Unveiling the unforeseen role of manganese constituent in creating a carbon-based composite as a high-efficiency persulfate activator: Catalyzing carbon phase graphitization and promoting persulfate binding affinity

Abstract

This study demonstrated that Mn as a metallic constituent catalyzed carbon graphitization during annealing and promoted porosity through facile MnS dissolution via acid washing, thereby enhancing the catalytic activity of the carbon-based composite (Mn-N-C). Given the poor correlation between persulfate activation capability and Mn content, along with the occurrence of mediated electron transfer as a major non-radical degradative route, the Mn phase contributed minimally as a redox-active site. Carbon graphitization, uniquely catalyzed by Mn among transition metals and enhanced with higher Mn dosage, was key to improving the electrical conductivity and persulfate binding affinity of Mn-N-C. DFT analysis of the interfacial persulfate-catalyst interaction suggested a secondary role of the carbon-encapsulated Mn-N moiety in facilitating persulfate adsorption, followed by charge transfer and peroxide bond dissociation. The present finding that the Mn phase modulated the catalytic properties of Mn-N-C in multiple ways offers new insights into the criteria for selecting metal components.