▎ 摘　　要

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.