Template-Free Synthesis of Two-Dimensional Fe/N Codoped Carbon Networks as Efficient Oxygen Reduction Reaction Electrocatalysts

A direct pyrolysis and template-free synthesis strategy is demonstrated to synthesize the two-dimensional (2-D) Fe/N codoped carbon networks by virtue of 2-D graphitic-carbon nitride (g-C3N4) intermediates derived from melamine. Because of the stabilization and steric hindrance of additional N ligands with bisnitrogen-containing groups (phenanthroline, phthalonitrile, and phenylenediamine), the thin graphitic-layered Fe/N codoped carbon materials have successfully inherited the 2-D morphology from the g-C3N4 intermediate after direct carbonization treatment. After the easy removal of inactive Fe particles, the resultant sample exhibits numerous well-dispersed Fe atoms embedded in the carbon layers with a hierarchical (meso- and micro-) porous structure. Owing to the high active site density and open porous structure, the thin graphitic-layered Fe/N codoped carbon electrocatalysts exhibit superior oxygen reduction reaction performance (a half-wave potential of 0.88 V and a kinetics current density of 3.8 mA cm-2), even better than the commercial Pt/C catalysts (0.85 V and 1.6 mA cm-2, respectively). The facile and effective synthesis strategy without template to build the graphene-like nanoarchitectures inherited from the 2-D intermediates will lead to a great development of 2-D carbon materials in various electrochemical applications.