Almost 100 % Peroxymonosulfate Conversion to Singlet Oxygen on Single-Atom CoN2+2 Sites

Single-atom CoN4 active sites have demonstrated excellent efficiency in peroxymonosulfate activation. However, the identification of CoN4 active sites and the detailed singlet oxygen generation mechanism in peroxymonosulfate activation remains ambiguous. We demonstrate a strategy to regulate the generation of reactive oxygen species by atomically dispersed cobalt anchored on nitrogen-doped carbon. As indicated by experiment and DFT calculations, CoN2+2 was the active site and singlet oxygen was the predominant reactive oxygen species with a proportion of 98.89 %. Spontaneous dissociation of adsorbed peroxymonosulfate on the CoN2+2 active sites was energetically unfavorable because of the weakly positive Co atoms and CoN2+2 coordination, which directed PMS oxidation by a non-radical pathway and with simultaneous singlet oxygen generation. The generated singlet oxygen degraded several organic pollutants with high efficiency across a broad pH range.