THE ADSORPTION AND OXIDATION OF METHANOL ON THIN PALLADIUM FILMS

The adsorption of methanol (MeOH) on clean and oxygen covered Pd films , deposited on a multicrystalline Re substrate, has been studied using TPD, XPS and ISS. Significant differences in the chemistry are seen b etween thin (1 monolayer) and multilayer (>10 monolayers) films, the t hicker him behaving in a very similar way to the Pd{111} surface and s howing a higher reactivity to MeOH decomposition, but also exhibiting higher desorption temperatures for the decomposition products when com pared to the thin layer case. This behaviour is described in terms of charge transfer between the Re substrate and the Pd overlayer. The pre adsorption of oxygen leads to significant structural differences in th e Pd film as determined by XPS and ISS depending on the preparation te mperature, and this in turn leads to significant differences in the re activity of MeOH. When the oxygen-covered him is prepared at 300 K and exposed to MeOH, no formaldehyde is formed on desorption, whereas fol lowing a preparation temperature of 1000 K, significant amounts of for maldehyde are evolved.