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 HCl O4, has been investigated by IRAS, voltammetry and differential capacity me asurements. For both electrodes, the presence of the vertically adsorbed be nzoate 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. F or 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 benz oic acid is present at negative potentials, and the vertically adsorbed ben zoate 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 rese rved.