New electrocatalysis for dioxygen reduction and water oxidation

Electrocatalysis is key to the efficient interconversion of elec. and chem. energies, an important component of future energy technologies. We have developed new electrocatalysts for the oxygen redn. reaction (ORR), incorporating proton relays in the second coordination sphere. Iron-tetrakis(2-carboxyphenyl)porphyrin chloride is an active, stable, and unusually selective ORR electrocatalyst in acidic acetonitrile, reducing O_2 almost entirely to H_2O rather than H_2O_2. The related tetrakis(2-pyridyl) porphyrin complex is also a relatively selective ORR electrocatalyst in acidic water, despite the long distance between the pyridyl nitrogen atoms and the iron center. The role of the proton relays, and now complexes with flexible tripodal ligands and pendent tertiary amines, will be discussed. New developments in the electrocatalysis of water oxidn. by copper-bipyridine species will also be presented.