Investigation of CO Oxidation Transient Kinetics on an Oxygen Pre-covered Au(211) Stepped Surface

The desire to explain the origin(s) of the unexpected catalytic activity of oxide-supported Au nanoparticles for CO oxidation discovered by Haruta and coworkers has stimulated numerous experimental and theoretical studies of Au nanoclusters in the gas phase and on metal oxide supports, and on Au single-crystal surfaces. In order to explore further the reactivity of low-coordination Au step sites, we have performed transient kinetics studies of CO oxidation on an O-precovered, stepped Au(211) single crystal surface. We found behavior similar to that observed previously on flat Au(111) and (110) surfaces; i.e., there is no evidence in these transient kinetics for any special reactivity associated with this stepped Au surface. The CO oxidation reaction rate was highly dependent on the initial oxygen coverage, and we determined an apparent activation energy for CO oxidation of -7.0 kJ mol(-1) for theta(init)(O) = 0.9 ML. Within the Langmuir-Hinschelwood (LH) reaction scheme, we estimate an activation energy of E-LH = 20-43 kJ mol(-1) on this surface for CO oxidation via this pathway. This is somewhat below the value of 67 kJ mol(-1) predicted by recent theoretical calculations.