Transformation of wheat husk to 3D activated carbon/NiCo2S4 frameworks for high-rate asymmetrical supercapacitors

Abstract Transforming carbon-containing biomass into valuable carbon materials is highly required. The approach reduces not only environmental pollution but also develops porous carbon electrodes for energy storage devices. Herein, a novel ex-situ synthesis of Nickel-Cobalt Sulfide/Wheat Husk Activated Carbon (NiCo2S4/WHAC) on Ni foam as an electrode material for supercapacitors was reported. The activated carbon was synthesized from the carbonization of the wheat husk, which was further activated using KOH. Afterward, the NiCo2S4/WHAC/Ni electrode was fabricated by the hydrothermal method. The capacitance of the NiCo2S4/WHAC/Ni electrode was 1962 F/g at a current density of 1 A/g. The improved electrochemical performance of NiCo2S4/WHAC electrode could be ascribed to rapid diffusion pathways delivered by WHAC and the fast redox reaction of NiCo2S4. Furthermore, the asymmetric supercapacitor device (NiCo2S4//WHAC) could operate at a potential window of 1.1 V and exhibited a capacitance of 252 F/g, which could provide specific energy of 42 Wh/kg at a specific power of 550 W/kg with 108% capacity retention.