Electronic structure and water splitting under visible-light irradiation of Zn and Ag co-doped In(OH)ySz photocatalysts

Zinc and silver co-doped In(OH)ySz with nanocubic blocks morphology were prepared by a one-step hydrothermal method and their photocatalytic activities were investigated. The as-synthesized products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) and UV–visible spectroscopy. The electron microscope observations revealed that the particle sizes of Zn-doped In(OH)ySz crystals were smaller than that of the non-doped In(OH)ySz, which accords with BET results. While Zn–Ag co-doped In(OH)ySz showed the nanocubic blocks with different particle sizes. The UV–vis spectra indicate that the single Zn ions doping leads to the absorbance band shifts toward lower wavelength upon increasing the Zn doping. Consequently, the band gap of In(OH)ySz also increases gradually with increasing the Zn doping. In contrast, an obvious red-shift is observed for Zn–Ag co-doped In(OH)ySz solid solution, which mainly attributed to the transition from Ag 4d + S 3p orbitals to Zn 4s + In 5s orbitals. The sample doped with 4 mol% Ag and Zn was found to have the highest activity, which is 20 times that of the In(OH)ySz.