| In recent years,semiconductor photocatalysis has been important mean of solving environmental pollution issues and relieving energy crises.Among various of photocatalysts,Cd S has been regarded as one of the most promising photocatalysts in the semiconductor photocatalytic field due to its proper band gap.However,Cd S exist defects of the fast electron hole recombination rate and easily photocorrosion,which greatly restricts its practical application.It is generally believed that the photocorrosion of Cd S result in S generated on its surface covers active sites,affecting the absorption of visible light,thereby inhibiting photocatalytic H2 evolution activity of Cd S.Yet,Element semiconductor,such as C,P,S and so on,has obtained widely attention in the process of seeking cheap,high efficiency photocatalysts owing to their unique quality.Among which,Research suggests that S acting as element semiconductor has week photocatalytic water splitting H2 evolution activity.Accordingly,On the basis of energy band matching,This thesis mainly to discuss the surface modification of Cd S through S with traits of being abandant,low lost and substantial stable,design of a composite photocatalyst with high activity and high stability,and further analysis photocatalytic enhancement mechanism by mean of the system characterization methods.The main research contents of this thesis are presented as follows:?1?A serious of Cd S/S composite photocatalysts were synthesized via a facile solvent evaporation-deposition-precipitation method.XRD,SEM,TEM,XPS,UV-vis DRS and electrochemical measurement were employed to study structure,morphology,components,optical and electrochemical properties of the as-prepared samples.Under visible light??>400 nm?,10% S/Cd S sample exhibited the highest photocatalytic H2 evolution activity.The enhanced photocatalytic activity could be mainly ascribe to the construction of heterojunction interface between Cd S and ?-S,which accelerates the separation of electron-hole pairs and effectively restrains therecombination of photoinduced carriers.This lays a foundation for exploring the positive role of ?-S as cocatalyst on metal sulfide.?2?Novel Z-scheme S/Au/Cd S composite photocatalysts was prepared by the loading of Au and S gradually using Cd S as precursor.High Resolution Transmission Electron Microscopy?HRTEM?patterns show that Au nanoparticle was discoverd between Cd S and S,thereby forming Z-scheme S/Au/Cd S three component system.Under visible light??>420 nm?,S/Au/Cd S composites displayed much higher photocatalytic activity than the binary S/Cd S,Au/Cd S systems as well as the single Cd S,S for H2 evolution.Particularly,S/Au/Cd S composite photocatalyst exhibited the best photocatalytic H2 evolution activity and the H2 evolution rate is 4.37mmol·g-1·h-1.The radical scavengers' experiments analysed the main reactive species of photocatalytic degradation of methyl orange?MO?,further confirmed Z-scheme transmission mechanism of photogenerated carriers from Cd S and S synergistic enhancement of photocatalytic hydrogen production activity and stability of S/Au/Cd S composites.As stated previously,Modification of Cd S by S to form S/Cd S heterojunction based on energy band matching and construction of Z-scheme S/Au/Cd S photocatalyst using Au as electron mediator greatly optimize the photocatalytic H2 evolution performance of Cd S.This paper provide a useful reference for researching the positive effect of S on metal sulfide. |
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