Revealing the Enhanced Visible-light-driven Photocatalytic Activity of In2S3/CeO2 Heterojunction: Bandgap Structure Analysis and Active Radicals Determination

Background: The widespread presence of persistent organic pollutants, such as dyes in effluent from printing and textile industries, poses a significant threat to aquatic life and human health. Photocatalytic degradation is widely recognized as a promising technology to address this pollution crisis. The efficiency of photocatalysis is intricately tied to both the active radicals and the band structure of the catalyst. These factors play a crucial role in governing the photodegradation of dye molecules.

Methods: In2S3/CeO2 heterojunctions were synthesized using an in-situ precipitation method and subsequently analyzed through SEM, XRD, and XPS techniques. Notably, the bandgap structure of the heterojunctions was examined through UV-Vis DRS. The photocatalytic performance of the synthesized samples was assessed by studying the degradation of methyl orange. To further validate the photocatalytic process, EPR spectroscopy was employed to confirm the presence of radicals generated within the heterojunction.

Results: The heterojunction displayed a characteristic type-II structure, enhancing light absorption and facilitating the separation of photoinduced carriers. Among the In2S3/CeO2 composites, the one with a 15 wt% CeO2 content exhibited the highest photocatalytic activity, achieving an 88% degradation of methyl orange after 90 min of exposure to visible light irradiation. Additionally, •O2 − is identified as the primary active species responsible for degradation.

Conclusion: UV-Vis DRS illustrated the improved transfer and separation of photogenerated electrons attributed to the optimized band structure of the heterojunction. EPR spectroscopy yielded valuable information on active radicals, thereby proposing the photocatalytic degradation mechanism.