Concentration dependence of graphene oxide–nanoneedle manganese oxide composites reduced by hydrazine hydrate for an electrochemical supercapacitor

Abstract

Graphene–MnO₂ composites are reduced from GO–MnO₂ using various concentrations of hydrazine hydrate with a fixed reduction time to optimize the hydrazine concentration to obtain excellent electrochemical performance. Changes in the oxygen-containing functional groups are observed as the concentration of hydrazine is varied. These changes affect the electrical conductivity and density of MnO₂ nanoneedles, which impact the surface area and can significantly affect the supercapacitive performance. The characterization of morphology and microstructure of the as-prepared composites demonstrates that MnO₂ is successfully formed on the GO surface and GO is successfully reduced by using hydrazine hydrate as a reducing agent. The capacitive properties of the graphene–MnO₂ electrodes which reduced 50 mM of hydrazine (RGO–MnO₂(50)) show a low sheet resistance value as well as a high surface area, resulting in excellent electrochemical performance (383.82 F g⁻¹ at a scan rate of 10 mV s⁻¹). It is anticipated that the formation of nanoneedle structures of MnO₂ on graphene oxide surfaces utilizing the 50 mM hydrazine reduction procedure is a promising fabrication method for supercapacitor electrodes.