Enhanced photocatalytic activity of electrosynthesised tungsten trioxide–titanium dioxide bi-layer coatings under ultraviolet and visible light illumination

Abstract

Bi-layer WO 3–TiO 2 coatings have been synthesised on stainless steel (SS) substrates by consecutive cathodic electrodeposition of WO 3 (from peroxytungstate solutions) and TiO 2 electrosynthesis (from titanium oxosulfate solutions). The resulting TiO 2–WO 3/SS photoelectrodes have been screened for their photoresponse under ultraviolet (UV) and visible (vis) light illumination by photovoltammetry in supporting electrolyte (sodium sulfate) and malachite green (a typical dye) solutions. They were also evaluated for malachite green photooxidation during constant potential bulk photoelectrolysis. It was found that both photocurrent values and dye removal rates were higher at TiO 2–WO 3/SS than at plain WO 3/SS photoelectrodes, under both UV and vis illumination (up to 85% and 67% malachite green degradation has been achieved respectively from its 10 ppm solutions after 2 h). The enhancement of the UV and, as reported here for the first time, vis photocatalytic activity of WO 3 by the inclusion of TiO 2 is interpreted by reduced electron-hole recombination rates due to electron transfer from TiO 2 to WO 3 (during UV activation) and hole transfer from WO 3 to TiO 2 (during UV and vis light activation).