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 (-NH2) 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. (c) 2019 The Electrochemical Society.