▎ 摘　　要

This paper introduces a green, safe and effective process for mass synthesizing graphene oxide (EGO) with high yield up to 90 wt %, excellent water solubility and good quality ((<) 5 layers reach to 95%) via electrochemical exfoliation method in acidic potassium permanganate electrolyte. Furthermore, the reacted EGO electrolyte continues to undergo a one-step hydrothermal treatment for preparing the MnO2/reduced graphene oxide (MnO2/rEGO) composite, and then it is used as an electrode material of supercapacitor. Experimental results reveal that the MnO2/rEGO composite exhibits a high specific capacitance of 342.8 Fg(-1) at a current density of 0.5 Ag-1, excellent rate capability and cycling stability with 90.3% capacitance retention after 3000 cycles. A two-electrode symmetric supercapacitor assembled device is fabricated and exhibits a high specific capacitance of 226.8 Fg(-1) at 0.5 Ag-1. It shows that the MnO2/rEGO composite provides potential applications in energy storage. (C) 2019 Elsevier Ltd. All rights reserved.