Asymmetric Coordination Induces Electron Localization at Ca Sites for Robust CO2 Electroreduction to CO

• Published in: Advanced materials (Weinheim) Vol. 35; no. 21; pp. e2300695 - n/a
• Main Authors: Wang, Qiyou, Dai, Minyang, Li, Hongmei, Lu, Ying‐Rui, Chan, Ting‐Shan, Ma, Chao, Liu, Kang, Fu, Junwei, Liao, Wanru, Chen, Shanyong, Pensa, Evangelina, Wang, Ye, Zhang, Shiguo, Sun, Yifei, Cortés, Emiliano, Liu, Min
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.05.2023
• Subjects: asymmetric coordination; Asymmetry; calcium; Carbon dioxide; Carbon dioxide concentration; Carbon monoxide poisoning; CO 2 electroreduction; Coordination; electron localization; Electrons; Electrowinning; Hydrogen evolution reactions; Infrared reflection; Infrared spectroscopy; Localization; Materials science; Orbitals; p‐orbital; Single atom catalysts; Spectrum analysis
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202300695

Main group single atom catalysts (SACs) are promising for CO2 electroreduction to CO by virtue of their ability in preventing the hydrogen evolution reaction and CO poisoning. Unfortunately, their delocalized orbitals reduce the CO2 activation to *COOH. Herein, an O doping strategy to localize electrons on p‐orbitals through asymmetric coordination of Ca SAC sites (Ca‐N3O) is developed, thus enhancing the CO2 activation. Theoretical calculations indicate that asymmetric coordination of Ca‐N3O improves electron‐localization around Ca sites and thus promotes *COOH formation. X‐ray absorption fine spectroscopy shows the obtained Ca‐N3O 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‐N3O promotes *COOH formation. As a result, the Ca‐N3O catalyst exhibits a state‐of‐the‐art turnover frequency 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‐N3O sites retain a FE above 90% even with a 30% diluted CO2 concentration. Improving electron localization around Ca single‐atom sites promotes CO2 activation for CO2 electroreduction to CO. A strategy to localize electrons on Ca p‐orbitals through O doping is reported. This results in the asymmetric coordination (N and O) of the atomic Ca sites. Theoretical and experimental analyses demonstrate the favorable *COOH formation under this asymmetric coordination strategy.