Metal-free Carbocatalysis for Persulfate Activation Toward Organic Oxidation

Abstract

Metal-free carbon-based materials (CBMs), as promising alternatives to conventional metal catalysts, have been demonstrated to be highly effective in heterogeneous activation of persulfate (PS) toward organic oxidation in recent years, exhibiting great engineering-application potentials for water and wastewater treatment. Nevertheless, the intrinsic mechanism for carbocatalysis in persulfate-based advanced oxidation processes is still ambiguous due to the unique and complicated structural/surface characteristics of CBMs. Herein, this chapter outlines the fundamental principles in carbocatalysis for PS activation including identification of radical/nonradical activation pathways and determination of catalytic sites. Thereupon, the current experimental and theoretical advances in the application of carbocatalysis-driven persulfate-based advanced oxidation processes (C/PS-AOPs) are systematically summarized to reveal insights into the mechanism on the basis of the structure–performance relationship in a sequence of dimensionality (0–3D). In addition, tailored modification, as an approach to promoting the catalytic activity of CBMs for PS activation, is thoroughly illustrated, such as active site enhancement and heteroatom doping. Subsequently, the relationship between radical and nonradical pathways is demonstrated, focusing on the activation mechanism, oxidation selectivity, and radical/nonradical path transformation. Finally, challenges concerning an authentic mechanism and prospects of future research direction are proposed to overcome the knowledge gaps and facilitate the practical application of C/PS-AOPs in environmental remediation.