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| 3. |
- Amann, Peter, et al.
(författare)
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The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 376:6593, s. 603-608
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Tidskriftsartikel (refereegranskat)abstract
- The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO2/CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO2/CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO2 methanol synthesis.
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| 4. |
- Askelöf, M, et al.
(författare)
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Eating behaviour and body image in overweight adolescent girls with or without hyperandrogenicity
- 2007
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Ingår i: Eating and Weight Disorders. - 1124-4909 .- 1590-1262. ; 12:1, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- We addressed the question of whether a combination of obesity and hyperandrogenicity has a more severe influence on psychosocial behaviours, as reflected by eating behaviour and body image, compared to obesity alone. AIM: To study eating behaviour and body image in age-, pubertal- and BMI-matched overweight adolescent girls with and without hyperandrogenicity, and to compare the data with those from a control group of normal weight girls. METHODS: Overweight adolescent girls in late puberty with (n=10) and without hyperandrogenicity (n=8) and a control group of normal weight girls (n=9) were studied. The Eating Disorder Inventory for children (EDI-C) questionnaire was used to obtain information on eating behaviours and psychological characteristics, and silhouettes were used to evaluate body image. RESULTS: The girls with overweight but without hyperandrogenicity showed more disturbed eating behaviour and more psychological problems than did the girls with both overweight and hyperandrogenicity as compared to the healthy controls. The overweight group also had more feelings of ineffectiveness than the hyperandrogenic group. Both the overweight and the hyperandrogenic girls estimated themselves as being significantly larger and their ideal shape as being significantly smaller than their Current shape. However, all overweight girls considered their Current shape to be significantly smaller than it was objectively. CONCLUSIONS: The girl With overweight alone seemed to have more disturbed eating behaviour and more psychological problems than girls with combined overweight and hyperandrogenicity. This could indicate that different therapeutic interventions might be needed in attempts to reduce weight in the two groups.
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| 5. |
- Bagger, Alexander, et al.
(författare)
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Ab Initio Cyclic Voltammetry on Cu(111), Cu(100) and Cu(110) in Acidic, Neutral and Alkaline Solutions
- 2019
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reactions depend on the electrochemical interface between the electrode surfaces and the electrolytes. To control and advance electrochemical reactions there is a need to develop realistic simulation models of the electrochemical interface to understand the interface from an atomistic point-of-view. Here we present a method for obtaining thermodynamic realistic interface structures, a procedure we use to derive specific coverages and to obtain ab initio simulated cyclic voltammograms. As a case study, the method and procedure is applied in a matrix study of three Cu facets in three different electrolytes. The results have been validated by direct comparison to experimental cyclic voltammograms. The alkaline (NaOH) cyclic voltammograms are described by H* and OH*, while in neutral medium (KHCO3) the CO3* species are dominating and in acidic (KCl) the Cl* species prevail. An almost one-to-one mapping is observed from simulation to experiments giving an atomistic understanding of the interface structure of the Cu facets. Atomistic understanding of the interface at relevant eletrolyte conditions will further allow realistic modelling of electrochemical reactions of importance for future eletrocatalytic studies.
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| 6. |
- Halldin Stenlid, Joakim, et al.
(författare)
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Electrochemical Interface during Corrosion of Copper in Anoxic Sulfide-Containing Groundwater-A Computational Study
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:1, s. 469-481
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of copper is an expensive degradation process of materials in engineered infrastructures and in various technical applications. It is also an important factor in the geological disposal of spent nuclear fuel, where sulfide-induced corrosion is expected to be the predominant chemical degradation process of copper canisters used for encapsulation and isolation of the radioactive material from the biosphere. One aspect of the corrosion process that is still under intense research is the corrosion morphology and how it might be affected by the composition of the groundwater. Using density functional theory, we investigate the electrochemical interface of corroding copper in aqueous solutions containing sulfides, with and without the presence of Cl-, HCO3-, and SO42- anions. Through state-of-the-art electrochemical models, we account for the effects of pH, concentrations, and potential on the interfacial structure and composition. Results are presented for the Cu(110) surface facet and compared to the (110) and (001) facets of chalcocite (Cu2S), i.e., the main product of sulfide-induced corrosion. It is found that at low potentials, H dominates on all surfaces, and at high potentials, sulfides. In the intermediate ranges, the surfaces differ with sulfides prevailing on Cu, while adsorbed H2O, Cl, or H dominate on Cu2S. The results are summarized as surface Pourbaix diagrams and are generally applicable in corrosion science and electrochemistry. The implications of the study are discussed in light of the expected conditions of planned spent nuclear fuel repositories in Sweden, Finland, and Canada.
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| 7. |
- Halldin Stenlid, Joakim, et al.
