INFLUENCE OF THE ADSORBATE STRUCTURE AND SURFACE-BARRIER AT MICROPORES - THE ADSORPTION ON COLUMNAR-STRUCTURED GOLD ELECTRODES OF PYRIDINE FROM AQUEOUS PERCHLORATE ION-CONTAINING SOLUTIONS

The electroadsorption on columnar Au electrodes (substrate) of pyridin e from x M pyridine + 0.1 M HClO4 and x M pyridine + 0.1 M KClO4 aqueo us solutions (10(-3) less than or equal to x less than or equal to 10( -2)), at constant potential and 298 K, was studied using voltammetry, chronocoulometry, and ac impedance combined with scanning tunneling mi croscopy to characterize the substrate topography. For a constant pyri dine concentration (c), the degree of surface coverage by pyridine ads orbate (theta) diminished as R was increased. The theta vs c plots, ir respective of R, were interpreted by a Frumkin adsorption isotherm inc luding a constant standard adsorption free energy. The evaluation of a dsorption isotherms reflects the existence of an excluded volume effec t, which can be related to a barrier effect due to adsorbates at nanom eter size pore entrances.