Rare earth doped TiO2-CdS and TiO2-CdS composites with improvement of photocatalytic hydrogen evolution under visible light irradiation

In this paper, we report the obtention of a series of rare earth doped composite Pt/RE/TiO2-CdS (RE=La3+, Eu3+, Er3+, Gd3+) and TiO2-CdS photocatalysts prepared by a simple mechanical mixed method. The photocatalysts properties were studied by means of ultraviolet-visible spectroscopy, photoluminiscence spectra, X-ray diffraction, transmission electron microscopy, specific surface areas and the electrochemistry method. Photocatalytic hydrogen evolution using Na2S/Na2SO3 as electron donor was investigated under visible-light (λ≥420 nm) irradiation. The rare earth doping enhances the activities of Pt/RE/TiO2-CdS samples (with 1.0 wt% deposited Pt). Under optimum conditions, the activities of La3+, Eu3+, Er3+, Gd3+ doped composite Pt/RE/TiO2-CdS increase by 62.0%, 40.4%, 34.7% and 30.0% respectively, when compared to that of Pt/TiO2-CdS, due to the prevention of electron–hole recombination and the flat-band potential of the conduction of TiO2 shifting negatively by the doping.