Wetting of mixed OH H2 O layers on Pt(111)

Georgina Zimbitas, Mark E. Gallagher, George R. Darling, Andrew Hodgson

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

We describe the effect of growth temperature and OH H2 O composition on the wetting behavior of Pt(111). Changes to the desorption rate of ice films were measured and correlated to the film morphology using low energy electron diffraction and thermal desorption of chloroform to measure the area of multilayer ice and monolayer OH H2 O exposed. Thin ice films roughen, forming bare (39×39) R16° water monolayer and ice clusters. The size of the clusters depends on growth temperature and determines their kinetic stability, with the desorption rate decreasing when larger clusters are formed by growth at high temperature. Continuous films of more than approximately 50 layers thick stabilize an ordered incommensurate ice film that does not dewet. OH coadsorption pins the first layer into registry with Pt, forming an ordered hexagonal (OH+ H2 O) structure with all the H atoms involved in hydrogen bonding. Although this layer has a similar honeycomb O Hx skeleton to ice Ih, it is unable to reconstruct to match the bulk ice lattice parameter and does not form a stable wetting layer. Water aggregates to expose bare monolayer (OH+ H2 O), forming bulk ice crystallites whose size depend on preparation temperature. Increasing the proportion of water in the first layer provides free OH groups which stabilize the multilayer. The factors influencing multilayer wetting are discussed using density functional theory calculations to compare water adsorption on top of (OH+ H2 O) and on simple models for commensurate water structures. We show that both the (OH+ H2 O) structure and "H-down" water layers are poor proton acceptors, bonding to the first layer being enhanced by the presence of free OH groups. Formation of an ordered ice multilayer requires a water-metal interaction sufficient to wet the surface, but not so strong as to prevent the first layer relaxing to stabilize the interface between the metal and bulk ice.

LanguageEnglish
Article number074701
Number of pages12
JournalJournal of Chemical Physics
Volume128
Issue number7
DOIs
Publication statusPublished - 28 Feb 2008

Fingerprint

Ice
wetting
Wetting
ice
Water
Multilayers
water
Monolayers
desorption
Growth temperature
Desorption
Metals
Thermal desorption
Low energy electron diffraction
Chloroform
chloroform
Crystallites
musculoskeletal system
metals
crystallites

Keywords

  • OH
  • H2O
  • Pt(111)
  • wetting behavior
  • ice
  • monolayers
  • desorption
  • adsorption
  • multilayer

Cite this

Zimbitas, G., Gallagher, M. E., Darling, G. R., & Hodgson, A. (2008). Wetting of mixed OH H2 O layers on Pt(111). Journal of Chemical Physics, 128(7), [074701]. https://doi.org/10.1063/1.2830266
Zimbitas, Georgina ; Gallagher, Mark E. ; Darling, George R. ; Hodgson, Andrew. / Wetting of mixed OH H2 O layers on Pt(111). In: Journal of Chemical Physics. 2008 ; Vol. 128, No. 7.
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abstract = "We describe the effect of growth temperature and OH H2 O composition on the wetting behavior of Pt(111). Changes to the desorption rate of ice films were measured and correlated to the film morphology using low energy electron diffraction and thermal desorption of chloroform to measure the area of multilayer ice and monolayer OH H2 O exposed. Thin ice films roughen, forming bare (39×39) R16° water monolayer and ice clusters. The size of the clusters depends on growth temperature and determines their kinetic stability, with the desorption rate decreasing when larger clusters are formed by growth at high temperature. Continuous films of more than approximately 50 layers thick stabilize an ordered incommensurate ice film that does not dewet. OH coadsorption pins the first layer into registry with Pt, forming an ordered hexagonal (OH+ H2 O) structure with all the H atoms involved in hydrogen bonding. Although this layer has a similar honeycomb O Hx skeleton to ice Ih, it is unable to reconstruct to match the bulk ice lattice parameter and does not form a stable wetting layer. Water aggregates to expose bare monolayer (OH+ H2 O), forming bulk ice crystallites whose size depend on preparation temperature. Increasing the proportion of water in the first layer provides free OH groups which stabilize the multilayer. The factors influencing multilayer wetting are discussed using density functional theory calculations to compare water adsorption on top of (OH+ H2 O) and on simple models for commensurate water structures. We show that both the (OH+ H2 O) structure and {"}H-down{"} water layers are poor proton acceptors, bonding to the first layer being enhanced by the presence of free OH groups. Formation of an ordered ice multilayer requires a water-metal interaction sufficient to wet the surface, but not so strong as to prevent the first layer relaxing to stabilize the interface between the metal and bulk ice.",
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Zimbitas, G, Gallagher, ME, Darling, GR & Hodgson, A 2008, 'Wetting of mixed OH H2 O layers on Pt(111)' Journal of Chemical Physics, vol. 128, no. 7, 074701. https://doi.org/10.1063/1.2830266

Wetting of mixed OH H2 O layers on Pt(111). / Zimbitas, Georgina; Gallagher, Mark E.; Darling, George R.; Hodgson, Andrew.

In: Journal of Chemical Physics, Vol. 128, No. 7, 074701, 28.02.2008.

Research output: Contribution to journalArticle

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AB - We describe the effect of growth temperature and OH H2 O composition on the wetting behavior of Pt(111). Changes to the desorption rate of ice films were measured and correlated to the film morphology using low energy electron diffraction and thermal desorption of chloroform to measure the area of multilayer ice and monolayer OH H2 O exposed. Thin ice films roughen, forming bare (39×39) R16° water monolayer and ice clusters. The size of the clusters depends on growth temperature and determines their kinetic stability, with the desorption rate decreasing when larger clusters are formed by growth at high temperature. Continuous films of more than approximately 50 layers thick stabilize an ordered incommensurate ice film that does not dewet. OH coadsorption pins the first layer into registry with Pt, forming an ordered hexagonal (OH+ H2 O) structure with all the H atoms involved in hydrogen bonding. Although this layer has a similar honeycomb O Hx skeleton to ice Ih, it is unable to reconstruct to match the bulk ice lattice parameter and does not form a stable wetting layer. Water aggregates to expose bare monolayer (OH+ H2 O), forming bulk ice crystallites whose size depend on preparation temperature. Increasing the proportion of water in the first layer provides free OH groups which stabilize the multilayer. The factors influencing multilayer wetting are discussed using density functional theory calculations to compare water adsorption on top of (OH+ H2 O) and on simple models for commensurate water structures. We show that both the (OH+ H2 O) structure and "H-down" water layers are poor proton acceptors, bonding to the first layer being enhanced by the presence of free OH groups. Formation of an ordered ice multilayer requires a water-metal interaction sufficient to wet the surface, but not so strong as to prevent the first layer relaxing to stabilize the interface between the metal and bulk ice.

KW - OH

KW - H2O

KW - Pt(111)

KW - wetting behavior

KW - ice

KW - monolayers

KW - desorption

KW - adsorption

KW - multilayer

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