Transient experiments on CO2 formation by the CO oxidation reaction over oxygen-rich Ru(0001) surfaces

Reactive scattering of CO molecules at oxygen-rich Ru(0001) surfaces with c oncentrations equivalent up to 16 monolayers and sample temperatures betwee n 300 and 700 K led to the identification of two distinct reaction channels in the transient CO2 rate. The first reaction channel is related to the re combination of CO molecules with oxygen atoms already located on the surfac e. The second reaction channel, which can be observed at sample temperature s above about 400 K, is controlled by the diffusion of oxygen atoms from th e near-surface region toward the surface.