ADSORPTION OF WATER AT PT(111) ELECTRODE IN HCLO4 SOLUTIONS - THE POTENTIAL OF ZERO CHARGE

FTIR reflection-absorption spectra at Pt(lll) show potential dependent bands near 3100 and 1620 cm(-1), corresponding respectively to the O- H stretching and H-O-H in-plane deformation of adsorbed water molecule s. At around 0.35 V vs. RHE, water orientation changes from hydrogen d own to oxygen down indicating that the zero charge potential of Pt(lll ) is close to this value. In the potential region corresponding to the anomalous wave of Pt(111) the bending frequency decreases, consistent with a strengthening of the H2O-Pt interaction. A band at 3270 cm(-1) is assigned to adsorbed hydroxyl ions formed by partial dissociation of water. The vibrational behavior is correlated with the features in the voltammogram.