Electrocatalytic Reduction of Carbon Dioxide: Let the Molecules Do the Work

This review summarizes the development of electrochemical CO2 reduction catalysts in the UNC Energy Frontier Research Center for Solar Fuels. Two strategies for converting CO2 to CO or formate have been explored. In one, polypyridyl complexes of Ru(II) have been used to reduce CO2 to CO in acetonitrile and in acetonitrile/water mixtures. In the absence of CO2 water is reduced to H-2 by these complexes. With added weak acids in acetonitrile with added water and CO2, reduction to syngas mixtures of CO and H-2 is observed. A single polypyridyl complex of Ru(II) has been shown to be both a catalyst for water oxidation and CO2 reduction in an electrochemical cell for CO2 splitting into CO and O-2. In parallel, Ir pincer catalysts have been shown to act as selective electrocatalysts for reducing CO2 to formate in acetonitrile with added water and in pure water without competition from electrocatalytic H-2 production. Details of the catalytic mechanisms of each have also been investigated.