IS NITROGEN IMPORTANT IN THE FORMULATION OF FE-BASED CATALYSTS FOR OXYGEN REDUCTION IN SOLID POLYMER FUEL-CELLS

The role of nitrogen and iron in the generation of catalysts for oxyge n reduction in acidic media has been investigated by using two indepen dent organic precursors. The Fe and N precursors were polyvinylferroce ne adsorbed on carbon black and acetonitrile vapor, respectively. Thes e precursors were pyrolyzed at 1000 degrees C. A catalyst is obtained only if Fe and N are present together in the reactor during pyrolysis. Inactive Fe clusters surrounded by a protective graphitic envelope ar e produced when adsorbed polyvinylferrocene is pyrolyzed alone at 1000 degrees C. The latter material may, however, be activated by a second pyrolysis in acetonitrile vapor. The characterization of the catalyst indicates that the iron is oxidized (Fe-II and Fe-III), but no strong Fe-N-x bonds were unequivocally detected by ToF SIMS. Lifetime testin g of the catalyst in a polymer electrolyte fuel cell demonstrated stab le currents for at least 300 h. The current density measured with a ca talyst containing 1 wt% Fe was about 1/3 of that measured with a comme rcial Pt-based catalyst containing 2 wt% metal loading. (C) 1997 Publi shed by Elsevier Science Ltd.