THE KINETICS OF STRUCTURAL-CHANGES IN ANIONIC ADLAYERS ON STEPPED AU(111)(S) ELECTRODES FROM SULFURIC-ACID-SOLUTIONS

The kinetics of structural changes in anionic adlayers on stepped Au(1 11), electrodes has been investigated in sulfuric acid solutions by po tential step experiments. The experimental transients obtained with '' quasi-ideal'' (miscut <0.5 degrees) surfaces could be modelled with th e exponential law of nucleation in combination with 2D surface diffusi on-controlled growth which is preceded by an adsorption process. The s emi-quantitative analysis was restricted to i vs, t-traces, which reve aled significantly different time constants of these two processes. Th e current transients with higher miscut angle showed (i) a systematic increase of the nucleation rate with increasing step density and (ii) a decrease of the macroscopically detectable charge density associated with the nucleation and growth process. The latter could be parameter ized within a first approximation employing the general Avrami-ansatz in combination with an adsorption process. In-situ STM experiments sho wed that increasing step density of the substrate surface is accompani ed with decreasing domain size of the ordered (root 3x root 7) (hydrog en) sulfate adlayer patches. Respective correlations with the kinetic data obtained will be discussed.