Faculty of Engineering and Natural Sciences
Role of Catalysis in Fuel Cells: Nanostructured CNx Catalysts for Oxygen Reduction Reaction in PEMFCs and DMFCs
Ümit S. Özkan
Department of Chemical & Biomolecular Engineering
The Ohio State University, Columbus, Ohio 43210
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 600oC. 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 is 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. Catalysts were also prepared by treating various preformed carbon structures with ammonia at temperatures in excess of 600oC. 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) and X-Ray Photo-electron Spectroscopy (XPS). High-resolution Transmission Electron Microscopy (TEM) images of the nano-structures were obtained with a Tecnai TF-20 microscope to determine the nanostructure of the materials formed. Catalytic activity of the new materials is comparable to the activity of commercial Pt cathode catalysts. Activity is found to be strongly dependant on the edge plane exposure and nitrogen functional groups present.
Umit S. Ozkan is a Professor of Chemical Engineering at The Ohio State University. She received her Ph.D from Iowa State University and joined the faculty of The Ohio State University in 1985. During the 1994-95 academic year, she spent her sabbatical leave at the Centre de la Recherche Nationale Scientifique (C.N.R.S.) - Catalysis Research Institute in Lyon-France as an Invited Senior Research Scientist. Between 2000 and 2005, she also served as the Associate Dean for Research in the College of Engineering.
Her current research interests include catalytic oxidation, environmental catalysis, emission control, hydrogenation and hydrogenolysis of heteroatom compounds found in petroleum and coal derivatives, fuel processing for fuel cell applications, catalytic phenomena involved in fuel cells, use of isotopic labeling techniques as a probe for mechanistic investigations, and in-situ characterization of catalysts using vibrational spectroscopy and surface analysis techniques. She has edited five books, has written over 100 refereed publications, given over 200 conference presentations and over 100 invited lectures in 20 different countries. Professor Ozkan has held and continues to hold many leadership positions in several professional organizations. She served as the Co-chair of the Continuing Symposia in Catalysis for the Colloids and Surface Chemistry Division (1994-2000), the ACS Petroleum Chemistry Division Secretary (1998-99), member of the Board of Directors of the Catalysis and Reaction Engineering Division of AICHE (1996-1999). In 1999, she was appointed to the National Coal Council, an advisory board for the U.S. Secretary of Energy. In 2002-2003, she served as the President of the ACS, Petroleum Chemistry Division. She is currently the Secretary for the North American Catalysis Society. She is on the Editorial Board of Journal of Molecular Catalysis, Catalysis Letters and Catalysis Today. Dr. Ozkan is a Professional Engineer registered in Ohio.
Professor Ozkan is the recipient of many honors and awards among which are Fulbright Senior Scholar Award (2007), French CNRS-Universite Claude-Bernard Lectureship award (2007, OSU College of Engineering Scott Faculty Excellence Award (2004), Technical Person of the Year Award, given by Columbus Technical Council (2003), the Society of Women Engineers Achievement Award (2002), American Chemical Society, Columbus Section Outstanding Research in Chemistry Award (2002), Top Contributor of Technology Award given by the Industry and Technology Council of Central Ohio (2002), the Ohio State University Distinguished Scholar Award (1999), Iowa State University, College of Engineering Professional Progress Award (1999), Pittsburgh-Cleveland Catalysis Society Award (1998), French C.N.R.S. Fellowship (1994-95), Keck Foundation Excellence in Engineering Education Award (1994), OSU College of Engineering Harrison Outstanding Faculty Award (1993), OSU College of Engineering Lumley Research Award (1991, 1996, and 2000, 2006), OSU College of Engineering McQuigg Outstanding Teaching Award (1990), and the Outstanding Engineering Educator of Ohio Award (1991) given by the Society of Professional Engineers.
July 17, 2007, 13:40, FENS 2019