Synergism between Fe2O3 and WO3 particles: Photocatalytic activity enhancement and reaction mechanism

In this work we have found that simple mixing of WO3 and Fe2O3 can result into significant enhancement in activity for phenol degradation in the presence of H2O2 either under UV or visible light. The enhanced activity varied with Fe2O3 content in the mixed oxide. The best catalyst was 1.0 wt% Fe2O3/WO3, whose activity, in relative to bare WO3, increased to 3.8-fold under UV light, and 2.1-fold under visible light. Control experiments indicated that phenol degradation was mainly initiated by the excited WO3 in Fe2O3/WO3, and that there was a synergistic effect between two oxides. A spin trapping electron paramagnetic resourance spectroscopy revealed that the production of hydroxyl radicals over Fe2O3/WO3 was greatly enhanced. Solid characterization with X-ray diffraction, N-2 adsorption and element mapping showed that Fe2O3 particles were highly dispersed in the sample, with a small size and high surface area. We propose that there occurs an electron transfer from the conduction band of WO3 to low energy trapping sites of Fe2O3, which promotes the separation of WO3 charge carriers, and consequently accelerates phenol degradation. (C) 2012 Elsevier B.V. All rights reserved.