COMPOSITION OF ELECTROSORBED METHANOL

The composition of the dehydrogenated species formed when methanol adsorbs from acid solution onto a smooth Pt electrode is examined by electrochemical techniques. Use is made of the fact that adsorption of methanol and oxidation of the adsorbed species can be studied separately. This allows determination of the charges involved in adsorbing (Qads) and stripping off (Qox) a given quantity of adsorbed intermediate. Qads is measured by integration of current-time curves for methanol adsorption and Qox by linear-sweep voltammetry after washing the electrode. The ratio Qads/Qox is potential dependent, a result for which several explanations are suggested Qoxmax is found to be 278 μC/cm2. The most probable composition of the adsorbed species is one for which two electrons are released when each particle is oxidized to CO2. At potentials below 0.4 V part of the adsorbed layer may be in a more reduced form. Comparison of current-voltage curves for adsorbed methanol, carbon monoxide, and reduced CO2" indicates some similarities among the three species and suggests that part of the surface layers formed on adsorption of methanol and "reduced CO2 is the same as adsorbed carbon monoxide."