Delayed onset of intermolecular bonding in the water adlayer on Ru(001) due to the presence of preadsorbed oxygen

Kretzschmar, K.; Sass, J.K.; Hofmann, Ph.; Ortega, Alejandra; Bradshaw, Alexander M.; Holloway, S.

doi:10.1016/0009-2614(81)80043-7

Cited by 35 publications

(12 citation statements)

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“…After more than 25 years of studying water adsorption on Ru͕0001͖, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] there is still an ongoing debate about the exact nature of the system. Feibelman's recent suggestion that the most stable adsorption structure is in fact a partially dissociated hydrogen-bonded network of H 2 O and OH ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

Modifying the adsorption characteristics of water on Ru{0001} with preadsorbed oxygen

et al. 2008

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The coadsorption of water and preadsorbed oxygen on Ru͕0001͒ was studied by synchrotron-based highresolution x-ray photoelectron spectroscopy. A dramatic change was observed in the interaction of water with oxygen between low and high oxygen precoverages. Low oxygen coverages below 0.18 ML induce partial dissociation, which leads to an adsorbed layer of H 2 O and OH. Around half the oxygen atoms take part in this reaction. All OH recombines upon heating to 200 K and desorbs together with H 2 O. Oxygen coverages between 0.20 and 0.50 ML inhibit dissociation, instead a highly stable intact water species is observed, which desorbs at 220 K. This species is significantly more stable than intact water on the clean surface. The stabilization is most likely due to the formation of hydrogen bonds with neighboring oxygen atoms. For intermediate oxygen coverages around 0.18 ML, the dissociation behavior depends on the preparation conditions, which points toward possible mechanisms and pathways for partial dissociation of water on Ru͕0001͖.

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Section: Introductionmentioning

confidence: 99%

Modifying the adsorption characteristics of water on Ru{0001} with preadsorbed oxygen

et al. 2008

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“…We propose that all three phenomena have the same origin: the formation of a hydrogen-bonded 0-H 2 0 structure with local order at 95 K and long-range order at 165 K. Indeed, Kretzschmar et al proposed that the ir activity of the 3400-cm" 1 absorption peak was suppressed by coadsorbed oxygen due to a hydrogen-bonded complex between the two adsorbed species. 2 A closer examination of v OH provides more insight into the connection between the IRAS and EELS data. In view of the fact that significant dissociation of H 2 0 does not occur in our coadsorption experiments, we begin by identifying the sharp v ou feature at 3480-3530 cm" 1 in these experiments as the same feature resolved in offspecular EEL measurements at 3520 cm"" 1 for H 2 0 on clean Ru(001).…”

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“…Comparison between the IRAS data of Kretzschmar et al 2 and EELS data is based partly upon the coverage dependences observed in both sets of experiments. Preadsorbed oxygen can suppress completely the ir absorption of v 0H if the coverage of H 2 0 is less than some critical value, 0 H2 o c .…”

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confidence: 99%

“…In the case of Ru, infrared reflection-absorption spectroscopy (IRAS) showed complete suppression of the infrared activity of the O-H stretching mode of adsorbed water in the presence of a critical coverage of coadsorbed oxygen. 2 On Pt, vibrational and photoelectron spectra were interpreted as evidence for H 2 0 dissociation and the formation of hydroxyl species only if oxygen is preadsorbed.' In all cases, therefore, the presence of adsorbed oxygen exerts a strong effect on the properties of water which is coadsorbed.…”

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Coadsorption of Oxygen and Water on Ru (001): Vibrational and Structural Properties

