Highly atom-economic synthesis of graphene/Mn3O4 hybrid composites for electrochemical supercapacitors

Abstract

A highly atom-economic procedure for the preparation of reduced graphene oxide/Mn₃O₄ (rGO/Mn₃O₄) composites is reported. Pristine graphene oxide/manganese sulfate (GO/MnSO₄) suspension produced by modified Hummers method is utilized with high efficiency, which has been in situ converted into GO/Mn₃O₄ hybrid composite by air oxidation, then into rGO/Mn₃O₄ composite by means of dielectric barrier discharge (DBD) plasma-assisted deoxygenation. The Mn₃O₄ content of the rGO/Mn₃O₄ composites can be readily tailored. It is observed that Mn₃O₄ nanoparticles of 15–24 nm are well-dispersed on graphene sheets with Mn₃O₄ loading as high as 90%. The specific capacitance of the as-prepared rGO/Mn₃O₄ hybrids with 90% Mn₃O₄ reaches 193 F g⁻¹ when employed as the electrode material in neutral Na₂SO₄ electrolyte solutions (76 F g⁻¹ for pristine graphene and 95 F g⁻¹ for pure Mn₃O₄), which indicates the positive synergetic effects from both graphene and attached Mn₃O₄. The method developed in this study should offer a new technique for the large scale and highly atom-economic production of graphene/MnO_x composites for many applications.