Effect of Electronic Structure over Late Transition-Metal M1–N4 Single-Atom Sites on Hydroxyl Radical-Induced Oxidations

Abstract

Hydroxyl radical (•OH)-induced oxidations are of great importance in chemical transformations. Carbon-supported late transition-metal single-atom catalysts (SACs) with bioinspired M1–N4 single-atom sites can effectively activate the peroxide group to produce •OH. Nevertheless, little is known about how electronic structures of M1–N4 sites affect •OH generation. Herein, dependent on the theoretical design and experimental realization of uniform M1–N4/C (M: Fe, Co, Ni, and Cu) SACs, a positive correlation relationship between •OH-induced oxidation activity and d-band center over the M1–N4 site has been revealed. In detail, by changing the M atoms with different numbers of d electrons, the d-band center of the M1–N4 could be turned. Moreover, the enhancement of d-band center heightens the interaction strength between the •OH intermediate and the M1–N4 site, which results in a higher oxidation activity. In this case, the efficient M1–N4 catalyst for the oxidation reaction can be screened by tuning the doped M atom. Moreover, notably, Fe1–N4 with the highest d-band center value has the lowest free energy change of the rate-determining step (0.06 eV) for •OH generation. Taking advantage of this, in both Fenton-like reaction and •OH-induced C–H bond activation reaction, the Fe1–N4 site displays at least 1 order of magnitude higher activity than the most of the supported late transition-metal catalysts and comparable activity to reported noble metal catalysts. This work is expected to provide guidance for designing high-efficiency heterogeneous catalysts in •OH-induced oxidations and bridge heterogeneous and enzymatic catalysis by using M1/C SAC as a platform.