On the adsorption of ionic phosphate species on Au(111) - An in situ FTIR study

The adsorption of phosphate species on the well ordered Au(lll) single crystal surfaces was studied with in situ FTIR spectroscopy in order to identify the spectral features of the adsorbed H2PO4-, HPO42- and PO43- selectively by changing the OH- content in solution. H2PO4- presents two potential dependent adsorbate features at 1100 and 980 cm(-1) due to the two symmetric stretching vibrations of the adsorbed ion under C-2v symmetry. HPO42- shows only one potential dependent band at about 1120cm(-1) which can be attributed to the symmetric A, stretching of the adsorbate, probably under C-3v symmetry. For the adsorbed PO43- one potential dependent feature located between ca. 1060 and 1083 cm(-1) was found. This band is assigned to the A, mode due to the splitting of the vibration of the F mode under C-3v or C-2v symmetry.