Structural effects and reactivity in methanol oxidation on polycrystalline and single crystal platinum

The electrooxidation of methanol on single crystal surfaces is characterized by the formation of strongly adsorbed intermediates. The splitting off of hydrogen atoms is superimposed on hydrogen desorption and gives rise to a well defined peak at polycrystalline and at Pt(100). The role of hydrogen as inhibitor of methanol adsorption is confirmed once more. Adsorbed CO and other hydrogenated adsorbed species like COH, HCOH and H2COH are detected by means of in situ FTIR spectra. The differential adsorption behavior of the three basal planes is emphasized by both the first scan of the respective voltammograms and the ir spectroscopy results. Eland center shifts of the CO adsorbate indicate island formation starting at the early stages of adsorption. The band shift can be addressed mainly to chemical coupling between adsorbed CO species. The onset potential for bulk oxidation increases in the order Pt(111)< Pt(110)< Pt(100). While the main reaction pathway for methanol oxidation to CO2 involves adsorbed CO species, a second pathway seems to occur via intermediate formation of formic acid which causes adsorption bands at 1710, 1430 and 1230 cm(-1).