Direct comparison of the reactivity of the non-oxidic phase of Ru(0 0 0 1) and the RuO2 phase in the CO oxidation reaction

Applying in situ surface X-ray diffraction (SXRD) together with on-line mass spectrometry during the CO oxidation over Ru(0 0 0 1) allows a direct comparison of the reactivity of the non-oxidic state with that of the RuO2(1 1 0) covered surface. This comparison reveals that the RuO2(1 1 0) surface is a catalytically active phase at least as active as the non-oxidic phase. At high CO and O2 pressures of 200 mbar and temperatures above 550 K, the CO oxidation reaction does not proceed isothermally on the RuO2(1 1 0) surface. The released reaction heat leads rather to an increase of the sample temperature of up to 130 K accompanied by a self-acceleration of the CO oxidation reaction.