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Hohmann, L., Marks, K., Chien, T.-E., Öström, H., Hansson, T., Muntwiler, M., . . . Harding, D. J. (2024). Effect of Coadsorbed Sulfur on the Dehydrogenation of Naphthalene on Ni(111). The Journal of Physical Chemistry C, 128(1), 67-76
Open this publication in new window or tab >>Effect of Coadsorbed Sulfur on the Dehydrogenation of Naphthalene on Ni(111)
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2024 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 128, no 1, p. 67-76Article in journal (Refereed) Published
Abstract [en]

There are several difficulties when experimentally determined reaction mechanisms are applied from model systems to real catalysis. Besides the infamous pressure and material gaps, it is sometimes necessary to consider impurities in the real reactant feedstock that can act as promoters or catalyst poisons and alter the reaction path. In this study, the effect of sulfur on the dehydrogenation of naphthalene on Ni(111) is investigated by using X-ray photoelectron spectroscopy and scanning tunneling microscopy. Sulfur induces a (5√3 × 2) surface reconstruction, as previously reported in the literature. The sulfur does not have a strong effect on the dehydrogenation temperature of naphthalene. However, the presence of sulfur leads to a preferred formation of carbidic over graphitic carbon and a strong inhibition of carbon diffusion into the nickel bulk, which is one of the steps of destructive whisker carbon formation described in the catalysis literature.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-226125 (URN)10.1021/acs.jpcc.3c04475 (DOI)001141749800001 ()2-s2.0-85180944787 (Scopus ID)
Available from: 2024-02-06 Created: 2024-02-06 Last updated: 2024-02-06Bibliographically approved
Marks, K., Erbing, A., Hohmann, L., Chien, T.-E., Yazdi, M. G., Muntwiler, M., . . . Gothelid, M. (2024). Naphthalene Dehydrogenation on Ni(111) in the Presence of Chemisorbed Oxygen and Nickel Oxide. Catalysts, 14(2), Article ID 124.
Open this publication in new window or tab >>Naphthalene Dehydrogenation on Ni(111) in the Presence of Chemisorbed Oxygen and Nickel Oxide
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2024 (English)In: Catalysts, E-ISSN 2073-4344, Vol. 14, no 2, article id 124Article in journal (Refereed) Published
Abstract [en]

Catalyst passivation through carbon poisoning is a common and costly problem as it reduces the lifetime and performance of the catalyst. Adding oxygen to the feed stream could reduce poisoning but may also affect the activity negatively. We have studied the dehydrogenation, decomposition, and desorption of naphthalene co-adsorbed with oxygen on Ni(111) by combining temperature-programmed desorption (TPD), sum frequency generation spectroscopy (SFG), photoelectron spectroscopy (PES), and density functional theory (DFT). Chemisorbed oxygen reduces the sticking of naphthalene and shifts H2 production and desorption to higher temperatures by blocking active Ni sites. Oxygen increases the production of CO and reduces carbon residues on the surface. Chemisorbed oxygen is readily removed when naphthalene is decomposed. Oxide passivates the surface and reduces the sticking coefficient. But it also increases the production of CO dramatically and reduces the carbon residues. Ni2O3 is more active than NiO.

Keywords
dehydrogenation, decomposition, naphthalene, nickel, oxygen, nickel oxide
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:su:diva-227740 (URN)10.3390/catal14020124 (DOI)001172450400001 ()2-s2.0-85187295000 (Scopus ID)
Available from: 2024-03-26 Created: 2024-03-26 Last updated: 2024-03-26Bibliographically approved
Öström, H., Zhang, B., Vallejo, T., Merrill, B., Huang, J. & LaRue, J. (2022). Methanol decomposition on Ni(111) and O/Ni(111). Journal of Chemical Physics, 156(2), Article ID 024704.
Open this publication in new window or tab >>Methanol decomposition on Ni(111) and O/Ni(111)
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2022 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 156, no 2, article id 024704Article in journal (Refereed) Published
Abstract [en]

