Effect of water on electrodeposition behavior of zinc in a ChCl-urea-ZnO deep eutectic system

The effect of water on the electrodeposition behavior of zinc in ChCl-urea deep eutectic solvent containing ZnO (ChCl-urea-ZnO) was investigated through electrochemical measurement and deposit characterization. Various thermodynamic and kinetic parameters were investigated as a function of water content (0 ~ 24 vol%) at 343 K. The increase in water content not only increased the diffusion coefficient, but also led to an increase in the charge transfer coefficient. The standard rate constant gradually increased with increasing water content, but decreased when the water content exceeded 7.5 vol%. Besides, the water content had an obvious effect on the nucleation and growth mode of Zn, morphology of the deposit, and current efficiency. It was found that the addition of water to ChCl-urea-ZnO increased the nucleation rate and improved the smoothness and compactness of the deposit.