Intrinsic nanoparticle-single-atom interplays steering radical versus nonradical pathways in catalytic ozonation

Compositional heterogeneity in metal/nitrogen-doped carbons (M-N-Cs) complicates the fundamental elucidation of the intricate interplay between the active metal species that rule the reactivity of single atomic catalysts (SACs). This study unveils the electronic disruptions of cobalt nanoparticles (Co NPs) to the catalytic behaviors of cobalt single-atom (Co SA). The intense electronic communications between high-density Co NPs and Co SA sites lead to dissociation O3 on the high-spin Co SA sites to generate surface-confined hydroxyl radicals (•OH). However, the tandem electron transfer yields superoxide radical (O2•–) with low reactivity and remarkably reduce ozone utilization efficiency (OUE). In contrast, independent Co SA sites far or free from adjacent Co NPs induce a nonradical O3 activation regime, which markedly improves electron utilization efficiency (~2.9-fold), OUE ( ~ 3.0-fold), and turnover frequency (TOF, ~2.5-fold) of Co SA. The nonradical catalytic ozonation process demonstrates high adaptability to complex water matrices and maintains long-term stability in the treatment of real petrochemical wastewater. The deciphered electronic interplays between metal nanoparticles and single atom sites advance a new paradigm to regulate the selectivity of single atom catalysis. Single-atom catalysts, particularly metal/nitrogen-doped carbons, have become a versatile platform for fine-tuning electronic interactions with reactants and controlling thermodynamic selectivity. Here, the authors show that the catalytic ozonation activity of single-atomic Co–N₄ sites can be electronically modulated by adjusting the density of Co nanoparticles on the carbon matrix.