Methanol decomposition on Ni(111) surfaces has been studied in the presence and absence of oxygen using temperature-programmed desorption and temperature-dependent sum frequency generation spectroscopy. Under both conditions the C–H and O–H bonds break, forming carbon monoxide and atomic hydrogen on the surface. No C–O bond scission was observed, limiting the number of reaction pathways. The O–H bonds break first (>150 K), forming surface methoxy, followed by C–H bond breakage (>250 K). All atomic hydrogen desorbs from the surface as H2 through H+H recombinative desorption. H2 desorbs at a higher temperature in the presence of oxygen (>300 K) than the absence of oxygen (>250 K) as the oxygen on the surface stabilizes the H atoms, forming surface hydroxide (OH). The surface oxygen also appears to stabilize the O–H and C–H bonds, leading to slightly higher dissociation temperatures. The CO molecules occupy both the bridge sites and the top sites of the Ni atoms as surface H appears to force the CO molecules to the top sites. There is a slight blueshift in the C–O bond vibration for both the O covered and O free surfaces due to CO being more mobile. On the O free surface, the C–O peak width broadens as low-frequency modes are activated. Finally, CO desorbs between 350 and 400 K.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-201897 (URN)10.1063/5.0072396 (DOI)000746468400004 ()35032981 (PubMedID)2-s2.0-85123568337 (Scopus ID)
Available from: 2022-02-09 Created: 2022-02-09 Last updated: 2022-11-14Bibliographically approved
Marks, K., Besharat, Z., Soldemo, M., Önsten, A., Weissenrieder, J., Halldin Stenlid, J., . . . Göthelid, M. (2019). Adsorption and decoposition of ethanol on Cu2O(111) and (100). The Journal of Physical Chemistry C, 123(33), 20384-20392
Open this publication in new window or tab >>Adsorption and decoposition of ethanol on Cu2O(111) and (100)
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 33, p. 20384-20392Article in journal (Refereed) Published
Abstract [en]

Ethanol dehydrogenation on metal oxides such as Cu2O is an important reaction for the production of renewable energy by fuel cells both via the production of H2 fuel and applied in direct alcohol fuel cells. To better understand this reaction we studied the adsorption, dissociation and desorption of ethanol on Cu2O(111) and (100) surfaces using high-resolution photoelectron spectroscopy (PES), vibrational sum frequency generation spectroscopy (SFG), and temperature programmed desorption (TPD) accompanied by density functional theory (DFT) calculations. On Cu2O(100) the first layer consists primarily of dissociatively adsorbed ethoxy. Second and third layers of ethanol physisorb at low temperature and desorb below 200 K. On the Cu2O(111) surface, adsorption is mixed as ethoxy, ethanol and the products following C-C cleavage, CHx and OCHx, are found in the first layer. Upon heating, products following both C-C and C-O bond breaking are observed on both surfaces and continued heating accentuates the molecular cracking. C-O cleavage occurs more on the (100) surface, whereas on the Cu2O(111) C-C cleavage dominates and occurs at lower temperatures than on the (100) surface. The increased ability of Cu2O(111) to crack ethanol is explained by the varied surface structure including both surface oxygen, electron rich O-vacancies and Cu.

National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-171369 (URN)10.1021/acs.jpcc.9b05394 (DOI)000482545700035 ()2-s2.0-85071416412 (Scopus ID)
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2022-11-02Bibliographically approved
Marks, K., Yazdi, M. G., Piskorz, W., Simonov, K., Stefanuik, R., Sostina, D., . . . Öström, H. (2019). Investigation of the surface species during temperature dependent dehydrogenation of naphthalene on Ni(111). Journal of Chemical Physics, 150(24), Article ID 244704.
Open this publication in new window or tab >>Investigation of the surface species during temperature dependent dehydrogenation of naphthalene on Ni(111)
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2019 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 24, article id 244704Article in journal (Refereed) Published
Abstract [en]

