Photocatalytic and photo electrochemical properties of cadmium zinc sulfide solid solution in the presence of Pt and RuS2 dual co-catalysts

Abstract

A new combination of co-catalysts and photocatalyst, Pt-RuS2-Cd0.5Zn0.5S, is found to exhibit enhanced photocatalytic activity for hydrogen generation from water. The presence of dual co-catalysts not only improves the photocatalytic activity but also increases the stability of the CdZnS photocatalyst. Increased visible light absorption and a decrease in bandgap occur for Cd0.5Zn0.5S in the presence of the co-catalysts. All samples exist as nanocrystalline materials with a particle size in the range of 20–50nm. In this system, Ru is in 4+ oxidation state and Pt is in metallic state. Photoluminescence studies suggest the presence of a number of defect levels/surface states in these catalysts, whose energy vary with the composition of the catalyst. The enhanced photocatalytic activity of Pt-RuS2-Cd0.5Zn0.5S is attributed to the better separation of photogenerated charge carriers assisted by the dual co-catalysts. Another remarkable property exhibited by this system is the increased stability for repeated use, which can be attributed to the effective transfer of photogenerated holes from Cd0.5Zn0.5S to RuS2, which minimizes the photo corrosion of the catalyst. Photoelectrochemical results show a significant increase in the photocurrent with applied voltage and excellent switching characteristics for both Pt-RuS2-Cd0.5Zn0.5S and Cd0.5Zn0.5S. No discernible improvement in photocurrent is seen for Pt-RuS2-Cd0.5Zn0.5S compared to Cd0.5Zn0.5S. The difference in the photocatalytic and photo electrochemical property is explained based on the inherent differences of the two phenomena.