Abstract: Infrared reflection-absorption spectra for primary, secondary and tertiary orthophosphate anions on a gold electrode in aqueous solution were studied by in situ FTIR spectroscopy.The spectra show that H₂PO₄^-, HPO₄^2- ions do not interact with the electrode surface as strong as PO₄^3- do.According to the surface selection rule, we deduce the modes of adsorption of these anions on the electrode from these spectra.The experiment also confirms the affection to adsorption of ion on the electrode due to ion-migration into thin-layer cavity.

Key words: In situ FTIR spectroscopy, Electrochemical adsorption, Gold electrode, Phosphate anions