Nanoscopic characterization of the water vapor-salt interfacial layer reveals a unique biphasic adsorption process

Yang, Liu; He, Jianfeng; Shen, Yi; Li, Xiaowei; Sun, Jian; Czajkowsky, Daniel M.; Shao, Zongshu

doi:10.1038/srep31688

Cited by 3 publications

(4 citation statements)

References 42 publications

(57 reference statements)

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“…After the advent of AFM, topography images of NaCl, KBr, and other alkali halide surfaces were obtained in controlled RH conditions. − Some of these studies reported the movement of the steps on NaCl to start at around 40–45% RH at RT and associated it with the formation of the liquid solvation layer (also called hydration layer for water) on the surface, in agreement with the transition from the first domain to the second domain found in ref and with infrared spectroscopy measurements in ref . The surface properties such as contact potential and friction coefficient change upon the formation of this liquid layer. , On a more recent study, it was claimed that no dissolution of ions takes place below 30% RH . For KBr, this transition was reported around 55% HR, and both the moving steps and the formation of the hydration layer were observed above this threshold. , In another recent study, large defects created by poking the KBr surface with an AFM tip were investigated .…”

Section: Introductionsupporting

confidence: 75%

“… 16 , 17 On a more recent study, it was claimed that no dissolution of ions takes place below 30% RH. 20 For KBr, this transition was reported around 55% HR, 11 and both the moving steps and the formation of the hydration layer were observed above this threshold. 16 , 21 In another recent study, large defects created by poking the KBr surface with an AFM tip were investigated.…”

Section: Introductionmentioning

confidence: 94%

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Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

2022

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Using atomic force microscopy in the pressure range of 10 –10 mbar to several tens of mbar at room temperature, we demonstrate the restructuring of nanostructured KBr surfaces assisted by the presence of water, methanol, and ethanol vapors and the formation of solvation islands. On a flat KBr surface, the two-dimensional solvation islands start nucleating at the step edges and grow with time and with increasing relative pressure. Solvation islands of water wet the terraces; however, solvation islands of methanol and ethanol are localized around the step edges and do not wet the terraces. Two processes are observed on nanostructured KBr surfaces: the movement of the atomic steps and the formation of solvation islands. The first process takes place at comparatively lower pressures at around 1% relative pressure, whereas the second process starts at higher pressures at around 25% relative pressure and above. Furthermore, the second process takes place only after the complete relocation of the step edges and thereby formation of a nearly flat surface. This implies that there is a competition between the restructuring of the atomic steps and solvation layer formation, as both processes require solvated ions. Unlike in the case of a flat surface, solvation islands of alcohols wet the restructured surface due to a higher density of low-coordination sites.

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Section: Introductionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 94%

Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

2022

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“…The adsorption of water on the cleavage face of various alkali halides (NaCl, KCl, KBr, KI) has been also studied as a function of humidity. It was found that a characteristic relative humidity value (CRH) exist that separates two water adsorption regimes identified by their strong differences in surface ionic conductivity [78,79] (Fig. 12a).…”

