▎ 摘　　要

A binder-free 3D electrode of MnO2 arrays on graphene@nickel foam was successfully prepared via a twostep method. The nickel foam was first coated with a graphene sheet by chemical vapor deposition (CVD) and then decorated with MnO2 of different morphologies, ultrathin MnO2 nanosheets and ultralong MnO2 nanowires, by facile hydrothermal method. Due to the large specific surface area, high electronic conductivity and good capacitance of electrode materials, the obtained electrode exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability. The electrode showed a high specific capacitance of 723 F cm(-2) at a high current density of 30 mA cm(-2) and a good cycling stability (with a negligible 2.4% decay in specific capacitances after 2300 cycles), promising its applications to high-performance supercapacitors. (C) 2017 Elsevier B.V. All rights reserved.