Improving electrochemical activity of activated carbon derived from popcorn by NiCo2S4 nanoparticle coating

We report a popcorn-derived activated carbon (PCs) from maize grains. Dispersed NiCo₂S₄ nanoparticles of dozens of nanometers in diameter are anchored onto the PC surface to yield PCs/NiCo₂S₄ composites. The adhesion of NiCo₂S₄ nanoparticles to the porous carbon substrate provides the PCs/NiCo₂S₄ composite electrode with an improved electrochemical performance. The highly electroconductive PCs substrate with porous structure and combination with dispersive NiCo₂S₄ nanoparticles, yields PCs/NiCo₂S₄ composites with a high specific capacitance of 605.2 F g⁻¹ at the current density of 0.5 A g⁻¹ in a voltage range of −0.1 to 0.4 V in 6 M KOH electrolyte, and an outstanding capacitance conservation of 91.3% after 5000 galvanostatic charge/discharge cycling. Moreover, the asymmetric supercapacitor demonstrates high energy density of 23.3 W h kg⁻¹ at the power density of 335.8 W kg⁻¹, and an excellent cycling stability of 92.7% capacitance retention after 5000 cycles. This research supplies a novel method to exploit biomass-based electrode material candidates for promising application on high-performance supercapacitors.