Capacitive Properties of Ferrimagnetic NiFe2O4-Conductive Polypyrrole Nanocomposites

This investigation addresses increasing interest in advanced composite materials, combining capacitive properties and spontaneous magnetization for energy storage applications in supercapacitors. The capacitive properties of ferrimagnetic NiFe2O4 (NFO) spinel nanoparticles with magnetization of 30 emu g−1 were enhanced using high-energy ball-milling and the use of advanced dispersant, which facilitated charge transfer. NFO electrodes with an active mass of 40 mg cm−2 showed a capacitance of 1.46 F cm−2 in 0.5 M Na2SO4 electrolyte in a negative potential range. The charging mechanism in the negative potential range in Na2SO4 electrolyte was proposed. NFO was combined with conductive polypyrrole polymer for the fabrication of composites. The analysis of the capacitive behavior of the composites using cyclic voltammetry, chronopotentiometry and impedance spectroscopy at different electrode potentials revealed synergy of contributions of NFO and PPy. The highest capacitance of 6.64 F cm−2 was obtained from cyclic voltammetry data. The capacitance, impedance, and magnetic properties can be varied by variation of electrode composition. Composite electrodes are promising for application in anodes of asymmetric magnetic supercapacitors for energy storage and magnetically enhanced capacitive water purification devices.