Fe, P, N- and FeP, N-doped carbon hollow nanospheres: A comparison study toward oxygen reduction reaction electrocatalysts.

In recent years, carbon materials co-doped with transition metals and heteroatoms have been widely used in the oxygen reduction reaction (ORR) as an alternative to platinum/carbon catalysts because of their high efficiency, low price, and appropriate sustainability. Herein, we report the synthesis of FeP, N-doped carbon (FeP, N-Carbon) hollow nanospheres (HNSs) and Fe, P, N-doped carbon (Fe, P, N-Carbon) HNSs. The FeP, N-Carbon was obtained via the pyrolysis of poly(o-phenylenediamine) (PoPD) HNSs in the presence of Fe(NO) and phytic acid (PA), whereas Fe, P, N-Carbon was obtained by first pyrolyzing PoPD HNSs with Fe(NO), followed by another cycle of pyrolysis with PA. Fe, P, N-Carbon exhibited a better ORR performance than FeP, N-Carbon, with an onset potential of 1.03 V, a half-wave potential of 0.89 V and a limiting current density of 5.75 mA cm. The findings will provide insights into the controlled synthesis of transition-metal-heteroatom-codoped carbon nanomaterials for the development of advanced ORR electrocatalysts.