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.