A Fermi-level engineering strategy for p-n inverted S-scheme CuO/TiO2 heterojunctions toward aromatic hydrocarbon abatement

초록

A series of CuO/TiO2 heterojunctions (CT-x, with x = 0.5–10 wt% CuO) is synthesized for the photocatalytic mineralization of aromatic volatile organic compounds. Band structure analysis via ultraviolet photoelectron spectroscopy and in situ irradiated X-ray photoelectron spectroscopy reveals distinct Fermi levels (EF) of 0.65 V vs. NHE for n-type TiO2 and 0.43 V vs. NHE for p-type CuO. Upon hybridization, EF equilibration drives electron transfer from CuO to TiO2, creating an internal electric field (IEF) accompanied by upward (CuO) and downward band bending (TiO2). Under irradiation, this n-p inverted S-scheme charge transfer pathway allows the IEF to promote recombination of weak charge carriers, while preserving more reductive electrons in the CuO conduction band (−0.613 V vs. NHE) and more oxidative holes in the TiO2 valence band (2.518 V vs. NHE). This mechanism, as verified by in situ EPR, shows concurrent generation of •O2− and •OH radicals. The optimal CT-1 composite achieves 100% toluene removal efficiency, a reaction kinetic rate of 24.5 μmol g−1 h−1, and an apparent quantum yield of 2.96E-02%. In situ DRIFTS analysis elucidates a complete mineralization pathway for toluene proceeding via benzyl alcohol, benzaldehyde, and benzoic acid. This work presents a Fermi-level-engineered S-scheme heterojunction strategy for the efficient abatement of aromatic VOCs in air.

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