An Iron Bis(carbene) Catalyst for Low Overpotential
CO2 Electroreduction to CO: Mechanistic Insights from Kinetic
Zone Diagrams, Spectroscopy, and Theory
Version 2 2021-12-10, 19:04Version 2 2021-12-10, 19:04
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journal contribution
posted on 2021-12-10, 19:04authored bySergio Gonell, Eric A. Assaf, Julio Lloret-Fillol, Alexander J. M. Miller
A common
challenge in molecular electrocatalysis is the relationship
between maximum activity and the overpotential required to reach that
rate, with faster catalysts incurring higher overpotentials. This
work follows a strategy based on independent tuning of ligands in
the primary coordination sphere to discover a previously unreported
iron catalyst for CO2 reduction with higher activity than
similar complexes while maintaining the same overpotential. Iron complexes
bearing a bis-N-heterocyclic carbene ligand (methylenebis(N-methylimidazol-2-ylidene), bis-mim) and a redox active
2,2′:6′,2″-terpyridine (tpy) ligand were synthesized
and found to catalyze the selective reduction of CO2 to
CO at low overpotential with water as the proton source. Mechanistic
studies based on kinetic zone diagrams, spectroscopy, and computation
enable comparisons with a previously studied pyridyl–carbene
analogue. Changing the bidentate ligand donor ability accelerates
catalysis at the same overpotential and changes the nature of the
turnover-limiting step of the reaction.