Inhibition of CO oxidation on RuO 2(110) by adsorbed H 2O molecules

Abstract

Catalytic CO oxidation on the RuO 2(110) surface was studied at 300 K by scanning tunneling microscopy (STM), high-resolution electron-energy-loss spectroscopy (HREELS), and thermal desorption spectroscopy (TDS). Upon repeatedly exposing the surface to several 10 L of CO and O 2 at 300 K, STM shows that unreactive features accumulate with each CO and O 2 titration run. HREELS and TDS show formation of increasing amounts of H 2O, retarded formation of O-cus atoms and incomplete removal of CO-bridge molecules during O 2 dosing, and a changing ratio of single- and double-bonded CO-bridge molecules. It is concluded that H 2O (presumably from the residual gas) is accumulating at the Ru-cus sites thus blocking them, so that the dissociative adsorption of oxygen is prevented and the CO oxidation reaction is suppressed. Some 10% CObridge remains on the surface even during oxygen exposure. Consistent with this interpretation, deactivation of the surface is suppressed at 350 K, at the onset of H 2O desorption. © 2004 American Institute of Physics.