Upgrading and expanding the electro-Fenton and related processes

The Fenton-based electrochemical advanced oxidation processes are currently recognized as the most effective technologies to achieve fast and complete degradation of target organic contaminants in water. Electro-Fenton was the pioneering process, but a larger mineralization is attained via UV and solar photoelectro-Fenton processes due to the occurrence of key photoreduction reactions. In practice, the decontamination effectiveness turns out to be limited as solution pH increases and the two-electron oxygen reduction reaction occurring at the cathode becomes inefficient or insufficient. Here, we focus on the current opinion in two crucial features of the reviewed processes: (i) trends in cathodic H2O2 electrogeneration, showing the oxygen reduction reaction upgrading upon use of new and/or more sustainable electrocatalysts, cathode configurations and reactor designs; and (ii) advances in iron-based catalysts, with the main purpose of expanding the application to a much wider pH range, eventually surpassing the classical acidic limitation associated to conventional Fenton's reaction.