Efficient electrocatalysis of the oxygen reduction reaction (ORR), O2 + 4e– + 4H+ → 2 H2O, is a key challenge in energy technologies such as fuel cells. Soluble iron porphyrin ORR electrocatalysts are an excellent model system because of the wide range of structures and substituents that are available. We have reported that electrocatalysis is improved by the introduction of potential proton relays in the second coordination sphere, such as in 2-carboxyphenyl porphyrins. We have now concluded that comparisons of ORR catalysts need to explicitly consider the role of the overpotential, which in organic solvents includes both the applied potential and the proton activity. The kinetics and mechanism of iron porphyrin ORR catalysis will be presented, including both experimental and computational results. Some catalysts have very high turnover frequencies, but operate at high overpotential.

Iron porphyrin electrocatalysts for oxygen reduction

251st National Meeting (2016)

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