LAUSR

The search for alternatives to Pt catalysts with a high density of active sites to achieve an enhancement in the oxygen reduction reaction (ORR) is essential for the utilization of fuel cell and metal–air batteries. Herein, we report the facile synthesis of an ultrathin carbon sheet by calcining Fe-based precursors and melamine. Diverse kinds of Fe species with sizes ranging from atomic stacks to the nano-order have been established in Fe3C/NC-800. Thanks to the high density of the active sites, good conductance, as well as the perfect pore structure, outstanding performance can be achieved at a very low mass loading of 150 μg cm−2 in both alkaline and acid solutions. Consequently, Fe3C/NC-800 showed a half-wave potential that was ca. 20 mV more positive than that of commercial Pt/C in 0.1 M KOH, and surpassed most of the non-precious metal electrocatalysts reported in 0.1 M HClO4.