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

Abstract

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.