NiO nanomaterial was synthesized at different calcination temperatures using cetyltrimethyl ammonium bromide (CTAB) as surfactant via microwave method. Thermogravimetric studies revealed the decomposition details of Ni(OH)2 precursor. The structure and morphology of the NiO was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). NiO calcined at 300 °C shows a nanoflake-like structure. A possible formation mechanism has been discussed with time evolution study. Electrochemical studies indicate that the sample calcined at 300 °C exhibits better charge storage. The NiO nanoflakes exhibit maximum specific capacitance of 401 F g(-1) at a current density of 0.5 mA cm(-2). The energy generated and hence the charges collected from wind and solar panels are slow but in many applications the power delivery has to be at a faster rate. Considering this aspect, slow-charge and fast-discharge tests have been performed and reported. The NiO nanoflakes appear to be a promising electrode material for supercapacitor application.
Via the green chemistry route, Mn3O4/amorphous
carbon nanoparticles have been synthesized. Dextrose was used as the
reducing agent, and starch was used as the capping agent. The X-ray
diffraction patterns reveal the Hausmannite tetragonal structure of
the synthesized Mn3O4 particles. EDAX analysis
confirms the presence of carbon and stoichiometry of Mn3O4. Morphological studies reveal the nanospherical nature
of the synthesized particles. The FTIR spectra confirm the presence
of Mn–O bonds. Mn3O4/AC 500 exhibits
highest specific capacitance of 522 F g–1 at a specific
current of 1 A g–1, when measured from the charge–discharge
process. This value is superior to previous reports on Mn3O4 nanoparticles as an electrode for supercapacitors.
Higher energy density of 58.72 W h kg–1 could be
observed for Mn3O4/AC 500, which is higher than
lead acid batteries and comparable to those for the nickel hydride
batteries. These results indicate that Mn3O4/AC 500 is a promising electrode for supercapacitor applications.
NiO/C nanocomposites were synthesized at different calcination temperatures using starch as the stabilizing agent. The NiO/C nanocomposites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The samples calcined at 500 °C exhibit a highly porous nature. Electrochemical investigations of NiO/C were carried out using cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. NiO/C-5 shows excellent electrochemical performance compared to NiO/C-4 and NiO/C-6. The NiO/C-5 electrode exhibits a specific capacitance value of 644 F g −1 at a scan rate of 2 mV s −1 . The charge transfer resistance is 0.59 Ω for the NiO/C-5 electrode. This NiO/C-5 appears to be a promising electrode material for supercapacitor applications.
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