Electrocatalysis is key to the efficient interconversion of electrical and chemical energies, an important component of future energy technologies. We have developed new porphyrin electrocatalysts for the oxygen reduction reaction (ORR), incorporating proton relays in the second coordination sphere. The relays are attached to the meso positions of the porphyrin, and examples include 2-carboxyphenyl, 2-pyridyl, and related amide derivatives. Many of these compounds are active, stable, and unusually selective electrocatalysts for the four-electron reduction of dioxygen to water in acidic media. These electrocatalysts have been studied as soluble species, in both aqueous and organic media, and adsorbed on electrodes. The complex pattern of rate constants, overpotentials, and selectivities observed will be discussed. These results, and parallel computational studies, shed light on the variety of ways that the relays influence the electrocatalysis. We will also discuss the challenges of determining the standard potential for O2 reduction in organic media. New developments in the electrocatalysis of water oxidation by soluble and surface-attached copper-diimine species will also be presented.

Studies of electrocatalytic dioxygen reduction and water oxidation

248th National Meeting (2014)

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