The Use of NiFe₂O₄ and CoFe₂O₄ Nanoparticles Produced by Green Synthesis as Electrode Material for Supercapacitors

Abstract

In this report, for the first time, we have applied green synthesized NiFe2O4 and CoFe2O4 nanoparticles as electrode materials for supercapacitors (SCs). Bean pods extracts were used for the green synthesis of NiFe2O4 and CoFe2O4 nanoparticles. The structure and morphology of the samples were characterized by fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), energy dispersive X‐ray (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). From XRD analysis, it was determined that NiFe2O4 and CoFe2O4 nanoparticles had a crystalline structure. EDX analysis confirms the presence of carbon and the stoichiometries of NiFe2O4 and CoFe2O4. In TEM analyses, it was determined that the sizes of nanoparticles varied in the range of 5–20 nm. The FTIR spectra supported the presence of Fe−O, Ni−O, and Co−O bonds. Electrochemical measurements of active materials were performed using cyclic voltammetry, galvanostatic charge‐discharge, and electrochemical impedance spectroscopy techniques in a 1 M H2SO4 solution. It was determined that the specific capacitance value of NiFe2O4 (129 F/g) was higher than that of CoFe2O4 (106 F/g). The cyclic stability of CoFe2O4 and NiFe2O4 was found to be 59 and 106 % retention at the end of 10000 cycles, respectively. The specific capacitance value and very good cyclic stability of NiFe2O4 showed that it is a good active substance that can be used in supercapacitor applications.