Study On The Photocatalytic Performance Of Transition Metal Sulfides

In recent years,transition metal sulfides have attracted much attention in the field of photocatalysis because of their narrow band gap and excellent catalytic performance.However,they are still limited by the low utilization of sunlight and fast secondary recombination of photogenerated carriers.In this paper,a variety of transition metal sulfides（Cd S,Co S_x,etc.）were studied.Their photocatalytic properties were modified by the construction of h eterojunction and element doping,and the mechanism of performance improvement is explored.（1）Firstly,n-type Cd S nanorods and p-type Co S_xnanosheets were prepared by hydrothermal method,and one-dimensional/two-dimensional（1D/2D）Cd S/Co S_xdirect Z-scheme heterojunction photocatalysts were prepared by simple mechanical stirring method.The construction of the Z-scheme heterojunction spatially separates the REDOX sites,effectively improves the separation efficiency of photogenerated carriers,and retains a strong REDOX ability.The results show that the hydrogen evolution rate of Cd S/Co S_x-25 composite photocatalyst is 473.3μmol·h^-1,which is 13.7 times of that of pure Cd S NRs.In addition,the degradation performance of Rh B under visible light was also significantly improved,and the complete decolorization of Rh B was achieved within40 min.The successful construction of Z-scheme heterojunction accelerated the photocatalysis process of photogenerated carriers with strong redox ability.（2）In addition,the common photocatalyst g-C₃N₄was selected as the base material,and the single-atom Co was introduced by simple composite calcination method.The theoretical calculation results show that the single-atom Co can be anchored in the3-s-triazine structural unit stably,and the single-site Co-S modified g-C₃N₄was prepared by in-situ hydrothermal vulcanization.The experimental results show that the composite single-site Co-S cocatalyst has excellent performance in promoting the light absorption,charge transfer kinetics and surface reaction of the photocatalytic system.The hydrogen production of single-site Co-S modified g-C₃N₄is 72.85μmol under the visible light,which is more than 9 times of that of pure g-C₃N₄.This work provides a reasonable method for the study of single-site co-catalyst.