Z-scheme Fe2O3/ZnS/CNTs nanohybrids with enhanced photocatalytic performance for sulfamethoxazole elimination under visible light illumination

The formation of composite is an efficient method to improve the performance of photocatalytic activity. Herein, the novel Z-scheme Fe₂O₃/ZnS/CNTs (FZC) nanohybrid photocatalyst was successfully synthesized via a facile hydrothermal process, establishing significantly improved efficiency of sulfamethoxazole (SMX) with visible light activity. This nanohybrid photocatalyst achieves a photodegradation capability of 95.1 %, which is 3.9 folds higher than that of the pristine Fe₂O₃ sample. Especially, the photodegradation efficiency constant (k_app) of the FZC nanohybrid is as high as 0.025 min⁻¹, which is 12.5 and 6.2 folds higher than that of pristine Fe₂O₃ and ZnS samples, respectively. Then, the FZC nanohybrid has superior stability and its photodegradation rate can still keep nearly 90 % after five cycles. The Z-scheme heterojunction and the vigorous interfacial coupling effect created by adding CNTs on the surface of Fe₂O₃/ZnS are the primary reasons for improved photocatalytic efficiency. It was also exhibited that the combining of electron donors mainly enhanced the photodegradation performance, whereas the addition of CNTs changed the photocatalytic rate, which implied a reduced photodegradation efficiency and a great enhancement in SMX removal. According to the analysis results, the photodegradation mechanism of the Z-scheme heterojunction was proposed, and the charge carrier transfer mode in the process was discussed in depth.