ELSEVIER Surface Science 385 (1997) 246-258 surface science Low temperature C-C bond scission during ethanol decomposition on Pt(331 ) Y. Cong, V. van Spaendonk 1, R.I. Masel * Department of Chemical Engineering, University of lllinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, IL 61801, USA Received 31 July 1995; accepted for publication 26 December 1996 Abstract The adsorption and decomposition of ethanol was studied on clean, and oxygen pre-covered Pt(331) surface by using mainly TPD, LEED and AES. It was found that ethanol adsorbed molecularly on the Pt(331 ) surface at 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 Htad) 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(~d) 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. © 1997 Elsevier Science B.V. Keywords: Alcohols; Catalysis; Platinum; Surface chemical reaction 1. Introduction Previous workers have examined the decomposi- tion and oxidation of ethanol on well-defined surfaces of transition metals in great detail. At low temperature, ethanol adsorbs molecularly on Pt(lll) [1], Pd(lll) [2,3], Cu(ll0) [4-6], Cu(100) [7], Cu(410) [8], Ag(ll0) [9-12], Rh(lll) [13] and Ni(lll) [14,15]. Some of the * Corresponding author. Fax: (+ I ) 217 244.8068; e-mail: r-masel@uiuc.edu 1 Present address: Procter & Gamble, Italia S.p.t., 00144 Rome, Italy. 0039-6028/97/$I 7.00 © 1997 Elsevier Science B.V. All rights reserved. Pll S0039-6028 (97)00164-7 ethanol desorbs upon heating around 200 K. However, on the surfaces of clean nickel, rhodium, platinum and palladium part of the ethanol decomposes to form ethoxy ligand (-OCHzCHa). The general trend of the ethanol decomposition on these surfaces except rhodium reveals that the ethoxy species will sequentially decompose into acetaldehyde O U CH3CI-I2OHc.~) - CH3CH(~ ) + 2H(~) (1) upon further heating the C-C bond in the acetalde- hyde breaks to produce adsorbed H, CO and CHx species.