The generation of hydroxyl radicals and electro-oxidation of diclofenac on Pt-doped SnO₂–Sb electrodes

Pt-doped SnO₂–Sb electrodes constitute promising candidates for the electrochemical abatement of refractory pollutants, but their efficacy to oxidize emerging pollutants remains uncertain. In this work, the electrochemical oxidation of diclofenac, pharmaceutical pollutant, on Pt-doped Ti/SnO₂–Sb electrodes has been studied by cyclic voltammetry and galvanostatic treatment in neutral medium. In parallel, the capability of these anodes to generate hydroxyl radicals (^[rad]OHs) has been analyzed by in-situ UV spectroelectrochemical measurements. For comparison purposes, the responses of Ti/SnO₂–Sb and commercial Ti/Pt and BDD anodes were also evaluated. The voltammetric and electrolysis results show that the different Ti/SnO₂–Sb anodes can effectively oxidize and mineralize diclofenac, so their electrochemical activity lies in between that of Ti/Pt and BDD. The incorporation of small amounts of Pt (3–13 at.%) into the SnO₂–Sb coatings, despite hindering the ^[rad]OHs generation, enhances the kinetics and efficiency for diclofenac oxidation and mineralization. This better overall response is attributed to a synergy between diclofenac-Pt interaction and efficient ^[rad]OHs generation. Pt-doped Ti/SnO₂–Sb electrodes are then presented as a cheaper potential alternative to BDD for treating pharmaceutics pollutants in waters.