Spray‐Assisted Synthesis of MnO@C/Graphene Composites as Electrode Materials for Supercapacitors

Abstract

The preparation of a composite consisting of amorphous carbon‐coated MnO nanoparticles deposited on graphene sheets (i.e., MnO@C/rGO) by a spray‐assisted method is reported. The MnO@C/rGO composite used as an active material for supercapacitors exhibits an excellent cyclability and a high specific capacitance in a two‐electrode system using 2 mol L−1 KOH aqueous solution as the electrolyte. High specific capacitances of 264 and 176 F g−1 at current densities of 1 and 20 A g−1, respectively, are achieved. A rate‐capability retention of about 67% is obtained when the current density increases from 1 to 20 A g−1, and the specific capacitance is retained at 78% after 10 000 cycles at a current density of 20 A g−1. The excellent electrochemical performance of the MnO@C/rGO is ascribed to the integration of graphene and the coating of amorphous carbon derived from glucose, which significantly improves the conductivity and alleviates the agglomeration of MnO. The unique architecture and good electrical conductivity increase the specific surface area and provide continuous electrical contact during the charge/discharge process. It is shown that carbon coating is an effective way to improve the electrochemical performance of metal oxides/graphene composites.