Sputtered vs. sol-gel TiO₂-doped films: Characterization and assessment of aqueous bisphenol A oxidation under UV and visible light radiation

In this work, TiO₂ thin films were deposited onto soda lime glass substrate by two different techniques: sol-gel (SG) and sputtering (SP). The photocatalytic film performance was assessed in a batch recycle reactor testing the photocatalytic degradation of aqueous solutions of bisphenol A (BPA). The use of supported catalysts in batch recycle reactor systems for the photocatalytic degradation of organic pollutants in waste water can be an alternative to nowadays more used slurry batch reactor systems and powdered catalysts, since it is more economically sustainable and not requiring the removal of catalyst particles after waste water treatment. The best photocatalytic activities were achieved with SG films due to their porosity, which allows BPA molecule to better access the catalytic site than in case of SP films. Raman spectroscopy also showed that SP films have more oxygen vacancies, which may end up acting as charge recombination centers. Doping of TiO₂ thin films, either with N or Cu, enabled us to trigger the catalytic activity of films also under UV-free visible light radiation. Regardless the order of stacking in the double-layered films, the latter did not result in an increased catalytic activity towards the photodegradation of BPA.