Formation of hydronium and methoxonium on Pt(110): Ab initio determination of spectroscopically observed species

Paul Blowers, N. Chen, R. I. Masel

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Abstract

Previously, other researchers have examined the coadsorption of water and hydrogen on Pt(111) with electron energy loss spectroscopy (EELS) and have seen the formation of a new species. This new species was originally designated to be a "hydronium" species, where hydronium referred to H3O+ surrounded by water. However, the formation of H3O+ on platinum has not been widely accepted in the literature because the formation of a bare H3O+ not surrounded by water is not a thermodynamically favored process. In this work, we use ab initio calculations at the MP2(full)/6-31g* level to predict the gas phase frequencies for a host of water and water-cluster species. These frequencies are compared to high resolution EELS spectra to identify which species form on Pt(110). We find that H5O+2, H7O+3, and H9O+4 fit the EELS spectra quite well, while H3O, H3O-, and H3O+ do not show the right vibrational modes. We have also done similar calculations for methanol. Methanol has a higher proton affinity than water, so it seems possible that methanol could also form a positively charged species like methoxonium, CH3OH+2. Once again, EELS spectra show a new species forms on Pt(110). Ab initio calculations are compared to a high resolution EELS spectrum of hydrogen coadsorbed with methanol on platinum. The most likely species to form here is methoxonium, possibly in a methanol cluster. This conclusion is supported by additional spectra of deuterated species that show the correct isotopic shifts in frequencies predicted by calculations. The conclusion from our study is that ions can form during coadsorption of hydrogen and water and hydrogen and methanol on Pt(110). The ions are probably hydrated, but the further EELS evidence strongly supports ion formation.

Original languageEnglish (US)
Pages (from-to)1750-1755
Number of pages6
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Volume17
Issue number4
StatePublished - Jul 1999
Externally publishedYes

Fingerprint

Electron energy loss spectroscopy
Methanol
methyl alcohol
energy dissipation
electron energy
Water
Hydrogen
water
spectroscopy
hydrogen
Ions
Platinum
platinum
ions
high resolution
affinity
Protons
vibration mode
Gases
vapor phases

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Physics and Astronomy (miscellaneous)
  • Surfaces and Interfaces

Cite this

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title = "Formation of hydronium and methoxonium on Pt(110): Ab initio determination of spectroscopically observed species",
abstract = "Previously, other researchers have examined the coadsorption of water and hydrogen on Pt(111) with electron energy loss spectroscopy (EELS) and have seen the formation of a new species. This new species was originally designated to be a {"}hydronium{"} species, where hydronium referred to H3O+ surrounded by water. However, the formation of H3O+ on platinum has not been widely accepted in the literature because the formation of a bare H3O+ not surrounded by water is not a thermodynamically favored process. In this work, we use ab initio calculations at the MP2(full)/6-31g* level to predict the gas phase frequencies for a host of water and water-cluster species. These frequencies are compared to high resolution EELS spectra to identify which species form on Pt(110). We find that H5O+2, H7O+3, and H9O+4 fit the EELS spectra quite well, while H3O, H3O-, and H3O+ do not show the right vibrational modes. We have also done similar calculations for methanol. Methanol has a higher proton affinity than water, so it seems possible that methanol could also form a positively charged species like methoxonium, CH3OH+2. Once again, EELS spectra show a new species forms on Pt(110). Ab initio calculations are compared to a high resolution EELS spectrum of hydrogen coadsorbed with methanol on platinum. The most likely species to form here is methoxonium, possibly in a methanol cluster. This conclusion is supported by additional spectra of deuterated species that show the correct isotopic shifts in frequencies predicted by calculations. The conclusion from our study is that ions can form during coadsorption of hydrogen and water and hydrogen and methanol on Pt(110). The ions are probably hydrated, but the further EELS evidence strongly supports ion formation.",
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T1 - Formation of hydronium and methoxonium on Pt(110)

T2 - Ab initio determination of spectroscopically observed species

AU - Blowers, Paul

AU - Chen, N.

AU - Masel, R. I.

PY - 1999/7

Y1 - 1999/7

N2 - Previously, other researchers have examined the coadsorption of water and hydrogen on Pt(111) with electron energy loss spectroscopy (EELS) and have seen the formation of a new species. This new species was originally designated to be a "hydronium" species, where hydronium referred to H3O+ surrounded by water. However, the formation of H3O+ on platinum has not been widely accepted in the literature because the formation of a bare H3O+ not surrounded by water is not a thermodynamically favored process. In this work, we use ab initio calculations at the MP2(full)/6-31g* level to predict the gas phase frequencies for a host of water and water-cluster species. These frequencies are compared to high resolution EELS spectra to identify which species form on Pt(110). We find that H5O+2, H7O+3, and H9O+4 fit the EELS spectra quite well, while H3O, H3O-, and H3O+ do not show the right vibrational modes. We have also done similar calculations for methanol. Methanol has a higher proton affinity than water, so it seems possible that methanol could also form a positively charged species like methoxonium, CH3OH+2. Once again, EELS spectra show a new species forms on Pt(110). Ab initio calculations are compared to a high resolution EELS spectrum of hydrogen coadsorbed with methanol on platinum. The most likely species to form here is methoxonium, possibly in a methanol cluster. This conclusion is supported by additional spectra of deuterated species that show the correct isotopic shifts in frequencies predicted by calculations. The conclusion from our study is that ions can form during coadsorption of hydrogen and water and hydrogen and methanol on Pt(110). The ions are probably hydrated, but the further EELS evidence strongly supports ion formation.

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