Formation and catalytic performance of novel colourful BiOI photocatalysts with adjustable bandgap under visible light

A series of novel colourful BiOI photocatalysts have been synthesised by a simple oil bath method at 160°C. Several characterisation tools including X-ray diffraction, a scanning electron microscope, energy-dispersive X-ray spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy were used to study the phase structure, morphologies, bandgap and catalytic performance of the prepared samples. The results show that BiOI exhibited higher photocatalytic efficiency under visible light (λ > 420 nm) in the degradation of methyl orange. This result could be because of the narrow bandgap, for which E_g is about 1.4-2.25 eV, and a number of active positions for catalysts. h⁺ acts as the main active species during methyl orange degradation.