Intermediates-induced CO2 reduction reaction activity at single-atom M-N2 (M = Fe, Co, Ni) sites.

Abstract

Single-atom M-N2 (M = Fe, Co, and Ni) catalysts exhibit high activity for CO2 reduction reaction (CO2RR). However, the CO2RR mechanism and the origin of activity at the single-atom sites remain unclear, which hinders the development of single-atom M-N2 catalysts.Here, we reveal intermediates-induced CO2RR activity at the single-atom M-N2 sites by density functional theory calculations.At the M-N2 sites, the asymmetric *O*CO configuration tends to split into *CO and *OH intermediates.Intermediates become part of the active moiety to form M-(CO)N2 or M-(OH)N2 sites, which can optimize the adsorption of intermediates on the M sites.The limiting potentials along the optimal CO2RR pathway are -0.30, -0.54, and -0.28 V for Fe-(OH)N2, Co-(CO)N2, and Ni-(OH)N2 sites, more positive than those of Fe-N2 (-1.03 V), Co-N2 (-1.24 V) and Ni-N2 (-0.73 V) sites.The intermediate modification can shift the d-band center of the spin-up (minority) state downward by regulating the charge distribution at the M sites, leading to less charge accepted by the intermediates from the M sites.This work provides new insights into the understanding of the activity of single-atom M-N2 sites.