Dynamics of sulfur adlayer transformations at metal/electrolyte interfaces

The dynamics of adsorbed sulfur on Au(111) at the metal/electrolyte interface has been followed by scanning tunneling microscopy. The increase in the negative surface charge density induces the transformation from rectangular S8 to a √3×√3 R30° lattice. This process involves desorption of sulfur atoms as HS− ions, formation of rectangular tetramer intermediates, and displacement of atoms from the intermediate to nearest hollow sites. A further increase in the negative charge density produces desorption of the √3×√3 R30° lattice from terraces. Sulfur atoms remain strongly bonded to step edges. Experimental data provide an estimation of the excess of binding energy close to step edges. Correlation between S and thiol adlayer desorption data has been found.