The recent progress of cathode materials for heterogeneous electro-Fenton reactions

As one of environmentally friendly and efficient oxidation techniques, the electro-Fenton (EF) processes allow to remove and mineralize organic pollutants. However, the transitional EF processes require an acidic environment, adding ferrous ions, treatment of iron sludge, and costly solution pH adjustment. Heterogeneous EF (hetero-EF) processes enable EF to function over a broad working pH region and recycle across multiple reaction rounds which reduces overall cost and displays great potential for practical engineering applications. Here, this work reviewed the reported cathode materials for the hetero-EF processes. We firstly described the mechanisms of homogeneous and heterogeneous EF reactions. Then, we summarized different types of cathode materials for hetero-EF reactions, including metal-free carbon materials, transition metal single-atom catalysts (SACs)/carbon materials, alloys catalysts/carbon materials, metal compounds/carbon materials and other materials. Finally, we overviewed the challenges and proposal strategies of hetero-EF technique in order to expand its wide-scale applicability and practical significance for advanced wastewater treatment.