Catalytic activity of nitrogen-containing functional groups supported on carbon structures for cathodic oxygen reduction reaction for PEM fuel cells

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ABSTRACTPI: Umit OzkanInstitution: Ohio State UniversityProposal Number: 0437451ResearchThe high costs associated with the use of platinum (Pt) catalysts coupled with the fact that the most significant potential loss in polymer electrolyte membrane (PEM) fuel cells is due to the kinetics of the oxygen reduction reaction (ORR) in the cathode have led several studies to focus on the development of novel ORR catalysts. Some of these studies are based on the nature-inspired concept of using hemoglobin-type molecules to perform the oxygen reduction function. Large organic macrocycles containing iron (Fe) or cobalt (Co) centers are reported to be active for ORR when supported on high-surface area carbon. Although these complex compounds are not stable for long periods of time in the fuel cell environment, when they are subjected to a heat treatment, the remaining nitrogen-containing carbon structures with metal centers are shown to be active and stable.Although there is ample evidence in the literature about the possible oxygen reduction activity of carbon-supported nitrogen functional groups (with and without metal centers) as potential cathode electrocatalysts for PEM fuel cells, there is no clear understanding about the nature of active sites and the mechanism of oxygen reduction reaction. The focus of this proposal is investigation of the nature of oxygen reduction active sites in nitrogen containing carbon nano-structures as potential cathode catalysts for PEM fuel cells. The main objectives are (a) acquiring a fundamental understanding of the nature of active sites, the role of the metal centers and the carbon support structure, (b) developing techniques for nano-scale synthesis of these catalysts and (c) building a knowledge base that would lead to the nano-scale design of novel, non-precious metal catalytic materials to be used as fuel cell electrodes. While the ultimate goal of the proposed research is the development of novel, platinum-free PEM fuel cell electrodes, the present study will focus on the synthesis of nitrogen-containing carbon electrode materials to specifically study and assess the factors contributing to oxygen reduction activity, the inter-relation between metal/nitrogen functional groups/carbon nano-structure/oxygen reduction activity, the active site(s) responsible for activity, the forms of precursor material necessary for active site formation, and the performance and stability of these materials under real conditions.Broad ImpactThe move to a hydrogen economy is a national target - consequently the development of technologies that facilitate wide application of fuel cells are becoming increasingly important. The results of this work could bring the application of fuel cells closer to reality. Other impacts include curriculum development (new course in "Catalysis and Fuel Cells", seminar series in OSU-IGERT program), providing a training ground for graduate and undergraduate researchers, and creating demonstration tools to be used in the "Orientation for Women Engineering Freshmen" program that would capture the imagination and that would get them excited about a career in engineering. The project will also strengthen an existing international collaboration between the P.I. and the French CNRS-Catalysis Research Institute.