Activation Of Co Over Ultrathin Manganese Oxide Layers Grown On Au(111)

Well-defined manganese oxide (MnOx) overlayers with a controlled chemical state and coverage were deposited on Au(111), and CO activation at the model MnOx/Au(111) surfaces was explored by combining treatments in high-pressure (up to 100 mbar) CO at elevated temperatures and in situ surface characterizations. We find that all MnOx nanostructures transformed into reduced MnO states (MnO1-y, 0 < y < 1) in the near-ambient pressure CO atmosphere, and dissociation of CO to carbon deposit occurs above 473 K. A volcano curve of the carbon deposit amount as a function of MnO coverage is clearly presented, indicating that MnO island edges are the active centers. Density functional theory calculations show that MnO/Au(111) interfaces provide edge Mn atoms coordinated with two oxygen atoms, where CO disproportionation occurs facilely through the CO dimer and further CCO* intermediates.