Defects Adjustment Induced Preparation Of Graphene-Metal Oxide Hybrid Materials And The Electrical Properties

The honeycomb structure comprised of sp2 carbon gives graphene great mechanical properties,extremely high carrier concentration and mobility,opening up wide applications in the fields of microelectronics,electrochemical energy storage,and catalysis for graphene-metal oxide hybrid materials.Among the abundant approaches for preparing graphene-metal oxide hybrid materials,the in-situ fabrication results in controllable interfaces without additional impurities,and thus improves the adjustment and optimization of properties.However,the lattice mismatches between graphene and most metal oxides are relatively too high to facilitate the epitaxies.In that case,the adjustment electrical properties via defects would be necessary.Nowadays,the graphene-metal oxide hybrids are mainly achieved by physical mixing or forming transition layers,and the defects adjustment induced in-situ fabrication still need further investigation.This thesis focuses on the defects of graphene,including oxygenated functional groups and microscopic morphologies,fabricates graphene-metal oxide hybrid materials via defects adjustment,and investigate the influence of defects on the fabrication and electrical properties.Details are as following:1.Preparation of rGO/ZnO heteroj unction via oxygen-containingfunctional groupsIn this work,GO and rGO were prepared via chemical oxidation-reduction,followed by the electrodeposition of ZnO,in which rGO/ZnO heterojunction was formed.Annealing under different temperature,time and atmosphere was applied to modify the oxygenated functional groups on the surface of rGO.Based on the studies of microscopic morphologies and electrical properties,it has been found that the rGO annealed at 400? for 30 min exhibited p-type conductivity.The study on oxygenated groups showed that a proper C-sp2 percentage(?54%)and C-sp2/(OH + C-O-C)ratio(-1.6)existing on rGO could result in rectifying I-V property.It has been proved that the evolution of hydroxyl and epoxy under different annealing conditions would significantly influence the electrical properties of rGO.2.Preparation of defective 3D graphene based on microscopic structure manipulationIn this work,graphene-ZnO-MgO-graphene 3D structure was constructed via CVD and electrodeposition,in which nickel foam was used as the initial template,while ZnO and MgO were applied to modify the microscopic morphologies.It has been found that defects such as wrinkles,pores and particles were largely formed during the fabrication and the removal of templates.The as-prepared defective graphene exhibited very good rate performance(2200 mAh/g at 0.5 A/g;300 mAh/g at 4 A/g)and stability(83%retention after 500 cycles)as the anode of lithium-ion batteries,which was better than most pure carbon based electrodes.