Adsorption and reaction of CO on RuO2(110) surfaces

RuO2(1 1 0) single crystal surfaces were prepared by exposing a Ru(0 0 0 1) surface to high doses of O-2 at 700 K. This surface exhibits coordinativel y unsaturated (cus) Ru atoms (Ru-cus) onto which CO may adsorb at 85 K. Act ually, high resolution electron energy loss spectroscopy reveals an energy of 262 meV (2115 cm(-1)) for the C-O stretch vibration of adsorbed CO indic ating relatively weak binding in terminal configuration on Ru-cus. Thermal desorption spectroscopy shows partial desorption for temperatures above 250 K and. in parallel. formation of CO? through reaction with neighboring sur face oxygen atoms called O-bridge. Thereby, underlying Ru atoms become acce ssible onto which CO adsorbs more strongly giving rise to CO stretch-mode e nergies of 235 (1895) and 235 (1975) meV (cm(-1)). Hence, above 250 K, Ru-c us is not able to stabilize CO but serves as transient source for CO land p resumably other adsorbates), thus enabling the remarkable catalytic activit y of this surface. (C) 2001 Elsevier Science B.V. All rights reserved.