Observing Gas-Catalyst Dynamics at Atomic Resolution and Single-Atom Sensitivity

Helveg, S., C.F. Kisielowski, J.R. Jinschek, P. Specht, G. Yuan and H. Frei, 2015
Fusion TEM holder tip
Image courtesy of Micron

Abstract

Transmission electron microscopy (TEM) has become an indispensable technique for studying heterogeneous catalysts. In particular, advancements of aberration-corrected electron optics and data acquisition schemes have made TEM capable of delivering images of catalysts with sub-Ångström resolution and single-atom sensitivity. Parallel developments of differentially pumped electron microscopes and of gas cells enable in situ observations of catalysts during the exposure to reactive gas environments at pressures of up to atmospheric levels and temperatures of up to several hundred centigrade. Here, we outline how to take advantage of the emerging state-of-the-art instrumentation and methodologies to study surface structures and dynamics to improve the understanding of structure-sensitive catalytic functionality. The concept of using low electron dose-rates in TEM in conjunction with in-line holography and aberration-correction at low voltage (80 kV) is introduced to allow maintaining atomic resolution and sensitivity during in situ observations of catalysts. Benefits are illustrated by exit wave reconstructions of TEM images of a nanocrystalline Co3O4 catalyst material acquired in situ during their exposure to either a reducing or oxidizing gas environment.

Impact Statement

A report on utilizing innovative tools and methods to study surface structures and dynamics in order to improve the understanding of structure-sensitive catalytic functions. The benefits of the state-of-the art technology and methodology is demonstrated with exit wave reconstructions of TEM images of a nanocrystalline Co₃O₄ catalyst material acquired in situ during exposure to either a reducing or oxidizing gas environment.