title: Adsorption configuration and local ordering of silicotungstate anions on Ag(100) electrode surfaces.
abstract: X-ray reflectivity, cyclic voltammetry, and scanning tunneling microscopy (STM) are used to examine the structure of alpha-SiW12O4(4-) or silicotungstic acid (STA) adsorbed on Ag(100) in acid solution. The voltammetry shows that STA passivates the Ag surface relative to electron transfer to a solution redox species. STM images reveal the formation of a series of lattice structures, one of which can be associated with a commensurate ( radical13x radical13)R33.69 degrees structural model. X-ray reflectivity measurements show uniquely that STA orients with its four-fold axis perpendicular to the Ag(100) surface and that the center of the STA molecule is 4.90 A above the top layer of the Ag substrate. Analysis of bond lengths leads to a footprint of STA on Ag(100), in which the four terminal O atoms are located near the hollow sites and have a Ag-O bond length of 2.06 A. This bond length is consistent with a strong covalent interaction between STA and the Ag surface.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: L
authors.initials: L
authors.lastname: Lee
authors.forename: J X
authors.initials: JX
authors.lastname: Wang
authors.forename: R R
authors.initials: RR
authors.lastname: Adzić
authors.forename: I K
authors.initials: IK
authors.lastname: Robinson
authors.forename: A A
authors.initials: AA
authors.lastname: Gewirth