Adsorption compression in surface layers

Abaza, S.; Aranovich, G. L.; Donohue, Marc D.

doi:10.1080/00268976.2011.648963

Cited by 11 publications

(5 citation statements)

References 47 publications

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“…Such compression has been observed by direct in situ experiments; examples include adsorption measurements of the area occupied by a molecule, X-ray diffraction, low energy electron diffraction, and microcalorimetry measurements . This compression has also been observed in molecular simulations. − Such compression is particularly evident for solid substrates having a high surface atomic density, such as carbons. Compression can occur in both the z -direction, normal to the surface, and in the xy plane parallel to the surface.…”

Section: Introductionmentioning

confidence: 89%

Pressure Enhancement in Confined Fluids: Effect of Molecular Shape and Fluid–Wall Interactions

2017

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Recently, several experimental and simulation studies have found that phenomena that normally occur at extremely high pressures in a bulk phase can occur in nanophases confined within porous materials at much lower bulk phase pressures, thus providing an alternative route to study high-pressure phenomena. In this work, we examine the effect on the tangential pressure of varying the molecular shape, strength of the fluid-wall interactions, and pore width, for carbon slit-shaped pores. We find that, for multisite molecules, the presence of additional rotational degrees of freedom leads to unique changes in the shape of the tangential pressure profile, especially in larger pores. We show that, due to the direct relationship between the molecular density and the fluid-wall interactions, the latter have a large impact on the pressure tensor. The molecular shape and pore size have a notable impact on the layering of molecules in the pore, greatly influencing both the shape and scale of the tangential pressure profile.

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Section: Introductionmentioning

confidence: 89%

Pressure Enhancement in Confined Fluids: Effect of Molecular Shape and Fluid–Wall Interactions

2017

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“…A number of papers employed molecular modeling techniques for predictions of adsorption-induced strains in various nanoporous materials: Monte Carlo simulations 40,[81][82][83][84][85][86][87][88][89][90][91][92] or classical density functional theory (DFT). [93][94][95][96] At the same time, several purely analytical theories were also proposed.…”

Section: B Quantitative Thermodynamic Theoriesmentioning

confidence: 99%

Adsorption-induced deformation of nanoporous materials—A review

Gor

Huber

Bernstein

2017

Applied Physics Reviews

214

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When a solid surface accommodates guest molecules, they induce noticeable stresses to the surface and cause its strain. Nanoporous materials have high surface area and, therefore, are very sensitive to this effect called adsorption-induced deformation. In recent years, there has been significant progress in both experimental and theoretical studies of this phenomenon, driven by the development of new materials as well as advanced experimental and modeling techniques. Also, adsorption-induced deformation has been found to manifest in numerous natural and engineering processes, e.g., drying of concrete, water-actuated movement of non-living plant tissues, change of permeation of zeolite membranes, swelling of coal and shale, etc. In this review, we summarize the most recent experimental and theoretical findings on adsorption-induced deformation and present the state-of-the-art picture of thermodynamic and mechanical aspects of this phenomenon. We also reflect on the existing challenges related both to the fundamental understanding of this phenomenon and to selected applications, e.g., in sensing and actuation, and in natural gas recovery and geological CO2 sequestration.

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“…The negative heat of hydrogen adsorption values at adsorbed H 2 volume of 0.3 cm 3 g –1 for some of catalysts might be ascribed to formation of multiple layers of hydrogen adsorption. Abaza et al have reported similar phenomena and found that multiple layers of adsorption and exchanges of molecules between multiple layers of adsorption could cause negative heats of adsorption …”

Section: Resultsmentioning

confidence: 78%

“…Abaza et al have reported similar phenomena and found that multiple layers of adsorption and exchanges of molecules between multiple layers of adsorption could cause negative heats of adsorption. 49 Turnover frequency (TOF) of ethylene hydrogenation at 110 °C for each sample is also presented in Table 2. The ethylene hydrogenation turnover frequencies for all overlayer samples were calculated using measured Pt loading with an assumed Pt dispersion of 100%, while turnover frequencies for all other samples were calculated based on total active sites (from H 2 chemisorption).…”

Section: Methodsmentioning

confidence: 99%

Use of Hydrogen Chemisorption and Ethylene Hydrogenation as Predictors for Aqueous Phase Reforming of Lactose over Ni@Pt and Co@Pt Bimetallic Overlayer Catalysts

et al. 2016

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Overlayer Pt on Ni (Ni@Pt) or Co (Co@Pt) were synthesized and tested for H2 generation from APR of lactose. H2 chemisorption descriptor showed that Ni@Pt and Co@Pt overlayer catalysts had reduced H2 adsorption strength compared to a Pt only catalyst, which agree with computational predictions. The overlayer catalysts also demonstrated lower activity for ethylene hydrogenation than the Pt only catalyst, which likely resulted from decreased H2 binding strength decreasing the surface coverage of H2. XAS results showed that overlayer catalysts exhibited higher white line intensity than the Pt catalyst, which indicates a negative d-band shift for the Pt overlayer, further providing evidence for overlayer formation. Lactose APR studies showed that lactose can be used as feedstock to produce H2 and CO under desirable reaction conditions. The Pt active sites of Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. The results suggest that overlayer formation using directed deposition technique could modify the behavior of the surface metal and ultimately modify the APR activity.

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Adsorption compression in surface layers

Cited by 11 publications

References 47 publications

Pressure Enhancement in Confined Fluids: Effect of Molecular Shape and Fluid–Wall Interactions

Pressure Enhancement in Confined Fluids: Effect of Molecular Shape and Fluid–Wall Interactions

Adsorption-induced deformation of nanoporous materials—A review

Use of Hydrogen Chemisorption and Ethylene Hydrogenation as Predictors for Aqueous Phase Reforming of Lactose over Ni@Pt and Co@Pt Bimetallic Overlayer Catalysts

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