Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

• Published in: Angewandte Chemie International Edition Vol. 53; no. 14; pp. 3675 - 3679
• Main Authors: Hu, Yang, Jensen, Jens Oluf, Zhang, Wei, Cleemann, Lars N., Xing, Wei, Bjerrum, Niels J., Li, Qingfeng
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Casing (process); Catalysis; Catalysts; electrocatalysis; fuel cells; Iron carbides; Low temperature; Media; Nanoparticles; nonprecious metal catalysts; Oxygen; oxygen reduction reaction; Pyrolysis; Reduction; Reduction (electrolytic); fuel cells; iron carbides; nonprecious metal catalysts; oxygen reduction reaction; electrocatalysis
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201400358

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 (Fe3C) 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. Oxygen reduction: Hollow spheres comprising uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers were synthesized (see picture). The spheres show excellent electrocatalytic activity and high stability in both acidic and alkaline media for the oxygen reduction reaction. A synergistic mechanism is proposed.