▎ 摘　　要

It's significant to find an atom-economic way to prepare graphene-manganese oxide nanocomposites for supercapacitors. Herein, a highly atom-efficient strategy is reported to synthesize reduced graphene oxide (rGO)-Mn3O4 nanoparticles composite for supercapacitors. First, rGO/MnSO4 suspension is obtained by hydrothermal reduction of graphene oxide (GO)/MnSO4 suspension, which is directly produced via Hummers method, and then rGO-Mn3O4 nanoparticles composites are prepared by precipitation of Mn3O4 nanoparticles anchored in-situ on rGO sheets. The as-prepared rGO-Mn3O4 nanocomposites with 86.96% Mn3O4 exhibit high specific capacitance of 258.6 F g(-1) and 186.2 F g(-1) at 0.25 A g(-1), when using 2 M KOH and 1 M Na2SO4 solution as electrolyte, respectively. More importantly, with the wastewater recovered in the preparation process as electrolyte, the rGO-Mn3O4 composites can deliver a high specific capacitance of 221.6 F g(-1) at 50 mA g(-1) and 97.1% of the initial capacitance is retained after 1000 cycles at 1 A g(-1). In addition, the rGO-MnO2 nanosheets composites can also be obtained via a similar strategy. Obviously, this work provides an atom-efficient way for preparation of rGO-manganese oxide nanocomposites for supercapacitors by fully utilizing effective components of the reaction system, including the wastewater. (C) 2016 Elsevier B.V. All rights reserved.