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, N2 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.

Graphical abstractDevelopment of a highly visible-light-driven photocatalyst is a challenge for chemical use of solar energy. In this work, we find that simple mixing of WO3 and Fe2O3 can result into significant enhancement in activity for phenol degradation in water in the presence of H2O2 under either UV or visible light. The enhanced activity greatly varied with the weight percent of Fe2O3 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, respectively. We propose that the observed synergistic effect between two oxides is due to the electron transfer from the conduction band of WO3 to low energy trapping sites of Fe2O3. Such interfacial charge transfer between two oxides would facilitate the separation of WO3 charge carriers, and consequently accelerate the surface reaction on both oxides for organic degradation.Figure optionsDownload full-size imageDownload high-quality image (171 K)Download as PowerPoint slideHighlights► Simple mixing of WO3 and Fe2O3 can significantly improve the photoactivity. ► The enhanced photoactivity greatly varied with Fe2O3 content in the mixed oxide. ► Fe2O3 particles were highly dispersed with a small size and high surface area. ► Synergism between Fe2O3 and WO3 are observed under UV or visible light.