Interfacial Solid-State Mediator-Based Z-Scheme Heterojunction TiO₂@Ti₃C₂/MgIn₂S₄ Microflower for Efficient Photocatalytic Pharmaceutical Micropollutant Degradation and Hydrogen Generation: Stability, Kinetics, and Mechanistic Insights

Interface engineering is a vital concern to achieve high efficiency in heterojunction photocatalysts. The judicious design of efficient interfacial electron mediators to accelerate the charge transfer efficiency in Z-scheme heterojunctions with interfacial contact for enhancing the performance of photocatalysts is essential and has been considered an immense challenge. Inspired by nature, multivariate all-solid-state Z-scheme TiO 2 @Ti 3 C 2 /MIS heterojunction composites were fabricated via a simple two-step oxidation strategy for highly promoted multiple photocatalytic applications. The morphological analysis of TiO 2 @Ti 3 C 2 /MIS composites demonstrated that MgIn 2 S 4 (MIS) microflowers were accumulated on the surface of Ti 3 C 2 @TiO 2 nanosheets, providing dense active sites to the MIS microflowers for efficient photocatalytic applications. The HRTEM and XPS characterization distinctly clarified the close interfacial interaction between MIS with Ti 3 C 2 and TiO 2 . The optimized TiO 2 @Ti 3 C 2 /MIS-15 photocatalysts exhibited the highest photocatalytic ciprofloxacin degradation (92%) and hydrogen evolution (520.3 μmol h –1 ) as compared to those of their pristine counterparts. From the mechanistic insights, the charge migration pathway was observed between MIS and TiO 2, where Ti 3 C 2 nanosheets served as an electron bridge in constructing the Z-scheme and thus extended the lifetime of the charge carriers photoinduced by MIS and TiO 2 . The significant participation of • O 2 – and • OH radicals during photocatalytic CIP degradation was verified by active species trapping experiments, EPR, and liquid chromatography–mass spectrometry (LC-MS) analysis. The current study provides a strategy to design mediator-based Z-scheme heterojunction interfaces for improving the catalytic activity of MXene-derived photocatalysts.