Two-dimensional Transition Metal Compound Mesoporous Carbon Composites:preparation And Electrocatalytic Properties

Oxygen electrode reactions,such as oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),are involved in new electrochemical energy storage and conversion technologies such as electrolyzed water hydrogen production,fuel cell and rechargeable metal-air cell.Due to the kinetic factors of the reaction process,problems such as high overpotential and poor cycle stability often occur,which reduce the energy conversion efficiency.At present,the widely used catalytic materials for oxygen electrode are mostly precious metals,with high cost and single catalytic performance,and can't meet the demand of charge and discharge for one electrode,which has become the bottleneck of the development of electrochemical energy storage equipment.With low production cost,mesoporous carbon's mesoporous structure can promote the mass transfer process of chemical reaction,the stability of carbon grid is strong,and its electronic structure can be controlled by a variety of element doping,so it has the potential to become a catalyst.Transition metal selenides,metal phosphorous sulfur compounds and other layered crystals,with active 3d electrons and high redox activity,could be exfoliated into a two-dimensional structure.After exfoliating,the specific surface area increases,the in-plane electron transport is convenient,and rich edges and active surfaces are exposed.In this thesis,two-dimensional nanosheets of transition metal selenides and metal phosphorous sulfur compounds were prepared by liquid phase method,and then combined with mesoporous carbon as a new type of catalyst.The synergistic effect of nanosheets and carbon substrate promotes the transmission of electrons,produces abundant active sites,and promotes the adsorption and desorption process of intermediate products in catalytic reaction,thus enhancing the dual effect catalytic performance of mesoporous carbon.Selected from series materials CoSe@NMC and NiPS3@NMC show higher catalytic activity compared with IrO2 and Pt/C,which proves the excellent bifunctional catalytic properties of the composite of two-dimensional nanosheets and mesoporous carbon,and provides a new idea for the design of catalytic materials for electrode materials.