Insights into Chemical Dynamics and Their Impact on the Reactivity of Pt Nanoparticles during CO Oxidation by Operando TEM

The
functionality of heterogeneous catalysts is influenced by a
delicate interplay of multiple parameters, including morphology and
structure, chemical potential gradients and related dynamics. Here,
we report on how these factors are interconnected. Combining time-resolved
transmission electron microscopy imaging and selected area electron
diffraction with online conversion detection, CO oxidation over Pt
nanoparticles was studied at a pressure of 700 mbar and temperatures
up to 500 °C. The different interactions between reactants and
catalysts over the entire range of catalytic conversion were investigated.
Chemical dynamics in this reaction were found to consist of both morphological
transformations and fluctuating structural dynamics. Morphological
transformations were observed mostly in low activity regimes, leading
to nanoparticles with increased stable surface facets. Meanwhile structural
changes were observed during high activity regimes where the partial
pressures remained constant. Furthermore, the observed changes were
found to occur in both the bulk and the surface of the catalyst. Catalytic
cycling revealed that morphological transformations and structural
dynamics have different implications on the reactivity and are mostly
irreversible.