Understanding the Stability of Pt-Based Nanocages under Thermal Stress Using In Situ Electron Microscopy.

We report a systematic study of the thermal stability of Pt-based cubic, octahedral, and icosahedral nanocages using high-resolution electron microscopy coupled with in situ heating. Our results indicate that all these nanocages could be used with no observable changes up to 150 °C, with their facets still preserved at even higher temperatures. We observed the same behavior in all the nanocages under thermal stress: hole enlargement and atom migration toward the edges to create nanoframes. This transformation could be rationalized by the thermodynamic driving force to minimize surface free energy. The octahedral nanocages were found to be more stable by 50 °C than the icosahedral nanocages, suggesting that the thermal stability of such catalysts can be potentially optimized to extend their usage toward different applications at elevated temperatures. [ABSTRACT FROM AUTHOR]