Underpotential deposition of Ag adlayers on Pt(111): Structures and determination of O(sub 2) adsorption on Pt(111)

摘要

The structure of Ag adlayers deposited at underpotentials in sulfuric acid on Pt(111), and the inhibition of O(sub 2) reduction they cause, have been studied using grazing incident angle x-ray diffraction measurements, as well as linear sweep voltammetry and in situ FTIR spectroscopy. Ag forms a hexagonal incommensurate bilayer, with two mutually commensurate monolayers. It is aligned with the Pt(111) substrate, although slightly expanded. The first monolayer has a commensurate (1 x 1) structure. A second layer causes a restructuring of the first monolayer. Deposition of each monolayer is associated with one voltammetry Peak. A complete inhibition of O(sub 2) reduction on Pt(111) has been observed upon deposition of both, Ag monolayer and bilayer. Analysis of the inhibition of O(sub 2) reduction as a function of the Ag coverage shows that during reduction O(sub 2) adsorbs in a bridge configuration on Pt(111).