New Insights into Selective Singlet Oxygen Production via the Typical Electroactivation of Oxygen for Water Decontamination

Selective production of singlet oxygen (¹O₂) as an electrophilic oxidant is crucial for the precise control of chemical targets in environmental fields. Herein, we proposed a strategy to construct a redox interface on electrodes, which can in situ produce inorganic metal hydroperoxides with appropriate oxidative ability during oxygen activation. Benefiting from atomic Cu sites (CuN₄) in a copper-carbon aerogel electrode, almost complete production of ¹O₂ was achieved, thereby refraining the competitive formation of other reactive oxygen species. The fast electron transfer rate between CuN₄ and electrogenerated H₂O₂ promoted the in situ formation of copper hydroperoxide (N₄-Cu-OOH), thereby selectively and efficiently oxidizing intermediate O₂^•- to ¹O₂. The optimized production of ¹O₂ was up to 2583 μmol L^-1 without additional chemical reagents. We further considered the high production of ¹O₂ for efficiently removing electron-rich organic pollutants from a complex water matrix. Fast kinetics was achieved and considered for removing various pollutants with electron-donating substituents in a nonradical oxidation pathway. The BPA degradation efficiency is less susceptible to the coexisting natural organic matter (NOM) and inorganic ions. Specifically, the kinetic constant for BPA removal is 34 times higher than that for a nanoparticle of a copper-carbon electrode while producing a hydroxyl radical. Our findings highlight the innovative interfacial surface engineering of an electrocatalytic O₂ activation system to selectively generate ¹O₂ for future potential applications.