Quantum-sized BiVO4 modified TiO2 microflower composite heterostructures: efficient production of hydroxyl radicals towards visible light-driven degradation of gaseous toluene

Abstract

In an effort to develop visible-light-driven heterostructured photocatalysts with high activity, a novel quantum-sized tubelike BiVO₄ sensitized TiO₂ microflower catalytic system was successfully fabricated by using a facile hydrothermal and ultrasonic adhering approach. The structural and optical properties of the as-prepared samples were comparatively characterized. The staggered band structure of quantum-sized BiVO₄ decorated TiO₂ not only extended the photo-response range but also promoted photoexcited charges transfer and separation. Photocatalytic activities of the as-prepared samples were examined by the degradation of toluene under visible light irradiation (λ > 400 nm). Compared to the individual TiO₂ microflower, BiVO₄ quantum tube, BiVO₄ nanoparticle and nano-BiVO₄/TiO₂, the quantum-BiVO₄/TiO₂ (Q-BiVO₄/TiO₂) composite exhibited higher photo activities. Electron spin resonance (ESR) examinations confirmed the generation of the photo-induced reactive oxygen species (˙OH and ˙O₂⁻) which were involved in the photocatalytic process of Q-BiVO₄/TiO₂ composites. Furthermore, the enhanced photocatalytic activity of the Q-BiVO₄/TiO₂ composite mainly originated from the high separation efficiency of photo-induced electron–hole pairs and the efficient production of hydroxyl radicals. A detailed mechanism accounting for the superior photocatalytic activity was proposed in terms of the energy band structures of the components.