Fourier-transform infrared spectroscopy of H2O molecules on the Cr2O3 surface

Kittaka, Shigeharu; Sasaki, Tania A.; Fukuhara, Noboru; Katô, Hiroshi

doi:10.1016/0039-6028(93)90931-9

Cited by 18 publications

(24 citation statements)

References 18 publications

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“…Here, we present the spectral change at lower temperatures to obtain further information on the state surface observed under vacuum; they show bands at 3714, 3656, 3614, and 3408 cm -1 from chemisorbed hydroxyl groups on the Cr 2 O 3 surface. 10 It is evident that with decreasing temperature all the bands become sharper and shift somewhat. A broad band at 3614 cm -1 is split into small sharp bands, i.e., 3616 and 3606 cm -1 , indicating no changes in the vibration mode of surface hydroxyls below 298 K (Figure 2a).…”

Section: Resultsmentioning

confidence: 93%

“…15,16 It has been found from the FT-IR study that the Cr 2 O 3 -H 2 O system showed broadening of the OH stretching vibrational bands in the spectra due to the lateral interaction between water molecules, and the center of above the 2D critical temperature compared with that below it. 10 However, this method does not afford us clear information about the phase of water on the Cr 2 O 3 surface in the region above and below the 2D critical temperature. The more effective way to study the phase properties is to elucidate the dynamics of the adsorbed molecules by using techniques such as NMR, dielectric relaxation, and quasielastic neutron scattering measurements.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

et al. 1999

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The dynamic properties of water molecules adsorbed on the hydroxylated chromium(III) oxide surface, whose two-dimensional critical temperature was 303 K, were investigated at around the two-dimensional critical temperature by FT-IR, quasielastic neutron scattering, and dielectric relaxation techniques. The Cr 2 O 3 sample covered with monolayer water gives an IR band having a broad nature at ∼3400 cm -1 , due to the mutual hydrogen bonding among the adsorbed water molecules. The quasielastic neutron scattering data have revealed that the motion of the adsorbed water molecules changes across the two-dimensional critical temperature, ranging from the motion of the supercritical fluid to that of a solidified phase with decreasing temperature. The dielectric spectra observed at 298 K and at the coverage of 1.1 monolayers have been interpreted in terms of the presence of two relaxations due to the interfacial and orientational polarizations. The characteristic frequency of the relaxation for the latter polarization was estimated to be ca. 300 Hz. It is concluded from these findings that the two-dimensionally condensed waters adopt the mutually hydrogen-bonded solid state having a commensurate structure with the hydroxylated (001) Cr 2 O 3 surface below the two-dimensional critical temperature of this system. In addition, the interfacial polarization was explained in terms of a hopping model of protons of the adsorbed molecules. The behavior of conductivity arising from this proton hopping also indicates the morphology of the two-dimensionally condensed water below the monolayer coverage: the small clusters of water are formed on the Cr 2 O 3 surface.

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

et al. 1999

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“…Several these observations, the 2885 and 2120 cm−1 losses can be assigned to strongly hydrogen-bonded OH IR studies on the interaction of water with a-Cr 2 O 3 powders have observed OH stretching and OD species, respectively, as opposed to impurities that give rise to CMH and CMD stretches. features corresponding to isolated and hydrogenbonded species [35][36][37]. These studies have A structural model for these species is presented below in Section 3.1.4. detected sharp features between 3600 and 3650 cm−1 that have been assigned to terminal…”

Section: 2 Hreels Resultsmentioning

confidence: 99%

HREELS, TPD and XPS study of the interaction of water with the α-Cr2O3(001) surface

2000

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The interaction of water with the (001) surface of a-Cr 2 O 3 was examined with temperature programmed desorption (TPD), high resolution electron energy-loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). Two a-Cr 2 O 3 (001) surfaces were examined, both of which were grown on a-Al 2 O 3 (001) substrates using oxygen plasma-assisted molecular beam epitaxy (MBE). The two surfaces differed in that one was grown with a-Fe 2 O 3 interlayers whereas the other was grown directly on a-Al 2 O 3 (001). The in-plane lattice spacing of the a-Cr 2 O 3 (001) surface on a-Fe 2 O 3 /a-Al 2 O 3 (001) was 2% expansively strained relative to the unstrained a-Cr 2 O 3 (001) surface grown directly on a-Al 2 O 3 (001). Both the strained and unstrained surfaces exhibited similar water TPD behavior, with the possible exception that the desorption states of water on the strained surface were shifted slightly to lower temperatures relative to those on the unstrained surface. Water adsorbs on a-Cr 2 O 3 (001) in both molecular and dissociative states, with the former desorbing in TPD at 295 K and the latter at 345 K. TPD uptake measurements and XPS data suggest that each surface Cr3+ atom has the capacity to bind two water molecules, one in a molecular state and one in a dissociative state. Water in the dissociative state is comprised of two distinct OH groups based on HREELS, one of which is a terminal group with a n(OH) mode at 3600 cm−1 and the other of which is presumably a bridging group with a n(OH) mode at 2885 cm−1. These losses shift to 2645 and 2120 cm−1 with D 2 O adsorption. The low loss energy for the bridging OH/OD group indicates its involvement in a very strong hydrogen-bonded interaction with another species, presumably the oxygen atom of the terminal OH group. This pairing behavior is likely responsible for the first-order desorption kinetics observed for the recombinative desorption state at 345 K. The hydrogen-bonding interaction is unusually strong, as exemplified by the very low n(OH) frequency for the bridging OH group. Studies on the oxygen pre-exposed surface indicate that oxygen atoms, formed by O 2 dissociation, block the H 2 O dissociative channel but do not block the molecular adsorption channel.

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“…Verification for this orientation is now underway using FT-IR measurements and modeling analysis. One supporting factor for this structure is the fact that the displacement of stretching band upon adsorption of water is clear, without any loss of sharpness, i.e., hydrogen bonds are not involved in the adsorption, as in general, the -OH group stretching vibration is broadened by hydrogen bonding, which is not observed in this system (Kittaka et al, 1992).…”

Section: Structure Of the Adsorbed Water Moleculesmentioning

confidence: 95%

“…The characteristic crystal plane for this phenomenon was determined to be the (001) plane among some kinds of possible planes. The change in vibrational properties of the adsorbed water was examined using FT-IR measurements (Kittaka et al, 1992). The two typical sharp IR stretch bands associated with surface hydroxyl groups (ca.…”

Section: Introductionmentioning

confidence: 99%

The Structure of Water Monolayers on a Hydroxylated Chromium Oxide Surface

et al. 2005

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We have investigated the structure of monolayer water molecules on a hydroxylated (001) plane of Cr 2 O 3 using GCMC simulations. The water molecules are adsorbed commensurately in the center of three surface hydroxyl groups by directing the proton of a water hydroxyl group towards the solid surface. Another type of water is adsorbed by bridging anchored water molecules, whereby, a two-dimensional (2D) condensed layer is formed. It was ascertained that 2D condensed monolayer water is not in a crystalline state below the 2D critical temperature (319 K), but is composed of many hexagonally linked rings. Above the 2D critical temperature, the hexagonal alignment of water changes to form a one-dimensional linked water structure.

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Fourier-transform infrared spectroscopy of H2O molecules on the Cr2O3 surface

Cited by 18 publications

References 18 publications

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

HREELS, TPD and XPS study of the interaction of water with the α-Cr2O3(001) surface

The Structure of Water Monolayers on a Hydroxylated Chromium Oxide Surface

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