The Preparation And Photocatalytic Activity For Hydrogen Evolution Of Spinel ZnGa₂O₄-based Composite

With the rapid development of economy and science and technology,the life level of human beings is improved.Meanwhile,the overexploitation of energy and the serious of environmental pollution have become two serious threats to the survival and development of human beings.Therefore,developing a technique to control environmental pollution and develop clean and renewable energy,is a primary task to realize the sustainable development of human society,and also becomes the world's major research topic.Solar energy is an inexhaustible ideal of clean and renewable energy.Semiconductor photocatalytic technology,which utilizes the energy of natural sunlight,has emerged as one of the most promising technologies in solving the environment pollution and energy crisis.Recently,semiconductor materials with d10 electronic structure have become a research hotspot because of high electron mobility and excellent performance in photocatalysis field.In this paper,we chose ZnGa2O4 with d10 electronic structure as main base material,in order to enhanced photocatalytic activity for hydrogen evolution of the ZnGa204 materials.Firstly,catalyst support(electron-transport matrix)and intimate interfacial contact have been studied to improve the photocatalytic activity for hydrogen evolution;Secondly,we synthesized novel morphology of ZnGa204 and cocatalyst under hydrothermal conditions.The main researches are showed as follows:In the first chapter,we briefly introduce the research background,the fundamental and requirement of semiconductor photocatalytic water splitting technology.Also,we systemtically study the research backgrand of composite photocatalysts and spinal ZnGa2O4 semiconductor.In addition,the research content of this thesis is briefly introduced.In chapter 2,we successfully synthesized size-controlled ZnGa2O4 nanospheres by adjusting the amount of surfactant trisodium citrate,and nitrogen doped graphene oxide from graphene oxide.And we use graphene oxide(GO)and nitrogen doped graphene oxide(NGO)as a supporting matrix to prepare ZnGa2O4/rGO and ZnGa2O4/N-rGO nanocomposite for photocatalytic hydrogen evolution from water.We investigate the influence of morphology of semiconductor and electrical conductivity of catalyst support on photocatalytic activity.In addition,the possible photocatalytic mechanism of ZnGa2O4/N-rGO is discussed.This work proposes a new insight to design and development graphene-based nanocomposite for various applications.In chapter 3,ZnGa2O4/ZnS/MoS2 composites were prepared through conventional hydrothermal method,and we investigate the influence of morphology of semiconductor and cocatalyst on photocatalytic activity and the role of zinc sulfide in photocatalytic reactions.Novel morphology of ZnGa2O4 and cocatalyst was identified by scanning electron microscopy(SEM)technologies.In addition,the possible photocatalytic mechanism of ZnGa2O4/ZnS/MoS2 is discussed.The ZnS can suppress the recombination of electron-hole pairs,and novel morphology can provides more effective proton reduction sites stem from the unsaturated sulfur atoms at the MoS2 edge for hydrogen production reaction,dramatically facilitating the hydrogen evolution reaction.This work provides a new strategy to improve the photocatalytic activity of ZnGa2O4,which proposes a new insight to design and development free-noble metal catalyst photocatalytic reaction.In chapter 4,we summarize the conclusions and innovative points of this dissertation,and preview the further studies.