Influence of Sr-doping on the photocatalytic activities of CdS–ZnS solid solution photocatalysts

Alkaline earth metal Sr was successfully doped into CdS–ZnS solid solutions for the first time. The as-prepared photocatalysts were characterized by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, UV–vis diffuse reflectance spectra (UV–vis), photoluminescence spectra (PL), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), etc. BET characterization indicated that all the prepared samples possessed mesoporous structures with large specific surface areas. Photocatalytic H2 evolution results showed that Sr-doping can efficiently improve the photocatalytic activities while the molar ratio of Zn was greater than 20% in the absence of noble metal as co-catalyst. The correlation between the Zn/Cd ratio of solid solution and the Sr-doping amount was investigated in detail. Results showed that the recombination of photoelectrons and holes could be efficiently suppressed by doping metal ions on the shallow surface of CdS–ZnS, which could become the centers of shallow electrons or holes traps, thus significantly improve the efficiency of charge separation.