Enhancing oxygen reduction reaction durability via coating graphene layers on iron-nitrogen supported carbon nanotubes

Abstract

Development of efficient, low-cost and good stability electrocatalysts as alternatives to platinum for the oxygen reduction reaction (ORR) is of significance for fuel cells. Here we report a novel type of Fe, N supported carbon nanotube encapsulated with nitrogen doped graphene as an ORR electrocatalyst synthesized by a hydrothermal method, for which nitrogen-enriched melamine, ferric chloride and disodium edentate were used as the nitrogen, iron and graphene precursors, respectively. Disodium edentate plays an important role in the performance towards the ORR because it is not only a graphene precursor, but also the key of forming FeN_x active sites. The prepared Fe-N-CNT@GN catalyst exhibits high ORR activity in alkaline media with an onset potential of −0.13 V, a limiting current density of 6.2 mA cm⁻², and higher selectivity (number of electron transfer n ∼ 3.8) which might be due to the FeN_x active sites. Moreover, the half-wave potential exhibits almost no changes after 8000 continuous cycles scanning from −0.3 V to 0.1 V. The tolerance to the methanol crossover effect in alkaline media is superior. The Fe-N-CNT@GN catalyst obtained by this method solves the problem of agglomeration, migration, dissolution and leaching of catalysts in alkaline media. This type of catalyst has great potential for use as a high-performance nonprecious metal cathode catalyst in PEMFCs.