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

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. [Display omitted] •N doped edge-rich GNRs intertwined on 3D graphene to obtain superb ORR performance.•3D graphene acts as skeleton, while GNRs expose edge defects offering doping site.•DFT calculations manifest the key role of edge defects in the GNRs.