(79d) Molecular-Level Insights into Electrocatalytic Carbon Dioxide Reduction at Cobalt Macrocycles

Electrolysis of carbon dioxide in aqueous media to generate carbon monoxide may provide a modular route to making a key chemical feedstock under ambient conditions. As a component of syngas, carbon monoxide can be converted into higher value hydrocarbons, alcohols, acids, and esters. Cobalt macrocycles, including cobalt phthalocyanines and cobalt porphyrins, are known to be selective catalysts for converting carbon dioxide into carbon monoxide. In our work, we have been able to develop immobilized versions of these catalysts with high turnover frequencies for reducing carbon dioxide. These catalysts have helped to elucidate a rich picture of the nature of the rate determining step, how it can be tuned between an electron transfer and proton-coupled electron transfer, and the interplay of kinetics and transport in the observed reactivity of cobalt macrocycles. Furthermore, we have been able to deconvolute both inductive and electrostatic effects on the activity of these catalysts, providing clear design principles for transition metal macrocycles which are immobilized at electrode-electrolyte interfaces.