Reduced graphene oxide/Mn₃O₄ nanohybrid for high-rate pseduocapacitive electrodes

Nanostructure Mn₃O₄ is a promising pseudocapacitive electrode material due to its low cost, environmental compatibility, and intrinsically high capacity. However, the poor electrical conductivity and low accessible active sites limit its performance. We report that one-dimensional (1D) nanoscale Mn₃O₄ has been coupled with reduced graphene oxide (RGO) to fabricate RGO/Mn₃O₄ nanohybrid (MORGO) as a pseudocapacitive electrode material with high capacitance. The selective reduction of graphene oxide (GO) in Mn₃O₄/graphene oxide (MOGO) to reduced graphene oxide (RGO) while sustaining the unchanged oxidation state of manganese is the key to obtain MORGO. Specific surface area of MORGO is 14 times higher than pure Mn₃O₄, and the charge transfer resistance decreases 3.2 times. These enhanced properties lead to excellent specific capacitance of 538 F g^-1 at the current density of 0.1 A g^-1, and of 472 F g^-1 at 10 A g^-1 in 1 M Na₂SO₄ aqueous electrolyte. The capacitance retained 89% after 2000 cycles, demonstrating its excellent long-term cycling stability.