Electrochemical Synthesis of Ni/TiO₂ Composite Coatings from Deep Eutectic Solvent and Electrocatalytic Characteristics of Deposits

Abstract—Kinetics of electrodeposition of composite Ni/TiO₂ coatings was studied using the electrolyte based on a deep eutectic solvent (DES) containing choline chloride, ethylene glycol, water additive, and nickel chloride. Degussa P 25 nanopowder was used as a dispersed phase in the electrolyte (1–10 g/dm³). The developed electrolyte allows depositing composite coatings with the content of titanium dioxide reaching ~10 wt %. The electrolytic deposition of the composite was shown to obey Guglielmi’s kinetic model. The main parameters of codeposition of TiO₂ particles into a nickel matrix were determined in the framework of this kinetic model. The codeposition of titanium dioxide was found to inhibit the reaction of the nickel ions' discharge. Electrocatalytic properties of the prepared composite Ni/TiO₂ coatings were evaluated with respect to the hydrogen evolution reaction in an aqueous alkaline solution. A noticeable improvement in the electrocatalytic activity was observed when titanium dioxide particles were introduced into an electrodeposited nickel matrix.