Iron–nitrogen co-doped hierarchically mesoporous carbon spheres as highly efficient electrocatalysts for the oxygen reduction reaction

Abstract

By using hierarchically mesoporous silica spheres as hard template, 2-aminopyridine and FeCl₃ as carbon, nitrogen and iron sources, respectively, iron and nitrogen co-doped hierarchically mesoporous carbon spheres (Fe–N–CS) were successfully prepared. The sample Fe–N–CS-900 obtained at a carbonization temperature of 900 °C exhibited a highly efficient electrocatalytic activity with positive half-wave potential (−0.11 V), high limiting current density (−4.79 mA cm⁻²) and high selectivity (electron transfer number around 4) for the oxygen reduction reaction (ORR) in alkaline media. Moreover, Fe–N–CS-900 shows higher stability and better methanol tolerance in comparison to commercial Pt/C catalyst in both alkaline and acidic media. Its highly efficient ORR activity could be ascribed to its high specific surface area, unique porous structure and homogeneous distribution of Fe–N_x active sites formed during pyrolysis.