| Because of its unique two-dimensional structure,graphene has excellent electrical,thermal,and mechanical properties.It is considered to be one of the advanced materials with the most potential for application in the 21st century.It has great potential in the field of energy and environmental electrochemistry.As a zero-band-gap semiconductor,intrinsic graphene material has fewer active sites and is easy to agglomerate,and their applications in fields such as electrochemical energy devices are limited.Therefore,reasonable modification of graphene can regulate the surface electronic structure and increase its free charge carrier density,which can significantly improve the electrochemical activity of the surface interface.Based on this,this thesis adopts two methods of halogen doping and metal nanoparticles/graphene composite to effectively modify the intrinsic graphene material and conduct application research on supercapacitors and electrocatalysis:(1)Direct functionalization study of electrolytic graphene:A method for electrochemically preparing in-situ brominated graphene(Gr-Br)has been developed.This method can not only obtain fewer layers of Gr-Br,but also achieve different levels of bromine doping.In the two-electrode system,a programmed pulse potential electrolysis strategy is used to balance the cutting,delamination,bromination and dispersion processes of electrolytic graphite to obtain high-yield and high-quality GrBr products.At the same time,the amount of bromine radicals(or bromine atoms)produced by the sources of bromine can be regulated by controlling different applied conditions(illumination,temperature control).According to this,the bromine content of the Gr-Br product is adjusted.Compared with the commonly used synthetic methods,this method can effectively solve the problems of serious environmental pollution,high energy consumption,high cost and unsafety.(2)Construction of metal nanocrystalline/graphene mode catalytic system and its electrocatalytic performance:In this thesis,the procedure potential regulation method is used to successfully deposit and synthesize monodisperse cubic copper nanocrystals on the surface of single-layer graphene.The copper nanocrystal catalyst is supported on the graphene to effectively improve the dispersibility of copper nanocrystals.Under the synergistic effect,its electrocatalytic performance is significantly improved.This experiment uses electrochemical methods to control the nucleation and growth of metal nanoparticles.According to the relationship between the surface energy of the crystal plane and the growth rate of the crystal plane,the cubic copper crystal/single-layer graphene composite material with regular shape,uniform size and controllable synthesis is controlled.Moreover,the size and density of metal nanoparticles can be adjusted by reasonably changing the experimental conditions such as nucleation potential or nucleation time.The composite material can be used for the electrocatalytic reduction of nitrobenzene and CO2.Electrochemical in-situ synthesis of hexagonal silver nanosheets on single-layer graphene,followed by a substitution reaction to prepare Ag-Pt nanocrystal/single-layer graphene composite materials.The experimental conditions for the construction of the interface between bimetallic nanoparticles/single-layer graphene by illumination and replacement fluid components were optimized.The above-mentioned electrochemical in-situ construction method has laid the foundation for the preparation of a monodisperse metal nanocrystal/monolayer graphene mode catalytic system with a clear structure and a controllable size,and the subsequent study on the structure-activity relationship. |
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