The Contribution of Heteroatoms in Amide Derivatives with an Identical Structure on Nickel Electrodeposits

Abstract

Four amide derivatives, urea (U), thiourea (TU), acetamide (A), and thioacetamide (TA), all of which are based on the same molecular structure, were used as additives in the electrodeposition of nickel from ammoniacal media. The influence of the thiocarbamoyl, carbonyl, methyl, and amino groups on the nickel deposits was systematically evaluated to determine the contributions of the heteroatoms in the amide derivatives. The introduction of amino (-NH 2 ) or thiocarbamoyl (-C=S) groups was found to potentially benefit nickel deposition. The additive TU can change the nucleation mechanism of nickel from progressive to instantaneous nucleation, and can refine the grain size of the nickel deposits. The preferred crystallographic orientation, Ni(111), did not change in the presence of any of the four additives. Nevertheless, when TU or TA was added, the Ni(200) crystal plane was suppressed and the Ni(220) crystal plane was promoted. The energies of the highest occupied molecular orbital and lowest unoccupied molecular orbital, as well as the dipole moment, were determined to characterize the molecular features of the amide derivatives, and further verified that the S atom was the most probable adsorption center. These results were beneficial for understanding the mechanisms of the additives and for facilitating the rational design of additives for metal electrodeposition.

Effect of Thiourea Containing Composite Additives on Nickel Electrodeposition in Ammoniacal Solution

“…Furthermore, although nickel electrodeposition from ammoniacontaining solutions also has the advantages mentioned above, unfavorable morphologies such as branched, spongy or mossy, as well as loose, black and brittle deposits were easily formed, which were unable to meet the product quality requirements, and its industrial applications are remarkably limited [26]. Fortunately, some measures, such as changing the electrodeposition conditions or adding single additive thiourea, have been taken to improve the deposits quality and performance in the precious study from NH 3 -NH 4 Cl-H 2 O system, and the results are quite acceptable, but there is still room for further improvement [27]. Based on that, it was assumed that adding thiourea with other organic additives, the deposits quality and performance would be modified because of their synergistic effect.…”