We use iridium single crystal to reproducibly prepare in-situ model Ir surfaces with different surface morphologies, ranging from planar surface to faceted surfaces with well-defined facet structures and controlled facet sizes on the nanometer scale. Upon annealing in oxygen, atomically rough planar Ir(210) surface coverts to faceted Ir(210) with a �hill and valley� structure that consists of nanoscale three-sided pyramids exposing (311), (31-1) and (110) faces on each pyramid. The morphology of faceted Ir(210) is independent of oxygen coverage, and average pyramid size ranging from 5nm to 14 nm increases with annealing temperature while the facet structures on each pyramid remain unchanged. Moreover, we have developed a novel method to routinely remove the oxygen from O-covered faceted Ir(210) via reaction with hydrogen at low temperature to generate clean faceted Ir(210) that retains its original facet structures and sizes. Faceted Ir(210) serves as nanoscale model catalyst to bridge the gap between planar surfaces of iridium single crystals and supported iridium particles. We will show a series of important reactions (e.g. oxidation of CO and reduction of NO) performed on clean planar Ir(210) and clean faceted Ir(210) with focus on structure sensitivity and size effects on the nanometer scale, an important issue in catalysis.  This work is supported by DOE (Contract No. DE-FG02-93ER14331).

Surface chemistry over unsupported model Ir catalysts with different morphologies

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.