Pseudocapacitive behavior of ferrimagnetic NiFe2O4-carbon nanotube electrodes prepared with a multifunctional dispersing agent

Abstract

We investigate the pseudocapacitive properties of ferrimagnetic NiFe2O4 ceramics in a 0.5 ​M Na2SO4 aqueous electrolyte. These ceramics have a high capacitance of 2.33 Fcm−2 since a more efficient colloidal technique is applied, which enhances the current response of the electrode in the negative potential range. NiFe2O4 is co-dispersed with multiwalled carbon nanotubes (MWCNTs) using Celestine Blue (CB) dye as a multifunctional co-dispersant. The capacitance measurements are performed by cyclic voltammetry, impedance spectroscopy and galvanostatic charge-discharge. The experiments reveal the synergistic effects of NiFe2O4 and conductive MWCNTs additives and the benefit they provide through co-dispersion with CB, which acts as an electron transfer mediator, enhancing pseudocapacitance. The mass ratio of NiFe2O4 and MWCNTs in the composite electrodes is varied to optimize the capacitance enhancement, lower electrical resistance at a high active mass loading of 40 ​mg ​cm−2, and achieve favorable capacitance retention at high charge-discharge rates. The results reveal a path for the development of pseudocapacitive ferrimagnetic ceramic composites that have advanced functionality.