Graphite-Wrapped Fe Core–Shell Nanoparticles Anchored on Graphene as pH-Universal Electrocatalyst for Oxygen Reduction Reaction

Development of high-performance nonprecious metals and their nanocomposites as oxygen reduction electrocatalysts is critical but still challenging for fuel cells and metal-air batteries. Here, we introduce a synthetic strategy to fabricate graphite-wrapped Fe core-shell nanoparticles anchored on graphene as an efficient and stable pH-universal electrocatalyst for oxygen reduction reaction (ORR). The coordination among Fe3+, ellagic acid, and graphene oxide would drive the formation of a sandwichlike assembly, which was subsequently converted into graphene-supported Fe@graphitic carbon core-shell nanoparticles (denoted as GEF). The obtained GEFs exhibited remarkable ORR activity and durability in a wide range of pHs. Most notably, GEF pyrolized at 900 °C showed that the onset and half-wave potential at 1.01 and 0.90 V were more positive than those of a commercial Pt/C (onset and half-wave potential: 0.94 and 0.84 V) in alkaline media. Meanwhile, it also demonstrated comparable or even better activity as compared with the commercial Pt/C catalysts in acidic and neutral electrolytes.