Construction of nitrogen-doped porous carbon nanosheets decorated with Fe–N4 and iron oxides by a biomass coordination strategy for efficient oxygen reduction reaction

Abstract

Exploring nonprecious and highly efficient electrocatalysts for the oxygen reduction reaction (ORR) is critically important for the large scale application of metal–air batteries. Herein, iron oxides and Fe–N₄ moieties anchored on nitrogen doped porous carbon nanosheets (Fe₂O₃@C/FeNC-900) are designed and constructed by coordinating egg white with iron ions, followed by nitrogen doping and one-step pyrolysis under nitrogen atmosphere. The synthesis procedure, without the need of using any toxic materials or acid leaching post-treatment, is convenient and environmentally friendly. The unique structure of Fe₂O₃@C/FeNC-900 with atomically dispersed Fe–N₄ moieties and iron oxide nanoparticles confined in sheet-like porous carbon is revealed using XRD, TEM, XPS and X-ray absorption fine structure spectroscopy (XAFS). The multiple active centers and strong synergistic effects endow Fe₂O₃@C/FeNC-900 with excellent ORR catalysis performance in alkaline electrolyte. It exhibits a positive half-wave potential of 0.89 V in 0.1 M KOH and excellent long-term stability. Beyond that, the zinc–air battery (ZAB) using Fe₂O₃@C/FeNC-900 as the cathode material shows excellent electrochemical performance and remarkable cycling performance. This research provides a facile and environmentally friendly strategy for the synthesis of nonprecious electrocatalysts beneficial to practical metal–air battery applications.