Thermal-driven Atom Diffusion Synthesis Of Single-atom Pt Or Pt-based Alloy Catalysts

Proton exchange membrane fuel cells are regarded as the most promising technology for power energy in the future due to their high energy density,low operating temperature and environmental friendly.At present,Pt-based materials are most widely used as the key component of cathode and anode catalyst for fuel cells,the low reserves and high price of platinum are bound to seriously hamper the large-scale commercialization of fuel cell.Therefore,improving the utilization of noble metals,reducing cost,and preparing high activity Pt-based catalysts for fuel cell is crucial for the widespread application of fuel cells,aiming to accelerating its commercialization process and promote the sustainable development of related industries.Herein,two works were carried out in this thesis as followed:（1）The ultra-dispersion of metal atoms is one of the most effective strategy to improve the utilization ratio of catalysts,which can lead to high activity.However,the ultra-small size metals are tending to sinter because of the Oswald ripening under high temperature by the reduction of surface free energy.Hence,we have studied the anti-Oswald maturation process of ripening with temperature change under high temperature.The Pt/C@PDA-Fe³⁺@Li Cl+KCl composite catalyst was prepared by the molten salt assist method.The result shows that,Pt nanoparticles were turned into single atoms at 400℃with the assist of Fe and molten salt.It was then aggregates into Pt Fe alloy nanoparticles because of the diffusion and migration of Pt atoms as the temperature gradually increases to 700℃.It was confirmed that Pt NPs have undergone anti-Oswald ripening and turned into single atoms from 400℃with the assistance of Fe and molten salt by combining spherical aberration correction scanning electron microscopy images and X-ray absorption fine structure spectrum.（2）Based on the previous research,regulating activity and anti-CO poisoning ability of Pt₃Co Ru/C@NC by high temperature and Si O₂ confinement for Methanal oxidation.Pt₃Co Ru/C@NC trimetallic nanoparticles with enhanced Methanol oxidation reaction activity and anti-CO poisoning ability was prepared by heat driven interface diffusion alloying and Si O₂ confinement.The result shows that,The MOR mass activity of the Pt₃Co Ru/C@NC catalyst(0.97 m A mg _Pt^-1)is 4.2 times larger than that of the commercial Pt/C catalyst(0.23 m A mg _Pt^-1).Moreover,the Pt₃Co Ru/C@NC catalyst exhibits a much lower CO oxidation onset potential than the commercial Pt/C catalyst（0.35V vs.0.82V）,which directly indicates the improved anti-CO poisoning ability of the catalyst.This enhancement in MOR activity as well as anti-CO poisoning ability of the Pt₃Co Ru/C@NC catalyst is mainly attributed to the synergistic effect of Ru（as a water activator）and Co（as an electronic modifier）.Indeed,this work not only provides a satisfactory strategy for improving the activity and anti-CO poisoning ability of MOR electrocatalysts but also gives a significant insight into simple and cost-effective alloying methods for developing homogeneous trimetallic alloy catalysts.