关键词: 银, 复合配位, 无氰体系, 成核机理, 循环伏安, 计时电流

Abstract:

Cyclic voltammetry and potential step methods were successfully used to study the electrochemical crystallization mechanism of silver deposition on glassy carbon electrode (GCE) in the practical cyanide-free silver plating electrolyte containing composite complexing agents. Scharifker-Hill (SH) theory was used to fitting the experimental data. The results showed that the electrodeposition of silver is a diffusion controlled irreversible electrode process according to three-dimensional instantaneous nucleation mechanism. When the step potential shifted from -750 mV to -825 mV, the peak deposition current Im was increased, while the induced nucleation time tm shortened. The calculated kinetic parameters showed that the diffusion coefficient (D) was basically constant, ranged (7.31 ±0.34) ×10-5 cm²·s^-1, and the active nucleation sites density (N₀) increased from 3.26 ±105 cm^-2 to 10.2±105 cm^-2. The morphologies for the initial deposition of Ag verified the three-dimensional instantaneous nucleation mechanism. Increasing the temperature could significantly improve the diffusion ability of the active silver coordination ions in the electrolyte, which shortened the nucleation time and enhanced the active nucleation sites density N₀.

Key words: silver, complex coordination, cyanide-free system, nucleation mechanism, cyclic voltammetry, chronoamperometric curves