Polyformamidine‐Derived Non‐Noble Metal Electrocatalysts for Efficient Oxygen Reduction Reaction

Abstract

Abstract A facile approach for the template‐free synthesis of highly active non‐noble metal based oxygen reduction reaction (ORR) electrocatalysts is presented. Porous Fe−N−C/Fe/Fe 3 C composite materials are obtained by pyrolysis of defined precursor mixtures of polyformamidine (PFA) and FeCl 3 as nitrogen‐rich carbon and iron sources, respectively. Selection of pyrolysis temperature (700–1100 °C) and FeCl 3 loading (5–30 wt%) yields materials with differing surface areas, porosity, graphitization degree, nitrogen and iron content, as well as ORR activity. While the ORR activity of Fe‐free materials is limited (i.e., synthesized from pure PFA), a huge increase in activity is observed for catalysts containing Fe, revealing the participation of the metal dopant in the construction of active electrocatalytic sites. Further activity improvement is achieved via acid‐leaching and repeated pyrolysis, a result which is attributed to the creation of new active sites located at the surface of the porous nitrogen‐doped carbon by dissolution of the Fe and Fe 3 C nanophases. The best performing catalyst, which was synthesized with a low Fe loading (i.e., 5 wt%) and at a pyrolysis temperature of 900 °C, exhibits high activity, excellent H 2 O selectivity, extended stability, in both basic and acidic media as well as a remarkable tolerance toward methanol.