Revealing the electrochemical merits of coral-reef-like nickel-doped mixed metal-organic framework composites as advanced supercapacitor electrodes

Abstract

Due to their porous characteristics, adjustable morphologies, better tunability, controllable crystal structures, and chemical compositions, metal-organic frameworks (MOFs) have been particularly interesting and employed in energy storage applications. Within MOFs, the organic framework enhances the double-layer capacitance, while incorporating mixed inorganic metal-organic frameworks leads to an additional pseudocapacitance, resulting in a synergistic effect that holds potential for significant advancements in energy storage technologies. In the current work, a facile wet chemical process was employed to fabricate the Ni-doped Co/Fe-MOF@Fe2O3 composite, which showed improved electrochemical properties for the resultant electrodes utilizing synergism between the Ni2+ and Co/Fe-MOF. Owing to their unique coral-reef-like morphology and improved textural behavior, the as-made Ni-doped Co/Fe-MOF@Fe2O3 offered abundant electroactive sites and shortened electron migration and electrolyte diffusion pathways. Interestingly, the prepared Ni-doped Co/Fe-MOF@Fe2O3 offered an excellent specific capacitance of 136.4 F g-1, a high-energy density of 37.1 W h kg-1, and a power density of 700 W kg-1 at 1 A g-1 in a hybrid two-electrode cell. Further, it maintained a considerable capacitance retention of 86.6 % over 5000 charge-discharge cycles. These findings open the door to employing them as promising electrode materials in hybrid supercapacitors.