Fourth Meeting of the
Catalysis Club of Chicago 2007-2008
Monday, January 14, 2008

Seven Bridges at Woodridge
One Mulligan Drive
Woodridge, Illinois 60517
Phone: (630) 964-7777
MAP
Cost $45 for professionals
$20 for students & post docs
 

Role of Catalysis in Fuel Cells: Nanostructured CNx Catalysts for Oxygen Reduction Reaction in PEMFCs and DMFCs

Professor Umit S. Ozkan
Heterogeneous Catalysis Research Group
Department of Chemical and Bimolecular Engineering
The Ohio State University, Columbus, OH 43210, USA
EMAIL

OSU Heterogeneous Catalysis Research Group

ABSTRACT

The development of less expensive and more active alternative catalysts to Pt for use in PEM fuel cell cathodes will help to initiate their wide-scale commercialization. Alternative catalysts based on organo-metallic macro cycles, such as Fe porphyrins, have been studied with some success, although their poor stability limits their practical use. It has been discovered that these catalysts can be stabilized in the electrode environment by subjecting them to pyrolysis above 600°C. More recently researchers have discovered that a wide variety of metal, nitrogen and carbon precursors will form active oxygen reduction reaction (ORR) catalysts upon pyrolysis. Work in our lab has revealed that Fe particles, when subjected to treatments in nitrogen and carbon containing atmospheres at elevated temperatures, act as catalysts for the formation of nitrogen-containing carbon nano-fibers with significant edge plane exposure. Although Fe was not necessary for elevated ORR activity, edge plane exposure and nitrogen content in the carbon was observed to increase activity.

In the current study catalysts for the ORR in acidic electrolytes were prepared by pyrolysis of acetonitrile over carbon and metal oxide supports impregnated with Fe or Ni acetate. In the case of metal oxide supports, the support and exposed metal particles were removed by washing the pyrolysis product with a strong acid.. Activity measurements were made using a Rotating Ring Disk Electrode (RRDE) half–cell set-up using 0.5 M sulfuric acid as the electrolyte, and a 5 cm² PEM fuel cell test stand. Materials were characterized with BET surface area analysis, pore volume distributions, Temperature Programmed Oxidation (TPO), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), X-Ray Photo-electron Spectroscopy (XPS) and High-resolution Transmission Electron Microscopy (TEM). Activity is found to be strongly dependant on the edge plane exposure and nitrogen functional groups present. Materials show promise as ORR catalysts for PEM and Direct Methanol fuel cells.