Molecular Catalysts for Fuel Cell Anodes

Only a few examples of molecular catalysts have so far been reported for the anode (fuel oxidation reaction) of fuel cells, because platinum is considered as the only and most active and stable catalyst for the oxidation of hydrogen or other fuels in fuel cells. However, it is widely acknowledged that the drawback of platinum is its cost competitiveness and serious poisoning by CO. Pt-Ru alloy is considered as the solution to this problem, but uprising cost of Ru is hindering its true commercialization. Another problem is the dissolution of Ru at much less noble potentials than Pt. In this chapter, new class of materials that can subsidize Pt or alloy catalysts with high CO tolerance are introduced and their possibilities are discussed for future applications to the anode catalysts. Composite catalysts are proposed that are made of platinum precursor and organic complexes containing nitrogen ligands and transition metal centers, supported on carbon powder and heattreated at moderate temperatures. The performance of novel catalysts is studied for methanol oxidation, formic acid oxidation, and H

2

oxidation reactions, all of which are important anode reactions in fuel cells. Structural analyses of the catalysts are presented by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, transmission and scanning electron microscopy, and thermal analyses. Possible mechanisms of CO tolerance of these new catalysts are discussed.