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BETA
Hermansson, Kersti, ProfessorORCID iD iconorcid.org/0000-0003-2352-0458
Alternative names
Publications (10 of 232) Show all publications
Du, D., Kullgren, J., Kocmaruk, B., Hermansson, K. & Broqvist, P. (2020). Simulated temperature programmed desorption experiments for calcined nanoceria powders. Journal of Catalysis, 384, 252-259
Open this publication in new window or tab >>Simulated temperature programmed desorption experiments for calcined nanoceria powders
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2020 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 384, p. 252-259Article in journal (Refereed) Published
Abstract [en]

Density functional theory calculations (DFT), coupled with microkinetic modelling, have been used to simulate Temperature Programmed Desorption (TPD) experiments for calcined ceria nanopowders with the aim to gain insight into the chemistry governing their high redox activity. Our simulations consider two main nanoparticle models. One is a perfect ceria octahedron supercharged with adsorbed oxygen molecules turned into superoxide ions, as has previously been used to explain the enhanced oxygen storage capacity (OSC) in nanoceria. The other model is a variant where we have introduced oxygen vacancies under ridge Ce ions, thereby reducing their coordination numbers to five. The results from our microkinetic modelling suggest that including such five-coordinated Ce adsorption sites results in a TPD spectrum that better matches the experimental counterpart in terms of both peak position and width. In addition, this new structural model allows for the co-existence of Ce3+ ions, superoxide ions and O-2 molecules, as seen in experiments in the literature.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-382449 (URN)10.1016/j.jcat.2019.12.042 (DOI)000525490600023 ()
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)eSSENCE - An eScience Collaboration
Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2020-05-26Bibliographically approved
Röckert, A., Kullgren, J., Broqvist, P., Alwan, S. & Hermansson, K. (2020). The water/ceria(111) interface: Computational overview and new structures. Journal of Chemical Physics, 152(10), Article ID 104709.
Open this publication in new window or tab >>The water/ceria(111) interface: Computational overview and new structures
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2020 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 152, no 10, article id 104709Article in journal (Refereed) Published
Abstract [en]

Thin film structures of water on the CeO2(111) surface for coverages between 0.5 and 2.0 water monolayers have been optimized and analyzed using density functional theory (optPBE-vdW functional). We present a new 1.0 ML structure that is both the lowest in energy published and features a hydrogen-bond network extending the surface in one-dimension, contrary to what has been found in the literature, and contrary to what has been expected due to the large bulk ceria cell dimension. The adsorption energies for the monolayer and multilayered water structures agree well with experimental temperature programmed desorption results from the literature, and we discuss the stability window of CeO2(111) surfaces covered with 0.5-2.0 ML of water. 

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2020
National Category
Theoretical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-408511 (URN)10.1063/1.5142724 (DOI)000519631300002 ()32171203 (PubMedID)
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Available from: 2020-04-09 Created: 2020-04-09 Last updated: 2020-04-09Bibliographically approved
Kettner, M., Duchon, T., Wolf, M. J., Kullgren, J., Senanayake, S. D., Hermansson, K., . . . Nehasil, V. (2019). Anion-mediated electronic effects in reducible oxides: Tuning the valence band of ceria via fluorine doping. Journal of Chemical Physics, 151(4), Article ID 044701.
Open this publication in new window or tab >>Anion-mediated electronic effects in reducible oxides: Tuning the valence band of ceria via fluorine doping
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2019 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 4, article id 044701Article in journal (Refereed) Published
Abstract [en]

Combining experimental spectroscopy and hybrid density functional theory calculations, we show that the incorporation of fluoride ions into a prototypical reducible oxide surface, namely, ceria(111), can induce a variety of nontrivial changes to the local electronic structure, beyond the expected increase in the number of Ce3+ ions. Our resonant photoemission spectroscopy results reveal new states above, within, and below the valence band, which are unique to the presence of fluoride ions at the surface. With the help of hybrid density functional calculations, we show that the different states arise from fluoride ions in different atomic layers in the near surface region. In particular, we identify a structure in which a fluoride ion substitutes for an oxygen ion at the surface, with a second fluoride ion on top of a surface Ce4+ ion giving rise to F 2p states which overlap the top of the O 2p band. The nature of this adsorbate F--Ce4+ resonant enhancement feature suggests that this bond is at least partially covalent. Our results demonstrate the versatility of anion doping as a potential means of tuning the valence band electronic structure of ceria.

