Low-Coordinated Ni Single Atom Catalyst with Carbon Coordination for Efficient CO2 Electroreduction

Abstract

In essence, electrocatalytic CO₂ reduction reaction (CO₂RR) process for the CO₂-to-CO conversion involves two critical reactive intermediates: *COOH and *CO. The trade-off between the adsorption of *COOH and the desorption of *CO is challenging for Ni-based CO₂RR catalysts. The high-valence Ni site is inadequate in supplying sufficient electrons for CO₂ activation and subsequent adsorption of *COOH; conversely, the metallic Ni site with abundant electron exhibits excessively strong π-backbonding with *CO, thus hindering its desorption. Here, the study reports a low-coordinated Ni single atom catalyst (SAC) characterized by a low-coordinated structure with carbon coordination, thereby engineering a moderate electron depletion at its Ni sites. This Ni SAC achieves a high selectivity for CO production up to 99.1% in H-cell. Additionally, it maintains an ultrahigh CO selectivity near 100% across a broad range of current densities in flow cell, coupled with sustained stability at a large current of 250 mA cm⁻² for 20 h. Both in situ characterization results and density functional theory (DFT) calculations confirm the dual functionality of this low-coordinated structure, as it enhances the adsorption of *COOH while concurrently facilitating the subsequent desorption of *CO, thus greatly promoting the overall CO₂RR process.