1982

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A thermally induced change in the vibrational properties of a coadsorbed oxygen-water overlayer on Ru(OOl) is attributed to the formation of a local 0-H 2 0 complex. An O-H stretching mode of this complex is observed in electron-energy-loss data, but not in infrared reflection-absorption data available from another laboratory. This provides the first direct experimental evidence of a case in which the surface dipolar selection rule applies in an infrared but not in an energy-loss measurement.PACS numbers: 82.65.Jv, 68.20.+t, 68.90.+g, 82.45,+z Recent studies of the coadsorption of oxygen and H 2 0 on hexagonally close-packed surfaces of Ni, Ru, and Pt have provided several very intriguing results. On Ni, electron-stimulateddesorption ion angular distribution (ESDIAD) measurements 1 indicate that adsorbed molecular water forms structures at 80 K which are azimuthally oriented with respect to the substrate atoms only if oxygen is coadsorbed. In the case of Ru, infrared reflection-absorption spectroscopy (IRAS) showed complete suppression of the infrared activity of the O-H stretching mode of adsorbed water in the presence of a critical coverage of coadsorbed oxygen. 2 On Pt, vibrational and photoelectron spectra were interpreted as evidence for H 2 0 dissociation and the formation of hydroxyl species only if oxygen is preadsorbed.' In all cases, therefore, the presence of adsorbed oxygen exerts a strong effect on the properties of water which is coadsorbed. This effect is evident in the present study also.We have used electron energy-loss spectroscopy (EELS) to study the vibrational properties of a mixed 0-H 2 0 adlayer on Ru(001). We observe that a critical coverage of oxygen can affect the intermolecular structure of the adsorbed water. The O-H stretching vibration which we observe in EELS for this structure has been shown to be IRAS inactive. 2 Therefore, different vibrational "selection rules" must be operative in the IRAS and EELS measurements in this case.The EEL spectra of water adsorbed on clean Ru(001) have been studied extensively in this laboratory, and experimental details have been reported previously. 4 Specific vibrational features have been shown to reflect the intermolecular and intramolecular structure of the adsorbed H 2 0 overlayer. The frequencies of the losses due to frustrated rotations of molecular H 2 0 depend upon the degree of local order in the adlayer. 4 Two of the other fundamental vibrations of H 2 0, the scissoring mode (v s ) and the O-H stretching mode (^OH)> are not sensitive to this type of order. However, v s can be used as evidence of nondissociative adsorption since it involves the motion of all three atoms in the H 2 0 molecule. Significant dissociation should affect strongly the intensity of this vibrational feature. The frequency of ^OH is sensitive to intermolecular hydrogen bond formation, occurring at 3630-3750 cm" 1 for isolated H 2 0 molecules, and 3000-3600 cm" 1 in ice. Figure 1 shows a series of EEL spectra following sequential adsorption of oxygen and H 2 0 on R...

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“…Esto indica la formación de una estructura de multicapas de hielo encima de la monocapa adsor bida, estructura que prácticamente no afecta a FT. Este modelo es confirmado por Kretzschmar y col [130] en base a experimentos con IR y EMDT, pero sostienen que la con figuración tetraédrica de enlace por puente de hidrógeno es respetada aún a bajos cubrimientos.…”

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Interacción de agua con películas delgadas de cobre

Asensio¹

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La adsorción de gases en superficies metálicas abarca una amplia variedad de disciplinas. Procesos como los de oxidación, corrosión, actividad catalítica y reactividad dependen críticamente del estudio de los fenómenos de superficie. Si bien con el advenimiento de nuevas técnicas de ultra alto vacío (UAV) y sensibles métodos de análisis se han resuelto graves inconvenientes en diversas áreas de aplicación, muchos procesos industriales se basan aún en conocimientos empíricos. Los estudios de superficie, en su mayoría, enfocan su atención en mecanismos que tienen lugar en superficies "modelos", las cuales difieren notablemente de las superficies :"reales" de gran interés tecnológico. En tal sentido, el estudio de reacciones heterogéneas catalizadas por películas metálicas delgadas, son el nexo imprescindible entre la fisicoquímica de superficies y las distintas áreas de la ciencia aplicada. En especial, la interacción de agua con superficies metálicas tanto desde el punto de vista de la catálisis heterogénea como de los fenómenos electroquímicos de corrosión es uno de los tópicos que más ha centrado la atención en estos últimos años. Además de sus múltiples aplicaciones prácticas, la particularidad que presenta el agua de formar fuertes uniones intermoleculares, comparables a la unión metal-adsorbato y la tendencia a la disociación registrada en numerosos metales , contribuyen a considerar el sistema agua-metal especialmente apto para el estudio de interacciones entre partículas adsorbidas y su relación con superficies metálicas. Por lo tanto, reviste notable interés un estudio extensivo de la interacción de agua con películas delgadas de cobre. En el presente trabajo (PT), junto con la caracterización detallada de las etapas elementales tales como: adsorción, desorción, migración superficial y reactividad, se investiga la influencia de la estructura del sustrato y de la presencia de especies coadsorbidas (oxígeno) en la actividad catalítica. De esta forma ha sido posible establecer las pautas generales para una variación sistemática de diferentes parámetros que modifican la actividad de las superficies de cobre frente al agua.

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Delayed onset of intermolecular bonding in the water adlayer on Ru(001) due to the presence of preadsorbed oxygen

Cited by 35 publications

References 10 publications

Modifying the adsorption characteristics of water on Ru{0001} with preadsorbed oxygen

Modifying the adsorption characteristics of water on Ru{0001} with preadsorbed oxygen

Coadsorption of Oxygen and Water on Ru (001): Vibrational and Structural Properties

Interacción de agua con películas delgadas de cobre

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