Investigation of Gold Electrosorption onto Gold and Carbon Electrodes using an Electrochemical Quartz Crystal Microbalance

Abstract

 The adsorption behavior of Au³⁺ ions on metal electrodes has been studied using an electrochemical quartz crystal microbalance combined with the cyclic voltammetry technique. The experiments were carried out for HAuCl₄ using 0.1 mol·L^-1 HCl (pH~1) as a background electrolyte solution. The kinetics of electroreduction of Au3+ ions on the rice husk based activated carbon and gold electrodes in chloride electrolytes by the cyclic voltammetry and the electrochemical quartz crystal microbalance with a variation of the scan rate in the range of 5‒50 mV·s^-1 has been studied. The diffusion coefficient of Au³⁺ ions for the tested solution on gold and carbon electrodes was determined by the cyclic voltammetry method on the basis of the Randles-Ševčik equation. It is found that electroreduction of gold goes via the discharge of AuCl₄^- complexes to the formation of metallic gold with a current efficiency of 97‒99%. The scanning electron microscopic images of the gold adsorbed carbon surface was taken to see gold particles and their morphology. In SEM images, it is clearly seen that the surface of carbon has a relief structure and gold has grown in the form of clusters. The smallest gold nanoparticles that could be examined were 100‒250 nm in diameter on the surface of the carbon electrode.