Tailoring nickel coatings via electrodeposition from a eutectic-based ionic liquid doped with nicotinic acid

Pure nickel (Ni) was electrodeposited onto a copper (Cu) substrate from choline chloride–urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl–urea IL) with 0–1200 mg/L additions of nicotinic acid (NA). The effect of NA on the voltammetric behavior of Ni (II) was investigated by cyclic voltammetry, whilst the nucleation/growth of Ni deposits was studied by chronoamperometry. The resultant surface morphologies and microstructures of the Ni coatings were revealed by SEM/EDXS, XRD and TEM, demonstrating that NA can inhibit, hence tailor, the Ni deposition and serve as a very effective brightener producing highly uniform and smooth Ni deposits. The nucleation/growth process of Ni was not affected by the presence of NA, proceeding via three-dimensional instantaneous nucleation. NA has a profound grain refining effect with a grain size of ∼4.2 nm achievable.