SILAR BiOI sensitized TiO2 films for visible light photocatalytic degradation of rhodamine B and 4-chlorophenol

BiOI nanoplates were deposited upon a film of TiO2 nanoparticles derived from a commercial source using a simple room temperature SILAR method. X-ray diffraction, X-ray photoelectron spectroscopy and electron microscopies have been used to confirm the crystal phase, chemical states of key elements and morphology of the BiOI nanoplate-TiO2 composites. Using both valence band x-ray photoelectron spectroscopy and UV-vis diffuse reflectance measurements the band structure of the composites is determined to be that of a type II heterojunction. Through initial screening of the photocatalytic activity of the SILAR-modified films it was determined that 5 SILAR cycles was optimal in the photocatalytic degradation of Rhodamine B. The visible light sensitisation effect of BiOI was then proven by examination of the photocatalytic degradation of the colourless organic pollutant 4-chlorophenol showing a large enhancement over an equivalent TiO2 film.