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180 results on '"Glezakou, Vassiliki-Alexandra"'

17. Insights into the physical and chemical properties of a cement-polymer composite developed for geothermal wellbore applications

Author

Rod, Kenton A., Nguyen, Manh-Thuong, Elbakhshwan, Mohamed, Gills, Simerjeet, Kutchko, Barbara, Varga, Tamas, Mckinney, Adriana M., Roosendaal, Timothy J., Childers, M. Ian, Zhao, Chonghang, Chen-Wiegart, Yu-chen Karen, Thieme, Juergen, Koech, Phillip K., Um, Wooyong, Chun, Jaehun, Rousseau, Roger, Glezakou, Vassiliki-Alexandra, and Fernandez, Carlos A.

Published
2019
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20. Carbon-supported Pt during aqueous phenol hydrogenation with and without applied electrical potential: X-ray absorption and theoretical studies of structure and adsorbates

Author

Singh, Nirala, Nguyen, Manh-Thuong, Cantu, David C., Mehdi, B. Layla, Browning, Nigel D., Fulton, John L., Zheng, Jian, Balasubramanian, Mahalingam, Gutiérrez, Oliver Y., Glezakou, Vassiliki-Alexandra, Rousseau, Roger, Govind, Niranjan, Camaioni, Donald M., Campbell, Charles T., and Lercher, Johannes A.

Published
2018
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27. Dynamic Copper Site Redispersion through Atom Trapping in Zeolite Defects.

Author

Purdy, Stephen C., Collinge, Gregory, Zhang, Junyan, Borate, Shivangi N., Unocic, Kinga A., Wu, Qiyuan, Wegener, Evan C., Kropf, A. Jeremy, Samad, Nohor River, Yuk, Simuck F., Zhang, Difan, Habas, Susan, Krause, Theodore R., Harris, James W., Lee, Mal-Soon, Glezakou, Vassiliki-Alexandra, Rousseau, Roger, Sutton, Andrew D., and Li, Zhenglong

Published
2024
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31. The role of sub-surface hydrogen on CO2 reduction and dynamics on Ni(110): An ab initio molecular dynamics study.

Author

Allec, Sarah I., Nguyen, Manh-Thuong, Rousseau, Roger, and Glezakou, Vassiliki-Alexandra

Subjects
WATER gas shift reactions, MOLECULAR dynamics, FORMIC acid, CARBON dioxide reduction, HYDROGEN atom, DENSITY functional theory, HYDROGEN
Abstract

The catalytic reduction in carbon dioxide is a crucial step in many chemical industrial reactions, such as methanol synthesis, the reverse water–gas shift reaction, and formic acid synthesis. Here, we investigate the role of bulk hydrogen, where hydrogen atoms are found deep inside a metal surface as opposed to subsurface ones, upon CO2 reduction over a Ni(110) surface using density functional theory and ab initio molecular dynamics simulations. While it has previously been shown that subsurface hydrogen stabilizes CO2 and can aid in overcoming reaction barriers, the role of bulk hydrogen is less studied and thus unknown with regard to CO2 reduction. We find that the presence of bulk hydrogen can significantly alter the electronic structure of the Ni(110) surface, particularly the work function and d-band center, such that CO2 adsorbs more strongly to the surface and is more easily reduced. Our results show an enhanced CO2 dissociation in the presence of bulk hydrogen, shedding light on a hitherto underappreciated mechanistic pathway for CO2 reduction on metal surfaces. [ABSTRACT FROM AUTHOR]

Published
2021
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32. Binding and stability of MgO monomers on anatase TiO2(101).

Author

Doudin, Nassar, Collinge, Greg, Persaud, Rudradatt R., Gurunathan, Pradeep Kumar, Lee, Mal-Soon, Glezakou, Vassiliki-Alexandra, Dixon, David A., Rousseau, Roger, and Dohnálek, Zdenek

Subjects
MONOMERS, SCANNING tunneling microscopy, ELECTRON spectroscopy, MAGNESIUM oxide, TITANIUM dioxide
Abstract

In catalysis, MgO is often used to modify the acid–base properties of support oxides and to stabilize supported metal atoms and particles on oxides. In this study, we show how the sublimation of MgO powder can be used to deposit MgO monomers, hither on anatase TiO2(101). A combination of x-ray electron spectroscopy, high-resolution scanning tunneling microscopy, and density functional theory is employed to gain insight into the MgO monomer binding, electronic and vibrational properties, and thermal stability. In the most stable configuration, the Mg and O of the MgO monomer bind to two surface oxygens and one undercoordinated surface titanium, respectively. The additional binding weakens the Mg–O monomer bond and makes Mg more ionic. The monomers are thermally stable up to 600 K, where the onset of diffusion into the TiO2 bulk is observed. The monomeric MgO species on TiO2(101) represent an ideal atomically precise system with modified acid–base properties and will be employed in our future catalytic studies. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Selective acetylene hydrogenation over single metal atoms supported on Fe3O4(001): A first-principle study.