(författare)
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On the Nature of the Cathodic Reaction during Corrosion of Copper in Anoxic Sulfide Solutions
- 2019
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:6, s. C196-C208
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Tidskriftsartikel (refereegranskat)abstract
- Sulfide-induced corrosion is expected to be the dominating long-term corrosion process for copper containers in technical concepts for deep geological disposal of spent nuclear fuel (SNF), adapted in several waste management programs around the world. The present study investigates the atomic-scale mechanism of the cathode side of the corrosion reaction using Density Functional Theory (DFT) calculations. Despite the central role of the reaction, neither the site of reaction nor the active species has been previously established. Here we compare the cathodic reaction leading to H-2-evolution on pure copper and on chalcocite (Cu2S) surfaces. The considered H-donors are OH-/H2O and HS-/H2S which are all available at the neutral to alkaline conditions anticipated at the SNF disposal sites. Assuming Volmer-Tafel-Heyrovsky kinetics, we find that the cathodic reactions are many orders of magnitude faster on copper compared to copper sulfide. Although we find that HS-/H2S have lower reaction barriers than H2O, our kinetic analysis suggest that H2O is expected to be the main H-source for the cathodic reaction under SNF repository conditions as results of the low sulfide concentrations (less than or similar to 10 mu M) expected in SNF repositories in Sweden, Finland and Canada.
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| 8. |
- Halldin Stenlid, Joakim, et al.
(författare)
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Properties of interfaces between copper and copper sulphide/oxide films
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- We compare different means of predicting and rationalizing properties of corrosion films aiming at gaining deeper understanding of the behaviour of copper in aqueous and sulphide-containing environments. Purely geometrical tools ranging from mean bulk information to anisotropic and facet-specific approaches are discussed, and their performances compared against DFT-based stability and property evaluations of a range of interfaces arising from combining low-index crystallographic planes of the compounds Cu, Cu2O, and Cu2S. We demonstrate the necessity to consider facet-specific interactions to understand nanolevel differences between Cu2S and Cu2O film behaviour, and that thin films cannot be directly described by bulk properties.
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| 9. |
- Halldin Stenlid, Joakim, et al.
(författare)
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Uncovering the electrochemical interface of low-index copper surfaces in deep groundwater environments
- 2020
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 362
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Tidskriftsartikel (refereegranskat)abstract
- Using a combination of a sophisticated modeling protocol and well-established electrochemical techniques, we unravel the chemical composition of the low-index surfaces of copper in groundwater environments at different ion concentrations, pHs, and redox potentials. By carefully linking density functional theory (DFT) and cyclic voltammetry (CV), we are able to extract fundamental information on interfaces of broad significance. Herein, we focus on the case of groundwater found in deep geological environments of importance to the planned constructions of disposal repositories for spent nuclear fuel around the world. Within the error margins of DFT, we can assign adsorption structures and compositions to the current peaks of the CVs. It is found that among the groundwater ions of main interest (i.e. sulfide, bisulfide, sulfate, chloride and bicarbonate), sulfides (HS-, S2-) bind strongest to the surface, and are likely to dominate at the interfaces under the deep geological conditions relevant for repositories of spent nuclear fuel.
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| 10. |
- Halldin-Stenlid, M, et al.
(författare)
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Akutbehandling av nyfödda barn
- 2005
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Ingår i: Anestesi. Chapter 38. - : Liber Stockholm. ; , s. 445-450
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Bokkapitel (refereegranskat)
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| 11. |
- Hedström, Svante, et al.
(författare)
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Photodriven CO dimerization on Cu2O from an electronic-structure perspective
- 2020
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry (RSC). - 2398-4902. ; 4:2, s. 670-677
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemically driven CO2 reduction into alcohols and hydrocarbons is a topic of intense study. Photocatalytic approaches, which instead are powered by light, are also reported, but these generally rely on two-component catalysts and yield only moderately reduced products with a single carbon atom. In this report, we use density functional theory, including its linear-response time-dependent implementation, to investigate the feasibility of photocatalytically driving the dimerization of CO chemisorbed on Cu2O, a crucial step in the chemical conversion of CO2 into C-2 products, such as ethanol and ethylene. We find that CO dimerization into OCCO is greatly aided by the photoinduced population of a low-lying LUMO that is bonding with respect to the C-C bond of two adjacently chemisorbed CO molecules.
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| 12. |
- Holm, Alexander, et al.
