STRUCTURE SENSITIVITY OF METHANOL DECOMPOSITION ON (1X1) AND (2X1) PT(110)

Recently, there has been some controversy about the mechanism of methanol decomposition on the (111) faces of platinum and palladium. Here, the decomposition of methanol on (1 x 1) and (2 x 1) Pt(110) is examined by temperature-programmed desorption and electron-energy-loss spectroscopy. It is found that on the (1 x 1) reconstruction of Pt(110), the methanol adsorbs molecularly at 100 K. Upon heating to 140 K, the C-O bond breaks to yield water and a mixture of CH(x ad) species. The CH(x ad) species then further react to form CH4, H(ad), C(ad), and some acetylenic complexes. By comparison, if the sample preparation procedure is changed to produce a (2 x 1) reconstruction, no water, methane, carbon, or higher hydrocarbons are detected. Instead, the methanol decomposes via a methoxy intermediate to yield CO and hydrogen. These results demonstrate that the mechanism of methanol decomposition on platinum is strongly affected by small changes in the sample preparation procedure and surface structure of the sample. This may explain some of the apparent discrepancies in the literature.