Transition metal oxides as reconfigured fuel cell anode catalysts for improved CO tolerance: Polarization data

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, thermogravimetric analysis, and Brunauer-Emmett-Teller techniques. Here we present performance data from polarization curves measured 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. (C) 2005 The Electrochemical Society. All rights reserved.