Performance Improvement Of Photocatalytic Hydrogen Production By Decorating Photocatalyst With Co-catalyst

The development of world is dependent on utilizing of fossil fuel since the industrial revolution.However,the overuse of fossil fuel has led to the energy crisis and environmental pollution.It is necessary to change the way of energy-obtained and search a green sustainable energy.Among the different methods of green sustainable energy obtained,photocatalytic hydrogen production technique is expected to solve the energy crisis and environmental pollution problems,it could convert convenient solar energy into green hydrogen energy.But the development of efficient and cheap photocatalyst remains challenging,which has restricted the large-scale application.In recent years,significant efforts have been made to improve the photocatalytic capacity of materials,including doping,deposition,structure engineering,hetero-junction building and so on.Among them,co-catalyst deposition is a facial strategy to promote hydrogen production,catalysts with excellent hydrogen evolution production capacity can also be used as co-catalysts for photocatalysis,the mainstream co-catalysts for photocatalysis are noble metals,non-noble metals,metal compounds,non-metallic materials and so on.Co-catalyst not only can offer abundant specific reaction sites area,but also build Schottky structure with photocatalyst to promote the photo-generated hole-electron carrier pair movement.The efficiency of co-catalyst in photocatalysis is affected by the surface hydrogen evolution capability,the amount of co-catalysts loading and the connection of co-catalyst.Therefore,the co-catalyst(the traditional co-catalysts,the link between co-catalyst with photocatalyst and novel co-catalysts)is still worth exploring.In this dissertation,the effect of co-catalyst on the photocatalyst hydrogen production has been systematically studied.The research work is described in detail as follows:1.MoSx/CdIn2S4 composite was synthesized by a facial photo-deposition method for photocatalytic hydrogen production.At first,the morphology and structure of as-prepared samples were observed and studied by XRD,XPS,SEM and TEM.It was found that MoSx was closely attached onto the surface of CdIn2S4 by sharing the same S atom which had further offered the rapidly electron transport channel for photocatalytic hydrogen production.Compared with pure CdIn2S4,MoSx/CdIn2S4-40 composite exhibited amazing photocatalytic hydrogen production capacity(2.85 mmol/g/h),which was 13.6 times higher than that of pure CdIn2S4.Moreover,MoSx/CdIn2S4-40 composite exhibited stable hydrogen production capacity.The photo-electrochemical experiment revealed that MoSx/CdIn2S4 composite showed good photoelectric properties and stability,and MoSx co-catalyst could improve the photogenerated charge ability.In optical test and band-gap calculation,MoSx/CdIn2S4 composite showed better optical absorption ability,and Schottky structure was built between MoSx and CdIn2S4 material,which effectively led the transfer of photo-generated electrons from CdIn2S4 photocatalyst to MoSx co-catalyst.Furthermore,MoSx also acted as hydrogen evolution reaction sites which led to more hydrogen production yield in LSV test.2.The MoSx/Cd0.6Zn0.4S composite photocatalyst was prepared by a photo-deposition route,MoSx was photo-deposited onto the surface of Cd0.6Zn0.4S and formed a unique Schottky structure.The as-prepared samples were characterized by XRD and XPS,and their morphology were observed by SEM and HRTEM,MoSx/Cd0.6Zn0.4S composite was verified.MoSx/Cd0.6Zn0.4S composite exhibited a greatly improved photocatalytic hydrogen production yield compared with Cdo.6Zno.4S,its hydrogen production rate reached 3.06 mmol/g/h,which was 33.87 and 3.61 times higher than that of CdS and Cd0.6Zn0.4S,respectively.Moreover,MoSx/Cd0.6Zn0.4S composite showed excellent photocatalytic cycling capacity in cycling test.The photocatalytic improvement mechanism was studied by UV-Vis spectra and electrochemical characterization.These results suggested that MoSx/Cd0.6Zn0.4S displayed better light absorption,a remarkable photogenerated charge separation and transfer capacity,and more active hydrogen production reaction sites.The results of optical and band-gap calculate showed better optical absorption ability,Schottky structure was built between MoSx and Cdo.6Zn0.4S material,which effectively led the transfer of photo-generated electrons from Cdo.6Zno.4S photocatalyst to MoSx co-catalyst.In LSV experiment,MoSx/Cd0.6Zn0.4S exhibited more hydrogen evolution reaction sites which led to more hydrogen production yield.These properties greatly improved the photocatalytic hydrogen production yield using MoSx/Cd0.6Zn0.4S.3.The co-catalyst(Cu-MoS2)had been studied,it was attached onto Cdo.6Zno.4S by a solvothermal route,and a unique Schottky structure(Cu-MoS2/Cd0.6Zn0.4S)has been prepared.The crystalline structure and phase of as-prepared samples were characterized by XRD and XPS,and their morphologies were further observed by SEM and HRTEM.It revealed that the Cu-MoS2 had been attached onto Cd0.6Zn0.4S closely.Cu-MoS2/Cd0.6Zn0.4S showed a remarkable improved photocatalytic hydrogen production rate compared with pure Cd0.6Zn0.4S,its hydrogen production rate reached 6.50mmol/g/h,which was 73.47 and 7.46 times higher than that of CdS and Cd0.6Zn0.4S,respectively.Moreover,Cu-MoS2/Cd0.6Zn0.4S composites showed excellent photocatalytic cycling capacity in cycling test.The photocatalytic improvement mechanism was studied by UV-Vis spectra and electrochemical characterization.These results suggested that Cu-MoS2/Cd0.6Zn0.4S displayed better light absorption,a remarkable photogenerated charge separation and transfer capacity,and more active hydrogen production reaction sites.4.TCPP/CuCd/CdS had been prepared by multiple prepared steps.The chemical state,crystalline phase and stable interfacial media were further confirmed by XRD,XPS,SEM and TEM.The photocatalytic production rate of TCPP/CuCd/CdS had reached 2.67mmol/g/h,which was 23.15 times than that of pure CdS.In this photocatalyst,CuCd played an important role in combining organic with semiconductor photocatalyst,which had led to valid photogenerated electron-hole pair separation and efficient photo-generated electrons transport.Moreover,TCPP/CuCd also could act as active sites which can take part in photocatalytic hydrogen production.It offered a new strategy to combine inorganic semiconductor and organics for photocatalytic hydrogen production.5.The photocatalytic properties graphdiyne(GDY)co-catalyst had been studied,GDY was prepared on surface of Cu sheet,and it was confirmed by structural and morphology characterization.ZnIn2S4 had been decorated to GDY via a facile solvothermal method after GDY peeled.The chemical component and morphology of GDY-ZnIn2S4 photocatalyst were characterized to understand scientific evidence.The photocatalytic performance of the GDY-ZnIn2S4 photocatalyst was evaluated in the photocurrent and hydrogen production,its hydrogen production rate reached 0.95mmol/g/h,which was 15.62 times higher than that of ZnIn2S4 photocatalyst.The mechanism of enhanced photocatalytic activity had been explored by understanding the relation between the material characteristics.The results revealed that ZnIn2S4-GDY composites showed better light absorption,remarkable photogenerated charge separation and transfer capacity,and more active hydrogen production reaction sites.