COMPARATIVE-STUDY BETWEEN BROMINE AND IODINE ADLAYERS ON A POLYCRYSTALLINE GOLD ELECTRODE BY A PIEZOELECTRIC TECHNIQUE

The specific adsorption of bromide ions on a polycrystalline gold elec trode was investigated by a piezoelectric technique and was compared w ith that of iodide ions previously reported. The potential of electroc apillary maximum or potential of zero charge (pzc) of the gold electro de could be evaluated from the piezoelectric signal curve. The iodide and bromide concentration dependencies of pzc have indicated that the adsorption order is I- > Br-. The another characteristic potential, E- 2 at which a sign-reversal of surface charge density seems to take pla ce, appeared in the potential region where the ordered structure of br omine or iodine adlayer on a single crystal gold was stably observed w ith STM and SXS. The possible model for the sign-reversal of surface c harge density at E-2 was proposed, assuming the structural change or p hase change of adlayer followed by the ordered structure formation.