Author

Yuk, Simuck F., Collinge, Greg, Nguyen, Manh-Thuong, Lee, Mal-Soon, Glezakou, Vassiliki-Alexandra, and Rousseau, Roger

Subjects
HYDROGENATION, ATOMS, METALS, ACETYLENE, DENSITY functional theory, METAL catalysts
Abstract

Supported single-atom catalysts (SACs) have gained increasing attention for improved catalytic activity and selectivity for industrially relevant reactions. In this study, we explore the hydrogenation of acetylene over single Pt, Ru, Rh, Pd, and Ir atoms supported on the Fe3O4(001) surface using density functional theory calculations. The thermodynamic profile of H diffusion is significantly modified by the type of single metal atoms used, suggesting that H spillover from the single atom dopant to the Fe3O4(001) surface is favored and will likely lead to high H coverages of the functioning catalyst. Correspondingly, as the surface H coverage increases, the important desorption step of ethylene becomes energetically competitive against the detrimental hydrogenation steps of ethylene to ethane. A kinetic model is employed to explore how the activity and selectivity of SACs toward ethylene production change as a function of mass of the catalyst loaded into a flow reactor. Overall, we show that the selectivity of SACs toward ethylene production can be tuned by considering the proper type of metal and controlling the redox state of the support. [ABSTRACT FROM AUTHOR]

Published
2020
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36. Enhancing CO2 Transport Across a PEEK‐Ionene Membrane and Water‐Lean Solvent Interface.

Author

Walter, Eric D., Zhang, Difan, Chen, Ying, Sung Han, Kee, Bazak, J. David, Burton, Sarah, O'Harra, Kathryn, Hoyt, David W., Bara, Jason E., Malhotra, Deepika, Allec, Sarah I., Glezakou, Vassiliki‐Alexandra, Heldebrant, David J., and Rousseau, Roger

Subjects
POLYETHER ether ketone, SOLVENTS, CARBON sequestration, KIRKENDALL effect, CARBAMIC acid, ATMOSPHERIC boundary layer
Abstract

Efficient direct air capture (DAC) of CO2 will require strategies to deal with the relatively low concentration in the atmosphere. One such strategy is to employ the combination of a CO2‐selective membrane coupled with a CO2 capture solvent acting as a draw solution. Here, the interactions between a leading water‐lean carbon‐capture solvent, a polyether ether ketone (PEEK)‐ionene membrane, CO2, and combinations were probed using advanced NMR techniques coupled with advanced simulations. We identify the speciation and dynamics of the solvent, membrane, and CO2, presenting spectroscopic evidence of CO2 diffusion through benzylic regions within the PEEK‐ionene membrane, not spaces in the ionic lattice as expected. Our results demonstrate that water‐lean capture solvents provide a thermodynamic and kinetic funnel to draw CO2 from the air through the membrane and into the bulk solvent, thus enhancing the performance of the membrane. The reaction between the carbon‐capture solvent and CO2 produces carbamic acid, disrupting interactions between the imidazolium (Im+) cations and the bistriflimide anions within the PEEK‐ionene membrane, thereby creating structural changes through which CO2 can diffuse more readily. Consequently, this restructuring results in CO2 diffusion at the interface that is faster than CO2 diffusion in the bulk carbon‐capture solvent. [ABSTRACT FROM AUTHOR]

Published
2023
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42. Sulfonated polybenzimidazole membrane with graphene oxide additive for 2,3-butanediol/water separation: A molecular simulation.

Author

Zhang, Difan, Glezakou, Vassiliki-Alexandra, and Rousseau, Roger

Subjects
*GRAPHENE oxide, *COMPOSITE membranes (Chemistry), *DENSITY functional theory, *MEMBRANE separation, *MOLECULAR dynamics
Abstract

Membrane separation for 2,3-butanediol (2,3-BDO) recovery from fermentation broth is highly valued for sustainable and renewable processes, but it requires efficient membrane materials. This work evaluates the sulfonated polybenzimidazole (sPBI) and its graphene oxide (GO) doped composite membrane for separating 2,3-BDO and water via atomistic simulations. Density functional theory calculations are applied to identify various forms of sPBI structures and quantify their binding interactions with 2,3-BDO and water. Classical molecular dynamic simulations are used to evaluate the structural changes, diffusivity, and selectivity of 2,3-BDO and water in different sPBI models, GO surfaces, and GO-doped sPBI composite models. Our results suggest that sPBI slightly increases the crystallinity of the membrane structures, enhances the adsorption strength for both 2,3-BDO and water, and improves the water/2,3-BDO selectivity by 2–3 times. The GO surfaces display a maximum selectivity at a surface coverage of 0.1–0.15 for both hydroxyl and epoxy surface groups. The addition of GO flakes to sPBI creates new interaction sites for 2,3-BDO and water at the interface of sPBI and GO, and the water/2,3-BDO selectivity of GO-doped sPBI models is further increased up to 3 times. This work illustrates how the integrated addition of sPBI and GO flakes offers a promising approach to selective separation of 2,3-BDO and water, providing theoretical guidance for polybenzimidazole-based membranes in the potential application of 2,3-BDO recovery. [Display omitted] • Sulfonated polybenzimidazole (sPBI) improves binding strength with water and 2,3-butanediol. • The sPBI increases the membrane crystallinity and enhances water/2,3-butanediol selectivity by 2–3 times. • Graphene oxide (GO) demonstrates maximum selectivity at 0.1–0.15 surface coverages. • GO-added sPBI shows a cumulative increase of water/2,3-butanediol selectivity by a factor of up to 7. [ABSTRACT FROM AUTHOR]

Published
2025
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