National Category
Theoretical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-393127 (URN)10.1063/1.5109955 (DOI)000478625700040 ()31370552 (PubMedID)
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Note

M. Kettner, T. Duchoň, and M. J. Wolf contributed equally to this work.

Available from: 2019-09-24 Created: 2019-09-24 Last updated: 2019-09-24Bibliographically approved
Broqvist, P., Kullgren, J., Zhang, C., Mitev, P. D. & Hermansson, K. (2019). Chemistry of Complex Materials. In: : . Paper presented at Swedish eScience Academy.
Open this publication in new window or tab >>Chemistry of Complex Materials
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2019 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395887 (URN)
Conference
Swedish eScience Academy
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25
Bako, I., Daru, J., Pothoczki, S., Pusztai, L. & Hermansson, K. (2019). Effects of H-bond asymmetry on the electronic properties of liquid water: An AIMD analysis. Journal of Molecular Liquids, 293, Article ID 111579.
Open this publication in new window or tab >>Effects of H-bond asymmetry on the electronic properties of liquid water: An AIMD analysis
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2019 (English)In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 293, article id 111579Article in journal (Refereed) Published
Abstract [en]

The effects of an asymmetric environment on the electronic properties of a water molecule in liquid water are in focus in this paper and were analysed from ab initio molecular dynamics simulations of liquid water at 300 and 350 K with the BLYP-D3 functional. We make the following observations. (1) The electronic DOS and the net molecular charge are more affected by the asymmetry of the water molecule's H-bond surroundings than by the number of H-bonded neighbours. The reverse is true for the dipole moment. (2) For all three properties, a 3-coordinated water molecule is more perturbed by accepting two H-bonds and donating one than by donating two and accepting one. (3) This order is not maintained in the calculated XES spectrum, which is less straightforward to interpret in terms of structure-property relationships than the DOS spectrum.

Keywords
Liquid water, Ab initio-MD simulations, Electronic properties, Density of states, Molecular dipole moments
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-397684 (URN)10.1016/j.molliq.2019.111579 (DOI)000494052700064 ()
Funder
Swedish Research Council
Available from: 2019-11-22 Created: 2019-11-22 Last updated: 2019-11-22Bibliographically approved
Kebede, G., Mitev, P. D., Broqvist, P., Eriksson, A. & Hermansson, K. (2019). Fifty Shades of Water: Benchmarking DFT Functionals against Experimental Data for Ionic Crystalline Hydrates. Journal of Chemical Theory and Computation, 15(1), 584-594
Open this publication in new window or tab >>Fifty Shades of Water: Benchmarking DFT Functionals against Experimental Data for Ionic Crystalline Hydrates
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2019 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 15, no 1, p. 584-594Article in journal (Refereed) Published
Abstract [en]

We propose that crystalline ionic hydrates constitute a valuable resource for benchmarking theoretical methods for aqueous ionic systems. Many such structures are known from the experimental literature, and they contain a large variety of water–water and ion–water structural motifs. Here we have collected a data set (CRYSTALWATER50) of 50 structurally unique "in-crystal" water molecules, involved in close to 100 nonequivalent O–H···O hydrogen bonds. A dozen well-known DFT functionals were benchmarked with respect to their ability to describe these experimental structures and their OH vibrational frequencies. We find that the PBE, RPBE-D3, and optPBE-vdW methods give the best H-bond distances and that anharmonic OH frequencies generated from B3LYP//optPBE-vdW energy scans outperform the other methods, i.e., here we performed B3LYP energy scans along the OH stretching coordinate while the rest of the structure was kept fixed at the optPBE-vdW-optimized positions.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-347222 (URN)10.1021/acs.jctc.8b00423 (DOI)000455558200051 ()30380849 (PubMedID)
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Note

