Green Synthesis of NiFe 2 O 4 Nano-Spinel Oxide-Decorated Carbon Nanotubes for Efficient Capacitive Performance-Effect of Electrolyte Concentration.

Energy storage applications received great attention due to environmental aspects. A green method was used to prepare a composite of nickel-iron-based spinel oxide nanoparticle@CNT. The prepared materials were characterized by different analytical methods like X-ray diffraction, X-ray photon spectroscopy (XPS), scanning electron microscopy (SEM), and transmitted electron microscopy (TEM). The synergistic effect between nickel-iron oxide and carbon nanotubes was characterized using different electrochemical methods like cyclic voltammetry (CV), galvanostatic charging/discharging (GCD), and electrochemical impedance spectroscopy (EIS). The capacitances of the pristine NiFe 2 O 4 and NiFe 2 O 4 @CNT were studied in different electrolyte concentrations. The effect of OH- concentrations was studied for modified and non-modified surfaces. Furthermore, the specific capacitance was estimated for pristine and modified NiFe 2 O 4 at a wide current range (5 to 17 A g -1 ). Thus, the durability of different surfaces after 2000 cycles was studied, and the capacitance retention was estimated as 78.8 and 90.1% for pristine and modified NiFe 2 O 4 . On the other hand, the capacitance rate capability was observed as 65.1% (5 to 17 A g -1 ) and 62.4% (5 to 17 A g -1 ) for NiFe 2 O 4 and NiFe 2 O 4 @CNT electrodes.