A surface-enhanced infrared absorption spectroscopic study of pH dependent water adsorption on Au

The potential dependent behavior of near-surface water on Au film electrodes in acidic and alkaline solutions is studied using a combination of attenuated total reflectance surface enhanced infrared spectroscopy and chronoamperometry. In acid, sharp v(OH) peaks appear at 3583 cm(-1) at high potentials attributed to non-H-bonded water coadsorbed in the hydration sphere of perchlorate near the electrode surface. Adsorbed hydronium bending mode at near 1680 cm(-1) is observed at low potentials in low pH solutions (1.4, 4.0, 6.8). At high pH (10.0,12.3), a potential-dependent OH stretching band assigned to adsorbed hydroxide emerges from 3400-3506 cm(-)1. The observation of adsorbed hydroxide, even on a weakly oxophilic metal such as Au, provides the framework for further studies of hydroxide adsorption on other electrodes to determine the role of adsorbed hydroxide on important reactions such as the hydrogen oxidation reaction. (C) 2015 Elsevier B.V. All rights reserved.