Influence of Pre-Adsorbed TiO₂Particles on the Nucleation and Growth Mechanism of Ni in Deep Eutectic Solvent Electro-Codeposition

Electrodeposition holds excellent potential for creating controllable nanoscale functional interfaces. However, the key characteristics of these processes remain elusive, especially the composite electrodeposition processes involving inert nanoparticles. Herein, the pre-adsorption of inert particles is considered in detail in electro-codeposition. The nucleation and growth mechanism of nickel nanoparticles under the influence of pre-adsorbed inert particles is studied in a choline chloride-ethylene glycol deep eutectic solvent (DES). Cyclic voltammetry results show that pre-adsorbed TiO2 particles can significantly increase the cathodic reduction current, while codeposited TiO2 particles hinder the reduction process. Chronoamperometry analysis demonstrates that pure Ni electrodeposition in a DES follows the mechanism of instantaneous nucleation and tridimensional growth at a high potential, while the Ni electrodeposition deviated from the instantaneous nucleation model due to the pre-adsorption of TiO2 particles. Moreover, considering the classical model description of multiphase 3D nucleation and diffusion-controlled growth, the typical kinetic parameters such as nucleation rate constant and diffusion coefficient were investigated under different applied potentials. It was found that the nucleation rate constant of Ni electrodeposition increased significantly in the presence of pre-adsorbed TiO2 particles. These findings are of great significance for understanding and perfecting the electro-codeposition process containing inert nanoparticles.