Electrodeposition of Ni–TiO2 Composite Coatings Using Electrolyte Based on a Deep Eutectic Solvent

Abstract

Deep eutectic solvents are nowadays considered to be very promising analogues of room temperature ionic liquids. They can make a significant contribution to the development of novel efficient, economic and environmentally friendly processes, particularly, in surface engineering and electroplating. The electrodeposition of Ni–TiO₂ composite coatings from an electrolyte based on a deep eutectic solvent, ethaline, was studied in this work. Titania particles were introduced into the plating bath in the form of Degussa P 25 nanopowder. The content of titania in electrodeposited composite coatings was shown to depend on the stirring rate, current density and TiO₂ concentration in the electrolyte and can reach ca. 2.35 wt %. The microstructure and the surface morphology of the obtained composite layers were characterized. The formation of nanocrystalline nickel matrix was detected. The introduction of TiO₂ particles into nickel-based coatings resulted in an increase in the microhardness of deposits. The data obtained via the electrochemical impedance spectra technique revealed an improvement in the corrosion resistance of coatings due to titania particles incorporation into deposits. The Ni–TiO₂ composite coatings manifested a photocatalytic activity towards the reaction of photochemical degradation of methylene blue organic dye in water solution.