CAPACITANCE DISPERSION ON SOLID ELECTRODES - ANION ADSORPTION STUDIESON GOLD SINGLE-CRYSTAL ELECTRODES

In order to explore the origin of the capacitance dispersion observed on solid electrodes, voltammetric and impedance measurements on single crystal gold electrodes have been carried out in the absence and pres ence of specifically adsorbed anions, mostly Br-. Evidence is presente d showing that (i) in the absence of specific adsorption, the double l ayer on these electrodes behaves as an ideal capacitance (were the imp edance approximated by a constant phase element, the exponent would be larger than 0.99); (ii) in the presence of specific adsorption, capac itance dispersion can be observed due to the sluggishness and/or diffu sion control of the adsorption step, to the surface reconstnrction/dec onstruction and to adlayer structural transformations.