The combination of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) has been achieved by nature, but not by chemists. Catalysts suitable for the ORR are not suitable for the OER and vice versa. Currently, the best systems use precious metals; Pt for the ORR and Ru or Ir for the OER.

Yelena Gorlin and Thomas Jaramillo, Stanford University, USA, have developed an nanostructured Mn(III) oxide thin film that acts as a catalyst in both these reactions.

The Mn oxide film was electrodeposited onto a carbon surface. It showed activity on par with the best reported Mn oxide OER catalyst, while its ORR activity matched or surpassed those of the best reported Mn oxide ORR catalysts. In addition, its activity approached those of the precious metal systems.

Bifunctional catalysts of this type could be used in unitized regenerative fuel cells to store and transfer energy as needed.

• A Bifunctional Nonprecious Metal Catalyst for Oxygen Reduction and Water Oxidation
  Y. Gorlin, T. F. Jaramillo
  J. Am. Chem. Soc. 2010, 132.
  DOI: 10.1021/ja104587v