Oxygen vacancies promote dual-channel electron migration behavior at the S-scheme heterojunction interface of SnO2@MgSn(OH)6 for efficient deep oxidation of toluene

Oxygen vacancies induce charge redistribution, facilitating oxygen adsorption. • S-scheme heterojunctions enable efficient charge separation while retaining high redox potential. • The dual-electron transfer pathway facilitates the rapid electron transfer to O 2 . • Lowered thermodynamic barrier of the rate-determining step by modulation of ROSs generation. Transition metal stannates are promising for efficient air purification due to their remarkable activity in volatile organic compounds (VOCs) degradation. However, the interfacial charge-transfer behavior and the fundamental mechanism of aromatic ring activation, specifically, C-H bond cleavage and ring-opening oxidation remain elusive, hindering rational catalyst design for toluene (C 7 H 8 ) mineralization. Herein, an oxygen-vacancy-enriched S-scheme heterojunction (SMSH-30) is constructed via a facile one-step hydrothermal strategy. The optimized heterostructure exhibits outstanding toluene removal (96.65%), mineralization efficiency (101.8%), and long-term stability (>600 min). Combined experimental and theoretical analyses unveil that oxygen vacancies (OVs) modulate charge transfer and reactive oxygen species (ROS) evolution: (1) OVs induce dual-channel electron migration, greatly facilitating interfacial charge transfer; (2) this enhanced transfer promotes O 2 activation into highly oxidative singlet oxygen ( 1 O 2 ); and (3) the optimized interface accelerates intermediate conversion with a favorable Gibbs free energy profile. This work provides molecular-level insights into charge dynamics and ROS modulation within S-scheme heterojunctions, offering a new paradigm for rational design of advanced photocatalysts toward deep VOC mineralization and sustainable air purification. Download: Download high-res image (156KB) Download: Download full-size image Combined experimental characterizations and density functional theory calculations revealed that oxygen vacancies serve as continuous O 2 activation centers, while the S-scheme interface promotes efficient charge separation and preserves high-redox-potential electrons for singlet oxygen generation toward complete anti-poisoning mineralization of toluene.