Preparation And Photocatalytic Performance Of Defective ZnIn₂S₄ Nanosheets And Their Composite

Zinc indium sulfide(ZnIn2S4)is a promising material for photocatalysis due to its non-toxic and stable characteristics.However,the photocatalytic performance of ZnIn2S4 is affected by its drawbacks such as low carrier migration rate.The rapid separation of photogenerated electrons and holes by improving the photogenerated carrier transport process of ZnIn2S4 plays a key role in improving the photocatalytic hydrogen evolution from ZnIn2S4.Therefore,this paper improves the photocatalytic hydrogen evolution performance of ZnIn2S4 by designing and synthesizing defective ZnIn2S4,introducing co-catalysts,and constructing ternary composite structures as strategies.The research in this paper is as follows:1.ZnIn2S4 nanosheets(DZIS)with surface sulfur vacancy defects were prepared by an ethylene glycol-assisted solvothermal method,and the presence of defects reduced the band gap and extended the absorption to the visible region.The photocatalytic H2 evolution of DZIS was determined to be 272.46 μmol g-1 h-1 under visible light,which is about 4.6 times higher than that of ZIS.The excellent photocatalytic performance of DZIS nanosheets was attributed to the fact that DZIS nanosheets can provide more surface active sites for the reaction.Moreover,the presence of sulfur vacancy defects in DZIS nanosheets,which can act as a center for trapping photoexcited carriers,inhibits carrier complexation and thus significantly improves the photocatalytic hydrogen evolution performance.2.The band gap was reduced from 2.45 eV to 2.10 eV due to the presence of Ni nanoparticles loaded on DZIS nanosheets by chemical reduction.The best performance of photocatalytic hydrogen evolution was achieved when the Ni loading was 0.2%,and the hydrogen evolution rate was 2.6 times higher than that of DZIS.Ni nanoparticles not only acted as a co-catalyst,but also formed Schottky junctions with the interface of DZIS,and electrons flowed from DZIS into Ni,which further accelerates the transfer of photogenerated electrons in 0.2%Ni/DZIS.In addition,the position of Ni was simulated by theoretical calculations,which is located in the hollow position of three S atoms in the sulfur vacancy on the ZnIn2S4(006)surface.3.CN/Ni/DZIS(CNZ)ternary composites were prepared by loading g-C3N4(CN)nanosheets on 0.2%Ni/DZIS nanosheets by impregnation method.The introduction of CN broadened the light absorption range,and after tuning the loading of CN,it was found that the optimal loading of photocatalytic hydrogen evolution performance was 50%,which was about three times of 0.2%Ni/DZIS.The formed composites of CNZ promote the carrier transport and thus improve their photocatalytic hydrogen evolution performance.