▎ 摘　　要

A nitrogen-doped graphene (N-GN) based electrocatalysts have been synthesized by a two-step solution based scalable procedure of direct annealing of grapheneoxide (GO)/melamine gel mixture. The specific surface area (SSA) of GO has been increased through the pre-gelation of melamine on GO sheets as spacing. Despite the low nitrogen content, the N-GNs displayed much more oxygen reduction reaction (ORR) activities with positive onset potentials and large current densities than the blank sample. Moreover, compared with the high quality commercial (46%) Pt/C, N-GN15 exhibits higher current density and excellent tolerance to methanol crossover effect in both acidic and alkaline electrolytes making it an economic noble metal-free candidate for practical fuel cells. The higher current densities of N-GNs over blank sample and Pt/C have been linked to the synergetic effect of surface graphitic N groups and larger SSA of N-GNs. (C) 2016 Elsevier B.V. All rights reserved.