Pathway modulation via directional radical regulation in Ov-rich Bi/BiOClBr solid solutions for enhanced photocatalytic mineralization of toluene

Volatile organic compounds (VOCs) such as toluene pose significant environmental and health risks due to their carcinogenicity and persistence. Although photocatalytic oxidation (PCO) technology has advanced, achieving efficient mineralization remains challenging. Herein, we engineered hierarchical Bi/BiOCl 0.1 Br 0.9 (BOCB) microspheres with optimized oxygen vacancies (Ov) and surface plasmon resonance (SPR) effects. The hierarchical architecture and Cl/Br heteroatomic substitution narrow the bandgap to 2.93 eV, enhancing visible-light absorption and modulating redox potentials to simultaneously generate superoxide (•O 2 ⁻) and hydroxyl (•OH) radicals. Bismuth nanoparticles induce SPR to produce hot electrons that drive •O 2 ⁻ formation, while Ov act as electron traps to capture photogenerated electrons, establishing a built-in electric field (IEF) that synergistically suppresses charge recombination. This Bi-Ov synergy spatially separates electrons and holes, enabling efficient water activation and dual-radical generation in the gas phase. Consequently, 91.7 % toluene degradation and 80 % mineralization are achieved within 2 h under simulated sunlight. In-situ FTIR spectroscopy and DFT calculations confirm that Ov-mediated adsorption/activation of H₂O and toluene alters the photocatalytic conversion pathway. Time-resolved photoluminescence spectra reveal a 3.1-fold enhancement in electron-hole separation efficiency compared to the Ov-free sample, ensuring efficient oxidation of parent VOCs and intermediates. This work elucidates the dual-radical mechanism underpinned by Ov-enhanced charge separation in Bi/BiOClBr and provides a scalable strategy for developing high-performance photocatalysts toward deep VOC mineralization.