In-situ XAFS studies of Br adsorption on the silver(111) electrode

The structures of adsorbed bromine on the Ag(111) electrode at different applied potentials have been studied by in situ X-ray absorption fine structure (XAFS) spectroscopy. The bromine coverage was estimated by the Br K-edge jump height as a function of the electrode potential. It turned out that the coverage does not change in passing through a characteristic peak appearing at 0.05 V (versus Ag \ AgCl) in the cyclic voltammogram (CV). Analysis of the Br K-EXAFS spectra just below the CV peak gave the Br-Ag bond distance of 2.72 +/- 0.05 Angstrom, while the spectra above the peak revealed the presence of two different Br-Ag bonds with 2.74 +/- 0.05 and 2.80 +/- 0.05 Angstrom distances. These results suggest that a drastic surface reconstruction takes place at the characteristic CV peak without changing the surface Br density. (C) 2000 Elsevier Science B.V. All rights reserved.