Novel S-scheme WO3/CeO2 heterojunction with enhanced photocatalytic degradation of sulfamerazine under visible light irradiation

In this work, hierarchical WO3-CeO2 hollow sphere heterojunctions were fabricated via a two-step hydrothermal method and applied for degradation of sulfamerazine antibiotic under visible light irradiation. The incorporation of CeO2 into the WO3 microspheres was confirmed by XRD, BET, HRTEM, and XPS analysis. The results revealed that the photocatalytic activity of WO3-CeO2 heterojunction was greatly enhanced compared to pure CeO2 and WO3 samples, and the highest degradation percentage of sulfamerazine was achieved on the WO3-CeO2 heterojunction with 30 mol. % CeO2 content. This could be ascribed to the efficient separation of charge carriers which was facilitated by oxygen vacancies formed at the interfaces of two coupled semiconductors. EIS analysis verified that the charge transfer resistance of WO3-30CeO2 heterojunction was decreased, which is due to the heterojunction effect. Moreover, based on the Mott-Schottky calculations, radical trapping experiments and ESR analysis, hydroxide radicals were identified as the main active species, and an S-scheme charge transfer mechanism was suggested to explain the enhanced photocatalytic activity. The possible degradation pathway of sulfamerazine was suggested through the detection of degradation intermediates by mass spectroscopy.