Role of polyethyleneimine as an additive in cyanide-free electrolytes for gold electrodeposition

The influence of polyethyleneimine (PEI) on the electrochemical behavior of cyanide-free electrolytes with 5,5-dimethylhydantoin (DMH) as a complexing agent was investigated using cyclic voltammetry (CV), chronoamperometry, and cathodic polarization measurements. The gold electrodeposition displayed three-dimensional (3-D) progressive nucleation in both the absence and presence of PEI according to the Scharifer and Hills (SH) nucleation model. With the addition of PEI, the cathodic overpotential showed an immense negative shift, and the limiting diffusion current density and the diffusion coefficient decreased. Gold electrodeposits were characterized by SEM and AFM for the micromorphology, XRD for the crystal structure, and XPS for the purity. There was preferential growth of gold crystals along the (111) crystal face in both the presence and absence of PEI, but overall growth was inhibited in the presence of PEI. The quality of the gold electrodeposit was significantly improved in the presence of PEI, with a bright golden color and high purity, smooth and compact morphology.