Preparation And Photocatalytic Performance Of Bimetallic Sulfide Solid Solution And Composite Material

At present,due to the increase in population and the rapid development of industry,energy demand is increasing and environmental problems are becoming more serious.Therefore,it is necessary to promote new technologies to generate clean energy.Sunlight and water are renewable natural resources on the planet that can be used to generate clean fuels such as H₂.Hydrogen has become a unique green chemical energy carrier due to its high energy density,product-free pollution and easy transportation.In view of this fact,the development of new and effective hydrogen production technologies based on systems simulating natural photosynthesis is of great significance in solving the energy shortage problem.Metal sulfide catalysts,which have attracted tremendous interests in photocatalytic H₂ production due to their excellent light harvesting performance,sufficient narrow band gap and excellent optical properties.Solid solution catalysts with tunable electronic structure have been proved to be an effective way to increase the utilization of visible light and promote the separation and transfer of photogenerated electron-hole pairs.In this paper,a series of metal sulfide solid solution and its composite catalyst were synthesized,and then the relationship between its microstructure,size and optical properties and photocatalytic moisture analysis hydrogen activity was studied.The main study is divided into the following two parts:?1?Mn_xCd_1-xS solid solution nanorods with a size of about 55-65 nm and good monodispersity were synthesized by colloidal chemical thermal injection using cadmium acetate,manganese chloride and oleylamine as raw materials.By changing the ratios of Mn and Cd,the band gap energies?Eg?of these solid solutions could be manipulated over the entire range?x=0-1,Eg=2.21-3.43 eV?.In particular,even without loading any co-catalyst,Mn_0.5Cd_0.5S exhibited the highest photocatalytic activity of about 26000?mol g^-1 h^-1 under visible light irradiation and the apparent quantum efficiency?AQE?is as high as 30.3%at 400nm,which far exceeded pristine CdS and Mn_xCd1-xS solid solutions prepared by hydrothermal method.Enhanced photocatalytic performance of these Mn_xCd_1-xS solid solutions was owing to the balance of the absolute positions of the valence band?VB?and conduction band?CB?,broad visible light absorption,and the efficient separation and transfer of photogenerated electrons and holes.?2?The hydrogen evolution efficiency of Zn_xCd_1-xS solid solution is much higher than that of CdS monomer.Therefore,based on Zn_x Cd_1-xS solid solution as catalyst,ZnO as a cocatalyst to further enhance the photocatalytic hydrogen evolution rate of Zn_xCd_1-xS solid solution.Using cadmium acetate and zinc chloride as precursors,Zn_xCd_1-xS solid solution was first synthesized,and then Zn_0.5Cd_0.5S/ZnO with different ZnO loading nanocomposites were synthesized by seed growth method.When 10 wt%of ZnO is loaded,Na₂S and Na₂SO₃ are used as sacrificial reagents.Under visible light??>400 nm?,the hydrogen evolution efficiency of Zn_0.5Cd_0.5S/ZnO can reach 31568?mol g^-1h^-1,which is 121 times higher than that of pure ZnO and it is 4.3 times higher compared with Zn_0.5Cd_0.5S.Besides,the catalyst of this system has good cycle stability.This is mainly because ZnO is supported as a promoter on the surface of Zn_0.5Cd_0.5S,which can suppress the rapid overlap of photogenerated electrons and holes,increase the carrier lifetime,and thus increase the rate of photocatalytic hydrogen evolution and ZnO in hydrogen evolution reaction provided more active sites.