and then carrying out solid-liquid separation, washing, drying and grinding to obtain a stable surface-height metallic platinum catalyst; and S6, washing the catalyst obtained in the step S5 with dilute hydrochloric acid to remove boron residues, then carrying out solid-liquid separation, washing, drying and grinding to obtain the final finished catalyst.
  2. 2. The method for rapidly converting platinum oxide form to high metal form of a hafnium-doped platinum catalyst according to claim 1, wherein the addition amount of the hafnium salt in step S3 is (5-15): 1 by mass ratio of platinum to hafnium based on platinum.
  3. 3. The rapid conversion process of the platinum oxidation state-to-highly metallic state of a hafnium-doped platinum catalyst according to claim 1, wherein the final finished catalyst is a hafnium-doped platinum catalyst.
  4. 4. The rapid conversion method of platinum oxidation state-high metal state of hafnium-doped platinum catalyst according to claim 1, wherein in step S3, the mass ratio of the catalyst to be treated to the super-hydride is 1g (0.02-2) g.
  5. 5. The rapid conversion process of platinum oxidation state-to-high metal state of a hafnium-doped platinum catalyst according to claim 1, wherein the hafnium salt is one of hafnium oxalate, hafnium chloride, hafnium sulfate.
  6. 6. The rapid conversion process of platinum oxidation state-to-highly metallic state of a hafnium-doped platinum catalyst according to claim 1, wherein the super-hydride is one of sodium borohydride, potassium borohydride, lithium triethylborohydride.
  7. 7. The rapid conversion method of platinum oxidation state-high metal state of hafnium-doped platinum catalyst according to claim 1, wherein in step S2, the high boiling point solvent is one of glycerol, ethylene glycol, butanediol and triethylene glycol, and the solid-to-liquid ratio of the carbon-supported platinum catalyst to the high boiling point solvent to be treated is 1g (500-1000 ml).
  8. 8. The rapid conversion method of platinum oxidation state-high metal state of hafnium-doped platinum catalyst according to claim 1, wherein in step S3, the inert gas is nitrogen or argon.
  9. 9. The rapid conversion method of platinum oxidation state-high metal state of hafnium-doped platinum catalyst according to claim 1, wherein the carbon-supported platinum catalyst to be treated is one of Zhuang Xinmo to HISPEC3000, HISPEC4000, HISPEC9100, and field noble metal TEC10E40E, TEC10E 20E.
  10. 10. The rapid conversion method of platinum oxidation state-high metal state of a hafnium-doped platinum catalyst according to claim 1, wherein the dilute acid is HNO 3 .

Description

Method for rapidly converting platinum oxidation state-high metal state of hafnium-doped platinum catalyst Technical Field The invention relates to the technical field of new energy catalytic materials and application, in particular to a method for rapidly converting platinum oxidation state-high metal state of a hafnium-doped platinum catalyst. Background In hydrogen fuel cells, the Oxygen Reduction Reaction (ORR) is a critical cathode reaction, the efficiency of which directly affects the performance of the overall fuel cell. Therefore, it is important to develop efficient, stable oxygen-reducing electrocatalysts. The platinum-carbon catalyst with carbon supported with platinum nano particles is one of the most widely used oxygen reduction electrocatalysts in commercial use at present due to its excellent catalytic activity and stability. However, nanoparticles possess a large specific surface area compared to the bulk material of equivalent mass. Meaning that it has a higher proportion of atoms exposed at the surface. These surface atoms are not completely coordinated by surrounding atoms as are atoms within the material and therefore are in a high energy, unstable state, i.e., have a very high "surface energy". To reduce the energy of itself, these highly reactive surface atoms are very reactive with other molecules in the environment (e.g., oxygen, water) to form more stable oxides. The negative impact of platinum oxide formation on catalyst performance is twofold. First, it directly leads to a decrease in catalytic activity. The primary active sites of ORR are the zero-valent metallic platinum (Pt 0) surfaces, while the resulting layer of PtO x, particularly PtO 2, has insulating or semiconducting properties that physically cover these active sites and alter the surface's electronic structure, thereby severely impeding the oxygen molecular adsorption and electron transfer processes, resulting in a dramatic drop in ORR activity. Second, the formation and reduction cycle of platinum oxide accelerates the irreversible degradation of the catalyst. The electrode potential may frequently fluctuate under dynamic conditions of fuel cell start-up and shut-down or load changes. This potential cycling causes repeated oxidation and reduction of the platinum surface, destroying the original lattice structure of the platinum atoms and increasing the dissolution rate of platinum. Dissolved platinum ions (Pt 2+) migrate into the electrolyte and subsequently redeposit elsewhere, resulting in increased size of the platinum nanoparticles (i.e., ostwald ripening) and agglomeration, ultimately resulting in a permanent loss of electrochemical active area (ECSA) and irreversible decay of catalyst performance. Therefore, a simple, efficient and rapid technology for converting oxidized platinum into a metal state is developed, the oxidized platinum species on the surface of a commercial platinum carbon oxygen reduction electrocatalyst can be effectively converted, meanwhile, the structural integrity of the catalyst and the dispersibility of platinum particles are maintained, and the method has important significance for improving the performance and stability of the catalyst. Disclosure of Invention Aiming at the defects that the surface of metal nano particles is easy to oxidize and the content of platinum in the oxidation state of the surface of a carbon-supported platinum catalyst is high, the invention aims to provide a method for rapidly converting the platinum oxidation state-high metal state of a hafnium-doped platinum catalyst. The method overcomes the high reduction potential of hafnium by utilizing the strong reduction environment and chemical energy released by the severe decomposition of the super-hydride, reduces the platinum in a high valence state into a metal state, and inlays the reduced hafnium atoms on the surface or subsurface layer of the platinum nano particles. According to the application, through the synergistic effect of the super-hydride and the hafnium salt, the rapid and efficient removal of the oxidation state of the platinum surface is realized, the d-band center of the platinum is optimized by utilizing the electronic effect and the geometric effect of the hafnium, and the oxygen reduction reaction activity and the stability of the catalyst are obviously improved. The method is simple to operate, low in cost and suitable for large-scale production, and the prepared catalyst meets the requirements of the hydrogen fuel cell on the high-efficiency and stable oxygen reduction electrocatalyst and has excellent performance and good application prospect in the hydrogen fuel cell. The application provides a rapid conversion method of platinum oxidation state-high metal state of a hafnium-doped platinum catalyst, which comprises the following steps: s1, presoaking a carbon-supported platinum catalyst to be treated in dilute acid for 10-30 minutes, and then centrifugally cleaning to be neutral; S2, dispe