title: Observing gas-catalyst dynamics at atomic resolution and single-atom sensitivity.
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.
authors.affiliation: Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Kgs. Lyngby, Denmark. Electronic address: sth@topsoe.dk.
authors.forename: S
authors.initials: S
authors.lastname: Helveg
authors.affiliation: Joint Center for Artificial Photosynthesis (JCAP), Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA; National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA. Electronic address: cfkisielowski@lbl.gov.
authors.forename: C F
authors.initials: CF
authors.lastname: Kisielowski
authors.affiliation: FEI Company, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands.
authors.forename: J R
authors.initials: JR
authors.lastname: Jinschek
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA.
authors.forename: P
authors.initials: P
authors.lastname: Specht
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
authors.forename: G
authors.initials: G
authors.lastname: Yuan
authors.affiliation: Joint Center for Artificial Photosynthesis (JCAP), Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA; Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
authors.forename: H
authors.initials: H
authors.lastname: Frei
keywords: Catalysis; Dynamics; Exit wave reconstruction; Gas-surface interactions; In situ studies; Nanocrystals; Transmission electron microscopy; Water-splitting