Dynamic Activation of Edge-Hosted Co–N4 Sites for Energy-Efficient Electrochemical CO2 Reduction at Industry-Level Current Density

Achieving energy-efficient electrochemical CO2 reduction (ECR) at an industry-level current density is both critically important and highly challenging, as it requires simultaneously maintaining high product selectivity and low overpotential under such demanding conditions. In this study, we present a single-atom Co–N–C catalyst with superior selectivity and activity for CO production at a low overpotential in ECR, enabled by the design of edge-hosted Co–N4 sites. The combined results of theoretical calculations and in situ characterizations reveal that axial *CO coordination forms dynamically on edge-hosted Co–N4 sites (CoN4C8–CO) during the ECR process. The CoN4C8–CO structure as an active site modulates the density of states of the Co atom, reduces the free energy barrier for *COOH formation, and also makes the CO desorption easy, thereby promoting CO2-to-CO conversion. As a result, the catalyst demonstrates a CO selectivity exceeding 99% at current densities of 600 mA cm–2 in a flow cell and 500 mA cm–2 in a membrane electrode assembly (MEA), respectively. Impressively, the MEA device demonstrates a high cell energy efficiency of up to 70.8% at 200 mA cm–2 and 55.7% at 500 mA cm–2 toward CO production, demonstrating great advantages compared with other state-of-the-art electrocatalysts.