PROBING PYRIDINE ADSORBED AT GOLD ELECTRODES BY CHRONOCOULOMETRY, RADIOCHEMISTRY AND RAMAN-SPECTROSCOPY

Chronocoulometry, radiochemistry and Raman spectroscopy were used to s tudy pyridine adsorption at a polycrystalline gold electrode. Fair agr eement between the surface concentrations determined from chronocoulom etric experiments and radiochemical measurements was observed. The chr onocoulometric technique proved to be more accurate than the radiochem ical method; however, it is restricted to ideally (or nearly ideally) polarizable electrodes. In contrast, the radiochemical technique is mo re universal and can be employed to study adsorption at both reactive and non-reactive electrode surfaces. Raman spectroscopy gave a signal which, because of the dipole depolarization effect, displays a non-lin ear dependence on the surface concentration of the adsorbed molecules for coverages greater than 2/3 monolayer. Therefore Raman spectroscopy has a limited value for quantitative analysis of adsorbed species.