Non-Metallic Films Electroplating on the Low-Conductivity Substrates: The Conscious Selection of Conditions Using Ni(OH)2 Deposition as an Example

Abstract

Mathematical modelling was used to study the influence of different parameters on the distribution of current density during electrodeposition of low-conductivity films on high-resistance substrates (FTO, ITO etc.). Experimental data were used to model the deposition of non-conductive Ni(OH)2 film onto FTO glass. The influence of substrate resistance, polarization resistance, electrolyte concentration, and other parameters on the current density distribution over the electrode surface was analyzed. The analysis of modelling results revealed that the fundamental differences in the current density distribution during deposition of coatings in electroplating and deposition of low-conductivity films are due to the high resistance of the substrate in the latter case. It was found that the impact on the uniformity of the current density distribution was decreasing in the series “substrate resistivity – polarization resistance – electrolyte conductivity”. The results of the conducted modelling allowed formulating recommendations for electrochemical deposition of low-conductivity films uniformly distributed over the surface of the substrate with low conductivity. In this case, the use of diluted electrolytes was justified. The results of galvanostatic deposition of Ni(OH)2 films onto FTO glass (7.5 Ω/□, 2 × 2 cm) from 1М and 0.01М solutions of Ni(NO3)2 and the subsequent colorization proved the modelling results experimentally. The width of Ni(OH)2 film deposited from 1M solution was less than 1mm, while the coating was absent on the rest of the surface. Deposition from 0.01 solution resulted in a uniform film with complete coverage of the working electrode area.