Fuel Cell Applications of Nanotube-Metal Supported Catalysts
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Fuel Cell Applications of Nanotube-Metal Supported Catalysts T. Gennett1, B. J. Landi1, J. M. Elich1, K. M. Jones2, J. L. Alleman2, P. Lamarre3, R. S. Morris3, R. P. Raffaelle1, M.J. Heben2 1 NanoPower Research Laboratories, Rochester Institute of Technology Rochester, NY 14623 U.S.A. 2 National Renewable Energy Laboratory, Golden, CO 80401 U.S.A. 3 Viatronix Inc. Waltham, MA 02451 U.S.A. ABSTRACT Novel carbon materials with nanometer dimensions are of potentially significant importance for a number of advanced technological applications. Within this report we describe the results for the electrochemical characterization of a series of single walled carbon nanotube (SWNT) metal supported catalysts as cathodes for basic fuel cell systems. Compared to the typical carbon black electrocatalysts, the nanotube supported platinum catalyst resulted in up to a 140% improvement in the efficiency for a proton exchange membrane (PEM) fuel cell. INTRODUCTION The successful conversion of chemical energy into electrical energy via fuel cells was realized over 150 years ago. However significant advancement in viable commercial products has been limited because of the inability to compete on a kWh cost basis with other technologies. Recently, as the demand for smaller, more efficient, environmentally friendly power supplies has increased, a significant research effort towards utilizing regenerative fuel-cell systems has developed. The goal of this research is to develop novel solid-state catalytic materials based on carbon single-walled carbon nanotubes (SWNTs) for use as inexpensive electrodes within fuel cells. Of particular interest is the increased surface area of a nanotube supported platinum catalyst as compared to the typical carbon black electrocatalysts, 1000-1500 m2/g versus 250 m2/g, and its effect on catalytic activity. Also the direct contact between the nanotubes and the nanostuctured catalysts that results from the synthesis, should dramatically improve the efficiency and performance of fuel cells with electrodes based on these materials. Utilizing a single wall carbon nanotube laser synthesis reactor with either a traditional furnace or an inductive heating system, significant yields of SWNTs from high refractory catalysts metals are possible. The net result is a composite material with a high dispersion of platinum, ruthenium, iridium, rhodium and/or palladium nanoparticles 2-50 nm in diameter, within the nanotube matrix. The high dispersion of metal catalyst particles via deposition processes has been shown to give rise to electrocatalytic activity with other carbon materials including: carbon black, carbon fibers and ordered nanoporous carbon. Recent reports with ordered nanoporous carbon of a similar surface area showed an increase in the electrocatalytic mass activity. [1-3] The advantages of SWNT-catalyst over processed materials are: the catalyst particles are in intimate contact with the carbon material, free-standing films can be made without a need for a template and the SWNT-catalyst materials can
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