One-Dimensional NiSe–Se Hollow Nanotubular Architecture as a Binder-Free Cathode with Enhanced Redox Reactions for High-Performance Hybrid Supercapacitors

Selenium-enriched nickel selenide (NiSe–Se) nanotubes supported on highly conductive nickel foam (NiSe–Se@Ni foam) were synthesized using chemical bath deposition with the aid of lithium chloride as a shape-directing agent. The uniformly grown NiSe–Se@Ni foam, with its large number of electroactive sites, facilitated rapid diffusion and charge transport. The NiSe–Se@Ni foam electrode exhibited a superior specific capacitance value of 2447.46 F g^–1 at a current density value of 1 A g^–1 in 1 M aqueous KOH electrolyte. Furthermore, a high-energy-density pouch-type hybrid supercapacitor (HSC) device was fabricated using the proposed NiSe–Se@Ni foam as the positive electrode, activated carbon on Ni foam as the negative electrode, and a filter paper separator soaked in 1 M KOH electrolyte solution. The HSC delivered a specific capacitance of 84.10 F g^–1 at a current density of 4 mA cm^–2 with an energy density of 29.90 W h kg^–1 at a power density of 594.46 W kg^–1 for an extended operating voltage window of 1.6 V. In addition, the HSC exhibited excellent cycling stability with a capacitance retention of 95.09% after 10,000 cycles, highlighting its excellent potential for use in the hands-on applications. The real-life practicality of the HSC was tested by using it to power a red light-emitting diode.