Theoretical and Experimental Insights of Magnesium-doped Cobalt Ferrites for Supercapacitor Applications

In the present study, we synthesize magnesium-doped cobalt ferrite (Co0.75Mg0.25Fe2O4) nanoparticles as stable and high-performance electrodes for supercapacitor application via the sol-gel combustion method and anneal them at 200 degrees C (MCF1), 300 degrees C (MCF2), and 500 degrees C (MCF3). Experimental and density functional theory (DFT) simulations of Co0.75Mg0.25Fe2O4 nanoparticles affirm a normal spinel cubic structure with partial tetrahedral occupancy and lattice expansion (8.3524 to 8.3704 angstrom) with subsequent temperature rise. The partial occupancies curtail the charge diffusion path length and favor a pronounced energy storage capacity. Morphological assessment also verifies the clustered and homogenous normal spinel cubic structure. Such cationic ordering increases the electronic bandgap (0.84 eV -> 1.57 eV) with d-orbital splitting due to crystal field effects. However, a non-linear impact upon the optical bandgap (1.214 eV to 1.212 eV (MCF1 to MCF2) and increases to 1.22 eV (MCF3)) is the consequence of bond dissociations favoring adequate e-h charge separations at elevated temperatures. Our experimental outcomes reveal a high specific capacitance of 579.3 Fg(-1) for MCF3 at 0.5 Ag-1 with a cyclic stability of 96.49% after 1000 cycles at 5 Ag-1.

Automated summary

In this study, magnesium-doped cobalt ferrite (Co0.75Mg0.25Fe2O4) nanoparticles were successfully synthesized via the sol-gel combustion method and annealed at different temperatures to obtain stable and high-performance electrodes for supercapacitor application. The nanoparticles exhibited a normal spinel cubic structure and showed improved energy storage capacity at elevated temperatures. The experimental results demonstrated that MCF3 had a high specific capacitance and good cyclic stability.