Anhydrous and water-assisted proton mobility in phosphotungstic acid

Michael J. Janik, Robert J. Davis, Matthew Neurock

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

Abstract

Nonlocal gradient-corrected density functional theoretical calculations were used to determine the energetics associated with proton migration in phosphotungstic acid. The activation energy for anhydrous proton hopping between two oxygen atoms on the exterior of the molecular Keggin unit was calculated to be 103.3 kJ mol-1. The quantum-tunneling effect on the rate of proton movement was determined using semiclassical transition-state theory and was found to be a major contributor to the overall rate of proton movement at temperatures below approximately 350 K. The adsorption of water on an acidic proton decreases the activation barrier for hopping to 11.2 KJ mol-1 by facilitating proton transfer along hydrogen bonds. The overall rate constant for proton hopping was determined as a function of temperature and water partial pressure. Small amounts of water greatly enhance the overall rate of proton movement.

Original languageEnglish (US)
Pages (from-to)5238-5245
Number of pages8
JournalJournal of the American Chemical Society
Volume127
Issue number14
DOIs
StatePublished - Apr 13 2005

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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