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

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 O-2(-) 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.