Title in thesis list of papers: Fifty shades of water: Benchmarking DFT functionals against diffraction and spectroscopic data for crystalline hydrates

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2019-02-19Bibliographically approved
Du, D., Kullgren, J., Hermansson, K. & Broqvist, P. (2019). From Ceria Clusters to Nanoparticles: Superoxides and Supercharging. The Journal of Physical Chemistry C, 123(3), 1742-1750
Open this publication in new window or tab >>From Ceria Clusters to Nanoparticles: Superoxides and Supercharging
2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 3, p. 1742-1750Article in journal (Refereed) Published
Abstract [en]

Several studies have reported a dramatically increased oxygen storage capacity (OSC) for small ceria nanoparticles (∼5 nm). Both experiments and theory have correlated this effect with superoxide ion formation. In previous studies, density functional theory (DFT) calculations with the PBE+U density functional have been used, and the obtained results were only in qualitative agreement with the experimental observations. One severe problem is the underbinding of the O2 molecule upon superoxide ion formation, which suggests that such species should not exist above room temperature. In this work, we use hybrid DFT functional to resolve this problem. We find that the discrepancy between theory and experiment originates from an incorrect estimate of the energy associated with the localized f-electrons with respect to the oxygen p-levels. By using average O2 adsorption energies from hybrid DFT calculations, extrapolated to large nanoparticles (3−10 nm), in conjunction with first-order desorption kinetics, we find that superoxide ions are indeed stable on nanosized ceria well above room temperature, in accordance with experiments.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-377356 (URN)10.1021/acs.jpcc.8b08977 (DOI)000457067500025 ()
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)eSSENCE - An eScience Collaboration
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-04-24Bibliographically approved
Cheng, C., Zhang, X., Yang, Z. & Hermansson, K. (2019). Identification of High-Performance Single-Atom MXenes Catalysts for Low-Temperature CO Oxidation. ADVANCED THEORY AND SIMULATIONS, 2(8), Article ID 1900006.
Open this publication in new window or tab >>Identification of High-Performance Single-Atom MXenes Catalysts for Low-Temperature CO Oxidation
2019 (English)In: ADVANCED THEORY AND SIMULATIONS, ISSN 2513-0390, Vol. 2, no 8, article id 1900006Article in journal (Refereed) Published
Abstract [en]

On the basis of first-principles calculations, Fe, Co, Ni, Cu, Zn, Ru, Rh, Ag, Ir, Pt, and Au decorated Mo2CO2-delta monolayers are investigated as potential single-atom catalyst (SAC) candidates for low-temperature CO oxidation reaction. From a first screening based on intuitive criteria concerning metal sintering, CO poisoning, and O-2 adsorption strength, the Zn/Mo2CO2-delta system is selected for further scrutiny by means of reactivity calculations for different CO concentrations. A lower barrier is found for Eley-Rideal reaction mechanism than for the Langmuir-Hinshelwood mechanism. The low Eley-Rideal barrier (0.15 eV) is attributed to the fact that the Zn atom weakens the O-O bond considerably and the electrophilic attack of CO weakens it further. The main conclusion is that this system is a promising low-temperature SAC candidate with a lower energy barrier for CO oxidation than noble metal and other 2D SAC systems investigated.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2019
Keywords
density functional theory, low-temperature CO oxidation, Mo2CO2, MXene, screening, single-atom catalysts
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-393342 (URN)10.1002/adts.201900006 (DOI)000478744400001 ()
Funder
Swedish Research Council
Available from: 2019-09-27 Created: 2019-09-27 Last updated: 2019-09-27Bibliographically approved
Kim, B.-H., Kullgren, J., Wolf, M. J., Hermansson, K. & Broqvist, P. (2019). Multiscale Modeling of Agglomerated Ceria Nanoparticles: Interface Stability and Oxygen Vacancy Formation. Frontiers in Chemistry, 7, Article ID 203.
Open this publication in new window or tab >>Multiscale Modeling of Agglomerated Ceria Nanoparticles: Interface Stability and Oxygen Vacancy Formation
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2019 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 7, article id 203Article in journal (Refereed) Published
Abstract [en]

