Synergistic effect of oxygen vacancies and Ni particles over the ZnWO4/CdS heterostructure for enhanced photocatalytic reduction and oxidation activities

Abstract

Optimization of charge-transfer pathway is of great significance in a capable photocatalytic system with a heterostructure for ensuring excellent reducibility and oxidizability. Herein, we synthesized well-built photocatalysts of oxygen vacancy decorated ZnWO₄ (Vo-ZnWO₄) nanorods coupled with CdS microspheres and Ni particles via a hydrothermal and photochemical deposition method, which may result in a change in the interface charge-transfer pathway from the traditional type-II to the Z-scheme mechanism. The Vo-ZnWO₄/CdS–Ni Z-scheme heterojunction presented significant enhancements in photocatalytic activities and stability for H₂ evolution, and the rate was up to 22.84 mmol g⁻¹ h⁻¹, approximately 2284 and 7 times higher than those of pure Vo-ZnWO₄ and CdS, respectively. In addition, it showed excellent activities in the photocatalytic reduction of CO₂ and in the oxidative degradation of tetracycline (TC) under visible-light irradiation. Benefiting from the introduction of oxygen vacancies and Ni particles with the dual function of an electron medium and cocatalyst, a feasible and efficient Z-scheme band alignment was constructed to steer the carriers in a predictable direction, addressing two major issues associated with the poor activity and stability. This work could appeal to researchers in designing an effective strategy to carry out multi-directional modification for enhancing photocatalytic reduction and oxidation activities.