Maximizing the Utilization of Single-Atom Sites on Carbon-Based Catalysts for Efficient Co2 Electroreduction with Ultrahigh Turnover Frequency

Increasing the amount of accessible active sites to reactants is an effective approach to enhance catalytic activity. Although single-atom catalysts are claimed to be capable of achieving 100% atomic utilization, there may be abundant single-atom sites buried and inaccessible to reactants in practice. Herein, two Ni, N-doped carbon catalysts with Ni-N4 sites are studied for CO2 electroreduction. In contrast to the Ni-N4/Carbon nanosheets with Ni loading of 2.42 wt%, the Ni-N4/Carbon black with lower Ni loading of 0.16 wt% excitingly exhibits higher activity for CO production. The atomically dispersed Ni-N4 sites over carbon black surface benefits the exposure and utilization of single-atom sites, leading to a significant increase of TOF from 2140 to 100347 h−1. Particularly, an extraordinarily high current density exceeding 200 mA cm-2 with CO selectivity up to ~100% are achieved for Ni-N4/CB in flow cell. This work demonstrates the significance of increasing single-atom sites utilization