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

Zinc and silver co-doped In(OH)_yS_z 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)_yS_z crystals were smaller than that of the non-doped In(OH)_yS _z, which accords with BET results. While Zn-Ag co-doped In(OH) _yS_z 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)_yS_z also increases gradually with increasing the Zn doping. In contrast, an obvious red-shift is observed for Zn-Ag co-doped In(OH)_yS_z 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)_yS_z.