Research On Preparation And Catalytic Performance Of Defective Carbon Supported Transition Metal Catalyst

The energy crisis and environmental pollution urgently require people to develop an environmentally friendly energy conversion device that can replace traditional energy sources.Electrochemical energy conversion technology is one of the ways to solve this problem.Since the core of these energy devices involves a series of electrochemical redox reactions,electrocatalysts play a key role in electrochemical energy conversion technology.Research in recent years has shown that defects in carbon materials are considered as active sites in the electrocatalytic process.Transition metal catalysts based on defect carbon materials have excellent ORR,HER and MOR performance,and therefore become one of the most promising catalysts to replace precious metals.In this paper,by constructing a variety of different types of carbon defects and using defective carbon as carriers to prepare transition metal-supported catalysts,the effects of the types of carbon defects and the structure-activity relationship between metal and carbon defects on the catalytic activity were studied.The main research contents of this paper are as follows:（1）The graphene material with a three-dimensional structure was prepared by a hydrothermal method,and vacancy defects were introduced into the three-dimensional graphene through two treatments:HNO₃ and H₂O₂.Through electrochemical tests,it is found that vacancy defects have good catalytic activity for ORR in acidic and HER in alkaline and acidic solution.Compared with the original three-dimensional graphene,the oneset potential of graphene with vacancy defects has increased by 80 mV.The onset potentials of HER in alkaline and acidic media increased by 230 mV and 241 mV,respectively.It can be seen that the introduction of vacancy defects has a significant effect on improving the catalytic activity of three-dimensional graphene materials.（2）The defect porous carbon（CMK-3-D）is prepared by pyrolyzing the Zn precursor impregnated in CMK-3 and performing acid etching post-treatment.The evaporation of Zn not only creates additional pores,but also acts as an anchor point for the"secondary capture"of atomic Co,increasing the load of Co-SAC.A-Co@CMK-3-D catalyst exhibits ORR activity equivalent to commercial Pt/C in alkaline medium,and its initial potential is 90 mV higher than Co NPs/CMK-3-D.In the assembled zinc-air The battery also showed stability for up to 45 hours.This indicates that the adjustment of the electronic structure in the Co-C defect site can significantly improve the catalyst ORR performance.（3）The PdNi/CMK-3-D catalyst was prepared by combining PdNi alloy nanoparticles with the defective carbon carrier CMK-3-D,and used as an efficient ORR and MOR dual-function electrocatalyst.PdNi/CMK-3-D catalyst showed enhanced activity of ORR and MOR in both alkaline media.It shows that modification of PdNi particles by defect sites can simultaneously improve ORR and MOR performance.（4）Co-N/C is prepared by doping Co and N in a three-dimensional macroporous carbon network in one step to be used as an efficient ORR catalyst.The Co-N/C catalyst exhibits excellent ORR activity in alkaline media.Its Tafel slope is 40 mV dec^-1 lower than commercial Pt/C,and it can maintain electrochemical stability for up to 10 h.This shows that N doping changes the electronic structure of the carrier surface and enhances the ORR performance and stability of the catalyst.