Bi5+ , Bi(3-x)+ , and Oxygen Vacancy Induced BiOClx I1-x Solid Solution toward Promoting Visible-Light Driven Photocatalytic Activity.

BiOClx I1-x solid solutions with different band gaps were synthesized by adjusting the initial Cl to I molar ratios through a chemical precipitation method at room temperature. The structures, morphologies and optical properties of the samples were characterized by XRD, XPS, Raman, SEM, TEM and UV/Vis, respectively. The photocatalytic experiments showed that the BiOCl0.9 I0.1 sample totally decomposed a large concentration of 50 mg L-1 aqueous Rhodamine B (RhB) solution within 12 minutes under visible light irradiation (λ>420 nm), which is 11 times higher than that of pure BiOI. Furthermore, the electron band structure and density of states of BiOCl, BiOI and BiOClx I1-x have been investigated using the DFT (density functional theory) calculation method and electrochemical methods. It was found that there are multiple crystal defects of Bi5+ , Bi(3-x)+ , and oxygen vacancies in the BiOClx I1-x samples. The results for Mott-Schottky plots and valence-band XPS spectra showed the position of conduction band (CB) for BiOCl0.9 I0.1 was up-shifted, which is favourable to the redox capacity for the photocatalysts. It could be elucidated that the synergistic effects of multiple crystal defects and unique band structure are critical to improving solar driven photocatalytic activity. This work provides a new highlight toward the construction of high property photocatalysts by tuning the crystal defect and band structure in a simple and efficient way.