Optimum conditions to prepare high yield, phase pure α-Ni(OH)2 nanoparticles by urea hydrolysis and electrochemical ageing in alkali solutions

Phase pure alpha nickel hydroxide (α-Ni(OH)2) is synthesized by a hydrothermal method using urea and nickel nitrate in an autoclave. Optimum conditions to obtain high yield and phase pure α-Ni(OH)2 are identified by varying experimental parameters such as urea concentration, ramp time, and temperature. In a typical experiment, a 94% yield of phase pure α-Ni(OH)2 is successfully prepared. The nickel content, analyzed by means of atomic absorption spectroscopy, is 44% in all samples. The α-Ni(OH)2 nanoparticles are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BET surface area and tap density of the nickel hydroxide nanoparticles are also determined. Electrochemical characterization is undertaken via cyclic voltammetry for which the nanoparticles are immobilized on the surface of paraffin impregnated graphite electrodes in 1.0 M alkali solutions. The ageing of the alpha phase occurs within 27 min (30 cycles) of exposure in alkali solutions.