Synergistic CuS–NiS nanoparticles with high capacitance and good cycling stability for supercapacitor applications
摘要
Transition-metal sulfides are emerging as promising candidates for next-generation supercapacitor electrodes due to their rich redox activity and high conductivity. This work presents a systematic optimization of copper sulfide–nickel sulfide (CuS–NiS) nanoparticles (NPs) prepared through a cost-effective co-precipitation method. Key reaction parameters including precursor ratio, temperature, pH, reagent addition time, and stabilizer concentration were systematically varied to achieve stable NPs with reduced size and improved electrochemical performance. The optimized CuS–NiS (1:1) nanoparticles, prepared at 40 °C, pH 3, and without polyvinylpyrrolidone (PVP), exhibited a crystallite size of ~ 14 nm and excellent stability. Electrochemical testing demonstrated a high specific capacitance of 1001 F g⁻1 at 5 mV s⁻1 (cyclic voltammetry) and 3066 F g⁻1 at 0.5 A g⁻1 (galvanostatic charge discharge), with improved capacitance retention of 96%. Complementary density functional theory (DFT) calculations suggest a reduced HOMO–LUMO energy gap (5.31 eV) for the mixed NPs, which is qualitatively consistent with the experimentally observed enhanced electrochemical behavior. These findings establish CuS–NiS nanoparticles as a high-performance electrode material for energy storage devices, bridging experimental and computational insights to advance supercapacitor technology.