Spin-Regulated Fenton-Like Catalysis for Nonradical Oxidation over Metal Oxide@Carbon Composites

Abstract

The spin state of the transition metal species (TMs) has been recognized as a critical descriptor in Fenton-like catalysis. The raised spin state of dispersed TMs in carbon will enhance the redox processes with adsorbed peroxides and improve the oxidation performance. Nevertheless, establishing the spin-activity correlations for the encapsulated TM nanoparticles remains challenging because of the difficulties in fine-tuning the spin state of TM species and the insufficient understanding of orbital hybridization states upon interaction with peroxides. Here, the advantage of the fast-temperature heating/quenching of microwave thermal shock is taken to engineer the structure and spin state of encapsulated TMs within the N-doped graphitic carbons. The reduced TMs particle size and enhanced TMs-carbon coupling increase surface entropy and regulate e_g electron filling of the high-spin TM-N coordination, endowing electrons with high mobility and facilitating peroxymonosulfate (PMS) adsorption. The strong interactions further uplift the PMS O 2p band position toward the Fermi level and thus elevate the oxidation potential of surface-activated PMS (PMS^*) as the dominant nonradical species for pollutant degradation. The deciphered orbital hybridizations of engineered high-spin TM and PMS enlighten the smart design of spin-regulated nanocomposites for advanced water purification.