Atomically Dispersed Cobalt Sites on Graphene as Efficient Periodate Activators for Selective Organic Pollutant Degradation.

Pollutant degradation via periodate (IO)-based advanced oxidation processes (AOPs) provides an economical, energy-efficient way for sustainable pollution control. Although single-atomic metal activation (SMA) can be exploited to optimize the pollution degradation process and understand the associated mechanisms governing IO-based AOPs, studies on this topic are rare. Herein, we demonstrated the first instance of using SMA for IO analysis by employing atomically dispersed Co active sites supported by N-doped graphene (N-rGO-CoSA) activators. N-rGO-CoSA efficiently activated IO for organic pollutant degradation over a wide pH range without producing radical species. The IO species underwent stoichiometric decomposition to generate the iodate (IO) species. Whereas Co and CoO could not drive IO activation; the Co-N coordination sites exhibited high activation efficiency. The conductive graphene matrix reduced the contaminants/electron transport distance/resistance for these oxidation reactions and boosted the activation capacity by working in conjunction with metal centers. The N-rGO-CoSA/IO system exhibited a substrate-dependent reactivity that was not caused by iodyl (IO) radicals. Electrochemical experiments demonstrated that the N-rGO-CoSA/IO system decomposed organic pollutants via electron-transfer-mediated nonradical processes, where N-rGO-CoSA/periodate* metastable complexes were the predominant oxidants, thereby opening a new avenue for designing efficient IO activators for the selective oxidation of organic pollutants.