Nitrogen-doped porous carbon derived from Fe-MIL nanocrystals as an electrocatalyst for efficient oxygen reduction

Abstract

Exploring cheap and stable electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) is now the key issue for the large-scale application of fuel cells. Herein, we report a novel mesoporous carbon material prepared by one-step pyrolysis of a dicyandiamide (DCD)-doped iron-based metal organic framework (MOF) compound—Materiaux de l'Institute Lavosier-101(Fe) (MIL-101(Fe)). The as-prepared nitrogen mesoporous carbon (MIL-5 DCD-800) is characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N₂ sorption isotherms and X-ray photoelectron spectroscopy. MIL-5 DCD-800 shows an onset potential of 1.08 V (vs. RHE) and a half-wave potential of 0.86 V (vs. RHE) in 0.1 M KOH, which are similar to those of commercial Pt/C (1.05 V@0.05 mA cm⁻²). Furthermore, the electrocatalyst also possesses a much better stability and resistance to methanol crossover than Pt/C. This excellent performance is attributable to the presence of pyridinic- and graphitic-N together with abundant Fe active sites that promotes the four-electron process in the ORR. High pore volume and appropriate mesopores boost the mass transfer and reactivity during electrocatalysis.