Neighboring Carbon Defects Enhanced Molecular Oxygen Activation of Cobalt Single Atom Catalysts Toward Efficient Aerobic Alcohols Oxidation

Abstract

The effective adsorption and activation of molecular oxygen (O₂) is crucial for aerobic alcohol oxidation; however, flexibly modulating the electronic structure of catalysts to improve the capability remains challenging. Herein, the concentration of carbon defects surrounding the nitrogen-coordinated cobalt (Co) single atoms on candle soot is controlled just through adjusting the amount of polyethyleneimine which chemically decorates the surface of candle soot to anchor Co ions. The concentration increase of carbon defects boosts the aerobic alcohol oxidation over the Co single-atom catalyst as well as ruthenium single-atom catalyst. Moreover, a series of alcohols, including those with sensitive groups, reach an outstanding yield. Significantly, the calculations and experiments verify that the carbon defects lead to the rearrangement of d-orbitals of Co atom and an elevation in the spin states of d_yz and $$ orbitals. Furthermore, compared with low-spin Co atom, the stronger electron-transfer interaction between high-spin Co atom and O₂ enhances the adsorption and activation of O₂ and the generation of more superoxide radicals to promote alcohol oxidation. Our findings provide a new way for developing advanced single-atom catalysts for sustainable aerobic alcohol oxidation via manipulating the spin configurations of single atoms.