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

Abstract

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.

Theoretical and experimental studies of the influence of gold ions and DMH on cyanide-free gold electrodeposition

“…The almost doubling of a demonstrates that the electron transfer of the gold electrodeposition process was obviously inuenced by the DMH in the electrolyte as the complexing agent for Au 3+ . Following eqn (3) and the tted j p vs. v 1/2 plots, the diffusion coefficient (D) of ions in the electrolyte were calculated as 8.69 Â 10 À6 cm 2 s À1 and 4.19 Â 10 À6 cm 2 s À1 , 49 respectively, indicating that D was reduced with the addition of DMH in the electrolyte. It indicated that with DMH as the complexing agent for Au 3+ in the gold electroplating electrolyte, the ion transfer was inhibited.…”

Experimental and theoretical studies of DMH as a complexing agent for a cyanide-free gold electroplating electrolyte

“…These results provide an indication that the surface quality of the gold electrodeposit could be further improved upon the addition of a suitable additive. 59 The phase structures of the gold electrodeposits that were obtained from the introduced cyanide-free gold electroplating electrolyte with and without additive, as well as those of the electrodeposits obtained from the HAuCl 4 electrolyte without DMH were conrmed using EDS and XRD. Unfortunately, when the additive was added to the HAuCl 4 electrolyte without DMH, the HAuCl 4 electrolyte became turbid and a precipitate was formed, as displayed in Fig.…”

Nano–silica functionalized with thiol–based dendrimer as a host for gold nanoparticles: An efficient and reusable catalyst for chemoselective oxidation of alcohols

“…In the XRD pattern of the catalyst (Figure ), the peaks indexed to Au (111), (200), (220), (311) and (222) crystal faces at 2 theta values of 38.2, 44.4, 64.6, 77.6 and 81.7 were obviously discovered (JCPDS file: 04–0784). The diffraction peak intensity of the (111) faces for gold is higher than that of any other peak, indicating that the reduction of Au (III) to Au occurred preferentially on Au (111) faces, as expected . It is clear that the typical silica is observed at a broad peak centered at 2θ = 22.5°, which indicates that the sample is semi‐crystalline phase…”