Carbon-Iodine Coordination Activates Co-N4 Sites for Efficient Peroxymonosulfate Activation toward...

Mass transfer limitations and inefficient nonradical oxidant generation often constrain the practical performance of Fenton-like catalysts for micropollutant removal. Here, we develop a synergistic architectural strategy to construct carbon-supported cobalt single-atom catalysts (Co-INC) via ammonium iodide-assisted chemical vapor deposition, integrating atomically dispersed Co-N4 sites with carbon-iodine (C-I) coordination motifs to simultaneously enhance reactant transport and singlet oxygen (1O2) production. Benefiting from in situ NH3-mediated etching, the architecture enhances active-site accessibility while achieving a high Co density of 0.165 mmol g-1, facilitating peroxymonosulfate (PMS) diffusion. Additionally, iodine incorporation creates an asymmetric Co-N4/C-I coordination environment that upshifts Co d-band center to -0.54 eV, strengthening PMS adsorption (-2.54 eV). This configuration promotes interfacial electron transfer and reduces the rate-determining energy barrier to -0.84 eV, substantially boosting 1O2 generation and achieving a steady-state concentration of 0.295 mM. Furthermore, the optimized pore architecture alleviates mass-transfer constraints, enabling efficient 1O2 utilization and a 2.3-fold increase in the ciprofloxacin mass-transfer coefficient. Consequently, Co-INC exhibits an exceptional normalized rate constant of 507 min-1·M-1 for ciprofloxacin degradation, outperforming pristine Co-NC by 10.3 times and surpassing most PMS-based catalysts. This study demonstrates that coupling active-site coordination with mass-transfer enhancement is pivotal for maximizing nonradical oxidation pathways in water treatment.