ABSTRACT
The structure of sulfuric acid species adsorbed on a Pt(111) electrode has been successfully determined by using the ultrahigh vacuum modeling tactics. An electrode potential change induces an interconversion between a bisulfate anion-hydronium cation coadsorbate and a sulfuric acid molecule. The solvation structure of the adsorbed ions indicates that single hydration water molecules per bisulfate anion-hydronium cation pair stabilizes the ion pair. The water molecules in the overlayers are subjected to a preferential orientation that is induced by the presence of the adsorbed anions in the first layer. These microscopic informations about the structure of an adsorbed electrolyte anion and water as a solvent would be indispensable to a true molecular level understanding of the electrochemical double layers and chemical reactions at the electrode surfaces.
