SULFIDE ION DOPING PROMOTES EFFICIENT PHOTOCATALYTIC DEGRADATION OF TOLUENE BY WO₃ NANOWIRES

Sulfide-doped WO₃ catalyst (S-WO₃) was prepared through hydrothermal synthesis and calcination methods with thioacetamide and peroxytungstic acid as precursors. The peroxytungstic acid was produced by dissolving tungsten in H₂O₂ aqueous solution. This study established an oxygen vacancy-mediated, highly active hydrophilic/oxygenophilic photocatalytic reaction system. It also delved into the intrinsic mechanisms by which sulfur doping and oxygen vacancies enhance the photocatalytic performance and reactive oxygen species generation capabilities of pristine WO₃. The efficacy of this system for environmental remediation was substantiated through a series of photocatalytic degradation experiments involving toluene. Notably, S-WO₃ achieved a toluene removal rate of 91.7% within 90 minutes, 3.3 times that of the original WO₃; the CO₂ conversion rate reached 90.1%, 15.8 times that of the original WO₃. The XRD and SEM results show that S^2- doping causes lattice distortion and stress fields in WO₃, leading to the redirection of crystal growth and transforming the structure from nano-blocks to nano-wires. The S-WO₃ nanowires exhibit a larger specific surface area and a higher density of active sites than WO₃, facilitating the deep degradation of toluene. Furthermore, EPR results suggested that S^2- doping induces oxygen vacancies in WO₃, which act as electron traps to capture photogenerated electrons and facilitate charge carrier separation, thereby enhancing photocatalytic performance. Contact angle experiments indicated that S-WO₃ exhibited stronger hydrophilicity compared to pristine WO₃, effectively adsorbing water molecules and oxygen molecule, and facilitating their oxidation into the highly oxidative ·OH radical and ·O₂^- radical. In a word, S^2- doping enables WO₃ superior degradative and mineralization capabilities for toluene. Moreover, for the self-supporting properties, the S-WO₃ nanowires consistently maintain high photocatalytic activity for toluene degradation even after five successive runs, and no toxic intermediates such as benzene were produced. The results illuminate the promising potential of S-WO₃ in practice.