Simultaneous Photocatalytic Tetracycline Oxidation and Cr(VI) Reduction by Z‑Scheme Multiple Layer TiO₂/SnIn₄S

Wastewater pollutants are a major threat to natural resources, with antibiotics and heavy metals being common water contaminants. By harnessing clean, renewable solar energy, photocatalysis facilitates the synergistic removal of heavy metals and antibiotics. In this paper, MXene was both a template and raw material, and MXene-derived oxide (TiO₂) and SnIn₄S₈ Z-scheme composite materials were synthesized and characterized. The synergistic mode of photocatalytic reduction and oxidation leads to the enhanced utilization of e–/h⁺ pairs. The TiO₂/SnIn₄S₈ exhibited a higher photocatalytic capacity for the simultaneous removal of tetracycline (TC) (20 mg·L–¹) and Cr­(VI) (15 mg·L–¹). The main active substances of TC degradation and Cr­(VI) reduction were identified via free radical scavengers and electron paramagnetic resonance (EPR). Additionally, the potential photocatalytic degradation route of TC was thoroughly elucidated through liquid chromatography–mass spectrometry (LC-MS).