Noble metal-free electrocatalysts for the oxygen reduction reaction based on iron and nitrogen-doped porous graphene

Iron and nitrogen-functionalized porous graphene (Fe/N/GR) was prepared using commercial ZnO as a template without surface modification of the template. Due to the high isoelectric point, the positively charged ZnO serves as a template for the adsorption of negatively-charged graphene oxide (GO). In the presence of the N precursor and Fe source, the pyrolysis of ZnO/GO and the subsequent removal of the Fe species and ZnO template produce porous Fe/N/GR. The increased distance between layers of porous Fe/N/GR and the large surface area effectively alleviate the aggregation of GR sheets and are favorable for the exposure of active sites for the oxygen reduction reaction (ORR). Many active sites of nonporous Fe/N/GR catalysts are secluded inside the aggregated GR sheets, while they are exposed at the surface of porous Fe/N/GR catalysts with a porous structure and large surface area. Porous Fe/N/GR may be further used as efficient and inexpensive noble metal-free ORR catalysts in both alkaline solutions and acidic solutions.