Physicochemical characterisation and hydrothermal stability investigation of cobalt-incorporated silica xerogels

Liu, Liang, Wang, David K., Martens, Dana. L., Smart, Simon, Strounina, Ekaterina and Diniz da Costa, João C. (2014) Physicochemical characterisation and hydrothermal stability investigation of cobalt-incorporated silica xerogels. RSC Advances, 4 36: 18862-18870. doi:10.1039/c4ra00498a


Author Liu, Liang
Wang, David K.
Martens, Dana. L.
Smart, Simon
Strounina, Ekaterina
Diniz da Costa, João C.
Title Physicochemical characterisation and hydrothermal stability investigation of cobalt-incorporated silica xerogels
Journal name RSC Advances   Check publisher's open access policy
ISSN 2046-2069
Publication date 2014-04-07
Sub-type Article (original research)
DOI 10.1039/c4ra00498a
Open Access Status Not Open Access
Volume 4
Issue 36
Start page 18862
End page 18870
Total pages 9
Place of publication Cambridge, United Kingdom
Publisher R S C Publications
Language eng
Subject 1500 Chemical Engineering
1600 Chemistry
Formatted abstract
The hydrothermal stability of the cobalt oxide silica xerogels was comprehensively investigated, including the effect of Co/Si molar ratio (0.00–0.50), vapour content (0–75 mol%), exposure time (0–100 h) and temperature (250–550 °C). Physicochemical properties of the xerogels were characterised by nitrogen sorption, FTIR, solid-state 29Si NMR (CP/MAS), micro-Raman, XRD and HR-TEM techniques. The structural characterisation indicated that increasing cobalt incorporation inhibited the degree of condensation in the silica network, and that the formation of tricobalt tetroxide (Co3O4) nanocrystals in the silica matrix was only observed in high cobalt loading samples (Co/Si ≥ 0.25). The hydrothermal stability of the xerogels assessed by N2 sorption was found to be strongly dependent on the cobalt loading; particularly when the presence of Co3O4 in the silica matrices was implicated. For the unstable xerogels (Co/Si < 0.25), the material's stability was significantly decreased by both vapour content and exposure time, resulting in an almost 90% surface area reduction. On the other hand, the high cobalt loading xerogels (Co/Si ≥ 0.25) were found to contain Co3O4 and were much more stable, losing less than 25% of surface area and maintaining microporous structure after exposing to a harsh condition of 75 mol% vapour at 550 °C for 40 h. A structural model is proposed whereby the cobalt oxide particles ‘shield’ the silica matrix and inhibit the hydrolysis and condensation of the silica in the pores walls. This effectively limits the structural rearrangement that hydrothermal treatment typically invokes and therefore confers improved hydrothermal stability.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2015 Collection
Centre for Advanced Imaging Publications
 
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