Preparation Of CdS-CoSx And CdS/ZnS Photocatalysts And Their Photocatalytic And Photoelectrochemical Characteristics For Hydrogen Production

At present,most of the energy used in the world is mainly fossil fuels.However,the stock of fossil fuels is completely limited,and the CO₂ produced by fossil fuel combustion will aggravate the“greenhouse effect”.Therefore,finding new renewable clean energy has become the focus of scientific research in various countries.Hydrogen has the advantages of high combustion heat value,wide sources and environment-friendly,making it the most important substitute for fossil fuels.Photocatalytic water splitting technology is an ideal way for hydrogen production,which can utilize the abundant solar energy and water resources on the earth.Semiconductor material-cadmium sulfide?Cd S?has always been regarded as one of the ideal materials for photocatalytic hydrogen production due to its excellent light absorption performance.However,Cd S itself is prone to photocorrosion under visible light irradiation and has poor stability,which limits its wide application.In this study,Cd S nanorod loaded on conductive glass?FTO?was modified with other materials to improve its photocatalytic hydrogen production performance and stability.The main research contents and conclusions are as follows:?1?Co Sx nanosheets were loaded on Cd S nanorods by chemical bath deposition and ion exchange methods to prepare a new structured catalyst Cd S-Co Sx.By adjusting the deposition time of chemical bath,the optimal Co Sx content was obtained,and the photocatalytic hydrogen evolution performance and stability of the composite catalyst were obviously better than that of pure Cd S catalyst.This composite catalyst was used as a photoanode for photoelectrochemical catalytic?PEC?hydrogen production.The hydrogen production rate reached 168.6?mol cm^-2 h^-1(37.77 L m^-2 h^-1)under the simulated solar light,which was 2.7times of that of Cd S and the same as that of Cd S-Pt.A series of experiments were designed to reveal the characteristics of Cd S-Co Sx for photocatalytic hydrogen production.In this work,the prepared structured catalyst is easy to be recycled,and Co Sx as a cocatalyst of Cd S for hydrogen evolution shows a promising application.?2?Uniform Cd S/Zn S core/shell composite semiconductor photocatalyst was prepared by hydrothermal coating Zn S on Cd S nanorods array.By controlling the hydrothermal time,the content and coating thickness of Zn S were regulated,and the optimal hydrothermal time was selected to be 12 h.The photocatalytic hydrogen evolution performance and stability of the prepared Cd S/Zn S composite catalyst are obviously improved compared with Cd S catalyst.The prepared Cd S/Zn S was used as a photoanode for PEC hydrogen production.Under visible light,the hydrogen production rate reached to 137?mol cm^-2 h^-1(30.69 L m^-2 h^-1),which was 1.5times of that of the single-component Cd S nanomrod array.Moreover,after 5 runs of 25 h cyclic reaction,the hydrogen production rate remained unchanged,showing excellent stability,while the hydrogen production rate of Cd S decreased to 39%of its original level after the third run of reaction.Therefore,Zn S coating can not only effectively improves the hydrogen production activity of PEC of Cd S,but also effectively inhibits the photocorrosion of Cd S,greatly improving the stability of Cd S.The conclusion that photogeneratd hole of Cd S can be transferred to Zn S in Cd S/Zn S core-shell structure is confirmed by reasonably designing experiments,and the carrier transfer path and hydrogen generation mechanism of this system are put forward in visible light photocatalytic reaction.