Iron oxide decorated N-doped carbon derived from poly(ferrocene-urethane) interconnects for the oxygen reduction reaction

Abstract

We report the synthesis of mixed iron oxide particles decorated on nitrogen-doped carbon by forming covalent polyurethane linkages between ferrocene and phloroglucinol. Contrasting the electrostatic interactions and the physical cross-linking of the Fe/N/C precursors, here poly(ferrocene-urethane) (PFU) was acquired exclusively by (i) conversion of dicarboxylic acids present in ferrocene to azide linkages; and (ii) chemically linking the ferrocene-diazides to phloroglucinol through urethane bonds. The as obtained poly(ferrocene-urethane) was pyrolyzed under argon at elevated temperatures (600, 800 and 1000 °C) to yield iron oxide decorated N-doped carbon interconnects. The resultant porous materials were found to have the right balance of hierarchical porosity (micro-, meso- and macro-), and N-doping and iron oxide phases in and on the carbon matrices, respectively. Among the PFU samples pyrolyzed at different temperatures, the sample pyrolyzed at 800 °C displayed a more positive onset potential, a higher current density, and direct four electron transfer kinetics with a lesser yield of H₂O₂ (5.6%) on par with the commercially available Pt catalysts for the oxygen reduction reaction (ORR) in alkaline KOH solution. The superior electrocatalytic activity of PFU-800 can be traced to the synergistic effect between the iron oxide on and N-doping of the porous carbon nanostructures and the balanced hierarchial porosity. The developed non-Pt based electrocatalyst can be considered as a promising electrocatalyst in alkaline fuel cell applications.