▎ 摘　　要

MnO2 nanoplates grown on graphene sheets have been directly synthesized during the graphite oxide (GO) reduction. The synthetic method is efficient, green and controllable with GO reduced and MnO2 nanoplates formed in one step. Compared with conventional methods, this method is easier to implement without using binders or any conductive additives. The as-prepared MnO2 nanoplates and graphene composites (GM) electrodes exhibit enhanced electrochemical performances, including ultrahigh specific capacitance (385 F g(-1), at current density of 1 A g(-1)) and excellent cycling stabilities with 1 M Na2SO4 electrolytes. This improvement is due to the tighter contact between graphene sheets and MnO2 nanoplates, and the higher conductive and capacitive characteristics of graphene. (C) 2014 Elsevier Ltd. All rights reserved.