Low temperature C-C bond scission during ethanol decomposition on Pt(331)

The adsorption and decomposition of ethanol was studied on clean, and oxygen pre-covered Pt(331) surface by using mainly TPD, LEED and AES. II was found that ethanol adsorbed molecularly on the Pt(331) surface al low temperature. Upon heating, part of the ethanol desorbed molecularly from surface at 220 K, and part of the ethanol underwent C-C bond scission to form methane and a variety of other products. There are two distinct methane peaks at 240 K and 310 K in the desorption spectrum suggesting that there are two different pathways for ethanol decomposition on this surface; both pathways-involve C-C bond scission since methane is a major desorption product. CO adsorption experiments as well as experiments with H-(ad) and O-(ad) suggest that the lower temperature pathway involves C-C bond scission at temperatures below that where the ethanol appreciably dehydrogenates, while the high temperature pathway involves dehydrogenation of the ethanol followed by C-C bond scission. O-(ad) additions suppress the low temperature pathway and enhances the high temperature pathway presumably by speeding the dehydrogenation of the ethanol. H-(ad) additions slightly enhance the low temperature pathway. We also observe hydrogenolysis of the ethanol to yield methanol at 180 K and methane at 240 K in the presence of excess hydrogen. These results show that the step sites on the Pt(331) surface have unusual activity for C-C bond scission in ethanol. (C) 1997 Elsevier Science B.V.