Gold Electrocrystallization on Carbon and Highly Oriented Pyrolytic Graphite from Concentrated Solutions of LiCl

Abstract

The early stages of the electrolytic deposition of gold on carbon electrodes from concentrated LiC1 electrolytes have been investigated by voltammetry, chronoamperometry, and microscopy. The analysis of current-time transients according to existing theories indicates that this process occurs by multiple three-dimensional nucleation, followed by diffusioncontrolled growth of nuclei. Diffusion coefficients calculated on the basis of nucleation theory were found to be higher than those from rotating disk experiments (RDE), suggesting that gold species are adsorbed on the electrode surface. Gold nucleation from 6 M LiC1 cannot be classified as either instantaneous or progressive nucleation. The kinetic parameters for nucleation, aN, (nucleation rate) and N, (number density of active sites on the substrate surface), were estimated by using a general Poisson nucleation law. Both quantities were found to vary with potential and with concentration of gold. The potential dependence of the nucleation rate, aN,, was interpreted according to classical and atomistic theory. For low gold concentrations, where adsorption of AuC1 or AuC13 might occur prior to nucleation, the number of atoms in the critical nucleus (Ne) was less than unity over the entire potential range analyzed. For high gold concentrations the number of atoms forming the critical nucleus depends on overpotential. In all solutions studied nucleation takes place on a limited

Optimized coverage of gold nanoparticles at tyrosinase electrode for measurement of a pesticide in various water samples

“…1, an initial cathodic current at 1.1 V and a sharp peak at 0.9 V corresponding to the reduction of adsorbed AuCl 4 − and solution bound Au (III) to Au (0), respectively. This voltammetric adsorption of Au complexes to carbon electrodes has been observed previously [26][27][28]. No anodic peak is observed on the reverse scan indicating the irreversibility of the reduction of AuCl 4 − .…”

Controlled Growth of Well-Aligned Carbon Nanotubes, Electrochemical Modification and Electrodeposition of Multiple Shapes of Gold Nanostructures

“…An initial sharp current spike is due to the charging of the double-layer which has been eliminated here. The curve then exhibits a hump shaped response following the charging current spike which commonly observed for the electrochemical nucleation and 3-dimensional (3-D) growth of metal crystallites [39]. After the hump, a current decay is observed indicating a planar diffusion regime.…”

Template-free electrosynthesis of gold nanoparticles of controlled size dispersion for the determination of lead at ultratrace levels

“…The standard redox potential of [AuCl 4 ] 2 / Au(0) reaction was 0.804 V vs. Ag/AgCl (sat'd) reference electrode. 14 Therefore, the cathodic peak of [AuCl 4 ] 2 /Au(0) appeared at an overpotential (g = E 2 E 0 ) of 2506 mV on the GC electrode and 2241 mV on deposited Au active sites remaining on the GC electrode. This is consistent with the thermodynamics which predicts that the deposition of gold requires less energy on gold than on GC.…”