(författare)
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Nanoscale Spatial Distribution of Supported Nanoparticles Controls Activity and Stability in Powder Catalysts for CO Oxidation and Photocatalytic H2 Evolution
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:34, s. 14481-14494
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Tidskriftsartikel (refereegranskat)abstract
- Supported metal nanoparticles are essential components of high-performing catalysts, and their structures are intensely researched. In comparison, nanoparticle spatial distribution in powder catalysts is conventionally not quantified, and the influence of this collective property on catalyst performance remains poorly investigated. Here, we demonstrate a general colloidal self-assembly method to control uniformity of nanoparticle spatial distribution on common industrial powder supports. We quantify distributions on the nanoscale using image statistics and show that the type of nanospatial distribution determines not only the stability, but also the activity of heterogeneous catalysts. Widely investigated systems (Au–TiO2 for CO oxidation thermocatalysis and Pd–TiO2 for H2 evolution photocatalysis) were used to showcase the universal importance of nanoparticle spatial organization. Spatially and temporally resolved microkinetic modeling revealed that nonuniformly distributed Au nanoparticles suffer from local depletion of surface oxygen, and therefore lower CO oxidation activity, as compared to uniformly distributed nanoparticles. Nanoparticle spatial distribution also determines the stability of Pd–TiO2 photocatalysts, because nonuniformly distributed nanoparticles sinter while uniformly distributed nanoparticles do not. This work introduces new tools to evaluate and understand catalyst collective (ensemble) properties in powder catalysts, which thereby pave the way to more active and stable heterogeneous catalysts.
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| 14. |
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| 15. |
- Tissot, H., et al.
(författare)
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Acetic acid conversion to ketene on Cu 2 O(1 0 0): Reaction mechanism deduced from experimental observations and theoretical computations
- 2021
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 402, s. 154-165
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Tidskriftsartikel (refereegranskat)abstract
- Ketene, a versatile reagent in production of fine and specialty chemicals, is produced from acetic acid. We investigate the synthesis of ketene from acetic acid over the (3,0;1,1) surface of Cu2O(1 0 0) through analysis of the adsorption and desorption characteristics of formic and acetic acids. The results allow us to establish a reaction mechanism for ketene formation. Observations from x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy, and temperature programmed desorption (TPD), supported by a comparison with formic acid results, suggest that acetic acid reacts with Cu2O through deprotonation to form acetate species coordinated to copper sites and hydroxylation of nearby surface oxygen sites. For formic acid the decomposition of adsorbed formate species results in desorption of CO2 and CO while, for acetic acid, high yields of ketene are observed at temperature >500 K. Modeling by density functional theory (DFT) confirms the strong interaction of acetic acid with the (3,0;1,1) surface and the spontaneous dissociation into adsorbed acetate and hydrogen atom species, the latter forming an OH-group. In an identified reaction intermediate ketene binds via all C and O atoms to Cu surface sites, in agreement with interpretations from XPS. In the vicinity of the adsorbate the surface experiences a local reorganization into a c(2 × 2) reconstruction. The total computed energy barrier for ketene formation is 1.81 eV in good agreement with the 1.74 eV obtained from TPD analysis. Our experimental observations and mechanistic DFT studies suggests that Cu2O can operate as an efficient catalyst for the green generation of ketene from acetic acid.
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| 16. |
- Tissot, Heloise, et al.
(författare)
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Acetic acid conversion to ketene on Cu2O(100) : Reaction mechanism deduced from experimental observations and theoretical computations
- 2021
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 402, s. 154-165
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Tidskriftsartikel (refereegranskat)abstract
- Ketene, a versatile reagent in production of fine and specialty chemicals, is produced from acetic acid. We investigate the synthesis of ketene from acetic acid over the (3,0;1,1) surface of Cu2O(1 0 0) through analysis of the adsorption and desorption characteristics of formic and acetic acids. The results allow us to establish a reaction mechanism for ketene formation. Observations from x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy, and temperature programmed desorption (TPD), supported by a comparison with formic acid results, suggest that acetic acid reacts with Cu2O through deprotonation to form acetate species coordinated to copper sites and hydroxylation of nearby surface oxygen sites. For formic acid the decomposition of adsorbed formate species results in desorption of CO2 and CO while, for acetic acid, high yields of ketene are observed at temperature >500 K. Modeling by density functional theory (DFT) confirms the strong interaction of acetic acid with the (3,0;1,1) surface and the spontaneous dissociation into adsorbed acetate and hydrogen atom species, the latter forming an OH-group. In an identified reaction intermediate ketene binds via all C and O atoms to Cu surface sites, in agreement with interpretations from XPS. In the vicinity of the adsorbate the surface experiences a local reorganization into a c(2 × 2) reconstruction. The total computed energy barrier for ketene formation is 1.81 eV in good agreement with the 1.74 eV obtained from TPD analysis. Our experimental observations and mechanistic DFT studies suggests that Cu2O can operate as an efficient catalyst for the green generation of ketene from acetic acid.
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