Tert-Pentanol Adsorption on Ag(100) and Ag(110) from an Aqueous Solution and its Comparison with that on Ag(111), Hg, Ga and Bi(001)

The adsorption behavior of tert-pentanol (TPT) on Ag(100) and Ag(110) single-crystal faces from aqueous 0.05M KClO4 was investigated on the basis of chronocoulometric and differential capacity measurements. The adsorption data on Ag(100) were analyzed thermodynamically and the standard Gibbs energy of adsorption, ΔG0 ads, was determined as a function of the electrode potential and of the charge density, σM, on the metal. The adsorption parameters for TPT adsorption on Ag(100) were compared with those on Ag(111), Hg, liquid Ga and Bi(001), available in the literature. The surface dipole potential of the TPT film at maximum coverage on the above metal surfaces was estimated by a novel approach that requires no a priori assumptions as to the predominance of either water desorption or TPT adsorption on the value of the shift, EN, of the potential of zero charge from zero to maximum coverage. Instead, the EN values for the different metals were estimated a posteriori, under the assumption that the water molecules that are still present at maximum TPT coverage maintain the same orientation as on the bare metal surface at the same charge density σM. The lack of a correlation between the ΔG0 ads values on the different metal surfaces and their hydrophilicity indicates that TBT adsorption depends primarily on its particular conformation and on the metal surface structure.