High Resolution HAADF Characterization of Ir/TiO2 Catalyst Reduced at 500 °C: Intensity Profile Analysis

A comparison is presented between experimental and simulated high resolution-high angle annular dark field images (HR-HAADF) of Ir/TiO2 catalyst reduced at 500 °C where classical strong metal–support interaction develops. The analysis is based on integrated intensity profiles of the atomic columns of iridium nanoparticles on the TiO2 support. The results were as expected, that when Ir/TiO2 catalyst is reduced at high temperature, partially reduced species from the support (TiOx) migrate to the surface of iridium nanoparticles. Two very important facts can be highlighted: one is that the Ti atoms sited on atomic columns in the [110] direction preserve the atomic ordering of the metallic particle (epitaxial growth), while those located in atomic columns at perpendicular directions to the observation axis are disordered, and as a consequence, they appear as an amorphous thin film. Finally, changes in the (111) interplanar spacing of TiO2-rutile structure could be due to an enrichment of Ti3+ species at the ...