Oxygen dissociation at Pt steps - art. no. 056103

Using scanning tunneling microscopy, thermal energy atom scattering, and de nsity functional theory we have characterized O-2 dissociation on Pt(111) s tepped surfaces at the atomic scale. The most reactive site is at the top o f the Pt steps. In both the molecular precursor state (MPS) and the transit ion state (TS), the O-2 has its axis aligned parallel to the step edge. Con trolled step decoration with Ag monatomic chains was used to locally tune t he reactivity of Pt step sites. The enhanced reactivity at the Pt step site s is not caused by a decrease of the local dissociation barriers from the M PS but is related to a stabilization of both the MPS and TS.