BiOClxBryIz (x + y + z = 1) solid solutions with controllable band gap and highly enhanced visible light photocatalytic performances

A series of BiOClxBryIz solid solutions with controllable band gap and highly enhanced visible light photocatalytic performances were synthesized by a simple hydrolysis method. The samples were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectra, scanning electron microscope, high-resolution transmission electron microscopy and Brunauer-Emmett-Teller analysis. By adjusting the molar ratio of halogen ions, the band gap of BiOClxBryIz could be controllable to the suitable value for a photocatalytic reaction. Especially, BiOClxBryIz with a 1:1:2 molar ratio of Cl, Br to I showed the highest visible light photocatalytic activity for the degradation of methyl orange than individual BiOX systems. The degradation efficiency could reach over 90% within 60 min. The possible mechanism of photogenerated carrier transfer and higher photocatalytic activity was analyzed by active species trapping and energy band theory.