Step-by-step tuning of morphology and band gap of ZnS/MoS2 photocatalyst for enhanced visible light to hydrogen fuel conversion

Abstract

To address the inherent limitations of ZnS and MoS2 as visible light photocatalysts, herein, we report a step-by-step tuning of mixed sulfide composite system (ZnS/MoS2) to achieve enhanced visible light to hydrogen fuel conversion efficiency in the absence of any sacrificial agents. In the first stage, ZnS/MoS2 composite was synthesized by using a single step hydrothermal route and the photocatalytic activity of the synthesized ZnS/MoS2 composite was tuned by varying the ratio of Zn and Mo in the composite. In the second stage, the photocatalytic efficiency of the composite was further enhanced by tuning the band gap and visible light absorption characteristics of the material through cobalt doping (Co-doping) in the MoS2 co-catalyst. The hydrogen generation activity of the tuned composition (1:1.3 ratio of Zn and Mo) of the ZnS/MoS2 composite with 3% Co-doping is obtained as the best (1256 μmol of H2 in 1 h) as compared to the other compositions of the doped composites (1%, 3% and 5% Co doping). The enhanced hydrogen generation through visible light induced water splitting of the developed mixed sulfide composite systems (ZnS/MoS2 and ZnS/Co-doped MoS2) even in the absence of any sacrificial agents is ascribed to their tuned band gap and low electron-hole recombination rate.