Dynamic behaviour of the inhibitor adsorption on gold (111) studied by in situ STM

The study of adsorption/desorption processes of 1-hydroxy- ethane-1,1-diphosphonic acid (HEDP) molecules, and the mixture of HEDP/zinc ion on gold surface has been investigated in neutral perchlorate solution using cyclic voltammetry and electrochemical scanning tunnelling microscopy (EC-STM). Cyclic voltammetry measurements showed that HEDP molecule has an effect on the anodic oxidation of gold. The reversible adsorption/desorption peak in presence of zinc cations is attributed to the effect of zinc ions on the adsorption of HEDP. Results of in situ EC-STM studies on the initial stages of HEDP adsorption on gold single crystal (111) are presented and compared with the adsorption of the mixture of HEDP/zinc ion. The morphology of the gold (111) surface changed during repeated cycles. Sub-mono-layer islands are formed in presence of HEDP molecules. The surface morphology changed significantly in presence of both HEDP and zinc in the solution. After repeated cycles the whole gold surface was covered with a network-type layer. This adsorbed layer varied in function of the gold (111) potential. The results were analysed and discussed. © 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.