Interfacial Hydroxylation of ZnSn(OH)6/TiO2 Enhances Charge Separation for Stable and Efficient Photocatalytic Toluene Mineralization

Volatile organic compounds (VOCs) pose significant environmental and health risks, necessitating effective remediation strategies. This study addresses these challenges by synthesizing ZnSn(OH) 6 /TiO 2 heterojunction composites using a coprecipitation-hydrothermal coupling technique. Experiments showed that the synergistic effect of ZnSn(OH) 6 and TiO 2 significantly reduced the band gap (3.10 eV) of the composites and enhanced the visible light absorption ability, whereas the photogenerated electron–hole pair complexation was effectively suppressed through the interfacial charge transfer mechanism. Under simulated sunlight, 15% ZnSn(OH) 6 /TiO 2 degraded toluene at an initial concentration of 2,500 ppm by up to 90.51% in 90 min, with a mineralization rate of more than 84.51%, which is about three times higher than the performance of pure ZnSn(OH) 6 . Cycling experiments showed that the degradation rate remained at 90.32% after five times of reuse, demonstrating excellent stability. A combination of density functional theory (DFT) calculations and radical trapping experiments revealed that ·OH and ·O 2 − were the main active species in the composites, and the hydroxyl structure of ZnSn(OH) 6 promoted the adsorption and activation of toluene. This work presents a novel interfacial engineering and crystallographic regulation strategy for deep mineralization of VOCs, providing insights for designing cost-effective, durable environmental photocatalysts. Graphical This study describes the synthesis, structural, and surface characterization of TiO 2 nanoparticle-decorated layered ZnSn(OH) 6 composite catalysts, systematically evaluates their photocatalytic activity, degradation kinetics, and long-term stability for gaseous toluene under simulated solar light, and investigates photogenerated electron-hole migration pathways, separation efficiency, and reactive oxygen species formation mechanisms.