Tuning of Capacitance Behavior of NiO Using Anionic, Cationic, and Nonionic Surfactants by Hydrothermal Synthesis

In this work, NiO powders with a spherical morphology were synthesized by a simple hydrothermal technique using organic surfactants as templates and urea as the hydrolysis controlling agent. The effect of cationic (cetyl trimethyl ammonium bromide), anionic (sodium dodecyl Sulfate), and nonionic (Triton X-100) surfactants for tuning the surface area, pore size, pore volume, and electrochemical properties of NiO powders was investigated. The NiO powders were characterized by X-ray diffraction, scanning electron microscopy, the Brunauer-Emmett-Tellet-method, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. We observed that the charge-storage mechanism ill Our NiO-based electrodes is significantly Faradic in nature rather than capacitive type. The ionic nature of the surfactant used ill the preparation of NiO powders shows a considerable effect oil their capacitance behavior. The specific capacitance Values were found to increase in the order of NiO-T (144 F g(-1)) < NiO-C (239 F g(-1)) < NiO-S (411 F g(-1)) at a current density of 200 mA g(-1) in 2 M KOH aqueous electrolyte Solution. The NiO-S sample exhibits the highest Surface redox reactivity and shows the specific capacitance of 235 F g(-1) over 100 cycles at a current density of 500 mA g(-1) in a life cycle test.