Photoelectrochemical and Photocatalytic Properties of TiO₂, WO₃ and WO₃-TiO₂ Porous Films in the Photodegradation of Rhodamine 6G in Aqueous Solution

The photoelectrochemical properties of TiO₂, WO₃ and WO₃-TiO₂ bilayer porous films deposited on transparent electrodes have been investigated and correlated to the photocatalytic activity for Rhodamine 6G (R6G) degradation in aqueous solution under polychromatic irradiation. The WO₃ film, consisting of flakes of 70 nm diameter nanoparticles, exhibited relatively poor activity in R6G photodegradation, which was attributed to low surface coverage. The TiO₂ film, consisting of agglomerated spherical particles (25 nm in diameter) of both anatase and rutile phases based on Raman measurement, showed much better photocatalytic activity. The WO₃-TiO₂ bilayer, consisting of a TiO₂ film deposited on the surface of a WO₃ film, exhibited morphology similar to that of the TiO₂ film and improved efficiency for R6G photodegradation. The degradation process followed pseudo-first order kinetics for the initial 3 hours for all three film electrodes, with apparent rate constants of 0.37, 2.3, and 2.8 min^–1. The improved performance of the WO₃-TiO₂ bilayer film electrode is attributed to enhanced light harvesting and reduced charge recombination.