Facile synthesis, enhanced annealing-structural investigation and supercapacitive potentials of NiFe₂O₄ spinel nanopowder

Herein, we examined and optimized the influence of annealing temperature on microstructural and electrochemical charge storage properties of spinel NiFe₂O₄ nanopowder synthesized from a simple one-pot sol-gel route. Microstructural techniques encompassing Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffractometry, and Fourier transform infra-red spectroscopy indicate the resulting powder are composed of spinel NiFe₂O₄ nanoparticle with metal oxygen vibration, crystal properties and lattice strain, all dependent on annealing temperature. Electrochemical charge storage performance of the electrode fabricated from the synthesized material were investigated with the aid of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The obtained results showed that the charge storage performance and rate capability of NiFe₂O₄ electrode is dependent on the annealing temperature. The study also showed that the electrode from the material annealed at 400 °C demonstrated optimum electrochemical charge storage performance having exhibited optimum specific capacitance and capacity values of 1128 Fg⁻¹ and 58 mAh g⁻¹ at 5 mVs⁻¹ scan rate and 0.5 Ag⁻¹ current density, respectively. The electrode EIS fitted equivalent circuit values were also found dependent on annealing temperature indicating the charge transfer process and rate capability of spinel NiFe₂O₄ nano-powder can be tailored by simply varying the annealing temperature. The study demonstrates cheap route by which spinel NiFe₂O₄ powder can be prepared. It also unveils the effect annealing temperature on the microstructural build-up and electrochemical charge storage performance of the material.