Spinel MnCo2 O4 Nanoparticles Supported on Three-Dimensional Graphene with Enhanced Mass Transfer as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

Abstract

The rational design of highly efficient and durable oxygen reduction reaction (ORR) catalysts is critical for the commercial application of fuel cells. Herein, three-dimensional graphene (3D-G) is synthesized by the template method, which used coal tar pitch as the carbon source and nano MgO as the template. Then, spinel MnCo₂ O₄ is in situ supported on the 3D-G by a facile hydrothermal method, giving MnCo₂ O₄ /3D-G. The resultant MnCo₂ O₄ /3D-G retains the multilayered mesoporous graphene structure where MnCo₂ O₄ nanoparticles are deposited on the inner walls of pores in the 3D-G. The catalyst MnCo₂ O₄ /3D-G shows high electrocatalytic activity with a half-wave potential of 0.81 V versus reversible hydrogen electrode, which is clearly superior to those of MnCo₂ O₄ /reduced graphene oxide (0.78 V), MnCo₂ O₄ /carbon nanotubes (0.74 V), MnCo₂ O₄ /C (0.72 V), and 20 wt % Pt/C (0.80 V). The electron transfer number of MnCo₂ O₄ /3D-G indicates a four-electron process of ORR. The durability test demonstrates that the MnCo₂ O₄ /3D-G catalyst has a much better durability than 20 wt % Pt/C. Our work makes an inspiring strategy to prepare high-performance electrocatalysts for the development of fuel cells.

Keywords: fuel cells; hydrothermal method; oxygen reduction reaction; spinel MnCo2O4; three-dimensional graphene.