ADSORPTION OF NORMAL HEXANOL ON BISMUTH SINGLE-CRYSTAL PLANE ELECTRODES

Cyclic voltammetry, impedance and chronocoulometry have been employed for a quantitative study of 1-hexanol(n-HA) adsorption at the bismuth single crystal plane\aqueous Na2SO4 solution interface. The adsorption characteristics obtained from the impedance and chronocoulometric mea surements are in reasonable agreement within the limits of surface cha rge densities -18 < sigma < 5 mu C cm(-2). The adsorption isotherms, G ibbs energies of adsorption Delta G(A)(0), the limiting surface excess Gamma(max) and other adsorption parameters, dependent on the crystall ographic structure of electrodes, have been determined. The adsorption of n-HA on Bi single crystal planes is mainly physical and is limited by the rate of diffusion of organic molecules to the electrode surfac e. Comparison of the. adsorption data for n-HA with normal propanol (n -PA), normal butanol (n-BA), butyl acetate (BAC), cyclohexanone (CHN), cyclohexane carboxylic acid (CHCA) and cyclohexanol (CH) shows that t he adsorption characteristics depend on the structure of the hydrocarb on radical, as well as on the chemical nature of the functional group of the adsorbate. The adsorption activity of adsorbates at the bismuth /solution interface increases in the sequence n-PA < n-BA < n-HA as th e adsorption at the air\solution interface increases. In the case of a ll compounds studied, the adsorption activity increases in the sequenc e of planes (111) < (001) < (01(1) over bar). According to the values of the standard Gibbs energy of adsorption it was established that the hydrophilicity of electrodes increases in the sequence Sb(<2(11)over bar>) < Sb(001) < Sb(111) < Bi(01(1) over bar) < Bi(<2(11)over bar>) < Bi(<(1)over bar 0 (1) over bar) less than or equal to Hg less than or equal to Bi(001) < Bi(111) < Cd(0001) < Cd(10 (1) over bar 0) < Cd(11 (2) over bar 0) < Ag(111) < Ag(100) < Ga < Ag(110) < Zn(0001) < Zn(10 (1) over bar 0) < Zn(11 (2) over bar 0). (C) 1998 Elsevier Science S. A.