The temperature dependent dehydrogenation of naphthalene on Ni(111) has been investigated using vibrational sum-frequency generation spectroscopy, X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory with the aim of discerning the reaction mechanism and the intermediates on the surface. At 110 K, multiple layers of naphthalene adsorb on Ni(111); the first layer is a flat lying chemisorbed monolayer, whereas the next layer(s) consist of physisorbed naphthalene. The aromaticity of the carbon rings in the first layer is reduced due to bonding to the surface Ni-atoms. Heating at 200 K causes desorption of the multilayers. At 360 K, the chemisorbed naphthalene monolayer starts dehydrogenating and the geometry of the molecules changes as the dehydrogenated carbon atoms coordinate to the nickel surface; thus, the molecule tilts with respect to the surface, recovering some of its original aromaticity. This effect peaks at 400 K and coincides with hydrogen desorption. Increasing the temperature leads to further dehydrogenation and production of H-2 gas, as well as the formation of carbidic and graphitic surface carbon. Published under license by AIP Publishing.

National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-170840 (URN)10.1063/1.5098533 (DOI)000473303200040 ()31255092 (PubMedID)2-s2.0-85068220749 (Scopus ID)
Available from: 2019-07-29 Created: 2019-07-29 Last updated: 2022-11-02Bibliographically approved
Nilsson, A., LaRue, J., Öberg, H., Ogasawara, H., Dell'Angela, M., Beye, M., . . . Pettersson, L. G. M. (2017). Catalysis in real time using X-ray lasers. Chemical Physics Letters, 675, 145-173
Open this publication in new window or tab >>Catalysis in real time using X-ray lasers
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2017 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 675, p. 145-173Article in journal (Refereed) Published
Abstract [en]

We describe how the unique temporal and spectral characteristics of X-ray free-electron lasers (XFEL) can be utilized to follow chemical transformations in heterogeneous catalysis in real time. We highlight the systematic study of CO oxidation on Ru(0001), which we initiate either using a femtosecond pulse from an optical laser or by activating only the oxygen atoms using a THz pulse. We find that CO is promoted into an entropy-controlled precursor state prior to desorbing when the surface is heated in the absence of oxygen, whereas in the presence of oxygen, CO desorbs directly into the gas phase. We monitor the activation of atomic oxygen explicitly by the reduced split between bonding and antibonding orbitals as the oxygen comes out of the strongly bound hollow position. Applying these novel XFEL techniques to the full oxidation reaction resulted in the surprising observation of a significant fraction of the reactants at the transition state through the electronic signature of the new bond formation.

National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:su:diva-143458 (URN)10.1016/j.cplett.2017.02.018 (DOI)000400200800025 ()
Available from: 2017-06-07 Created: 2017-06-07 Last updated: 2022-03-23Bibliographically approved
Besharat, Z., Halldin Stenlid, J., Soldemo, M., Marks, K., Önsten, A., Johnson, M., . . . Göthelid, M. (2017). Dehydrogenation of methanol on Cu2O(100) and (111). Journal of Chemical Physics, 146(24), Article ID 244702.
Open this publication in new window or tab >>Dehydrogenation of methanol on Cu2O(100) and (111)
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24, article id 244702Article in journal (Refereed) Published
Abstract [en]

Adsorption and desorption of methanol on the (111) and (100) surfaces of Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120-620 K, in combination with density functional theory calculations and sum frequency generation spectroscopy. The bare (100) surface exhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (root 3 x root 3)R30 degrees-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surface oxygen.

National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-145191 (URN)10.1063/1.4989472 (DOI)000404302600033 ()28668016 (PubMedID)2-s2.0-85021446807 (Scopus ID)
Available from: 2017-07-31 Created: 2017-07-31 Last updated: 2022-10-19Bibliographically approved
Yazdi, M. G., Moud, P. H. H., Marks, K., Piskorz, W., Östrom, H., Hansson, T., . . . Göthelid, M. (2017). Naphthalene on Ni(111): Experimental and Theoretical Insights into Adsorption, Dehydrogenation, and Carbon Passivation. The Journal of Physical Chemistry C, 121(40), 22199-22207
Open this publication in new window or tab >>Naphthalene on Ni(111): Experimental and Theoretical Insights into Adsorption, Dehydrogenation, and Carbon Passivation
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 40, p. 22199-22207Article in journal (Refereed) Published
Abstract [en]

