Highly efficient electrocatalytic CO <sub>2</sub> reduction by a Cr <sup>III</sup> quaterpyridine complex
Jia‐Wei Wang, Zhi‐Mei Luo, Guangjun Yang, Marcos Gil‐Sepulcre, Stephan Kupfer, Olaf Rüdiger, Gangfeng Ouyang
Abstract
Design tactics and mechanistic studies both remain as fundamental challenges during the exploitations of earth-abundant molecular electrocatalysts for CO 2 reduction, especially for the rarely studied Cr-based ones. Herein, a quaterpyridyl Cr III catalyst is found to be highly active for CO 2 electroreduction to CO with 99.8% Faradaic efficiency in DMF/phenol medium. A nearly one order of magnitude higher turnover frequency (86.6 s −1 ) over the documented Cr-based catalysts (<10 s −1 ) can be achieved at an applied overpotential of only 190 mV which is generally 300 mV lower than these precedents. Such a high performance at this low driving force originates from the metal–ligand cooperativity that stabilizes the low-valent intermediates and serves as an efficient electron reservoir. Moreover, a synergy of electrochemistry, spectroelectrochemistry, electron paramagnetic resonance, and quantum chemical calculations allows to characterize the key Cr II , Cr I , Cr 0 , and CO-bound Cr 0 intermediates as well as to verify the catalytic mechanism.