Adsorption of sodium dodecyl sulfate on the bismuth (1 1 1), (0 0 1) and (011¯) planes

Impedance spectroscopy has been employed for a quantitative study of sodium dodecyl sulfate (SDS) adsorption kinetics at the Bi(h k l) electrodes. Analysis of the impedance data demonstrates that the adsorption process of SDS at high negative surface charge density is limited by the rate of the diffusion and heterogeneous adsorption steps (mixed kinetics). At small ac frequency and higher SDS concentrations, two-dimensional association or semimicelle formation of the SDS is possible in the adsorption layer. The double layer and adsorption capacitances and diffusion resistance depend on the electrode potential, adsorbate concentration and Bi(h k l) structure. The thermodynamic adsorption parameters have been calculated using modified Frumkin–Damaskin adsorption theory. The Gibbs adsorption energy, attraction interaction constant, limiting capacitance and limiting adsorption potential shift and Gibbs adsorption depend on the Bi(h k l) structure studied.