Adsorption of 1-pentanol on bismuth single-crystal plane electrodes

Cyclic voltammetry, impedance and chronocoulometry have been employed for the quantitative study of 1-pentanol (n-PenOH) adsorption at the bismuth single-crystal plane | aqueous Na₂SO₄ solution interface. The adsorption isotherms, Gibbs energies of adsorption ΔG _A ^∘, the limiting surface excess Γ_max and other adsorption parameters, dependent on the crystallographic structure of the electrodes, have been determined. The adsorption of n-PenOH on Bi single-crystal planes is mainly physical and is limited by the rate of diffusion of organic molecules to the electrode surface. Comparison of the adsorption data for n-PenOH with 1-propanol (n-PrOH), 1-butanol (n-BuOH), cyclohexanol (CH) and 1-hexanol (n-HexOH) shows that the adsorption characteristics depend on the structure of the hydrocarbon group. The adsorption activity of adsorbates at the bismuth | solution interface increases in the sequence n-PrOH < n-BuOH < CH ≤ n-PenOH < n-HA as the adsorption activity at the air | solution interface increases. For all the compounds studied, the adsorption activity increases in the sequence of planes (111)<(001)<(011ˉ).