Bridging material and pressure gaps in heterogeneous catalysis by using environmental-HRTEM

COLL 455

Suzanne Giorgio, giorgio@crmcn.univ-mrs.fr, Martiane Cabié, and Claude R. Henry, henry@crmcn.univ-mrs.fr. CRMCN-CNRS, Campus de Luminy, Case 913, 13288 Marseille cedex 09, France
We have used a 300kV Jeol high resolution TEM equiped with a closed environmental cell to study in situ the shape and structure evolutions of metal nanoparticles under reactive environments at a pressure up to 10 mbar and a temperature from RT to 350°C. Due to the small volume of the cell it is possible to measure a catalytic reaction rate by a differentially pumped mass spectrometer. We will present the shape evolution of Au and Pd nanoparticles supported on carbon films and Titania powders during cycles of H2/O2 treatments. The shape changes are analyzed following the concept of equilibrium shape. Clean particles under vacuum or Hydrogen present a truncated octahedron shape. Gold particles are reversibly rounded under oxygen while Pd particles flatten. First results on the structural evolution of Au and Pd particles during CO oxidation will be also presented.