New Atomic-Scale Insight into Self-Regeneration of Pt-CaTiO3 Catalysts: Incipient Redox-Induced Structures Revealed by a Small-Angle Tilting STEM Technique

A small-angle tilting technique, applied to scanning transmission electron microscopy (STEM), was used together with multislice image simulation to reveal new atomic-scale information about the structural evolution of single-crystalline Pt-doped CaTiO 3 thin films, grown by pulsed laser deposition, that occurs in response to reduction and reoxidation treatments. Specifically, we were able to confirm that Pt atoms are randomly dispersed throughout the as-grown film, most often occupying Ti sites, show that the smallest (∼1 nm) Pt-rich clusters embedded within CaTiO 3 after reduction have a structure consistent with metallic Pt, and demonstrate that the Pt atoms from these clusters occupy mainly Ca sites, in the form of ordered Pt-atom arrays, after reoxidation.