Lawrence Berkeley National Laboratory

Stepped Platinum surfaces were found to undergo extensive and reversible restructuring when exposed to CO at pressures above 0.1 Torr. This radically new and previously unknown restructuring phenomenon, has important implications for Pt based catalytic reactions. Novel Scanning Tunneling Microscopy and Photoelectron Spectroscopy techniques operating under gaseous environments near ambient pressure and temperature revealed that as the CO surface coverage approaches 100percent, the originally flat terraces of stepped Pt crystals break up into nanometer size clusters. At room temperature the crystal surface reverts to its initial flat morphology after pumping away the gas phase CO. Density Functional Theory energy calculations provide a rationale for the observations whereby the creation of increased concentrations of low coordination Pt sites at the edges of the formed nanoclusters relieves the strong CO-CO repulsion in the highly compressed adsorbate film.