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  4. New insights into the pore development mechanism of layered hydroxides upon thermal activation
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New insights into the pore development mechanism of layered hydroxides upon thermal activation

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Description

Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are extensively used as precursors for the preparation of (photo-)catalysts, electrodes, magnetic materials, sorbents, etc. The synthesis typically involves the transformation to the corresponding mixed metal oxide via calcination, resulting in atomically dispersed mixed metal oxides (MMOs). This process alters the porosity of the materials, with crucial implications for the performance in many applications. Yet, the mechanisms of pore formation and collapse are poorly understood. Combining an integrated in situ and ex situ characterization approach, here we follow the evolution of porosity changes during the thermal decomposition of LDHs integrating different divalent (Mg, Ni) and trivalent (Al, Ga) metals. Variations in porous properties determined by high-resolution argon sorption are linked to the morphological and compositional changes in the samples by in situ transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which is facilitated by the synthesis of well crystallized LDHs of large crystal size. The observations are correlated with the phase changes identified by X-ray diffraction, the mass losses evidenced by thermogravimetric analysis, the structural changes determined by infrared and nuclear magnetic resonance spectroscopy, and the pore connectivity analyzed by positron annihilation spectroscopy. The findings show that the multimetallic nature of the LDH governs the size and distribution (geometry, location, and connectivity) of the mesopores developed, which is controlled by the crystallization of the MMO phase, providing key insights for the improved design of porous mixed metal oxides.

Date Created
2017-05
Contributors
  • Murty, Rohan Aditya (Author)
  • Deng, Shuguang (Thesis director)
  • Nielsen, David R. (Committee member)
  • Chemical Engineering Program (Contributor)
  • Barrett, The Honors College (Contributor)
Topical Subject
  • chemical engineering
  • Layered Hydroxides
  • Positron Annihilation Lifetime Spectroscopy
Resource Type
Text
Extent
35 pages
Language
eng
Copyright Statement
In Copyright
Primary Member of
Barrett, The Honors College Thesis/Creative Project Collection
Series
Academic Year 2016-2017
Handle
https://hdl.handle.net/2286/R.I.43506
Level of coding
minimal
Cataloging Standards
asu1
System Created
  • 2017-10-30 02:50:58
System Modified
  • 2021-08-11 04:09:57
  •     
  • 1 year 5 months ago
Additional Formats
  • OAI Dublin Core
  • MODS XML

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