▎ 摘　　要

Herein we report for the first time, a unique three- dimensionally (3-D) interconnected and surface N functionalized (25%) graphene quantum dots (c-GQDs), which has been designed by a simple hydrazine hydrate treatment of GQDs in acidic condition at low temperature followed by a heat treatment that has remarkably enhanced electrocatalytic activity. A comparable exchange current density (i(0): 0.8 x 10(-3) A/cm(2)) with respect to the Pt/C and a low overpotential (220 mV; eta(2)(10mA/cm)) has been observed for c-GQDs. The improved performance of the material is attributed to the unique structure of the N-interlinkage among the individual GQDs where the pyridinic-N-oxide develops electron rich active sites in the carbon framework for favourable H+ adsorption and desorption. We hope that our study may build up a new platform to the graphene based materials for various energy applications.