Construction of novel In2S3/Ti3C2 MXene quantum dots/SmFeO3 Z-scheme heterojunctions for efficient photocatalytic removal of sulfamethoxazole and 4-chlorophenol: Degradation pathways and mechanism insights

In this study, we successfully designed a novel Ti3C2 MXene quantum dots (MQDs)-modified In2S3/MQDs/ SmFeO3 (IMS) Z-scheme heterojunction. We then investigated the crystal phases, chemical states, morphologies, and band structures of the Z-scheme catalysts in detail. The as-prepared IMS heterojunctions greatly facilitated the photocatalytic degradation of sulfamethoxazole (SMX) and 4-chlorophenol (4-CP) compared with the single and binary catalysts. The degradation of SMX under visible-light using the optimized IMS-3 ternary composite was clearly enhanced, and the degradation rates of 4-CP were 98.0 % and 95.4 % after 120 and 90 min of irradiation, respectively. The significantly enhanced photoactivity of the IMS composite was attributed to the effective spatial separation and charge transfer owing to the introduction of MQDs as charge-transport bridges in the Z-scheme system. Additionally, the unique properties of MQDs further accelerated the surface redox kinetics of the IMS catalyst, thus stimulating the formation of reactive species for pollutant degradation. Furthermore, these results indicate that MQDs not only act as electron mediators but also maintain the strong redox stability of IMS heterojunctions. This study offers a new avenue for developing efficient MQD-based Z-scheme photocatalysts and provides in-depth insights into the SMX degradation mechanism.