Surface Chemistry of Catalytically Active Surfaces

The Killelea group is studying the structures of metal surfaces relevant to heterogeneous catalysis to provide insight to their fundamental chemistry. Our primary technique is ultra-high vacuum scanning tunneling microscopy (UHV-STM). Of particular interest is the formation of subsurface species on transition metals. We have recently shown that rhodium surfaces efficiently absorb gas-phase O atoms into the selvedge of the metal, yet the surface structure reflects surface coverages well below the total amount of O present. This suggests that O absorption does not require high O-coverages surface features and other mechanisms are important. We are also studying the surface structure of Ag(111) at high O coverages and for various energies of the incident O atoms. A separate research direction is investigations of the structures water molecules adopt on platinum surfaces. On flat Pt surfaces, water is ordered in a network of 5,6, and 7 membered rings. Using DFT, our collaborators at Leiden University in The Netherlands have predicted that different structures will form on stepped Pt surfaces. We are imaging miscuts of the Pt(111) surface with submonolayer water coverages to verify the DFT results.