Sorption isosteres and isotherms of silver on NBG-17 graphite

Walton, Kyle L.; Jacobson, Nathan; Kowalski, Benjamin A.; Brockman, John D.; Loyalka, Sudarshan K.

doi:10.1016/j.jnucmat.2021.153264

Cited by 5 publications

(7 citation statements)

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“…A recent study reported the heat of Ag vapor adsorption versus coverage on graphite measured using equilibrium adsorption isosteres at very high temperatures, 72 but that approach seems unreasonable given the strong thermodynamic driving force for Ag on graphene to agglomerate into large particles as shown in Figures 4 and 5 above. Indeed, the Ag particles in that study were found to have diameters of a few hundred nanometers, and the sample had a lot of alumina particulate impurity.…”

Section: Experimental Methodsmentioning

confidence: 99%

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

2022

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Interest in the use of carbon supports for late transition metal nanoparticle catalysts has expanded rapidly due to the increasing importance of electrocatalysts for clean energy and environmental technologies and the use and storage of renewable electricity. Compared to oxide supports, almost nothing is known about the effect of metal nanoparticle size on the energies of the metal atoms within carbon-supported nanoparticles, yet these energies are crucial for understanding their surface reactivity and sintering kinetics. Here, the growth morphology and adsorption energetics of vapor-deposited Ag onto clean graphene/Ni(111) surfaces have been studied using a combination of single-crystal adsorption calorimetry (SCAC) and He+ low-energy ion scattering (LEIS). The differential heat of Ag adsorption is 207 kJ/mol for making ∼30 atom Ag particles on graphene terraces at 100 K and 16 kJ/mol higher for making ∼9 atom Ag clusters at defect sites at the same temperature. The heat of adsorption increases rapidly with Ag coverage as 3D Ag nanoparticles nucleate and grow in size, asymptotically reaching within 5 kJ/mol of the bulk Ag sublimation enthalpy (285 kJ/mol) by 2 ML. The heats of adsorption and Ag nanoparticle densities from LEIS (∼1016/m2) were combined to provide the Ag/graphene adhesion energy (E adh = 1.8 J/m2 in the large-particle limit) and the Ag chemical potential (μ) versus effective particle diameter (D). The Ag chemical potential was well-fitted by μ(D) = (3γv/M – E adh)(1 + (1.5 nm)/D)(2V m/D), where γv/M is the surface energy of bulk Ag and V m is its molar volume. The same equation is known to fit similar data for late transition metals on clean surfaces of metal oxide single crystals. The adhesion energy of Ag measured here on graphene falls within the wide range measured for Ag on those oxide surfaces and is almost as large as on the oxide that binds Ag particles most strongly, namely CeO2(111), which is well-known to be very effective at resisting catalyst deactivation by metal sintering. These results imply that carbon supports will be effective at resisting sintering and that Ag particles smaller than 6 nm on graphene will bind small adsorbed reaction intermediates more weakly than supports with weaker adhesion to Ag, like MgO(100).

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Section: Experimental Methodsmentioning

confidence: 99%

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

2022

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“…(Myers, et al, 1974) Many of the values in Table 3 were determined from historical nuclear graphites, so they may vary somewhat from the properties of modern graphites (for example: IG-110, PCEA, NBG-17). There are no experimentally determined values for silver sorption on matrix material; therefore, NBG-17 graphite parameters extracted from Walton et al (2021) were used. As the model provided in the literature for silver was obtained in a limited temperature range and concentrations well above those observed here, the parameters obtained provided nonphysical results for these conditions.…”

Section: One-dimensional Finite-element Methods Modelmentioning

confidence: 99%

“…As the model provided in the literature for silver was obtained in a limited temperature range and concentrations well above those observed here, the parameters obtained provided nonphysical results for these conditions. Instead of using the parameters as derived by Walton et al (2021), a bounded regression was used to estimate model parameters which are shown in Table 3, though the regression obtained is not of high confidence.…”

Section: One-dimensional Finite-element Methods Modelmentioning

confidence: 99%

Status of Modifications to the AGR-3/4 Fission Product Transport Model

Riet

2023

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“…The loading dependence of partial pressures of the vapor species can be used to derive a sorption isotherm. Walton et al 319 have examined Langmuir, IAEA‐Freundlich, and IAEA‐isotherm models for Ag desorption from NBG‐17 graphite powders. For this particular case, Langmuir and IAEA‐isotherm models gave the best fit.…”

Section: Novel Applications Of Kemsmentioning

confidence: 99%

“…Hilpert et al have studied the sorption of Sr and Cs on graphitic materials 317,318 using KEMS. Seelig et al 129 and Walton et al 319 have used KEMS to study sorption of Ag on graphitic materials. Other methods can, of course, be used to study sorption, but KEMS has proven to be very versatile for these applications given its high sensitivity.…”

Section: Novel Applications Of Kemsmentioning

confidence: 99%

Knudsen effusion mass spectrometry: Current and future approaches

Jacobson,

Colle,

Stolyarova

et al. 2024

Rapid Comm Mass Spectrometry

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RationaleKnudsen effusion mass spectrometry (KEMS) has been a powerful tool in physical chemistry since 1954. There are many excellent reviews of the basic principles of KEMS in the literature. In this review, we focus on the current status and potential growth areas for this instrumental technique.MethodsWe discuss (1) instrumentation, (2) measurement techniques, and (3) selected novel applications of the technique. Improved heating methods and temperature measurement allow for better control of the Knudsen cell effusive source. Accurate computer models of the effusive beam and its introduction to the ionizer allow optimization of such parameters as sensitivity and removal of background signals. Computer models of the ionizer allow for optimized sensitivity and resolution. Additionally, data acquisition systems specifically tailored to a KEMS system permit improved quantity and quality of data.ResultsKEMS is traditionally utilized for thermodynamic measurements of pure compounds and solutions. These measurements can now be strengthened using first principles and model‐based computational thermochemistry. First principles can be used to calculate accurate Gibbs energy functions (gefs) for improving third law calculations. Calculated enthalpies of formation and dissociation energies from ab initio methods can be compared to those measured using KEMS. For model‐based thermochemistry, solution parameters can be derived from measured thermochemical data on metallic and nonmetallic solutions. Beyond thermodynamic measurements, KEMS has been used for many specific applications. We select examples for discussion: measurements of phase changes, measurement/control of low‐oxygen potential systems, thermochemistry of ultrahigh‐temperature ceramics, geological applications, nuclear applications, applications to organic and organometallic compounds, and thermochemistry of functional room temperature materials, such as lithium ion batteries.ConclusionsWe present an overview of the current status of KEMS and discuss ideas for improving KEMS instrumentation and measurements. We discuss selected KEMS studies to illustrate future directions of KEMS.

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Sorption isosteres and isotherms of silver on NBG-17 graphite

Cited by 5 publications

References 20 publications

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

Size-Dependent Adsorption and Adhesion Energetics of Ag Nanoparticles on Graphene Films on Ni(111) by Calorimetry

Status of Modifications to the AGR-3/4 Fission Product Transport Model

Knudsen effusion mass spectrometry: Current and future approaches

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