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 NiFe 2 O 4 and CoFe 2 O 4 nanoparticles as electrode materials for supercapacitors (SCs). Bean pods extracts were used for the green synthesis of NiFe 2 O 4 and CoFe 2 O 4 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 NiFe 2 O 4 and CoFe 2 O 4 nanoparticles had a crystalline structure. EDX analysis confirms the presence of carbon and the stoichiometries of NiFe 2 O 4 and CoFe 2 O 4 . 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 H 2 SO 4 solution. It was determined that the specific capacitance value of NiFe 2 O 4 (129 F/g) was higher than that of CoFe 2 O 4 (106 F/g). The cyclic stability of CoFe 2 O 4 and NiFe 2 O 4 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 NiFe 2 O 4 showed that it is a good active substance that can be used in supercapacitor applications.