Section: Water On Saltsmentioning

confidence: 99%

Water at surfaces and interfaces: From molecules to ice and bulk liquid

Shimizu

Maier

Verdaguer

et al. 2018

Progress in Surface Science

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The structure and growth of water films on surfaces is reviewed, starting from single molecules, two-dimensional wetting layers, and liquid interfaces. This progression follows the increase in temperature and vapor pressure environmental conditions from a few degrees Kelvin in ultra-high vacuum, where Scanning Tunneling and Atomic Force Microscopies (STM and AFM) provide crystallographic information at the molecular level, to ambient conditions where surface sensitive spectroscopic techniques provide electronic structure information. We show how single molecules bind to metal and non-metal surfaces, their diffusion and aggregation. We examine how water molecules can be manipulated by the STM tip via excitation of vibrational and electronic modes, which trigger molecular diffusion and dissociation. We review also the adsorption and structure of water on non-metal substrates including mica, alkali halides, and others under ambient humid conditions. We finally review recent progress in the exploration of the molecular level structure of solid-liquid interfaces, which impact our fundamental understanding of corrosion and electrochemical processes. variety of names: atomic force microscopy (AFM) and its variants of contact and non-contact), lateral friction, and attractive electrostatic force microscopies, known as scanning polarization force microscopy (SPFM) and Kelvin Probe Force Microscopy (KPFM). The non-contact attractive AFM modes allow us to observe water films formed on solids with minimal disruption. We will first discuss adsorption configurations, diffusion, aggregation, and dissociation of water on metal surfaces induced thermally, vibrationally and electronically using STM. These topics were reviewed also by Hodgson and Haq in 2009 [3] from the theoretical point of view. We then move to formation of larger clusters and monolayers. The discussion of the "ice" layers is followed by liquid water films minerals (salts, oxides) in ambient conditions. In the last section, we also review recent studies of liquid water near a solid, electrified surface. Here the knowledge obtained from X-ray absorption spectroscopy (XAS) has proved useful for better understanding of atomistic pictures of electrochemical processes. Single molecules: diffusion, aggregation, dissociation Water on metal surfaces at low coverage-monomers and small clusters STM studies of adsorption of water on metal surfaces started in the early 2000's, with noble metals, including Au, Ag, Cu, and more reactive transition metals, such as Pt, Pd, Rh, Ru have been used as substrates. The first observation of individual water molecules was reported in 2001 by Lauhon and Ho [4] on Cu(001) using low-temperature STM. They pointed out several phenomena occurring during imaging of adsorbed water: 1) stable clusters form at relatively low coverage, 2) imaging of small clusters (less than 6 molecules) often leads to the tip inducing molecular motions, and 3) large clusters have internal structures that are often difficult to resolve. Morgenstern et al. [5-9] st...

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“…12,13 The adsorption of water on solid surfaces is of general interest from both fundamental and applied perspectives but the adsorption of water on nonoxide ionic substrates is not well understood, although some investigations have been carried out on NaCl. 18 The reported CaF 2 adsorbents usually have relatively low Brunauer−Emmett−Teller (BET) surface areas, generally lower than 35 m 2 g −1 , resulting in low wateradsorption capacities. 11 In addition, the effects of the surface area and morphology of CaF 2 on water-adsorption properties have not been systematically investigated yet.…”

Section: ■ Introductionmentioning

confidence: 99%

Preparation of CaF₂ Microspheres with Nanopetals for Water Vapor Adsorption

et al. 2020

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The hierarchically structured flower-like CaF2 microspheres with nanopetals, named FL-CaF2, were synthesized via a hydrothermal method using calcium acetate Ca(Ac)2 and NaBF4 as calcium and fluorine sources, respectively, assisted by the chelating reagent trisodium citrate (Na3Cit) with the optimal pH of the synthesis solution. Meanwhile, a reference sample, named FL-CaF2-R, was reproduced using ethylenediaminetetraacetic acid disodium salt (Na2EDTA) as the chelating reagent, based on the recipe and synthesis procedure from the literature. Various techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, and N2 adsorption–desorption at 77 K were then used to characterize the synthesized samples. The results show that FL-CaF2 with a larger diameter has a much higher thermal stability than FL-CaF2-R because the larger the nanocrystallite size, the higher the thermal stability. The adsorption of water vapor on CaF2 is irreversible because CaF2 can interact with the adsorbed water molecules strongly. The dual-site Langmuir model was used to describe the measured adsorption isotherms of water vapor on FL-CaF2 at low water vapor pressures and 298, 308, and 318 K. FL-CaF2 has a much higher water-adsorption capacity than those reported in the literature. Furthermore, the isosteric heat of adsorption as a function of loading, derived from the measured isotherms, varies from ca. 46 to 43 kJ mol–1 in the whole loading range investigated. Finally, the applications of FL-CaF2 are anticipated in the dehydration of hydrogen fluoride gas as well as in catalysis.

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Nanoscopic characterization of the water vapor-salt interfacial layer reveals a unique biphasic adsorption process

Cited by 3 publications

References 42 publications

Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

Water at surfaces and interfaces: From molecules to ice and bulk liquid

Preparation of CaF₂ Microspheres with Nanopetals for Water Vapor Adsorption

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Nanoscopic characterization of the water vapor-salt interfacial layer reveals a unique biphasic adsorption process

Cited by 3 publications

References 42 publications

Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

Water Vapor and Alcohol Vapor Induced Healing of the Nanostructured KBr Surface

Water at surfaces and interfaces: From molecules to ice and bulk liquid

Preparation of CaF2 Microspheres with Nanopetals for Water Vapor Adsorption

Contact Info

Product

Resources

About

Preparation of CaF₂ Microspheres with Nanopetals for Water Vapor Adsorption