Photoelectrochemical mineralization of emerging contaminants at porous WO3 interfaces

Abstract

Nanocrystalline WO3 absorbs visible light up to 470nm and generates OH radicals via valence band injection. Therefore, it promotes the OH mediated oxidation of organic pollutants, when applied to the near UV–vis photodegradation of environmentally relevant target molecules like atenolol and carbamazepine. They both represent potentially hazardous recalcitrant contaminants of emerging concern (CEC) in waters. In the case of WO3 electrodes, a considerable acceleration of the degradation kinetics (up to 4–5 times) occurs through the application of a 1.5V potential bias, which is instrumental to optimize the charge separation within the thin films and to maximize holes transfer rate to the electrolyte. Moreover, after sufficiently long irradiation, the complete mineralization of the organics is obtained. Interestingly, the photo-electrochemical degradation process (applied bias condition) maintains its effectiveness and a large efficiency margin over conventional open circuit conditions. Photoelectrocatalysis is observed even in diluted supporting electrolyte conditions, representing the average salinity of natural freshwater samples, demonstrating the advantageous practical feasibility of the photo-electrochemical approach.