Chemically deposited nanocrystalline NiO thin films for supercapacitor application

A chemical synthesis process for the fabrication of NiO is described. In the present work, we report a chemical route for preparation of nickel hydroxide thin films on the glass substrate from solution containing Ni(2+) ions and ammonia. The deposition process based on the thermal decomposition of ammonia complex with nickel ions at temperature 333 K. As-prepared films were annealed at 623 K in air for 2 h to remove hydroxide phase and used for structural, surface morphological and optical characterizations. It was found that after annealing β-phase of Ni(OH)2 was transformed to a cubic phase structured NiO. Honeycomb like surface morphology of “β-Ni(OH)2” films was merged and resulted in decrease in porosity after annealing. A red shift in band gap energy was observed after annealing. The capacitive characteristics of the films deposited on steel substrate were investigated in KOH electrolyte using cyclic voltammetry. The supercapacitive properties of NiO were strongly affected by scan rate, concentration of electrolyte and deposited mass of the material. The maximum specific capacitance of 167 F g−1 was obtained in 2 M KOH electrolyte.