A simple and effective hydrothermal synthesis of spherical α-Ni(OH)2 particles and α-Ni(OH)2/carbon composites was proposed. The mechanism of ultrafine α-Ni(OH)2 phase forming and correlations between synthesis conditions, morphology, electrical conductivity were analyzed. It was found that carbon nanoparticles form an electric conductive cover on nickel hydroxide microparticles during synthesis which increases overall electronic conductivity of the composite material. α-Ni(OH)2 and α-Ni(OH)2/C samples were tested as electrodes for hybrid supercapacitors. It was found that carbon coverings stabilize α-Ni(OH)2 phase in the alkaline medium. The comparison of the influence of laser irradiation and ultrasonic treatment on the electrochemical performance of the obtained materials was made.
To improve the specific capacitance, power and energy of electrical energy storage devices, in particular hybrid capacitors, various methods of cathode material modification are used. One of the methods of modifying nanostructured materials without applying high temperatures, pressures and long reaction times is ultrasonic treatment. Although the interaction of ultrasound with the structure and surface of electrode materials is well enough studied, there are few works that investigate the optimal duration of ultrasonic treatment and its relationship with the capacitive characteristics of these materials. Therefore, we investigated the efficiency of ultrasonic dispersion of nanocrystalline nickel molybdate hydrate for 15, 60 and 90 minutes. The appearance of two cathodic peaks on cyclic voltammetry patterns was analyzed and the charge / discharge mechanism of the electrode based on nanocrystalline NiMoO4 hydrate was presented. Based on the results of potentiodynamic and galvanostatic studies the specific capacitances of the initial NiMoO4 and the material modified by ultrasound for 15, 60 and 90 minutes were calculated. The proton diffusion coefficients of nickel molybdate hydrate were determined on the basis of the Randles–Sevcik equation. NiMoO4 subjected to ultrasonic dispersion for 60 min as a cathode material in a hybrid electrochemical system was tested.
The paper presents the results of studies of the crystal structure, surface morphology and electrical properties of nickel molybdate obtained by hydrothermal method and modified by ultrasound. The influence of the duration of ultrasonic dispersion on the crystallites size, specific surface area, pore size distribution and activation energy of charge carriers of nickel molybdate hydrate is determined. It was found that ultrasound with a frequency of 22 kHz and a duration of 90 min leads to an increase in the total volume of mesopores from 0.135 cm2/g to 0.223 cm2/g with an average diameter of 28.5 nm.
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