Influence of platinum on catalytic activity of polycrystalline WO3 employed for phenol photodegradation in aqueous suspension

A series of polycrystalline WO3 solids loaded with platinum (0.5; 1.0; 2.0 and 3.0 wt%) were prepared and characterised by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, specific surface areas determination, X-ray photoelectron spectroscopy. XPS and X-ray results indicate that the samples loaded with Pt up to 1 wt% contained on the surface mainly Pt(2+) species, while those loaded with higher amounts contained Pt(0). Moreover, the samples were employed for a probe reaction, i.e. phenol photooxidation in aqueous suspension, and their photoactivity was compared with that of two TiO2 commercial samples, mainly in the anatase phase. All the Pt-WO3 samples were more photoactive than the bare WO, for the partial photooxidation of phenol and particularly those containing 2 and 3 wt% of platinum were also more photo active that the TiO2 samples used for comparison. On the contrary, as indicated by the total organic carbon analyses; the mineralisation (complete photooxidation) of phenol was faster on TiO2 samples. Cathecol, quinone and muconic acid were found as main intermediates, both in the presence of Pt-WO3 and TiO2 samples, while hydroquinone was found only when TiO2 samples were used. (C) 1998 Elsevier Science B.V. All rights reserved.