Three-Dimensional Graphene/MnO₂ Nanowalls Hybrid for High-Efficiency Electrochemical Supercapacitors

In this paper, a facile method is designed to fabricate three-dimensional (3D) graphene (GR)/manganese dioxide (MnO₂) nanowall electrode material. The 3D GR/MnO₂ hybrid is prepared by a combination of electrochemical deposition (ELD) and electrophoresis deposition (EPD), followed by thermal reduction (TR). Firstly, the 3D graphene oxide (GO)/MnO₂ hybrid is obtained by the ELD-EPD method. Secondly, the 3D GR/MnO₂ hybrid is obtained through hydrogen reduction at a certain temperature. The as-fabricated hybrid has been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The electrochemical properties have been also measured by cyclic voltammetry. The results showed that the 3D GR/MnO₂ nanowalls hybrid has a high specific capacitance of 266.75Fg-1 and a high energy density of 25.36Whkg-1. Moreover, a high specific capacitance (240.15Fg-1) at a high scan rate of 200mVs-1 (90% capacity retention) has been also obtained. Additionally, the hybrid can serve directly as the electrodes of supercapacitor without adding binder. This work provides a novel road to fabricate a binder-free 3D GR-based hybrid for high-performance energy storage devices.