Axial enhancement on non-radicals generation in PMS activation process mediated with Co single-atom catalyst...

While numerous studies on catalysts with varying metal site sizes in Fenton-like systems have explored synergistic mechanisms between single atoms (SAs) and nanoparticles (NPs), the axial enhancement mechanism of NPs toward SAs remains underexplored. Here, we revealed the mechanism by which nitrogen-doped graphitic carbon encapsulated NPs axially enhance the activation of surface SAs over peroxymonosulfate (PMS). A novel Co_NPs-SAs@N-C catalyst coexisting with Co SAs and encapsulated Co NPs was synthesized, in which the internalization of Co NPs accelerated the interfacial mass transfer rate resulting in 4.8-fold increase in the degradation efficiency of the composite catalytic system relative to the single-atom system. Density functional theory (DFT) calculations showed that Co NPs can enhance the interfacial electron transfer rate of surface Co SAs and strengthen the interaction of Co SAs with PMS to produce more ¹O₂, besides fundamentally altering the coordination environments and electronic structures of Co SAs. Additionally, the composite system showed exceptional prospects for practical applications, with long term stability for the treatment of real wastewater. Our findings deepen the understanding of nano-single-atom composite catalysis and may inspire innovations in emerging water purification technologies and other multiphase catalytic applications.