| 1. |
- Hellman, A, et al.
(författare)
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Predicting catalysis : understanding ammonia synthesis from first-principles calculations
- 2006
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Ingår i: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207. ; 110, s. 17719-17735
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Tidskriftsartikel (refereegranskat)abstract
- Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state theory with or without tunneling corrections, and quantum dynamics) to a range of relevant elementary reaction steps, such as N(2) dissociation, H(2) dissociation, and hydrogenation of the intermediate reactants. A complete kinetic model based on the most relevant elementary steps can be established for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations. Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully integrated tool in the search for the next generation of catalysts.
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| 2. |
- Valdes, A., et al.
(författare)
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Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory
- 2012
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:1, s. 49-70
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Forskningsöversikt (refereegranskat)abstract
- An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals.
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| 3. |
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| 4. |
- Bork, N., et al.
(författare)
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The atomic structure of protons and hydrides in Sm1.92Ca0.08Sn2O7-delta pyrochlore from DFT calculations and FTIR spectroscopy
- 2012
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 112:3
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Tidskriftsartikel (refereegranskat)abstract
- A combined density functional theory and Fourier transform infrared spectroscopy study of the structure and specific site preference of protons and hydrides in the pyrochlore Sm1.92Ca0.08Sn2O7-delta is presented. Two protonic sites of particular high stability are identified, both located on O(1) oxygen atoms closely associated with a Ca dopant. Further, the unexpected presence of Ho hydride defects in undoped, oxygen deficient Sm2Sn2O7 is reported. Finally, the stretching frequencies and relative intensities for these and other sites are calculated. The main features of the Fourier transform infrared spectra are hereby resolved. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737786]
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| 5. |
- Busch, Michael, 1983, et al.
(författare)
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The Influence of Inert Ions on the Reactivity of Manganese Oxides
- 2018
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:1, s. 216-226
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Tidskriftsartikel (refereegranskat)abstract
- Inert ion doping is a possible method to modify electrical conductivity and catalytic activity of transition-metal oxide electrocatalysts. Despite the importance of dopants, little is known about the underlying mechanisms for the change of the system properties. We have performed density functional theory calculations to investigate the influence of different valent ions on the O 2 evolution reaction activity of β-MnO 2 and Mn 2 O 3 . While Mn 2 O 3 is unaffected by dopants, β-MnO 2 is strongly affected by ions placed in a subsurface position. Doping does not affect the ion charge at the active site, but instead it effects the bond character. This is concluded through an analysis of the density overlap regions indicator and the density of states showing that the partially covalent nature of the bonds in β-MnO 2 is responsible for the changes in the adsorbate binding energies. This mechanism is not active in the mostly ionic Mn 2 O 3 . These results highlight the need to explicitly consider the detailed bonding situation and to go beyond simple charge transfer considerations when describing doping of transition metal oxide catalysts.
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| 6. |
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| 7. |
- Rossmeisl, Martin, et al.
(författare)
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Metabolic effects of n-3 PUFA as phospholipids are superior to triglycerides in mice fed a high-fat diet: Possible role of endocannabinoids
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: n-3 polyunsaturated fatty acids, namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), reduce the risk of cardiovascular disease and can ameliorate many of obesity-associated disorders. We hypothesised that the latter effect will be more pronounced when DHA/EPA is supplemented as phospholipids rather than as triglycerides. Methodology/Principal Findings: In a 'prevention study', C57BL/6J mice were fed for 9 weeks on either a corn oil-based high-fat obesogenic diet (cHF; lipids ~35% wt/wt), or cHF-based diets in which corn oil was partially replaced by DHA/EPA, admixed either as phospholipids or triglycerides from marine fish. The reversal of obesity was studied in mice subjected to the preceding cHF-feeding for 4 months. DHA/EPA administered as phospholipids prevented glucose intolerance and tended to reduce obesity better than triglycerides. Lipemia and hepatosteatosis were suppressed more in response to dietary phospholipids, in correlation with better bioavailability of DHA and EPA, and a higher DHA accumulation in the liver, white adipose tissue (WAT), and muscle phospholipids. In dietary obese mice, both DHA/EPA concentrates prevented a further weight gain, reduced plasma lipid levels to a similar extent, and tended to improve glucose tolerance. Importantly, only the phospholipid form reduced plasma insulin and adipocyte hypertrophy, while being more effective in reducing hepatic steatosis and low-grade inflammation of WAT. These beneficial effects were correlated with changes of endocannabinoid metabolome in WAT, where phospholipids reduced 2-arachidonoylglycerol, and were more effective in increasing anti-inflammatory lipids such as N-docosahexaenoylethanolamine. Conclusions/Significance: Compared with triglycerides, dietary DHA/EPA administered as phospholipids are superior in preserving a healthy metabolic profile under obesogenic conditions, possibly reflecting better bioavalability and improved modulation of the endocannabinoid system activity in WAT. © 2012 Rossmeisl et al.
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| 8. |
- Siahrostami, Samira, 1982, et al.
(författare)
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Enabling direct H2O2 production through rational electrocatalyst design
- 2013
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 12:12, s. 1137-1143
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Tidskriftsartikel (refereegranskat)abstract
- Future generations require more efficient and localized processes for energy conversion and chemical synthesis. The continuous on-site production of hydrogen peroxide would provide an attractive alternative to the present state-of-the-art, which is based on the complex anthraquinone process. The electrochemical reduction of oxygen to hydrogen peroxide is a particularly promising means of achieving this aim. However, it would require active, selective and stable materials to catalyse the reaction. Although progress has been made in this respect, further improvements through the development of new electrocatalysts are needed. Using density functional theory calculations, we identify Pt-Hg as a promising candidate. Electrochemical measurements on Pt-Hg nanoparticles show more than an order of magnitude improvement in mass activity, that is, Ag-1 precious metal, for H2O2 production, over the best performing catalysts in the literature.
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| 9. |
- Sjövall, Peter, et al.
(författare)
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Dietary uptake of omega-3 fatty acids in mouse tissue studied by time-of-flight secondary ion mass spectrometry (TOF-SIMS)
- 2015
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 407:17, s. 5101-5111
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Tidskriftsartikel (refereegranskat)abstract
- Dietary intake of omega-3 fatty acids is associated with considerable health benefits, including the prevention of metabolic disorders such as cardiovascular disease and type 2 diabetes. Furthermore, incorporation of the main omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), at the systemic level has been found to be more efficient when these fatty acids are supplied in the form of marine phospholipids compared to triglycerides. In this work, the uptake of omega-3 fatty acids and their incorporation in specific lipids were studied in adipose, skeletal muscle, and liver tissues of mice given high-fat diets with or without omega-3 supplements in the form of phospholipids or triglycerides using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results demonstrate significant uptake of EPA and DHA, and the incorporation of these fatty acids in specific lipid molecules, in all three tissue types in response to the dietary omega-3 supplements. Moreover, the results indicate reduced concentrations of arachidonic acid (AA) and depletion of lipids containing AA in tissue samples from mice given supplementary omega-3, as compared to the control mice. The effect on the lipid composition, in particular the DHA uptake and AA depletion, was found to be significantly stronger when the omega-3 supplement was supplied in the form of phospholipids, as compared to triglycerides. TOF-SIMS was found to be a useful technique for screening the lipid composition and simultaneously obtaining the spatial distributions of various lipid classes on tissue surfaces.
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