Role of adsorbed species in methanol oxidation on Pt studied by ATR-FTIRAScombined with linear potential sweep voltammetry

摘要

Methanol adsorption/oxidation on a polycrystalline platinum electrode was investigated by ATR-FTIRAScombined with linear potential sweep voltammetry after initial adsorption at 0.05 V in 0.05-1.0 M HC104containing 0.04-1.0 M methanol. Methanol adsorption exhibits a pronounced maximum around 0.56 V,which coincides with the onset potential of the oxidation. This suggests that adsorbed CO is not a cata-lytic poison but an intermediate of the oxidation. The low methanol oxidation activity on Pt is notascribed to the poisoning action by the adsorbed CO but to inability of Pt to dissociate water to adsorbedOH species needed for the CO and methanol oxidation. It was found for the first time that methanoladsorption at 0.05 V is significantly diminished in dilute perchloric acids. This was interpreted in termsof reduced physisorption of methanol at the adsorption potential which becomes more negative withrespect to the pzc. Band intensity of the formate species with a symmetric O-C-O vibration around1320 cm' remains unchanged with increase of methanol concentration from 0.04 M to 1 M, while thepeak current of methanol oxidation increases by ca. three times in 1 M HClO_4.The result suggests a minorrole of the formate in the methanol oxidation mechanism.