An attractive solution to mitigate tars and also to decompose lighter hydrocarbons in biomass gasification is secondary catalytic reforming, converting hydrocarbons to useful permanent gases. Albeit that it has been in use for a long time in fossil feedstock catalytic steam reforming, understanding of the catalytic processes is still limited. Naphthalene is typically present in the biomass gasification gas and to further understand the elementary steps of naphthalene transformation, we investigated the temperature dependent naphthalene adsorption, dehydrogenation and passivation on Ni(111). TPD (temperature-programmed desorption) and STM (scanning tunneling microscopy) in ultrahigh vacuum environment from 110 K up to 780 K, combined with DFT (density functional theory) were used in the study. Room temperature adsorption results in a flat naphthalene monolayer. DFT favors the dibridge[7] geometry but the potential energy surface is rather smooth and other adsorption geometries may coexist. DFT also reveals a pronounced dearomatization and charge transfer from the adsorbed molecule into the nickel surface. Dehydrogenation occurs in two steps, with two desorption peaks at approximately 450 and 600 K. The first step is due to partial dehydrogenation generating active hydrocarbon species that at higher temperatures migrates over the surface forming graphene. The graphene formation is accompanied by desorption of hydrogen in the high temperature TPD peak. The formation of graphene effectively passivates the surface both for hydrogen adsorption and naphthalene dissociation. In conclusion, the obtained results on the model naphthalene and Ni(111) system, provides insight into elementary steps of naphthalene adsorption, dehydrogenation, and carbon passivation, which may serve as a good starting point for rational design, development and optimization of the Ni catalyst surface, as well as process conditions, for the aromatic hydrocarbon reforming process.

National Category
Physical Sciences
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-149014 (URN)10.1021/acs.jpcc.7b07757 (DOI)000413131700047 ()2-s2.0-85031329487 (Scopus ID)
Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2022-10-20Bibliographically approved
LaRue, J., Krejčí, O., Yu, L., Beye, M., Ng, M. L., Öberg, H., . . . Ogasawara, H. (2017). Real-Time Elucidation of Catalytic Pathways in CO Hydrogenation on Ru. The Journal of Physical Chemistry Letters, 8(16), 3820-3825
Open this publication in new window or tab >>Real-Time Elucidation of Catalytic Pathways in CO Hydrogenation on Ru
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2017 (English)In: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 8, no 16, p. 3820-3825Article in journal (Refereed) Published
Abstract [en]

The direct elucidation of the reaction pathways in heterogeneous catalysis has been challenging due to the short-lived nature of reaction intermediates. Here, we directly measured on ultrafast time scales the initial hydrogenation steps of adsorbed CO on a Ru catalyst surface, which is known as the bottleneck reaction in syngas and CO2 reforming processes. We initiated the hydrogenation of CO with an ultrafast laser temperature jump and probed transient changes in the electronic structure using real-time X-ray spectroscopy. In combination with theoretical simulations, we verified the formation of CHO during CO hydrogenation.

National Category
Chemical Sciences Nano Technology Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:su:diva-147080 (URN)10.1021/acs.jpclett.7b01549 (DOI)000408187400017 ()28759996 (PubMedID)2-s2.0-85027451951 (Scopus ID)
Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2024-07-04Bibliographically approved
Beye, M., Öberg, H., Xin, H., Dakovski, G. L., Dell'Angela, M., Föhlisch, A., . . . Wurth, W. (2016). Chemical Bond Activation Observed with an X-ray Laser. The Journal of Physical Chemistry Letters, 7(18), 3647-3651
Open this publication in new window or tab >>Chemical Bond Activation Observed with an X-ray Laser
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2016 (English)In: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 7, no 18, p. 3647-3651Article in journal (Refereed) Published
Abstract [en]

The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.

National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:su:diva-135185 (URN)10.1021/acs.jpclett.6b01543 (DOI)000383641800019 ()27584914 (PubMedID)2-s2.0-84987786651 (Scopus ID)
Available from: 2016-11-21 Created: 2016-11-01 Last updated: 2024-07-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-3920-6965

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