A direct Z-scheme S-Co3O4/Bi2WO6 heterostructure for enhanced photoelectrocatalytic degradation of tetracycline under visible light

Abstract

The decomposition efficiency of refractory organic pollutants depends strongly on the characteristics of the photoanode semiconductors in the photoelectrocatalytic (PEC) process. The selection of superior materials with excellent PEC efficiency is a challenge in the practical application of PEC oxidation technology. Herein, a novel S-Co₃O₄/Bi₂WO₆ heterojunction photoanode was fabricated using a simple hydrothermal procedure. Compared with Bi₂WO₆ nanoflowers, the as-prepared S-Co₃O₄/Bi₂WO₆ photoanode had a large electroactive surface area, low charge transfer resistance, strong light absorption ability, and high separation efficiency for induced photogenerated electron/hole pairs (e⁻/h⁺). This relies on the fact that S doping not only controls the morphology of Co₃O₄ but also changes its intrinsic electronic structure to improve the interlayer polarization. Notably, the Z-scheme heterojunction formed by the combination of S-Co₃O₄ and Bi₂WO₆ not only enhances the e⁻/h⁺ separation efficiency but also results in a stronger redox ability than that of pure Bi₂WO₆. In addition, reactive species trapping experiments and electron spin resonance tests demonstrated that the S-Co₃O₄/Bi₂WO₆ photoanode plays a dominant role in the degradation of tetracycline (TC) by ˙O₂⁻ and ˙OH radicals. Therefore, the prepared S-Co₃O₄/Bi₂WO₆ photoanode exhibits better PEC performance than Co₃O₄, S-Co₃O₄ and Bi₂WO₆ in the degradation of TC. The optimized S-Co₃O₄/Bi₂WO₆ composite showed a degradation rate of 87.4% in 30 mg L⁻¹ TC solution. This work provides a new strategy for the construction of efficient photoelectroanodes.