Capacitance behavior of composites for supercapacitor applications prepared with different durations of graphene/nanoneedle MnO₂ reduction

Graphene/MnO₂ composites were prepared by hydrazine hydrate-mediated reduction of graphene oxide (GO)/MnO₂ at various reduction times to determine the optimal conditions for obtaining materials with excellent electrochemical performance. Variations in the oxygen-containing surface functional groups were observed as the reduction time was varied. These changes were found to affect the electrical conductivity and density of nanoneedle MnO₂, which influence the surface area and significantly affect the supercapacitive performance of the composites. Morphological and microstructural characterizations of the as-prepared composites demonstrated that MnO₂ was successfully formed on the GO surface and indicated the efficacy of hydrazine hydrate as a reducing agent for GO. The capacitive properties of the graphene/MnO₂ electrodes prepared at a reduction time of 28 h (rGO(28)/MnO₂) exhibited a low sheet-resistance value as well as a high surface area, resulting in a GO/MnO₂ composite with excellent electrochemical performance (371.74 F g^-1 at a scan rate of 10 mV s^-1). It is anticipated that the formation of MnO ₂-based nanoneedles on GO surfaces by the demonstrated 28-h hydrazine-reduction protocol is a promising method for supercapacitor electrode fabrication.