Fabrication of noble-metal-free Cd_0.5Zn_0.5S/NiS hybrid photocatalyst for efficient solar hydrogen evolution

Up to now, most of the semiconductor photocatalysts can only achieve their high photocatalytic activity for hydrogen production with the loading of noble metals, such as Pt or Ru, as cocatalysts, which drastically increases the total cost of the designed photocatalyst. Herein, we report the design and fabrication of a highly efficient Cd_0.5Zn_0.5S photocatalyst decorated with nanosized NiS surface heterojunctions. The hydrogen evolution rate over this photocatalyst reached 1.4 mmol/h, with a remarkable quantum yield of 33.9%. This efficiency is even much higher than many noble metal loaded photocatalysts. In this hybrid photocatalyst, the nanosized NiS on the surface can serve as electron trapping sites, by which, photogenerated electrons were extracted from Cd_0.5Zn_0.5S substrate, leading to spatially separated photoreduction and oxidation reactions. More interestingly, it was found that NiS played a similar role as noble metal, providing active sites for proton reduction, and hence efficiently enhancing the overall hydrogen production rate. Our work demonstrates the possibility of substitution of noble metal cocatalyst by a properly engineered surface hetero-junction to achieve efficient and low cost photocatalytic hydrogen production.