Issue 10, 2023

Axially coordinated Co–N4 sites for the electroreduction of nitrobenzene

Abstract

Single-atom cobalt (Co–N–C) catalyst has been proposed as a superior catalyst, but the symmetrical structure of Co–N4 shows unfavorable energetics, leading to much debate on its chemical nature responsible for its high activity. We found that the axial coordination between the well-defined Co–N4 site (pentafluorophenyl-porphyrin cobalt, CoTFP) and polarizable N-doped graphene (NG) can alter the spatial structure of Co–N4 site and lead to the transformation of Co(II) to monovalent Co(I) as the active center (defined as CoITFP@NG). Taking the electroreduction of nitrobenzene (NB) on the as-prepared catalyst as a model reaction, CoITFP@NG showed an increase of about three times the reaction kinetics and turnover frequencies (TOFs) compared with those of CoIITFP@OG, where CoTFP was immobilized on O-doped graphene (OG) via regular π–π stacking interactions. Augmented by density functional theory (DFT) calculations, axial bonds can serve as communication channels for electron transfer, deriving a decrease in the redox potential and then contributing to the catalytic reduction of NB. Intelligently prefabricating an axial coordination for Co–N4 sites represents an effective and feasible means for the rational ligand-field engineering of single-atom catalysts.

Graphical abstract: Axially coordinated Co–N4 sites for the electroreduction of nitrobenzene

Supplementary files

Article information

Article type
Paper
Submitted
04 Oct 2022
Accepted
02 Dec 2022
First published
10 Dec 2022

J. Mater. Chem. A, 2023,11, 5095-5103

Axially coordinated Co–N4 sites for the electroreduction of nitrobenzene

M. Pan, J. Li, X. Zhang, S. Liu, J. W. Chew and B. Pan, J. Mater. Chem. A, 2023, 11, 5095 DOI: 10.1039/D2TA07751E

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