Dynamics of Potential-Dependent Transformations in Sulfur Adlayers on Au(111) Electrodes

The potential ( E )-dependent transformations of adsorbed sulfur on Au(111) in 0.1 M NaOH + 3 × 10 -3 M Na 2 S have been followed by in situ STM imaging. When E is changed from −0.6 to −0.8 V, the transformation from rectangular S 8 surface structures to a √3 × √3 R30° S lattice takes place. This process involves sulfur atom desorption, the formation of rectangular tetramerical surface structures, and the displacement of sulfur atoms to nearest hollow sites. When E moves from −0.8 to −1.0 V fast desorption of the √3 × √3 R 30° lattice from Au (111) terraces is observed while sulfur atoms become progressively bonded to step edges. Sulfur atom readsorption to form the √3 × √3 R 30° lattice takes place by returning to E = −0.8 V. Experimental data provide an estimation of the excess of binding energy close to step edges.