Bifunctional metallic composite catalyst cathode in heterogeneous electro-Fenton process: Classification, preparation and reactive species

Abstract

The application of conventional electro-Fenton (EF) is limited by the narrow pH range and iron-containing sludge production, while the bifunctional cathodes in the heterogeneous electro-Fenton (HEF) can realize the synchronous generation and activation of H2O2, broaden the adaptable pH range and render catalyst easy to recycle, which has gained wide attention in electrochemical advanced oxidation processes (EAOPs). In this review, we summarized the classification of bifunctional metallic composite cathodes in HEF, the preparation and loading methods of catalyst on the cathode, as well as the advantages and the corresponding characterization of the bifunctional cathodes. The approaches to enhance the catalysts performance for H2O2 generation and activation and electrode stability were addressed. The origin, identification and transformation of reactive species in degradation mechanism were explored. Finally, the challenge and trend of bifunctional cathode for HEF was prospected. We hope this review can provide a useful guideline for the design and application of bifunctional cathodes in HEF.