Journal article
Environmental TEM study of the dynamic nanoscaled morphology of NiO/YSZ during reduction
Department of Energy Conversion and Storage, Technical University of Denmark1
Imaging and Structural Analysis, Department of Energy Conversion and Storage, Technical University of Denmark2
Mixed Conductors, Department of Energy Conversion and Storage, Technical University of Denmark3
Department of Chemistry, Technical University of Denmark4
Center for Electron Nanoscopy, Technical University of Denmark5
The reduction of a metal oxide is often a critical preparation step for activating catalytic behaviour. This study addresses the reduction process of NiO in pure form and in a composite of NiO/yttria-stabilized zirconia (YSZ) in hydrogen relevant for solid oxide electrochemical cells by comparing results from environmental transmission electron microscopy (ETEM) with thermogravimetric analysis (TGA).
The temperature dependent reduction profiles obtained from TGA confirm an inhibitive effect from YSZ on the NiO reduction. The ETEM images show the growth of Ni in decaying NiO and reveal the nanoscale morphological changes such as pore formation in NiO above 280°C and densification and collapse of the pore structures above 400°C.
The accelerated Ni front in NiO illustrates the auto catalysis of the reaction. A rapid temperature ramping from room temperature to 780°C in hydrogen in 1 second resulted in immediate morphological changes at the nanoscale from dense NiO to dense Ni. The analysis suggests that the inhibitive effect of YSZ on the NiO reduction reaction is not due to a direct local interaction between YSZ and NiO, but instead due to gas and/or mass transport limitations.© 2014 Elsevier B.V.
All rights reserved.
Language: | English |
---|---|
Year: | 2015 |
Pages: | 147-154 |
ISSN: | 18733875 and 0926860x |
Types: | Journal article |
DOI: | 10.1016/j.apcata.2014.10.045 |
ORCIDs: | Simonsen, Søren Bredmose , Agersted, Karsten , Hansen, Karin Vels , Wagner, Jakob Birkedal , Hansen, Thomas Willum and Kuhn, Luise Theil |
Autocatalysis ETEM In situ TEM NiO Nickel oxide reduction SOEC SOFC YSZ