Title: In Situ TEM studies of catalysts using windowed gas cells

Abstract

Atomic-scale insights into the structure evolution of nanocatalysts under reaction conditions are critical for correlating their structure-properties relationship. Detailed information at atomic scale, obtained by in situ TEM is therefore an essential complement to other in situ techniques (e.g., XPS, FTIR, etc.). In this talk, we present our in situ TEM studies of two nanocatalyst systems: (1) the CO-induced Pt nanoparticle surface reconstruction at saturation coverage (2) the facet-dependent oxidation of Pt3Co ORR catalysts. Atomic-scale insights into how supported metal nanoparticles catalyze chemical reactions are critical for the optimization of chemical conversion processes. It is well-known that different geometric configurations of surface atoms on supported metal nanoparticles have different catalytic reactivity and that the adsorption of reactive species can cause reconstruction of metal surfaces. Here, we characterize atomic-scale details associated with the structural rearrangement of supported Pt nanoparticle surfaces induced by the adsorption of CO at saturation coverage and elevated temperature. It was observed that the truncated octahedron shape adopted by bare Pt nanoparticles undergoes a reversible, facet specific reconstruction due to CO adsorption, where flat {100} facets roughen into vicinal stepped high Miller index facets, while flat {111} facets remain intact.