Preparation And Properties Of Cu-based And Ag-based Composite Photocatalysts With Plasma Resonance Effect

Energy crisis has always been the leading problem of the world today.On the one hand,the finite reserved fossil fuels are facing the danger of running out in the coming centuries or even decades.On the other hand,the emissions of greenhouse gase from fossil fuel burning cause many environmental problems,such as the global warming and acid rain.It is urgent to develop environment-friendly renewable energy to replace fossil fuels.The emerging technology of photocatalytic hydrogen production from water spiltting provides a possible solutions to that problem.After decades of development,semiconductor photocatalysis has received extensive attention and research,and the surface plasma photocatalysis has gradually come into people's field of vision.Cu and Ag,two plasma metals,are relatively inexpensive compared to noble metals such as Pt and Au,and have unique surface plasmonic effect.In this thesis,Cu-based and Ag-based composite catalysts with the surface plasmonic effects are developed for photocatalytic water spillting.The details are as follows:?1?Individual Cu nanoparticles?Cu NPs?are susceptible to oxidation and agglomeration in the air.Three-dimensionally?3D?structured Cu-embedded graphene hydrogels?Cu-r GH?composite photocatalyst was prepared by one-step self-assembly and photoreduction methods,of which Cu nanoparticles were successfully loaded on the graphene hydrogels skeleton.Graphene?G?has high conductivity,high specific surface area,and high carrier mobility at room temperature.Besides,when it uses as the carrier,its carbon vacancies and defects can stabilize the copper nanoparticles by affecting the electronic structure of Cu NPs.Three-dimensional?3D?graphene hydrogel?r GH?is a highly porous nanomaterial,and its cross-linked multidimensional network provides the transfer channel for photo-induced electron,making it an ideal photocatalytic carrier material.The effect of the copper content of Cu-r GH binary catalyst on the rate of hydrogen evolution was investigated.It was found that Cu-r GH composite catalyst with copper content of 11.3%exhibited the best hydrogen evolution rate(16.92 mmol·g^-1·h^-1)under the condition of lactic acid as a sacrificial agent.And after 40 hours of cycle test,it still exhibits excellent hydrogen production activity.Photocurrent response,transient and steady-state fluorescence spectroscopy,electrochemical impedance and Motschottky test confirmed that the introduction of r GH improved the carrier separation rate and reduced the recombination of holes and electrons.A possible mechanism for improving the photocatalytic performance was speculated.?2?The plasmon resonance effect of elemental silver nanoparticles has played an important role in improving photocatalytic hydrogen production.Polyaniline?PANI?is a conductive polymer with a?-?conjugated electronic structure.It is also regarded as an organic narrow band gap?2.8e V?semiconductor,which acts as a good electron donor and hole acceptor under light and is conducive to the separation of photo-generated carriers.The Ag/PANI/G composite catalyst was prepared by photopolymerization and the effects of different synthesis routes on catalyst morphology and photocatalytic performance of the catalyst were investigated.Four kinds of Ag nanoparticles with different morphologies were prepared by different methods,and the photocatalytic properties of Ag/PANI composites with different morphologies were investigated.Ag nanospheres/PANI exhibits the highest photocatalytic hydrogen production rate of 628?mol g^-1 h^-1,and the photocatalytic performance of Ag nanospheres?sheets?/PANI dominated by?111?crystal plane was better than that of Ag nanospheres?lines?/PANI dominated by?200?crystal plane.