Nanoconfinement steers nonradical pathway transition in single atom fenton-like catalysis for improving oxidant utilization

The introduction of single-atom catalysts (SACs) into Fenton-like oxidation promises ultrafast water pollutant elimination, but the limited access to pollutants and oxidant by surface catalytic sites and the intensive oxidant consumption still severely restrict the decontamination performance. While nanoconfinement of SACs allows drastically enhanced decontamination reaction kinetics, the detailed regulatory mechanisms remain elusive. Here, we unveil that, apart from local enrichment of reactants, the catalytic pathway shift is also an important cause for the reactivity enhancement of nanoconfined SACs. The surface electronic structure of cobalt site is altered by confining it within the nanopores of mesostructured silica particles, which triggers a fundamental transition from singlet oxygen to electron transfer pathway for 4-chlorophenol oxidation. The changed pathway and accelerated interfacial mass transfer render the nanoconfined system up to 34.7-fold higher pollutant degradation rate and drastically raised peroxymonosulfate utilization efficiency (from 61.8% to 96.6%) relative to the unconfined control. It also demonstrates superior reactivity for the degradation of other electron-rich phenolic compounds, good environment robustness, and high stability for treating real lake water. Our findings deepen the knowledge of nanoconfined catalysis and may inspire innovations in low-carbon water purification technologies and other heterogeneous catalytic applications.