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In Situ Aberration-Corrected Environmental TEM: Reduction of Model Co3O4 in H2 at the Atomic Level

Authors

  • Michael R. Ward,

    1. The York-JEOL Nanocentre, University of York, Heslington, York YO10 5DD (UK)
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    • All authors belong to the Department of Physics, Prof. E. D. Boyes to the Department of Electronics and Prof. P. L. Gai to the Department of Chemistry.

  • Prof. Edward D. Boyes,

    1. The York-JEOL Nanocentre, University of York, Heslington, York YO10 5DD (UK)
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    • All authors belong to the Department of Physics, Prof. E. D. Boyes to the Department of Electronics and Prof. P. L. Gai to the Department of Chemistry.

  • Prof. Pratibha L. Gai

    Corresponding author
    1. The York-JEOL Nanocentre, University of York, Heslington, York YO10 5DD (UK)
    • The York-JEOL Nanocentre, University of York, Heslington, York YO10 5DD (UK)
    Search for more papers by this author
    • All authors belong to the Department of Physics, Prof. E. D. Boyes to the Department of Electronics and Prof. P. L. Gai to the Department of Chemistry.


Abstract

Understanding the dynamic evolution of structural changes in catalysts at the atomic level under controlled reaction conditions is one of the most challenging areas in heterogeneous catalysis. Here we present aberration-corrected environmental TEM at the atomic level and electron diffraction of the reduction of model Co3O4 catalysts in H2 to directly observe the dynamic phase evolution in the reduction process. New insights into the reduction of Co3O4 to the intermediate CoO include the formation of an advancing atomic scale interface between Co3O4 and CoO regions. The interface penetrates further into the Co3O4 crystal, with the CoO regions replacing the previous Co3O4 structure, with increasing reduction. The reduction to CoO proceeds at approximately 200 °C at rounded edges containing atomic steps on the surfaces. The interfaces are observed in crystals larger than approximately 15 nm in size but not in smaller crystals, which indicates the rapid reduction of smaller nanoparticles. The most dramatic changes are observed at 350 °C in larger crystals of size 50 nm.

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