Cobalt or iron confined in a nitrogen-containing carbon matrix (M-N/C, M = Co or Fe) have emerged as promising alternatives to Pt-based materials for the cathodic oxygen reduction reaction (ORR) in fuel cells. The ORR catalysts in the fuel cell utilize electrons and protons delivered via the electrode and membrane to reduce O<sub>2</sub>. We have found that related catalyst compositions may be employed as aerobic oxidation catalysts. In this case, an organic molecule (a hydroquinone) provides the source of electrons and protons for O<sub>2</sub> reduction. This talk will present a systemic comparison of the electrocatalytic ORR and hydroquinone aerobic oxidation catalytic activity of a series of Co- or Fe-N/C catalysts. The materials are synthesized by adsorption of a metal-nitrogen complex onto a carbon support followed by high temperature pyrolysis. A variety of N ligands such as polyaniline, cyanimide, porphyrin, phthalocyanine, and 1,10-phenanthroline are used. The synthesized Co- and Fe-N/C materials display good activity in the oxidation of a stable tetra-substituted hydroquinone. Selected catalysts have been combined with quinone mediators in a flow cathode fuel cell that achieves high power densities.

Electrocatalysts as aerobic oxidation catalysts and the use of organic redox mediators as “soluble electrodes”

2019 Spring National Meeting

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