Solid-state synthesis of nickel selenide for high-performance supercapacitors

This study focuses on the synthesis and electrochemical characterization of nickel diselenide (NiSe₂) as a promising electrode material for supercapacitors. NiSe₂ was synthesized through a facile solid-state process involving the mixing of nickel acetylacetonate and selenous acid, followed by drying and sintering at 500 °C under inert conditions. The resulting NiSe₂ exhibited a granular structure with worm-like surface architecture and particle size ranging from 20 to 100 nm. The electrochemical performance of NiSe₂ was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a 6 M KOH electrolyte. NiSe₂ demonstrated a high specific capacitance of 744.7 F g⁻¹ at a discharge rate of 1 A g⁻¹, with an outstanding rate capability retaining the capacitance of 483.6 F g⁻¹ at 10 A g⁻¹, and exceptional long-term cycling stability. The kinetic analysis revealed that the energy storage mechanism in NiSe₂ primarily involves diffusion-controlled charge storage. EIS further confirmed the favorable charge transfer properties of the NiSe₂ electrode. Overall, NiSe₂ synthesized via the proposed method shows great promise for application in high-performance supercapacitors.