Constructing Graphitic-Nitrogen-Bonded Pentagons in Interlayer-Expanded Graphene Matrix toward Carbon-Based Electrocatalysts for Acidic Oxygen Reduction Reaction.

Metal-free carbon-based materials with high electrocatalytic activity are promising catalysts for the oxygen reduction reaction (ORR) in several renewable energy systems. However, the performance of carbon-based materials is far inferior to that of Pt-based catalysts in acid electrolytes. Here, a novel carbon-based electrocatalyst is reported toward ORR in 0.1 m HClO4 with half-wave potential of 0.81 V and better durability (100 h reaction time) than commercial 20 wt% Pt/C. It is achieved by constructing graphitic-nitrogen (GN)-bonded pentagons in graphitic carbon to improve the intrinsic activity of the carbon sites and increasing the amount of active sites via expanding the interlayer spacing. X-ray absorption spectroscopy and aberration-corrected electron microscopy characterizations confirm the formation of GN-bonded pentagons in this carbon material. Raman and X-ray photoelectron spectroscopy reveal that the activity is linearly associated with the amounts of both pentagons and adjacent GN atoms. Density function theory further demonstrates that adjacent GN atoms significantly increase the charge density at the carbon atom of a GN-bonded pentagon, which is the activity origin for the ORR.