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Fuel Cells: Molecular Catalysis

  1. Kenichi Oyaizu

Published Online: 18 JAN 2011

DOI: 10.1002/0470862106.ia819

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Oyaizu, K. 2011. Fuel Cells: Molecular Catalysis. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Waseda University, Tokyo, Japan

Publication History

  1. Published Online: 18 JAN 2011

Abstract

Popularization of fuel cells has been impeded by the low activity of electrocatalysts for the O2 reduction reaction that involves the four-electron transfer step. Platinum nanoparticles have been considered the best cathode catalyst toward the reduction of O2 by four electrons into H2O. However, platinum is an expensive and limited resource, and it is important to find platinum-free catalysts. This article provides a review on the recent studies on various types of platinum-free catalysts such as nonprecious metal nanoparticles and alloys, carbon-based catalysts, and metal complexes, focusing on the role of structure of the catalytically active site of metal complex catalysts in the O[DOUBLE BOND]O bond scission to produce H2O. Emphasis is placed on the studies on cobaltporphyrins, which have been demonstrated to serve as the catalysts for the four-electron reduction of O2, especially in the forms of dicobalt cofacial porphyrins and multinuclear cobaltporphyrins. Simple metalloporphyrins with spontaneous face-to-face aggregation properties have also been examined as a catalyst. For practical application as fuel cell cathode catalysts, it is necessary to use metalloporphyrins dispersed on carbon particles with high surface area. We summarize the recent developments on porphyrin-based catalysts and the attempts to prepare face-to-face aggregates of metalloporphyrins adsorbed dispersively on carbon black. A design principle for the active site to allow the O2 reduction at positive potentials is proposed.

Keywords:

  • oxygen reduction;
  • electrode catalyst;
  • platinum nanoparticle;
  • porphyrin;
  • carbon nanoparticle;
  • four-electron transfer