Synergistic photocatalytic O₂ activation toward formaldehyde oxidation on Ti₃C₂ quantum dot-modified ZnIn₂S₄

Replacing conventional oxidation methods with solar-driven catalytic oxidation of volatile organic compounds (VOCs) offers a sustainable alternative. The rational design of multifunctional photocatalysts capable of activating O₂ and oxidizing VOCs is crucial for efficient air purification and environmental remediation. In this study, a photo-assisted system comprising Ti₃C₂ quantum dots (TQDs) and ZnIn₂S₄ (ZIS) was designed and fabricated for the simultaneous detection and oxidation of formaldehyde (HCHO). The incorporation of TQDs into ZIS significantly boosts charge separation and redistribution, thereby lowering the thermodynamic barrier for O₂ activation and promoting the generation of reactive oxygen species. Notably, the TQDs/ZIS exhibits ca. 2.81- and 2.73-fold higher yields of ^•O₂^- and ¹O₂, respectively, as compared to ZIS. Furthermore, under high HCHO concentrations, the abundant reactive oxygen species adsorbed on the TQDs/ZIS surface effectively interacted with HCHO, resulting in a pronounced gas response and high selectivity toward specific gas molecules (e.g., C₂H₅OH and HCHO). Simultaneously, under visible-light irradiation, the photocatalytic HCHO oxidation rate of TQDs₁₀/ZIS reaches 0.032 min⁻¹, which is 3.55 times higher than that of ZIS (0.009 min⁻¹). The density functional theory (DFT) calculations further demonstrate that TQDs effectively modulate the electronic structure of ZIS, thereby promoting O₂ activation and facilitating ROS reaction pathways. This work offers a novel and promising strategy for the development of multifunctional photocatalysis system with integrated capabilities for treating reactive pollutants.