Efficient electrocatalysis of the oxygen reduction reaction (ORR), O2 + 4e– + 4H+ à 2 H2O, is a key challenge in energy technologies such as fuel cells. Presented here will be studies of iron porphyrin ORR electrocatalysis, with particular emphasis on catalysts 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 catalysts, both electrochemically and with chemical reductants. Comparisons will be presented between different catalysts, and of the same catalyst in different media. These comparisons show the dependence of rate and selectivity upon parameters such as overpotential and the nature and concentration of the acid. 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.

Studies of electrocatalytic dioxygen reduction

249th National Meeting (2015)

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