Synthesis and characterization of carbon nanostructures as catalyst support for PEMFCs

A detailed procedure for synthesis, characterization, and possibility of carbon nanostructures (CNS) as support for catalysts in polymer electrolyte membrane fuel cells (PEMFCs) is presented. The fabrication process is two-staged ballmilling of carbon graphite in the presence of hydrogen and transition metals (Fe, Co) followed by heating of the milled carbon initially in an argon atmosphere. The milling induces amorphous forms of carbon and metal, as well as C-H bonds. During the second stage, the production of methane by catalytic reaction of the bonded carbon and hydrogen is first observed, followed by the formation of metallic nanocrystals, and, finally, the formation of carbon structures on the metallic nanocrystals at a temperature of 700 degrees C. Subsequently, metals and carbon nanoparticles are removed from the as-prepared sample. The purified samples are platinized after surface treatment by either air or chemical oxidation. Material characterization results obtained by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectrocopy, and atomic adsorption spectroscopy are presented. In addition, we also report their measured electrical conductivity, specific surface, and porosity. The real electrochemical active surface area was evaluated by cyclic voltammetry on a thin porous coated electrode. (c) 2007 The Electrochemical Society.