Oxygen Reduction Performance Study Of Cerium Dioxide Doped Nitrogen-Carbon Carrier Loaded Platinum Catalysts

With the surge in global energy demand,sustainable energy sources and efficient energy storage systems have been widely studied.Among them,proton exchange membrane fuel cells are considered as one of the ideal energy sources to alleviate environmental and energy problems due to their environmental friendliness and high energy efficiency.Its commercial development is mainly limited by the slow kinetics of the cathodic oxygen reduction reaction,and therefore the development of high-performance oxygen reduction catalysts is crucial.In this paper,the preparation of high-performance Pt catalysts and the mechanism of catalyst performance enhancement are investigated.Firstly,CeO₂@ZIF-8 was prepared as a carrier precursor by ZIF-8 encapsulation of CeO₂,and 20%Pt/CeO₂@NC composite catalysts were prepared by carbonizing CeO₂@NC and loading Pt on it.The effects of different carbon coating methods,the concentration of CeO₂ during the precursor preparation and the reaction temperature of Pt reduction by microwave-polyol on the catalyst performance were investigated in detail.It was found that the best catalytic performance of Pt/CeO₂@NC catalysts was obtained with ZIF-8 coating of CeO₂,CeO₂concentration of 15 m M and reaction temperature of 110℃.The catalytic performance of Pt/CeO₂@NC exceeded that of commercial Pt/C in oxygen reduction tests,and the comparison of the characterization tests demonstrated that CeO₂ could modulate the electronic structure of the Pt loaded on it,thus improving the catalyst activity.At the same time,the interaction between Pt and CeO₂ resulted in a more stable anchoring of Pt on the CeO₂@NC carrier,thus improving the stability of the catalyst.The refined Pt/CeO₂-NC catalyst was constructed by optimizing the treatment of the carrier to further improve the electrocatalytic activity and stability of the catalyst.The optimal preparation process was determined by using cerium（III）chloride as the doped cerium source,backfilling with cerium ions,doping cerium ion concentration of 10 m M and heat treatment at 950℃in Ar for 2.5 h.The half-wave potential of the catalyst reached0.921 V and its mass-to-mass activity was 0.165 A mg _Pt^-1,which was about 2.5 times that of the commercial Pt/C catalyst.Its stability was also significantly improved.Thus,the optimized treatment of the carrier led to a significant improvement of the oxygen reduction catalytic performance of the Pt/CeO₂-NC catalyst.With the optimized CeO₂-NC carrier,CeO₂ is uniformly distributed on the CeO₂-NC surface with smaller particle size,and more refined three-phase interfacial structure is formed after loading Pt NPs.While improving the utilization rate of each component of the composite catalyst,the functionalization effect of CeO₂ component on Pt NPs was greatly enhanced,which in turn improved the catalytic performance of the catalyst.