Exploring the synergy in energy storage and magnetic properties of core–shell ferrimagnetic γ–Fe2O3-polypyrrole and carbon nanotubes-polypyrrole composites

This investigation demonstrates the fabrication of advanced electrodes for supercapacitors with high active mass loading, which show capacitance of 6.22 F cm−2, high capacitance retention at high charge discharge rates, low resistance in Na2SO4 electrolyte and advanced magnetic properties. Composite electrodes contain polypyrrole (PPy) polymer, ferrimagnetic γ-Fe2O3 particles and conductive multiwalled carbon nanotubes (MWCNT). The approach is based on the use of catechol violet (CCV) as a multifunctional co-dispersant for γ-Fe2O3 particles and MWCNT as well as a dopant for PPy polymerization. The use of CCV facilitates the fabrication of core–shell PPy coated γ-Fe2O3 particles and core–shell PPy coated MWCNT. The morphology and composition of the particles and electrodes are optimized for obtaining high capacitance, low resistance and high magnetization using nickel foam or graphene coated nickel foam current collectors. Advanced properties are achieved by the application of high energy ball milling of the γ-Fe2O3 particles, formation of core–shell particles, synergy of contributions of individual components to magnetic and capacitive properties and application of graphene coated current collectors. The capacitive and magnetic properties of the composites can be varied. Obtained results open an avenue for the fabrication of advanced electrodes for magnetically aided energy storage and water purification devices.