Kinetics of adenine adsorption on Au(1 1 1) electrodes: An impedance study

The adsorption/desorption kinetics of adenine on Au(1 1 1) electrodes is studied by Electrochemical Impedance Spectroscopy (EIS) in 0.5 M NaF solutions at four adenine concentrations. The experimental procedure is designed in order to obtain impedance data unaffected by surface reconstruction on the entire potential region of adsorption. The frequency dispersion of the impedance at potentials of the adsorption region has been analysed according to the Frumkin–Melik–Gaykazyan adsorption theory without any “a priori” assumption about the potential dependence of the adsorption rate constant. The analysis provides the values of the adsorption capacitance, Cad, adsorption resistance, Rad and the Warburg coefficient, σad, at every potential, and from them the relaxations times τH and τD. A mixed adsorption–diffusion control has been detected and the specific rate constant of adsorption has been obtained in a wide potential region.