Anomalous behavior of Ru for catalytic oxidation: A theoretical study of the catalytic reaction CO + 1/2 O_2 -> CO_2

Recent experiments revealed an anomalous dependence of carbon monoxide oxidation at Ru(0001) on oxygen pressure and a particularly high reaction rate. Below we report density functional theory calculations of the energetics and reaction pathways of the speculated mechanism. We will show that the exceptionally high rate is actuated by a weakly but nevertheless well bound (1{times}1)-oxygen adsorbate layer. Furthermore, it is found that reactions via scattering of {ital gas-phase} CO at the oxygen covered surface may play an important role. Our analysis reveals, however, that reactions via {ital adsorbed} CO molecules (the so-called Langmuir-Hinshelwood mechanism) dominate. {copyright} {ital 1997} {ital The American Physical Society}