Synthesis Of Graphene And Transition Metal Disulfides Based Composites For Catalytical Applications

Fossil fuels depeletion is a serious problem nowdays,to develop sustainable energy is therefore an urgent task for the researchers.Solar energy is a kind of solution for this problem,the utilization efficiency of solar energy is however limited due to the activity of photocatalysts.Environment pollution is another serious social problem that will affect our daily lives.The degradation of organic pollutants in the water is important not only for drink water but also for the industrial wastewater.In this study,we chose the hot material stars,graphene and transition metal disulfides as the basis for the fabrication of useful composites.The obtained materials are very acitive in the energy generation and environment protection.In the first part,we synthesized graphite encapsulated nickel foam（Ni@GF）using the CVD method.A composite of Ni@GF@Ni₂S₃ will be obtained using thiourea as the sulfur source with a hydrothermal method.Because of its excellent mechanical propoties,this composite could be used as free-standing electrode for electrochemical hydrogen evolution in both alkaline and acidic electrolytes.Graphene and transition metal disulfides,such as MoS₂ and WS₂ are all efficient photocatalytic cocatalysts.By loading them as cocatalysts,the photocatalytic activity can be enhanced for semiconductors.In this study,we combined the graphene and MoS₂ together to prepare a MoS₂/rGO hybrid.CdS nanoparticles can then grown on the surface of the hybrid for a ternary photocatalysts CdS-MoS₂/rGO.The activity of CdS-MoS₂/rGO can be adjusted by change the percentage of MoS₂/rGO hybrid in the photocatalyst or the percentage of rGO in the MoS₂/rGO cocatalyst.The final CdS-MoS₂/rGO was proved to be effective for the photocatalytic reduction of4-nitrophenol to 4-aminophenol under visible light.Using MoS₂/rGO hybrid as support,Au,Ag,Pt,and Pd nanoparticles can also be generated on its face with sodium citrate as reductant.The obtained composites could be used as sensor material for the detection of 4-nitrophenol in aqueous solution.Furthermore,they can also be used as catalysts for the reduction of 4-nitrophenol with NaBH₄ as the reductant.In the last section,we fabricated a Cu₂O/WS₂ photocathode using a layer by layer assemble method.Mixed phase WS₂ was first exfoliated with N-butyllithium as intercalation agent.This mixed phase WS₂ is highly active in the HER,and it is therefore can be used as cocatalyst for the modification of Cu₂O.The obtained Cu₂O/WS₂ exhibited excellect activity for the photoeletrochemical hydrogen evo-lution,and has great potential to utilize solar energy.In conclusion,we fabricated kinds of composites using graphene and transition metal disulfides,the obtained composites shows great potential in energy generation and environment protection.We will use these 2D nanomaterials to prepare more composites in different application fields in the future,thus to provide more choice to improve our daily lives.