Activation energies for permeation of He and H2 through silica membranes: An ab initio calculation study

P. Hacarlioglu, D. Lee, G. V. Gibbs, S. T. Oyama

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80 Scopus citations

Abstract

The permeation of hydrogen and helium through vitreous glass and silica membranes is modeled using ab initio density functional calculations. The total energy of the system is obtained as the permeating species approach and pass through H2nSinOn (n = 4-8) cyclosiloxane n-membered rings of different size to give activation energies of permeation. Comparison of the calculated activation energies to those reported for vitreous glass (20-40 kJ mol-1) indicate the presence of 5- and 6-membered siloxane rings, consistent with the accepted structure of glass as a disordered form of β-cristobalite. Similar comparison to activation energies measured for silica membranes (10-20 kJ mol-1) indicate the presence of 6- and 7-membered rings, and suggest that the structure of the membranes is more open than that of the vitreous glass.

Original languageEnglish
Pages (from-to)277-283
Number of pages7
JournalJournal of Membrane Science
Volume313
Issue number1-2
DOIs
StatePublished - 10 Apr 2008

Keywords

  • Activation energy
  • DFT
  • Helium
  • Hydrogen
  • Silica membranes

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