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 H₂ by these complexes. With added weak acids in acetonitrile with added water and CO₂, reduction to syngas mixtures of CO and H₂ 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 O₂. 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 H₂ production. Details of the catalytic mechanisms of each have also been investigated.