On the Control and Effect of Water Content during the Electrodeposition of Ni Nanostructures from Deep Eutectic Solvents

The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride urea (1:2 ChCl-U) deep eutectic solvent (DES) containing different amounts of water.By combining electrochemical techniques, with ex-situ FE-SEM, HAADF-STEM and EDX, the effect of water content on the electrochemical processes occurring during nickel deposition was better understood.At highly negative potentials and depending on water content, Ni growth is halted due to water splitting and the formation of a mixed layer of Ni/NiO x (OH) 2(1-x)(ads) .Moreover, under certain conditions, the DES components can also be (electro)chemically reduced at the electrode surface, blocking further 3D growth of the Ni NPs.Hence, a 2D crystalline Ni containing network can be formed in the inter-particle region.