title: Hollow spheres of iron carbide nanoparticles encased in graphitic layers as oxygen reduction catalysts.
abstract: Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3 C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.
authors.affiliation: Department of Energy Conversion and Storage, Technical University of Denmark, Kemitorvet 207, 2800 Lyngby (Denmark); Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 130022, Changchun (China).
authors.forename: Yang
authors.initials: Y
authors.lastname: Hu
authors.forename: Jens Oluf
authors.initials: JO
authors.lastname: Jensen
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Lars N
authors.initials: LN
authors.lastname: Cleemann
authors.forename: Wei
authors.initials: W
authors.lastname: Xing
authors.forename: Niels J
authors.initials: NJ
authors.lastname: Bjerrum
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Li
keywords: electrocatalysis; fuel cells; iron carbides; nonprecious metal catalysts; oxygen reduction reaction