Driving S-scheme charge transfer via Fermi level disparity: efficient toluene mineralization over oxygen vacancy engineered Bi2WO6 coupled with TiO2

초록

Photocatalytic degradation is a sustainable strategy for the remediation of stable aromatic volatile organic compounds such as toluene. Yet, the energy-efficient mineralization of these pollutants under ambient conditions remains a critical bottleneck. Herein, an n–n S-scheme heterojunction photocatalyst is constructed via in situ hydrothermal coupling of TiO2 with oxygen-vacancy-engineered Bi2WO6 (TB-x: x represents the TiO2/Bi2WO6 molar ratio). A work function difference of 0.39 eV induces band bending and an internal electric field from Bi2WO6 to TiO2, enabling an efficient S-scheme charge transfer pathway. Consequently, the optimized TB-2 exhibits a longer charge carrier lifetime (21.1 ps) than the pristine components. In a fixed-bed flow system, TB-2 achieves 97.2% degradation of 5 ppm toluene within 60 min under UV irradiation, delivering a high dynamic clean air delivery rate (1940 L h−1 g−1) and an apparent quantum yield of 0.1%, with high stability across reuse cycles and under varying humidity conditions. In situ DRIFTS, EPR, and DFT analyses reveal a stepwise oxidation pathway via benzyl alcohol and benzaldehyde intermediates, ultimately forming CO2 and H2O. This work highlights the critical role of interfacial band engineering in constructing an efficient air purification system based on direct mechanistic evidence for oxygen-vacancy-assisted S-scheme charge transfer in TiO2/Bi2WO6 heterojunctions.

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