Reorientation of chemisorbed water on Ni(110) by hydrogen bonding to second layer

Abstract

Water chemisorbs molecularly on Ni(llO) at 180 K producing a c(2x2) overlayer, at 0.5 ML (ML= monolayer -1.15x 10 15 molecules cm -2 ). This water is undetectable by ir methods which indicates the absence of clustering (and, hence, no intermolecular H bonding) in the first 0.5 ML. Population of a second "icelike" layer, which is nearly saturated after an additional 0.5 ML, makes the first 0.5 ML ir active and produces strong H-bonding interactions. The plane of the chemisorbed water, which is originally parallel to the surface, is reoriented towards the surface normal on filling of the second layer.PACS numbers: 82.65.My, 33.20.EaThe interaction of water with solid surfaces has become of increasing interest in recent years. x This is due both to practical considerations related to electrochemistry and corrosion and to the rich chemistry and physics that arise from the complex interactions between adsorbed water molecules and the substrate and/or each other. The presence of hydrogen bonding (H bonding), which can be of comparable magnitude to the moleculesurface bond strength, leads to a range of phenomena such as clustering at low coverages, low-order desorption kinetics, and control of the double-layer properties in electrochemical systems, etc. x In this Letter, we show that it is possible to produce ordered chemisorbed overlayers of water on Ni(llO) in which clustering is not present, and to detect the molecular reorientation in the first layer of chemisorbed water caused by the adsorption of a specific coverage of water into the "second" layer. This second layer still shows residual interactions with the Ni(llO) surface and is distinguishable from bulk ice. We show that the H-O-H plane of the water molecules in the first chemisorbed layer must lie close to parallel to the plane of the surface. After adsorption into the second layer to form a bilayer, the H-O-H plane must lie much closer to the surface normal.The apparatus have been described in detail elsewhere. 2 "" 4 Briefly, the measurements were carried out in a standard ultrahigh vacuum chamber (base pressure -Ixl0~1 0 torr) to which water can be admitted through a differentially pumped, shuttered capillary array and by admission to the background. The chamber is equipped with an automated multimass quadrupole mass spectrometer and Kelvin probe to measure changes in work function A<f> (sensitivity -1 mV, t c~~0 .1 s), and is interfaced to a Fourier-transform ir spectrometer for Fourier-transform ir-reflection-absorption spectroscopy (FTIR-RAS). 4 The ir radiation is incident at about 82° from the surface normal and a mercury cadmium telluride (MCT) detector is used. The lowest detectable absorbance has proven to be ~(2-3)xl0~5 absorbance units (a.u.) for a single reflection. A signal-to-noise ratio of > 100:1 can be obtained on adsorbed CO on Ni (110) in 90 s. The crystal was cleaned by a combination of Ar + -ion sputtering and annealing. The cleanliness was judged by Auger electron spectroscopy, by nuclear reaction analysis (NRA) in another chamber 2...

NO–methanol interaction on the surface of Pt(332)

“…All the experiments were carried out in a standard UHV system described elsewhere [21,22]. Briefly, a stainless steel UHV chamber is pumped by a turbo-molecular pump, which is in turn backed by an oil diffusion pump.…”

Unique water-water coordination tailored by a metal surface

“…4(b)), which are separated by a zigzag pattern of exposed Cu atoms alternating between rows and troughs, three protruding protons share the charge accumulated on a single Cu atom in the trough in a Bjerrum defect type structure. This defect is made possible by the oscillation of charge density at the surface, which occurs along the [001] but not along the [1][2][3][4][5][6][7][8][9][10], which explains the [001] chain orientation observed with STM. 12,14 This can also explain the shape of water aggregates at very low coverage, in which four or six protrusions are arranged in rectangular shapes.…”

“…12,14 This can also explain the shape of water aggregates at very low coverage, in which four or six protrusions are arranged in rectangular shapes. 61 The fact that only double rows of protrusions along the [1][2][3][4][5][6][7][8][9][10] are observed in the rectangular aggregates is explained by preferential development of Bjerrum defects along the [001]. Together, these factors provide the electrostatic driving force for water to take an unexpected turn in the low-coverage phase and generate an interesting structure hitherto not observed at a metal surface for a pure water adsorption phase.…”

“…XPS and XAS spectra were obtained using total energy resolution better than 0.3 and 0.1 eV, respectively. Two crystals were mounted with the [001] direction perpendicular to each other in order to enable recording angle-dependent spectra with the E-vector along the [1][2][3][4][5][6][7][8][9][10], [001], and [110] directions. The XAS was recorded in Auger electron yield (AEY) mode at I511 by collecting the Auger electrons resulting from oxygen KVV transitions with a Gammadata-Scienta SES-200 electron energy analyzer.…”

“…These factors influence the structure and bonding of water at metals and determine barriers to dissociation, interaction with multilayer ice, and wetting properties with enormous implications for a number of environmentally and technologically important reactions, from biology to materials science to electrocatalysis and corrosion. [1][2][3][4] Numerous experimental studies, particularly with STM, have revealed complicated variations in the observed or proposed structure of the low-coverage phase of water at different metal surfaces, such as lacey rosettes 5 and honeycomb island structures 6 on Pd(111), from dimers 7 to non-hydrogen-bonded water molecules on Ni(110), 8 hydrogen-bonded cyclic water hexamers at low coverage and low temperatures on Cu(111), Ag(111), and Ru(0001), [9][10][11] zigzag chain or cyclic forms of clusters at low coverage and low temperatures on Cu(110) 12,13 and a proposed chaingrowth of hexamer 12 or pentamer 14 units on Cu(110). The interaction of water with the Cu(110) surface is a particularly interesting case because, although water adsorbs molecularly on this surface at low temperatures, 15 the energy a) Present address: Energy Frontier Research Center, Columbia University, New York, New York 10027, USA.…”