Engineering spin polarization of encaging Co nanoparticles in atomic CoNx sites evoke high valent Co species for boosting organic compound oxidation

Abstract

Precise manipulation of the catalytic spin configuration and delineation of the relationship between spin related properties and oxidation pathways remain significant challenges in Fenton-like processes. Herein, encapsulated cobalt nanoparticles and cobalt-nitrogen-doped carbon moieties, endowed with confinement effects and variations in shell curvature were constructed via straightforward pyrolysis strategies, inducing alterations in magnetic anisotropy, electronic energy levels and spin polarization. The enhanced spin polarization at cobalt sites leads to a reduction in crystal field splitting energy and an increase in electronic spin density. This phenomenon facilitated electron transfer from cobalt orbitals to p_z orbitals of oxygen species within peroxymonosulfate molecules, thereby promoting the formation of high-valent cobalt species. The encapsulation effectively stabilized cobalt nanoparticles, mitigating their dissolution or deactivation during reactions, which in turn enhances stability and durability in continuous flow processes. The high-valent cobalt species within the shell exhibit increased exposure and generate localized high concentrations, thereby intensifying interactions with migrating pollutants and enabling efficient and selective oxidation of emerging compounds with elevated redox potentials. This work underscores the profound impact of confined encapsulation curvature and spin polarization characteristics of metal sites on catalytic oxidation pathways and performance, opening novel avenues for spin engineering in practical environmental catalysis.