Electrochemical reduction behaviours of silver ions in ChCl–urea deep eutectic solvents (DESs) were investigated by cyclic voltammetry. The results showed that equilibrium potential $E_{\rm eq}$ of the electrode system in ChCl–urea DESs was $-$0.112 V. The Tafel curve was used to obtain the exchange current density $j^0 = 2.92 \pm 0.2$ cm$^{-2}$ and the transfer coefficient $\alpha = 0.16 \pm 0.2$. The nucleation and growth mechanism of silver were studied by cyclic current method. The results showed that electrodeposition consisted of two processes, 3D nucleation with diffusion-controlled growth $j_{\rm 3D-dc}(t)$ and a small amount of water in the reduction $j_{\rm WR}(t)$. By calculating the percentage of different charge densities of $j_{\rm 3D-dc}$ and $j_{\rm WR}$, the contribution rate of different processes to the total current was analysed. With the increase in potential, the charge in water reduction process decreased, while the charge in silver 3D nucleation process increased. Scanningelectron microscope and energy spectrum scanning were used to characterize the surface and section micro-morphologies of silver coating. The results showed that silver grew dendritically at $-$0.97 V, and the thickness was 22.98 $\mu$m. The results of X-ray photoelectron spectroscopy showed that silver coating was composed of Ag$_2$O and Ag.

Choline chloride-ethylene glycol (ChCl-EG) deep eutectic solvents were used as the electrolytes to study the cathode reduction process. The electrochemical behaviour of nickel and copper ions in ChCl-EG, the morphology, phasecomposition and corrosion resistance of the coatings were characterized. The results showed that the increase in the temperature of the electrodeposition solution system can make the reduction potentials of nickel and copper ions approaching, making it easier to achieve co-deposition. When the temperature of the solution was 70°C, a nickel-copper alloy similar to the commercial Monel (Ni70Cu30) with good corrosion resistance can be obtained.