Phosphonic acid functionalized silicas for intermediate temperature proton conduction

Jin, Y. G., Qiao, S. Z., Xu, Z. P., Yan, Z., Huang, Y., Da Costa, J. C. D. and Lu, G. Q. (2009) Phosphonic acid functionalized silicas for intermediate temperature proton conduction. Journal of Materials Chemistry, 19 16: 2363-2372. doi:10.1039/b819379g


Author Jin, Y. G.
Qiao, S. Z.
Xu, Z. P.
Yan, Z.
Huang, Y.
Da Costa, J. C. D.
Lu, G. Q.
Title Phosphonic acid functionalized silicas for intermediate temperature proton conduction
Journal name Journal of Materials Chemistry   Check publisher's open access policy
ISSN 0959-9428
1364-5501
Publication date 2009-01-01
Year available 2009
Sub-type Article (original research)
DOI 10.1039/b819379g
Open Access Status Not Open Access
Volume 19
Issue 16
Start page 2363
End page 2372
Total pages 10
Editor Carol Stanier
Place of publication Cambridge, UK
Publisher Royal Society of Chemistry
Language eng
Subject C1
090403 Chemical Engineering Design
100703 Nanobiotechnology
850401 Fuel Cells (excl. Solid Oxide)
850606 Hydrogen Storage
091205 Functional Materials
Abstract Highly proton conductive silicas with phosphonic acid functionalization were synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane in a sol-gel process, followed by acidification of the phosphonate groups. These functionalized silicas with various phosphonic acid contents were extensively characterized to examine their structures and properties; in particular their intermediate temperature proton conductivity at 100–150 °C were systematically investigated under a variety of relative humidity (RH) conditions. The prepared samples have a mesoporous or nonporous structure depending on the DPTS amount used in the synthesis, and show high thermal stability under inert and oxidative atmospheres. We found that the present silicas still exhibit water-dependent proton conduction, but their conductivity under low humidity conditions has been significantly enhanced by up to two orders of magnitude compared to those phosphonic acid functionalized silicas previously reported. Herein, the highest conductivity has been obtained at 150 °C ranging from 4.4 × 10-4 S cm-1 at 20% RH to 0.031 S cm-1 at 100% RH. In general, proton conductivity is largely influenced by the content of phosphonic acid and the porous structure of the materials. Notably, the uniform mesostructure with a high surface area was found to greatly improve the proton conductivity at low humidity. The vehicle mechanism dominates the proton conduction at high humidity, whereas the conductivity at low humidity is likely a consequence of the structure diffusion (the Grotthuss mechanism). In addition, these materials are insoluble in water, rendering a practical suitability for fuel cell applications.
Keyword Polymer Electrolyte Membranes
Fuel-cell Applications
Sol-gel Process
Protogenic Group
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Thu, 03 Sep 2009, 18:21:17 EST by Mr Andrew Martlew on behalf of Aust Institute for Bioengineering & Nanotechnology