Asymmetric Coordination Induces Electron Localization at Ca Sites for Robust CO 2 Electroreduction to CO.

Main group single atom catalysts (SACs) are promising for CO 2 electroreduction (CO 2 RR) to CO by virtue of their ability in preventing the hydrogen evolution reaction (HER) and CO poisoning. Unfortunately, their delocalized orbitals reduce the CO 2 activation to *COOH. Herein, we developed an O doping strategy to localize electrons on p orbitals through asymmetric coordination of Ca SAC sites (Ca-N 3 O), thus enhancing the CO 2 activation. Theoretical calculations indicate that asymmetric coordination of Ca-N 3 O improves electron-localization around Ca sites and thus promoting *COOH formation. X-ray absorption fine spectroscopy shows the obtained Ca-N 3 O features: one O and three N coordinated atoms with one Ca as a reactive site. In situ attenuated total reflection infrared spectroscopy proves that Ca-N 3 O promotes *COOH formation. As a result, the Ca-N 3 O catalyst exhibits a state-of-the-art turnover frequency (TOF) of ∼15,000 per hour in an H-cell and a large current density of -400 mA/cm 2 with a CO Faradaic efficiency (FE) ≥ 90% in a flow cell. Moreover, Ca-N 3 O sites retain a FE above 90% even with a 30% diluted CO 2 concentration. This article is protected by copyright. All rights reserved.