title: Elucidating Oxygen Reduction Active Sites in Pyrolyzed Metal-Nitrogen Coordinated Non-Precious-Metal Electrocatalyst Systems.
abstract: Detailed understanding of the nature of the active centers in non-precious-metal-based electrocatalyst, and their role in oxygen reduction reaction (ORR) mechanistic pathways will have a profound effect on successful commercialization of emission-free energy devices such as fuel cells. Recently, using pyrolyzed model structures of iron porphyrins, we have demonstrated that a covalent integration of the Fe-Nxsites into π-conjugated carbon basal plane modifies electron donating/withdrawing capability of the carbonaceous ligand, consequently improving ORR activity. Here, we employ a combination ofin situX-ray spectroscopy and electrochemical methods to identify the various structural and functional forms of the active centers in non-heme Fe/N/C catalysts. Both methods corroboratively confirm the single site 2e-× 2e-mechanism in alkaline media on the primary Fe2+-N4centers and the dual-site 2e-× 2e-mechanism in acid media with the significant role of the surface bound coexisting Fe/FexOynanoparticles (NPs) as the secondary active sites.
authors.affiliation: Northeastern University Center for Renewable Energy Technology, Department of Chemistry and Chemical Biology, Northeastern University , 317 Egan Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States.
authors.forename: Urszula
authors.initials: U
authors.lastname: Tylus
authors.affiliation: Northeastern University Center for Renewable Energy Technology, Department of Chemistry and Chemical Biology, Northeastern University , 317 Egan Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States.
authors.forename: Qingying
authors.initials: Q
authors.lastname: Jia
authors.affiliation: Northeastern University Center for Renewable Energy Technology, Department of Chemistry and Chemical Biology, Northeastern University , 317 Egan Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States.
authors.forename: Kara
authors.initials: K
authors.lastname: Strickland
authors.affiliation: Northeastern University Center for Renewable Energy Technology, Department of Chemistry and Chemical Biology, Northeastern University , 317 Egan Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States.
authors.forename: Nagappan
authors.initials: N
authors.lastname: Ramaswamy
authors.affiliation: Department of Chemical and Nuclear Engineering, 1 University of New Mexico, University of New Mexico , Albuquerque, New Mexico 87131, United States.
authors.forename: Alexey
authors.initials: A
authors.lastname: Serov
authors.affiliation: Department of Chemical and Nuclear Engineering, 1 University of New Mexico, University of New Mexico , Albuquerque, New Mexico 87131, United States.
authors.forename: Plamen
authors.initials: P
authors.lastname: Atanassov
authors.affiliation: Northeastern University Center for Renewable Energy Technology, Department of Chemistry and Chemical Biology, Northeastern University , 317 Egan Research Center, 360 Huntington Avenue, Boston, Massachusetts 02115, United States.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Mukerjee