Chalcogen heteroatoms doped nickel-nitrogen-carbon single-atom catalysts with asymmetric coordination for efficient electrochemical CO2 reduction

The electronic configuration of central metal atoms in single-atom catalysts (SACs) is pivotal in electrochemical CO2 reduction reaction (eCO2RR). Herein, chalcogen heteroatoms (e.g., S, Se, and Te) were incorporated into the symmetric nickel-nitrogen-carbon (Ni-N4-C) configuration to obtain Ni-X-N3-C (X: S, Se, and Te) SACs with asymmetric coordination presented for central Ni atoms. Among these obtained Ni-X-N3-C (X: S, Se, and Te) SACs, Ni-Se-N3-C exhibited superior eCO2RR activity, with CO selectivity reaching ~98% at −0.70 V versus reversible hydrogen electrode (RHE). The Zn-CO2 battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm–2 and maintained remarkable rechargeable stability over 20 h. In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution, and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO2RR. Especially, for Ni-Se-N3-C, the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of *COOH formation, contributing to the promising eCO2RR performance for high selectivity CO production by competing with hydrogen evolution reaction.