Band gap-tunable (CuAg)_xIn_2xZn₂( _1-2x)S₂ solid solutions synthesized by hydrothermal method with ultrasonic assistance and their photocatalytic H₂ production performance

A series of (AgCu)_xIn_2xZn₂( _1-2x)S₂ solid solutions, which were usually obtained at high temperature, were successfully prepared in an environmental-friendly condition via a simple and cost-effective hydrothermal method with ultrasonic assistance. The physical and photophysical properties of these multicomponent semiconductor solid solutions were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectra (UV-Vis) and N₂ adsorption-desorption techniques. XRD patterns of prepared samples shifted to lower angles as the value of x increased, indicating that (AgCu) _xIn_2xZn₂(_1-2x)S₂ solid solutions had been formed. UV-Vis spectra of the solid solutions shifted monotonically to long wavelength side as M/Zn (M = Cu and Ag) increased, demonstrating that the band gap of the solid solution photocatalysts could be precisely controlled with the variation of the composition. SEM and TEM images showed that the solid solutions were microspheres in morphology. The microspheric morphology, as well as a proper band structure of the solid solutions, influenced its photocatalytic activity. The photocatalytic H ₂ evolution from an aqueous solution containing Na₂S and Na₂SO₃, under visible-light irradiation over (AgCu) _xIn_2xZn₂(_1-2x)S₂ solid solutions were evaluated. The Ru (1.5 wt%)-loaded (AgCu)_0.1In ₀₂Zn_1.6S₂ had the highest photocatalytic activity for H₂. evolution.