Enhancement of photocatalytic activity by semiconductor heterojunctions:: α-Fe2O3, WO3 and CdS deposited on ZnO

alpha-Fe2O3, WO3 and US deposited on ZnO have been prepared and their photocatalytic activity was determined by photooxidation of dichloro acetic acid (DCA) in aqueous solution illuminated under medium pressure mercury lamp. These particulates were examined spectroscopically and by surface analytical methods such as surface area, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of the alpha-Fe-O-2(3), WO3 and US contents on the photocatalytic activities were studied. The experiments were carried out under three different conditions: (1) under continuous purging with molecular oxygen, (2) in the presence of naturally dissolved oxygen and (3) in the absence of oxygen. The results reveal that the mixtures of ZnO with alpha-Fe2O3 (0.5 wt.%), WO3 (0.02 wt.%) and US (0,2 wt.%) exhibit higher photocatalytic activity than pure ZnO. (C) 2002 Published by Elsevier Science B.V.