Fabrication of hybrid supercapacitor device based on NiCo₂O₄@ZnCo₂O₄ and the biomass-derived N-doped activated carbon with a honeycomb structure

Highly efficient supercapacitor devices are fabricated with the hybrid nanocomposite material and biomass-derived N-doped activated carbon with tunable morphology, composition and structures. NiCo₂O₄ materials with different morphologies including spherical, urchin, rod and granular are synthesized using different surfactants. These electrode materials display the maximum specific capacity of 419, 543, 506, and 456 C g⁻¹ at 1 A g⁻¹ respectively in 2 M KOH. The optimized urchin-like NiCo₂O₄ is hybridized with different concentration of ZnCo₂O₄ nanosheets. The hybridization process significantly increased the specific capacity to 1029 C g⁻¹ at 1 A g⁻¹ for NiCo₂O₄@ZnCo₂O₄-2 (NZC2). In order to make the hybrid supercapacitor device, honeycomb porous structured N-doped activated carbon is prepared with the Ricinus Communis seed. The prepared material shows an interconnected pore structure with a high nitrogen content and exhibits the maximum specific capacity of 236 C g⁻¹ at a current density of 1 A g⁻¹. The hybrid supercapacitor device made from NZC2 and the N-doped activated carbon offers the highest energy density of 101.6 W h kg⁻¹ with the corresponding power density of 1.62 kW kg⁻¹.