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

Chronocoulometry, radiochemistry and Raman spectroscopy were used to study pyridine adsorption at a polycrystalline gold electrode. Fair agreement between the surface concentrations determined from chronocoulometric experiments and radiochemical measurements was observed. The chronocoulometric technique proved to be more accurate than the radiochemical method; however, it is restricted to ideally (or nearly ideally) polarizable electrodes. In contrast, the radiochemical technique is more 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-linear 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.