Boosted electrochemical performance of magnetic caterpillar-like Mg 0.5 Ni 0.5 Fe 2 O 4 nanospinels as a novel pseudocapacitive electrode material

Ni-incorporated MgFe O (Mg Ni Fe O ) porous nanofibers were synthesized using the sol-gel electrospinning method. The optical bandgap, magnetic parameters, and electrochemical capacitive behaviors of the prepared sample were compared with pristine electrospun MgFe O and NiFe O based on structural and morphological properties. XRD analysis affirmed the cubic spinel structure of samples and their crystallite size is evaluated to be less than 25 nm using the Williamson-Hall equation. FESEM images demonstrated interesting nanobelts, nanotubes, and caterpillar-like fibers for electrospun MgFe O , NiFe O , and Mg Ni Fe O , respectively. Diffuse reflectance spectroscopy revealed that Mg Ni Fe O porous nanofibers possess the band gap (1.85 eV) between the calculated value for MgFe O nanobelts and NiFe O nanotubes due to alloying effects. The VSM analysis revealed that the saturation magnetization and coercivity of MgFe O nanobelts were enhanced by Ni incorporation. The electrochemical properties of samples coated on nickel foam (NF) were tested by CV, GCD, and EIS analysis in a 3 M KOH electrolyte. The Mg Ni Fe O @Ni electrode disclosed the highest specific capacitance of 647 F g at 1 A g owing to the synergistic effects of multiple valence states, exceptional porous morphology, and lowest charge transfer resistance. The Mg Ni Fe O porous fibers showed superior capacitance retention of 91% after 3000 cycles at 10 A g and notable Coulombic efficiency of 97%. Moreover, the Mg Ni Fe O //Activated carbon asymmetric supercapacitor divulged a good energy density of 83 W h Kg at a power density of 700 W Kg .