The oxidation of CO on RuO2(110) at room temperature

RuO2(110) surfaces were prepared by exposing Ru(0001) to 10(7) L of O-2 at 700 K. Postexposure of O-2 at 300 K resulted in an additional oxygen specie s (O-cus) adsorbed on coordinatively unsaturated Ru atoms (Ru-cus). The sur face was then exposed to CO at 300 K and studied by thermal desorption spec troscopy (TDS) and high-resolution electron energy loss spectroscopy (HREEL S). It is demonstrated that CO is oxidized at 300 K through reaction with b oth the O-cus as well as with surface O-atoms held in bridge positions (O-b ridge). Although-at room temperature-CO adsorbs intermediately on the Ru-cu s atoms, it is stable only at the Ru atoms underneath the O-bridge after th e latter has been reacted off. At room temperature only surface oxygen take s part in the CO oxidation and the oxygen-depleted surface can be restored by O-2 exposure, so that under steady-state flow conditions an oxygen-defic ient surface will exist whose stoichiometry will be determined by the ratio of partial pressures. (C) 2001 American Institute of Physics.