Synthesis of (FeCoNiCuMn)3O4 spinel-high entropy oxide and green carbon from agricultural waste for supercapacitor application

Abstract

This article highlights (FeCoNiCuMn)₃O₄ high-entropy oxide prepared via liquid state induction melting techniques for supercapacitor application. Nanostructured high entropy oxides have higher active sites to boost the surface redox process with transition metal cations, such as Fe²⁺, Mn³⁺, Ni²⁺, Co²⁺, and Cu⁺, which helps to improve specific power, long-term cyclic stability, and specific capacitance. Melted and ball-milled HEA Nps were annealed to form the high entropy oxide, which uses a positive electrode for supercapacitor application; this results in the highest specific capacitance of 313 F g⁻¹ for a current rate of 5 mV s⁻¹ for the optimized 3 M KOH electrolyte. The biochar prepared through the pyrolysis of rice straw biochar shows a maximum specific capacitance of 232 F g⁻¹ for 5 mV s⁻¹. The fabricated aqueous devices display the highest specific capacitance of 83 F g⁻¹ at 2 A g⁻¹ with a specific energy of 33.4 W h kg⁻¹ at 1700 W kg⁻¹.