| Summary: | A novel BiOI/TiO<sub>2</sub> nano-heterojunction was prepared using hydrothermal and sol-gel methods. The composite material was characterized by X-ray diffraction, ultraviolet-visible diffuse reflection spectroscopy, scanning electron microscopy, and transmission electron microscopy. The crystallinity and response to light of BiOI/TiO<sub>2</sub> were controlled by preparation conditions such as the optimal solvent condition and heat treatment temperature. The photocatalytic activity of the BiOI/TiO<sub>2</sub> catalyst was examined using benzene as a test molecule. The benzene degradation rate of the composite catalyst under visible light was enhanced compared to pure TiO<sub>2</sub>, thus reaching 40% of the original benzene concentration, which increased further to >60% after surface acidification. The fluorescence spectra, light current, and electron paramagnetic resonance confirmed that the enhanced activity was attributed to carrier separation by the heterojunction. The acid sites and active chlorine of hydrochloric acidification offer a novel mechanism for photocatalytic reactions.
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