The adsorption of sulfate on gold(111) in acidic aqueous media: adlayer structural inferences from infrared spectroscopy and scanning tunneling microscope

摘要: The potential-dependent adsorption of sulfate on ordered Au(111) from acidic aqueous electrolytes has been examined in situ by means IR reflection-absorption spectroscopy (IRAS) and atomic-resolution scanning tunneling microscopy (STM) order to explore further the nature adsorbate bonding structural changes attending formation adlayer at high potentials, as observed recently using STM. Solution conditions that encompassed sulfuric acid, acid/sulfate varying pH dilute excess perchloric acid were selected facilitate comparisons with recent compositional data extracted chronocoulometric radiotracer measurements which utilized last mentioned type electrolyte. Essentially same structures deduced STM form suitably potentials (≳ 0.8 V/SCE) both mixed sulfate/excess media. adlayer, exhibits a (√3 × √7) symmetry, involves fractional coverage 0.2, accordance chronocoulometic data. possibility incorporates coadsorbed hydronium cations is discussed; such coadsorption suggested presence additional maxima images. IRAS display prominent SO stretching band νso 1155–1220 cm−1, intensity correlates surface concentrations reported earlier. appearance this feature also insensitive electrolyte conditions, including pH, consistent its assignment adsorbed rather than bisulfate. frequency only slight (ca. 5 cm−1) downshift upon forming indicating ordering incurs no marked speciation or bonding.