The new enzyme, named H2ase S–77, can release the electrons from hydrogen molecules and these electrons can be used in a fuel cell to generate electric current. Though H2ases are not new, their application to the polymer electrolyte fuel cell (PEFC) has not been possible until now because they deactivate upon exposure to oxygen. H2ase S–77, however, remains active in the presence of oxygen, which enabled Ogo and his coworkers to construct a working fuel cell with no platinum in the hydrogen anode component.
An enzymatic fuel cell catalyst is a worthy goal in itself, but of particular interest was its surprising efficiency. This enzyme demonstrated a mass activity (roughly the current obtained divided by the mass of catalyst per cm2 of electrode) that was over 600 times greater than that of platinum. Until now, platinum has far exceeded any other catalyst in terms of mass activity, resulting in the exclusive use of this rare and precious metal in commercial fuel cells. The H2ase S–77 result, however, demonstrates that molecular catalysts could be serious contenders as a replacement for metallic platinum.
Professor Ogo intends to study the working mechanism of H2ase S–77 so that his research group can produce a stripped-down working model. Such a model would be expected to be even more efficient, as well as stable, in the hot, acidic conditions of commercial fuel cells. H2ase S–77 was discovered by Professor Ogo and his family on an expedition to Mt. Aso, an active volcano on the island of Kyushu, Japan. He was greatly helped by his wife, Saori Ogo, and has dedicated this discovery to her, taking her first initial for the name, S–77.
This work was supportedby ?New Energy Sources from Hydrogenase–Photosysnthesis Models? from the Japan Society for the Promotion of Science; the Basic Research Programs CREST Type from the Japan Science and Technology Agency; and Scientific Research on Innovative Areas from MEXT.