Exploring highly active, durable and low-cost catalysts toward hydrogen evolution reaction (HER) holds a key to clean energy technologies. Heteroatoms-doped graphene-based materials are emerging as the most promising metal-free HER catalysts, but their catalytic activity remains largely unexplored. Herein, by rationally engineering the macroscopic architecture of graphene and its chemical/defective structures, we developed a three-dimensional' (3D), N-doped, plasma-etched graphene (3DNG-P) as a highly active metal-free HER catalyst. The obtained 3DNG-P combined the merits of freestanding 3D porous architecture, high-level N-doping and plasma-induced enriched defects, resulting in a highly enhanced HER activity with a low overpotential of 128 mV at 10 mA cm(-2) in acidic medium. Furthermore, the 3DNG-P displayed a favorable HER activity and stability over a wide pH range. The present study thus provides a new methodology for the design of graphene-based metal-free catalysts with high HER performance. (C) 2016 Elsevier B.V. All rights reserved.