Chemical Bath Precipitation and Properties of β-Ni(OH)2 Films Prepared in Aqueous Ammoniac Solutions

Colloidal-chemical transformations accompanying the thermal degradation of a homogeneous aqueous solution of nickel(II) ammoniac complexes are investigated by thermodynamic and kinetic methods. A competitive growth mechanism of β-Ni(OH) 2 nano- and microcrystals in the solution bulk and on the solution–solid interface is proved. The weight growth rate for each of the kinetic routes is controlled by the kinetics of the first-order homogeneous reaction of degradation. The reason for the competitive weight gain of the sol and β-Ni(OH) 2 film lies in the different activation energies for conversion to sol microcrystals (131.0 ± 27.0 kJ/mol) and to the film (94.0 ± 24.0 kJ/mol). This gives rise to the existence of two different temperature areas where sol or film growth is preferable. At 70–75°C, the sol and film growth rates are equal. An interpretation of the temperature-dependent colloidal growth mechanism of Ni(OH) 2 crystals is proposed. The influence of the morphology and thickness of β-Ni(OH) 2 films on their optical band gap width, photocatalytic and electrical activities is determined.