Dramatic visible light photocatalytic activity of MnOx-BiOI heterogeneous photocatalysts and the selectivity of the cocatalyst

Charge separation is very important for increasing the activity of semiconductor-based photocatalysts. Here we show that the main active species of BiOI are photo-induced holes, rather than (OH)-O-center dot and O-2(center dot-), under visible light irradiation. Based on this finding, the cocatalyst MnOx was used to enhance the transfer of the photoinduced holes, resulting in much higher photocatalytic activity, compared with the photocatalyst without MnOx. MnOx-BiOI heterogeneous nanostructure photocatalysts have been prepared by photo-deposition in Mn(NO3)(2) solution, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectroscopy. As-prepared MnOx-BiOI exhibited higher photoactivity than BiOI and Pt-BiOI for the degradation of Rhodamine B (RhB) dye under visible light irradiation. The PL spectrum showed that MnOx enhances the separation efficiency of the photo-induced electrons and holes of BiOI. Finally, BiOI was selectively combined with a deriving-hole-type cocatalyst to enhance the photocatalytic activity, and the reason for the cocatalyst selectivity is also discussed. This finding may be useful in bismuth-based photocatalysts to construct highly efficient solar energy conversion systems.