A new family of cobalt catalysts featuring redox-active macrocycles has been developed for the electrocatalytic reduction of CO2 to CO. Three electrocatalysts were developed with macrocyclic character in mind such that as the moving across the series, the ligand framework increases in rigidity (in going from pseudo-tetrahedral to square planar geometry). Electronic structure calculations reveal a delicate electronic balance between metal and ligand-based redox chemistry that dictates selectivity for the CO2 reduction reaction (CO2RR) over the competing hydrogen evolution reaction (HER). This critical interplay leads to a significant structure-activity relationship, where increasing the rigidity of the ligand framework increases the selectivity for CO2RR. Experimental results indicate that the most rigid cobalt catalyst can reduce CO2 to CO with a Faradaic yield of 93% at an overpotential of ~420 mV in 0.1 M NaHCO3 buffer.

Computational study for CO2-to-CO conversion using cobalt-based electrocatalysts in acetonitrile and aqueous conditions

ACS Fall 2021

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