The interface formation and its effect on redox processes in agglomerated ceria nanoparticles (NPs) have been investigated using a multiscale simulation approach with standard density functional theory (DFT), the self-consistent-charge density functional tight binding (SCC-DFTB) method, and a DFT-parameterized reactive force-field (ReaxFF). In particular, we have modeled Ce40O80 NP pairs, using SCC-DFTB and DFT, and longer chains and networks formed by Ce40O80 or Ce132O264 NPs, using ReaxFF molecular dynamics simulations. We find that the most stable {111}/{111} interface structure is coherent whereas the stable {100}/{100} structures can be either coherent or incoherent. The formation of {111}/{111} interfaces is found to have only a very small effect on the oxygen vacancy formation energy, E-vac. The opposite holds true for {100}/{100} interfaces, which exhibit significantly lower E-vac values than the bare surfaces, despite the fact that the interface formation eliminates reactive {100} facets. Our results pave the way for an increased understanding of ceria NP agglomeration.

Place, publisher, year, edition, pages
FRONTIERS MEDIA SA, 2019
Keywords
multiscale modeling, density functional theory, self-consistent charge density functional tight binding, reducible oxides, cerium dioxide, nanoparticles, agglomeration
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-385974 (URN)10.3389/fchem.2019.00203 (DOI)000468727800001 ()
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)eSSENCE - An eScience Collaboration
Available from: 2019-06-19 Created: 2019-06-19 Last updated: 2019-06-19Bibliographically approved
Sassolini, A., Colozza, N., Papa, E., Hermansson, K., Cacciotti, I. & Arduini, F. (2019). Screen-printed electrode as a cost-effective and miniaturized analytical tool for corrosion monitoring of re-inforced concrete. Electrochemistry communications, 98, 69-72
Open this publication in new window or tab >>Screen-printed electrode as a cost-effective and miniaturized analytical tool for corrosion monitoring of re-inforced concrete
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2019 (English)In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 98, p. 69-72Article in journal (Refereed) Published
Abstract [en]

Herein, we report the first electrochemical sensor based on a screen-printed electrode designed to evaluate the corrosion level in iron-reinforced concrete specimens. The combination of an Ag pseudoreference electrode with a gel polymeric electrolyte allows for fast, stable and cost-effective potentiometric measurements, suitable for evaluating the corrosion of iron bars embedded in concrete samples. The sensor was found to be capable of discriminating between a standard non-corroded sample and samples subject to corrosion due to the presence of chloride or carbonate in the concrete matrix. The potential in concrete-based specimens containing carbonate (pH 9, - 0.35 +/- 0.03 V) or chloride (4% w/w, - 0.52 +/- 0.01 V) was found to be more negative than in a standard concrete-based sample ( - 0.251 +/- 0.003 V), in agreement with the ASTM standard C876 method which uses a classical Cu/CuSO4 solid reference electrode. Our results demonstrate that a printed Ag pseudoreference electrode combined with KC1 agar provides an efficient and reliable electrochemical system for evaluating the corrosion of iron bars embedded in concrete-based structures.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-372642 (URN)10.1016/j.elecom.2018.11.023 (DOI)000454898600015 ()
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2352-0458

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