Ultrasound assisted synthesis of Mn3O4 nanoparticles anchored graphene nanosheets for supercapacitor applications

• Room temperature synthesis of Mn3O4–graphene (MG) composite via ultra sound assisted method.
• TEM images shows Mn3O4 nanoparticles are uniformly distributed on the surface of graphene nanosheets.
• MG composite exhibited high specific capacitance of 312 F g−1 in 1 M Na2SO4 which was three times greater than pristine Mn3O4.
• 76% of the initial capacitance was retained even after 1000 cycles.
• The higher specific capacitance of the MG nanocomposite due to the synergistic effect between the Mn3O4 nanoparticles and graphene nanosheets.

Mn3O4 nanoparticles anchored graphene nanosheets (MG) have been successfully synthesized by a simple ultrasound assisted synthesis at room temperature without the use of any templates or surfactants for supercapacitor applications. Upon ultrasound assisted synthesis, the formation of Mn3O4 nanoparticles and the graphene oxide reduction occurs simultaneously. The crystalline structure of thus prepared MG nanocomposite have been characterized by the powder X-ray diffraction (XRD) analysis. Thermo Gravimetric Analysis (TGA) is used to determine the mass content of graphene (17 wt%) in the MG nanocomposite. Transmission electron microscopy (TEM) and Atomic force microscopy (AFM) studies shows that the Mn3O4 nanoparticles (4–8 nm) were uniformly anchored on the surface of graphene nanosheets. The electrochemical properties of the MG nanocomposite were investigated by employing cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The capacitive properties of MG nanocomposite studied in the presence of 1 M Na2SO4 exhibited high specific capacitance of 312 F g−1 which was approximately three times greater than that of pristine Mn3O4 (113 F g−1) at the same current density of 0.5 mA cm−2 in the potential range from -0.1 to +0.9 V. About 76% of the initial capacitance was retained even after 1000 cycles establishes the fact that MG nanocomposite exhibited good electrochemical stability and capacitance retention capability also.

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