Adsorption of benzoic acid on Au(111) and Au(110) electrodes in acidic media by IRAS

Adsorption of benzoic acid onto Au(111) and Au(110) electrodes in 0.1 M HClO4, has been investigated by IRAS, voltammetry and differential capacity measurements. For both electrodes, the presence of the vertically adsorbed benzoate anion was confirmed by IRAS. A reversible current peak corresponding to the appearance of the COO band for Au(111) was observed around 0.4 V. For the Au(111) electrode, the capacity curve at negative potentials and the IRA spectrum observed at 0.3 V suggest the presence of adsorbed species in other than the vertical orientation. This suggests that the Aat-lying benzoic acid is present at negative potentials, and the vertically adsorbed benzoate increases at positive potentials. The amount of the vertical type for Au(111) reached saturation at 0.8 V, while that for Au(110) increases for all the potentials observed. (C) 2000 Elsevier Science Ltd. All rights reserved.