Improving visible-light photocatalytic activity for hydrogen evolution over ZnIn₂S₄: A case study of alkaline-earth metal doping

A series of alkaline-earth metal doped ZnIn₂S₄ photocatalysts were prepared by the microwave-assisted hydrothermal method, and characterized using various analysis techniques, such as XRD, Raman, UVvis spectra, photoluminescence spectra and SEM. The successful incorporation of Ca, Sr and Ba into the lattices of ZnIn₂S₄ was proved by Raman spectra. Photocatalytic results demonstrated that Ca doping could greatly enhance the activity of ZnIn₂S₄, with about two times higher than undoped ZnIn₂S₄, while Sr and Ba doping could not. The varied photocatalytic activities of doped ZnIn₂S₄ as a function of alkaline-earth metals as dopants were discussed on the basis of the sophisticated photoluminescence process.