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.