Internal electric field-mediated sulfur vacancies-modified-In2S3/TiO2 thin-film heterojunctions as a photocatalyst for peroxymonosulfate activation: Density functional theory calculations, levofloxacin hydrochloride degradation pathways and toxicity of intermediates

Photocatalytic activation of peroxymonosulfate is considered an effective method for degrading organic pollutants. However, the difficulty in recovering powder photocatalysts restricts their practical applications. In this study, we hydrothermally generated sulfur-vacancy-modified In2S3/TiO2 thin films on fluorine-doped tin oxide substrates. We further investigated the formation mechanism of heterojunctions and the degradation pathways of levofloxacin hydrochloride by activated PMS using density functional theory calculations. Results from a series of experiments showed that the levofloxacin hydrochloride degradation performance by thin-film catalyst-activated peroxymonosulfate is comparable to that of powder photocatalysts, while the ease of recycling makes the thin film more suitable for applications in a real environment. Furthermore, the construction of heterojunctions and introduction of sulfur vacancies compensated for the poor separation efficiency of photogenerated electron-hole pairs in single photocatalysts. Overall, this study provides novel insights into the degradation of organic pollutants using thin-film photocatalysts in advanced oxidation processes.