Single-step solvothermal synthesis of highly uniform CdxZn1−xS nanospheres for improved visible light photocatalytic hydrogen generation

Abstract

Appropriate band gap engineering of a semiconductor material allows its use as a visible light photocatalyst with improved performance. Herein, we report on controlling the band gap of Cd_xZn_1−xS by varying the Cd to Zn atomic ratio. A simple single step solvothermal method is demonstrated to synthesize Cd_xZn_1−xS (1 ≥ x ≥ 0) at 150 °C and a short duration of 8 h. Highly uniform nanospheres composed of nanoparticles are formed in all the cases while a decrease in the diameter of nanospheres is observed with an increase in the Zn content in the solid solution. The measured band gaps of Cd_xZn_1−xS are found in the wide range of 2.29–3.33 eV depending on the Cd/Zn atomic ratio. An optimized Cd_0.2Zn_0.8S exhibits a maximum photocatalytic hydrogen generation rate of 608.15 μmol h⁻¹ g⁻¹, which is ∼7 times higher than that of pure CdS and ∼90 times higher than that of pure ZnS. The band gap along with the valence band and conduction band positions of Cd_0.2Zn_0.8S plays a major role in improved visible light H₂ generation activity.