In-situ and real time structural studies of underpotential deposition of silver on a gold (111) electrode using a transmission X-ray surface differential diffraction technique

An in-situ surface X-ray differential diffraction (SDD) in transmission geo metry has been applied for the first time to the study of silver adlayer st ructure on Au (111) in the underpotential region. Hitherto surface differen tial diffraction has been used to determine vertical positions of adsorbate s from the substrate, but has given no information upon the lateral positio n of the adsorbate relative to the substrate. By conducting experiments usi ng a ((1) over bar 11) reflecting plane, we show that it is possible to det ermine the adsorption site in three dimensions via SDD. The studies confirm that silver is adsorbed on multiple sites in a sulphate electrolyte wherea s a single adsorption site was found for both acetate and fluoride electrol ytes. (C) 2001 Elsevier Science B.V. All rights reserved.