“Methanol-Tuned Spray Pyrolyzed Highly Porous Nickel Oxide Thin Films for High-Capacitance NiO@Graphite Asymmetric Supercapacitors and Electrokinetic Analysis”

Pristine nickel oxide thin films were synthesized via spray pyrolysis using methanol, ethanol, and propanol-based precursor solutions to probe the solvent effect on structure, surface, and electrochemical properties. XRD and HRTEM confirmed polycrystalline NiO with solvent-dependent crystallite size, while FESEM, AFM, and BET analyses revealed enhanced porosity and surface roughness in the methanol-derived film. Wettability studies demonstrated hydrophilicity in methanol-based films, favoring ion transport. Electrochemical evaluation showed the methanol electrode achieved 113.67 F g⁻¹ at 0.002 V s⁻¹ with 92 % capacitance retention over 5000 cycles. Electrokinetic analysis confirmed 86 % capacitive contribution, indicating fast redox kinetics. An asymmetric Nm@Graphite device delivered 75.02 Wh kg⁻¹ energy density and retained 83–87 % capacitance after 1000 cycles. These results highlight solvent-tuned NiO electrodes as promising candidates for high-performance supercapacitors.