Effect of the solution composition and the applied potential on the kinetics of roughness relaxation at gold electrodes in slightly acid electrolytes

Abstract

The roughness relaxation of thin columnar Au electrodeposits at constant potential and 25°C in 0.05 M NaF, 0.05 M KCl and 0.05 M K₂SO₄ has been studied. These measurements were taken in the −0.6 to 0.8 V (vs Hg/Hg₂SO₄ reference electrode) potential range. The kinetic data were obtained from the roughness factor decay over 5 × 10⁴ s. The value of the surface diffusion coefficient Ds of Au atoms was derived from the roughness decay law at constant potential and pH. At any potential, the value of Ds increases in the order NaF < K₂SO₄ < KCl. This sequence correlates with the specific adsorption of anions on Au. In K₂SO₄ and NaF solutions, as the electroformation of AuOH species takes place, the effect of SO₄²⁻ and F⁻ ions is no longer observed. In contrast, in 0.05 M KCl solution, the value of D_s increases steadily as the applied potential is increased positively.