Metal-nitrogen-carbon catalysts for peroxymonosulfate activation to degrade aquatic organic contaminants: Rational design, size-effect description, applications and mechanisms

Peroxymonosulfate-assisted advanced oxidation processes (PMS-AOPs) have attracted increasing attention in the past few years due to their outstanding reactivity and oxidation capacity. Metal-nitrogen-carbon (MNC) materials have been widely applied for activating PMS to degrade various refractory organic pollutants. This article discussed the advance of PMS activation by MNC catalysts. Firstly, the synthesis methods of MNC catalysts including chemicals derivatization, metal–organic frameworks (MOFs) derivatization and biomass derivatization were summarized. Secondly, the recent progress on diverse MNC catalysts (e.g. FeNC, CoNC, CuNC, MnNC and NiNC) for PMS activation was reviewed. Thirdly, the activation mechanisms of MNC catalysts and their fundamental behaviors in PMS systems were elucidated. These composite components (metal, nitrogen and carbon) are not perfunctorily mixed and play respective indispensable roles. There are ingenious synergistic effects between them. In addition, metal sites in MNC catalysts exist in different size forms including nanoparticles, atomic clusters and single atoms. The subtle effects of metal size and dispersity on the pathway of PMS activation (free-radical and non-radical mechanisms) were classified and illustrated. Finally, the challenges faced by MNC catalysts and improvements needed in the practical application were distinctly proposed. This review should be of value in promoting the research of PMS activation by MNC hybrid materials for organics degradation and corresponding sensible applications.