Mechanism of Au electrodeposition onto indium tin oxide

Abstract

Cyclic voltammetric and chronoamperometric methods were used to study the initial stage of Au electrodeposition on an indium tin oxide (ITO) surface. The nucleation process was controlled by the diffusion of [AuCl4]-. The cyclic voltammetry curves showed that the electrochemical reduction included two steps which were [AuCl4]-→ [AuCl2]-, and [AuCl2]- → Au. Only one reduction peak was observed when the scan rate was comparatively slow and this peak separated into two peaks when the scan rate was increased. This phenomenon resulted from the disproportionation of [AuCl2]- during the electrodeposition process. Chronoamperometry also proved the two step reaction mechanism and the diffusion coefficient of [AuCl4]- was calculated to be 1.3×10-5 cm2·s-1. From the theoretical nucleation curves, an instantaneous three-dimensional nucleation mechanism was proposed for the nucleation of gold on ITO. Au electrodeposits were observed by field emission scanning electron microscopy (FE-SEM). SEM images of the electrodeposits showed that the morphology of the gold deposits was affected by the electrochemical deposition potential and time. © Editorial office of Acta Physico-Chimica Sinica.