The nucleophilic superoxide radical (O2•-)-based dehalogenation reaction shows great potential to degrade the toxic halogenated organic compounds (HOCs). But such an O2•--mediated reductive reaction often suffers from the competition of the secondary oxidative species (e.g., •OH), leading to inferior electron efficiency and possible disinfection byproduct formation. Here, an O2•--dominant ultrafast dehalogenation system is developed via molecular O2 activation by the oxygen vacancy (OV)-rich CuO nanoparticles (nCuO). The nCuO delivers a remarkable dechlorination rate constant of 3.92 × 10-2 L min-1 m-2 for 2,4-dichlorophenol, much higher than that of the conventional zerovalent (bi)metals. The absorbed O2 on the nCuO surface is exclusively responsible for O2•- generation, and its reactivity increases with the elevated OV content because of the enhanced orbital hybridization between the O p- and Cu d-orbitals. More importantly, the ubiquitous carbonate species firmly bound to the surface OVs block the formation of the secondary oxidative species via H2O2 activation, assuring the dominant role of the in situ generated O2•- for the selective HOC dehalogenation. The carbonate-deactivated OVs of the nCuO can be feasibly recovered via air annealing for sustainable dehalogenation. This work provides a new opportunity for selective O2•- generation via interfacial defect engineering for dehalogenation and other environmental applications.
Keywords: CuO nanoparticles; molecular oxygen; oxygen vacancy; superoxide radical; ultrafast reductive dechlorination.