Ordered mesoporous carbons codoped with nitrogen and iron as effective catalysts for oxygen reduction reaction.

Abstract

Doping with foreign atoms is an effective approach to significantly enhance the catalytic performance of carbon materials for oxygen reduction reaction (ORR). In this paper, a colloidal silica template method was employed to synthesize nitrogen and iron codoped ordered mesoporous carbon for ORR electrocatalysis. The carbon materials were thoroughly characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy measurements. The porosity was quantified by nitrogen adsorption/desorption measurements that showed the formation of ordered mesoporous structures with a BET specific surface area up to 953.8 m2 g-1 and the mesopores mostly centered at ca. 25 nm, close to the size of the colloidal silica. The resulting mesoporous carbon exhibited apparent ORR activity in alkaline media, which was highly comparable to that of commercial Pt/C (20 wt%), with the onset potential at +0.99 V vs. RHE. This was ascribed largely to nitrogen dopants, with additional contributions from the trace amounts of iron dopants, and the reactions appeared to be facilitated by the formation of a mesoporous structure. Moreover, the mesoporous carbon showed better stability, resistance against fuel crossover, and selective activity than Pt/C. This work demonstrates a new paradigm for the preparation of heteroatom-doped carbon materials that are promising alternatives to Pt-based catalysts for fuel cells.