From nickel schiff base molecular precursor to NiO/rGO functional nanocomposite: A tailored route for high-performance supercapacitor electrodes

Nickel oxide (NiO) nanoparticles were synthesized via thermal decomposition of a one-pot salicylideneamine nickel complex (Ni(L₁)₂), serving as a molecularly defined precursor. This coordination chemistry-based approach enables the direct transformation from complex to oxide, providing enhanced control over purity and particle size. The resulting NiO nanoparticles were uniformly incorporated onto reduced graphene oxide matrix (rGO) through a controlled calcination process at 450 °C. The resulting NiO/rGO composite demonstrated superior charge storage behavior relative to unmodified NiO. Specifically, it achieved a capacitance reaching 2850 F g⁻¹ at a current density of 1 A g⁻¹ in a 1 M KOH electrolyte, notably outperforming the 1796 F g⁻¹ obtained for pristine NiO. Moreover, the NiO/rGO electrode retained 84 % of its initial storage capability following 500 continuous charging and discharging cycles, demonstrating notable durability across cycles. Upon integration into a hybrid-type supercapacitor system, the NiO/rGO deposited on nickel foam functioned as the negative electrode, with activated carbon acting as the positive counterpart. This configuration achieved an energy density of 119.27 Wh kg⁻¹ alongside a power density of 750 W kg⁻¹. Even after 1000 cycles, the device preserved 75 % of its initial electrochemical performance, emphasizing the strong applicability of NiO/rGO composites as robust, high-efficiency electrodes for advanced energy storage applications.