Disorder induced augmentation of the specific capacitance of δ-MnO2 nanoflowers by incorporating Fe3O4 nanodiamonds for supercapacitor electrodes†

Abstract

In this study, delta manganese dioxide (δ-MnO₂) nanoflowers and magnetite (Fe₃O₄) nanodiamond incorporated δ-MnO₂ nanoflowers (δ-MnO₂/Fe₃O₄ nanocomposites) were synthesized via a simple hydrothermal method for electrode materials in supercapacitors. The Fe₃O₄ content was varied between 0 and 5 wt% to determine the optimized combination of δ-MnO₂ and Fe₃O₄ for the nanocomposite that would exhibit superior electrochemical properties for high-performance energy storage devices. In a three-electrode system, the δ-MnO₂/Fe₃O₄ nanocomposite with 3 wt% Fe₃O₄ exhibited the highest specific capacitance of 459 F g⁻¹ at a current density of 0.3 A g⁻¹, compared to 76 F g⁻¹ for pure δ-MnO₂ nanoflowers and retained about 75% of its initial capacitance after 4000 charge–discharge cycles at a high current density of 6 A g⁻¹. The modulation of the electrochemical performance of the nanostructured composites was evaluated in terms of crystallographic and morphological aspects like interplanar spacing, crystallinity, defect formation and internal surface modification of the nanostructures and electrochemical impedance spectroscopic analysis. This study demonstrates that the optimized δ-MnO₂/(3%) Fe₃O₄ nanocomposite, with its high charge storage capacity and good long-term stability, is a relatively more effective electrode material for high-performance supercapacitors compared to other combinations with different morphologies.