Photocatalysis over visible-light-responsive semiconductors represents an advanced and cost-efficient technology in the utilization of solar energy for environmental remediation and solar fuel generation. Extensive efforts have been made to enhance their absorption of sunlight and depress the recombination of photo-generated charge carriers towards higher energy conversion efficiency. Bismuth oxyhalide (BiOX, X=Cl, Br, I) has been proved with excellent photocatalytic performance under visible-light irradiation resulting from its special crystal and electrical structure. P-type semiconductor BiOBr has high photocatalytic reactivity despite its limited absorption of sunlight; BiOI has narrow bandgap but its photocatalytic oxidation power is considerably low due to the shallow valence band (VB) position. The solid solutions of BiOBrxI1-x at certain composition, which synergistically combined the merits of BiOBr and BiOI, are expected to achieve superior photocatalytic performance, though the nature of the composition-dependence semiconductors remains uncertain.Here we were motivated to prepare a series of BiOBrxI1-x solid solutions through tailored low-temperature synthesis to tune the band structure and improve the light-absorbance ability. The gradual shift of diffraction peaks verified that the BiOBrxI1-x samples are solid solutions rather than mixtures. Their UV-Vis diffuse reflectance spectra further proved that the corresponding bandgaps of the solid solutions are highly dependent on the composition. All the samples are active under visible-light irradiation in photocatalytic degradation of refractory pollutant. Although the samples containing large content of iodine may absorb light in longer wavelength, only the samples with low iodine content are more active than BiOBr. This may be a comprehensive result of the enhanced light absorbance and the desired band structure. The valence band maximum edge of the samples gradually shifts towards lower binding energy, suggesting the oxidation power decreased despite the narrowing of the band gap. According to Mulliken electronegativity theory, the estimated valence and conduction band of BiOBrxI1-x were correlated with their photocatalytic performance.

Bismuth oxyhalide visible-light-driven BiOBr<sub>x</sub>I<sub>1-x </sub>solid solutions: Essences for the highly efficient photocatalyst

246th National Meeting (2013)

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Bismuth oxyhalide visible-light-driven BiOBrxI1-x solid solutions: Essences for the highly efficient photocatalyst

Bismuth oxyhalide visible-light-driven BiOBr_xI_1-xsolid solutions: Essences for the highly efficient photocatalyst