Theoretical investigation of adsorption charactieristics of typical additives for zinc electroplating

Abstract

Quantum chemical parameters~(QCPs) of four additives were calculated by using DFT, and MD simulations were performed. By comparing binding energies of four additives (benzalacetone~(BA), sodium benzoate~(SB), polyoxyethylene nonylphenylether~(NP) and dispersant NNO), with Zn~(001) surface, BA has the smallest binding energy, which is due to the smallest hardness parameter, and NNO has the largest binding energy, which is due to the largest dipole moment despite its small hardness parameter. In order to enhance the adsorption of BA onto Zn~(001) surface, NP was selected to be combined with BA, because BA has the lowest energy level of LUMO, which is more capable of accepting electrons from Zn~(001) surface than others, and NP has the highest energy level of HOMO, which is more capable of donating electrons to Zn~(001) surface than others. By calculating the binding energies of the complex of BA and NP, it has larger binding energy than individual BA, SB, and NP, but smaller than NNO.