An innovative family of cobalt catalysts featuring redox-active bipyridyl-N-heterocyclic carbene-based macrocycles has been developed for the electrocatalytic reduction of CO2 to CO. The series of three catalysts was developed with macrocyclic character in mind such that moving across the series, the ligand framework increases in rigidity (going from pseudo-tetrahedral to square planar geometry). Electrochemical studies and electronic structure calculations reveal a delicate electronic balance between metal and ligand-based redox chemistry that dictates selectivity for CO2 reduction versus the competing proton reduction reaction. This critical interplay leads to a significant structure-activity relationship, where increasing the rigidity of the ligand scaffold increases the catalyst’s activity and selectivity for CO2 reduction. Notably, experimental results indicate that the most rigid cobalt catalyst can perform catalysis in aqueous conditions, where controlled potential electrolysis (CPE) studies in CO2-saturated aqueous solutions reveal CO2 reduction occurs at an overpotential of ~420 mV in 0.1 M NaHCO3 buffer with a Faradaic yield for CO of 93%.

New family of cobalt-based bipyridyl-NHC electrocatalysts for the reduction of CO2 in acetonitrile and aqueous conditions

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.