▎ 摘　　要

The present study investigates the fabrication of hierarchical 3D nanostructures with multi-component metal oxides in the presence of highly-porous graphene and characterized for its applications in high-performance supercapacitors. A hierarchical flowers like 3D nanostructure of Co3O4 @MnO2 on nitrogen-doped graphene oxide (NGO) hybrid composite was synthesized by thermal reduction process at 650 degrees C in the presence of ammonia and urea. The synthesized Co3O4 @MnO2/NGO hybrid composites were studied via Raman, XRD, X-ray XPS, FE-SEM, FE-SEM with EDX, FE-TEM and BET analyses. The electrochemical analysis of Co3O4 @MnO2/NGO hybrid composite electrode was investigated using cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements. The hybrid composite electrode showed significant specific capacitance results of up to 347 F/g at 0.5 A/g and a corresponding energy density of 34.83Wh kg(-1) with better rate performance and excellent long-term cycling stability were achieved for 10,000 cycles. The obtained electrochemical results paved a way to utilize Co3O4 @MnO2/NGO composite electrode as a promising electrode material in high performance supercapacitors.