Highly Porous Iron-Doped Nitrogen-Carbon Framework on Reduced Graphene Oxide as an Excellent Oxygen Reduction Catalyst for Proton-Exchange Membrane Fuel Cells

Iron-doped nitrogen carbon (Fe-NC) is a suitable catalyst for the oxygen reduction reaction (ORR) in acidic and alkaline environments. However, challenges remain in controlling the porosity of the catalyst and distribution of the active sites. Herein, we have prepared a highly porous Fe-doped nitrogen-carbon framework on reduced graphene (A-Fe-NC/rGO) for ORR and proton-exchange membrane fuel cell (PEMFC) studies. The A-Fe-NC/rGO catalyst was fabricated via carbonization of Fe-doped zeolitic imidazolate framework-8 (ZIF8) on graphene oxide, followed by thermal treatment in the presence of NH3 to create mesopores and modify the nitrogen species present in the catalyst. As a result, highly porous, hierarchical, and conductive A-Fe-NC/rGO with a specific surface area of 1226.2 m(2) g(-1) was synthesized. The catalyst exhibited superior performance using linear sweep voltammetry (LSV) in 0.1 M HClO4 and 0.1 M KOH electrolytes when compared to a commercially available Pt/C catalyst. The excellent performance has been attributed to (1) the hierarchical structure enabling rapid mass transfer, (2) the highly porous carbon framework exposing a large number of active Fe sites on the surface, and (3) reduced graphene oxide enhancing the conductivity of the catalyst. Our PEMFC study has shown that a maximum power density of 310 mW cm(-2) can be achieved at 764 mA cm(-2). We believe that A-Fe-NC/rGO can be used as a high-quality cathode catalyst for PEMFC applications.