Synthesis Of Heteroatom-doped Porous Graphene Supported ?-MnO₂ And Its Catalytic Performance For Oxygen Reduction

Zinc-air batteries have the advantages of low internal resistance and low environmental pollution,and have become one of the focuses of extensive research in the field of new energy in recent years.In the internal composition of zinc-air batteries,the air cathode catalytic layer?for dual-function catalytic OER/ORR?plays a vital role in battery performance.Therefore,the study of air cathode electrode catalysts has become the focus of zinc-air batteries.However,the dynamic speed of the air electrode is relatively slow,and the catalytic cathode reaction activity is not high.It hinders large-scale commercial application,which restricts the general development of zinc-air batteries.In view of this,the development of air cathode catalysts with high performance,good stability and low price has become the focus of research.Three-dimensional porous graphene?3D-hGO?,a carbon material with a large specific surface area,high porosity,and high conductivity.The doping of heteroatoms?especially nitrogen and sulfur atoms?exposes the graphene surface to reactive sites Point,with a high oxygen reduction ORR catalytic reaction active site,heteroatom-doped porous graphene can not only be used as a carrier for the catalyst,it will also show excellent catalytic performance due to the increase in specific area due to the porous effect.In this thesis,a two-step composite catalyst of nitrogen atom?supplied by urea?,nitrogen atom and sulfur diatomic?supplied by thiourea?doped with graphene and?-manganese dioxide was prepared by one-step hydrothermal reaction.In this paper,the catalysts with a molar ratio of manganese source to doped atoms of 1:0,1:1,1:2 and 2:1 were prepared and studied by one-step hydrothermal method,and their structures and electrochemical properties were tested and compared.The results show that the catalyst with the manganese source and the doped nitrogen and nitrogen-sulfur diatomic molar ratio of 1:1 has the best performance.Its Tafel slope is 34 mV·dec^-1,the AC impedance is 3.27?,and the cyclic voltammetry test is 1000.After the second time,its catalytic activity can still maintain more than90%,the specific surface area reaches 268.37 m²·g^-1,and the pore size is about 20 nm mesoporous.Secondly,by introducing sulfur atom doping,its performance is further improved,its Tafel slop is 32 mV·dec^-1,AC impedance is 3.25?,after 1000 cyclic voltammetry tests,its catalytic activity can still maintain about 95%,specific surface area It reaches mesopores of 282.66 m²·g^-1 with a pore size of about 35 nm.Sulphur doping expands the oxygen inlet and outlet channels and is more conducive to oxygen diffusion.Finally,a comprehensive comparison shows that the performance of heteroatom-doped porous graphene-supported?-MnO₂ catalysts is better than that of undoped doped porous graphene-supported?-MnO₂,and the nitrogen-sulfur diatomic co-doped porous graphene supports The performance of?-MnO₂ is superior to the performance of?-MnO₂ loaded with porous graphene with nitrogen atom single doping.This may be due to the fact that nitrogen-sulfur co-doping provides more reactive sites than nitrogen single doping and expands the catalyst Caused by the pore size and specific surface area.