Fundamentals and advances on the mechanisms of electrochemical generation of persulfate and sulfate radicals in aqueous medium

Electrochemical advanced oxidation processes (EAOPs) generating homogeneous or heterogeneous hydroxyl radicals have received great attention because these represent a real solution to fulfill Sustainable Development Goal 6 (SDG6), however, persulfate/sulfate-radical-based EAOPs (S2O82−/SO4•−-EAOPs) have been widely investigated during the past decade, as an innovative and efficient electrochemical SDG6 solution for degrading refractory organic contaminants and waterborne agents. In this minireview, the state-of-the-art of the electrocatalytic production of S2O82− and SO4•− is comprehensively analyzed and classified, and then, the current progress on the research of the mechanisms related to the electrosynthesis and electroactivation is summarized. Several viewpoints and controversies on the mechanisms are given as well as the developments that might be addressed in future, are highlighted in the end. Overall, further developments on the S2O82−/SO4•−-EAOPs depend on design, nature, and high-efficiency electrocatalysts’ composition to achieve an efficient reaction-process control as well as a real applicability (as in situ or ex situ approaches) and boosting the reaction systems.