Effects of surface chemistry on structure and thermodynamics of water layers at solid-vapor interfaces

David B. Asay, Anna L. Barnette, Seong Kim

Research output: Contribution to journalArticle

64 Citations (Scopus)

Abstract

The effects of surface chemistry on the isotherm thickness and structure of the adsorbed water layer as well as the isosteric heat of adsorption and entropy of adsorption were studied using attenuated total reflection infrared spectroscopy. The degree of hydrophilicity seems to distinctively change the structure and thermodynamic properties of the water layers adsorbed on silicon oxide surfaces. On the highly hydrophilic silicon oxide surface covered with silanol groups, the water layer adsorbed at low humidities exhibits the OH stretching peak at 3230 cm-1 (characteristic of a solid-like water structure), and the isosteric heat of adsorption is much higher than the latent heat of ice sublimation. As the concentration of surface silanol groups decreases, both the initial isosteric heat of adsorption of water and the amount of solid-like water decrease. The water layer adsorbed on the hydrophilic surface at low humidities seems to have much lower entropies than bulk water, while the entropy of the water layer on the partially methylated surface is not much lower than that of bulk water. At high humidities, the liquid water structure becomes dominant in the adsorbed layer. The possible origins of high isosteric heat of adsorption and low entropy are discussed.

Original languageEnglish (US)
Pages (from-to)2128-2133
Number of pages6
JournalJournal of Physical Chemistry C
Volume113
Issue number6
DOIs
StatePublished - Feb 12 2009

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Surface chemistry
Vapors
Thermodynamics
vapors
chemistry
thermodynamics
Water
water
Adsorption
Entropy
adsorption
entropy
humidity
heat
Atmospheric humidity
Silicon oxides
silicon oxides
Sublimation
Latent heat
Hydrophilicity

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Cite this

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abstract = "The effects of surface chemistry on the isotherm thickness and structure of the adsorbed water layer as well as the isosteric heat of adsorption and entropy of adsorption were studied using attenuated total reflection infrared spectroscopy. The degree of hydrophilicity seems to distinctively change the structure and thermodynamic properties of the water layers adsorbed on silicon oxide surfaces. On the highly hydrophilic silicon oxide surface covered with silanol groups, the water layer adsorbed at low humidities exhibits the OH stretching peak at 3230 cm-1 (characteristic of a solid-like water structure), and the isosteric heat of adsorption is much higher than the latent heat of ice sublimation. As the concentration of surface silanol groups decreases, both the initial isosteric heat of adsorption of water and the amount of solid-like water decrease. The water layer adsorbed on the hydrophilic surface at low humidities seems to have much lower entropies than bulk water, while the entropy of the water layer on the partially methylated surface is not much lower than that of bulk water. At high humidities, the liquid water structure becomes dominant in the adsorbed layer. The possible origins of high isosteric heat of adsorption and low entropy are discussed.",
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Effects of surface chemistry on structure and thermodynamics of water layers at solid-vapor interfaces. / Asay, David B.; Barnette, Anna L.; Kim, Seong.

In: Journal of Physical Chemistry C, Vol. 113, No. 6, 12.02.2009, p. 2128-2133.

Research output: Contribution to journalArticle

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