Ethylene oxide interaction with Pd surfaces: Experimental and theoretical results

Abstract

Ethylene oxide (EO) interaction with the clean Pd(110) surface was investigated under ultrahigh vacuum conditions using temperature programmed desorption/reaction. Most of the layer adsorbed at 120 K desorbs at 170–220 K, but a fraction decomposes indicating ring opening reactivity. The stoichiometric release of CO and the absence of water formation during EO decomposition on Pd(110) indicated that no more than one C–O bond was broken per molecule; subsequent C–C scission led to methane desorption at ∼325 K. Using the surface-cluster analogy, we have also applied density functional theory to assess electronic interactions involved in EO interaction with palladium surfaces. In particular, interaction with Pdn clusters (n=1,4,10) modeling the surface chemistry of EO on palladium surfaces has been investigated in this work. EO binding energies on these clusters range from 8 to 13 kcal/mol. In contrast to the experimental observation of ring opening of EO on Pd(110) and Pd(111) surfaces, theoretical results at this level do not indicate any significant perturbation of C–O and C–H bonds in adsorbed EO.