N-doped graphene nanoribbons intertwined on 3D graphene skeleton as superior metal-free electrocatalyst for oxygen reduction

Abstract

Increasing the active sites of graphene by forming edge-rich graphene nanoribbons (GNRs) represents a promising pathway for improving the behaviors of metal-free electrocatalyst. N-doped GNRs intertwined on 3D graphene skeleton with aerogel structure (N-GNRs/G) is synthesized by hydrothermal method and subsequent pyrolysis process. In the N-GNRs/G aerogel, 3D graphene acts as the skeleton frame to construct a 3D porous structure, while GNRs with irregular edges expose abundant edge defects which offer doping sites for heteroatoms. Thus, the synergetic effect of GNRs and 3D graphene endows the synthesized N-GNRs/G with tremendous pyridinic-N and graphitic-N active sites towards the oxygen reduction reaction (ORR). The N-GNRs/G hybrid exhibits excellent ORR catalytic activity, superior stability, and selectivity. The onset potential and half-wave potential can reach 0.98 V and 0.856 V, respectively, which are close to those of the commercial Pt/C. This work paves a pathway to modulate the surface charge redistribution by means of morphology controlling and heteroatom doping for efficient and low-cost electrocatalysts.