Transition Metal Oxides as Reconfigured Fuel Cell Anode Catalysts for Improved CO Tolerance: Polarization Data

Abstract

We are developing a fuel-cell-integrated approach for enhancing the effectiveness of air-bleed for CO tolerance of hydrogen and reformate polymer exchange membrane fuel cells PEMFCs, called the ‘‘reconfigured anode’’ RCAF. A. Uribe, J. A. Valerio, F. H. Garzon, and T. A. Zawodzinski, Electrochem. Solid-State Lett., 7, A376 2004. It consists of a small modification to the backing cloth placed on the anode side of each membrane electrode assembly in a stack. A catalyst layer is placed on the gas-feed side of the cloth to catalyze oxidation of CO, utilizing the oxygen introduced in a small air-bleed. The purpose is to enhance the effectiveness of the air-bleed to achieve a high CO tolerance. We synthesized model RCA catalysts based on transition metal oxides, which were characterized using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, thermo- gravimetric analysis, and Brunauer-Emmett-Teller techniques. Here we present performance data from polarization curves mea- sured on fuel cells with air bleed using these model RCA catalysts. The results indicate that by using an RCA and air-bleed it is possible to raise the CO tolerance of a Pt/C anode to the same level as that of an anode with a Pt-Ru/C catalyst with similar platinum loading and without other means of CO mitigation. The RCA represents a built-in safety net for CO transients, which could be applied to PEMFCs destined to operate on a reformer-derived, hydrogen-rich fuel stream.