Mesoporous layered spinel zinc manganese oxide nanocrystals stabilized nitrogen-doped graphene as an effective catalyst for oxygen reduction reaction

The design of low-cost, highly efficient, and the durable catalyst is essential to replace commercial platinum metal-based catalysts for the oxygen reduction reaction (ORR) in fuel cell applications. Herein, a novel mesoporous hybrid based on nitrogen-doped graphene nanosheets-stabilized layered spinel zinc manganese oxide (Zn₂Mn₃O₈-NG) is successfully engineered and applied as an effective catalyst to accelerate the ORR process in alkaline medium. Electrochemical performance analysis of this catalyst shows excellent catalytic activity with high current density, positive onset potential (-0.013 V), and positive half-wave potential (-0.12 V), which are relative to the commercial Pt/C in 0.1 M KOH electrolyte. The kinetic study of the synthesized catalyst towards ORR demonstrates a direct 4e^- transfer pathway. The methanol tolerance and long-term stability test suggest its superior behavior to Pt/C. The excellent performance of the Zn₂Mn₃O₈-NG is attributed to the synergistic effects of nanosized Zn₂Mn₃O₈ nanocrystals and NG nanosheets, which effectively improve the electroactive surface area, conductivity, diffusion channels, and mass transfer ability. This result suggests that the resulting catalyst could be used as a potential alternative of Pt-based catalysts towards ORR application.