| 1. |
- Anikina, Ekaterina, et al.
(författare)
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Li-decorated carbyne for hydrogen storage : charge induced polarization and van't Hoff hydrogen desorption temperature
- 2020
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Ingår i: Sustainable Energy & Fuels. - : ROYAL SOC CHEMISTRY. - 2398-4902. ; 4:2, s. 691-699
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Tidskriftsartikel (refereegranskat)abstract
- We have studied carbyne as a promising hydrogen storage material. Density functional theory simulations with vdW corrections have been used to investigate lithium sorption on carbyne and the interaction of pristine and Li-functionalized carbon chains with molecular hydrogen. We showed that Li adatoms at small concentrations stay atomically dispersed on carbyne, donating 0.9e to the chain. Moreover, in the presence of Li, hydrogen adsorption energy increases by more than 5 times in comparison with pristine carbyne. Overall, up to three hydrogen molecules per Li adatom have an adsorption energy close to the range of 200-600 meV per H-2, which is necessary for effective sorption/desorption cycles. The resulting theoretical uptake (7.1 wt%) is higher than the U.S. Department of Energy's ultimate goal (6.5 wt%). The calculated van't Hoff desorption temperatures exceed considerably the boiling point of liquid nitrogen. Our results confirm the potential of Li-decorated carbyne for hydrogen storage.
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| 2. |
- Anikina, E. V., et al.
(författare)
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Influence of Kubas-type interaction of B–Ni codoped graphdiyne with hydrogen molecules on desorption temperature and storage efficiency
- 2020
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Ingår i: Materials Today Energy. - : Elsevier. - 2468-6069. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated functionalized 2D carbon allotrope, graphdiyne (GDY), as a promising hydrogen storage media. Density functional theory with a range of vdW corrections was employed to study Ni decoration of pristine and boron-doped GDY and the interaction of resulting structures with molecular hydrogen. We showed that boron-doped GDY is thermally stable at 300 K, though, its synthesis requires an endothermic reaction. Also, boron doping enhances Ni binding with the graphdiyne by increasing the charge transfer from Ni to GDY. Ni doping drastically influenced hydrogen adsorption energies: they rise from ~70 meV per H2 molecule on pristine GDY to a maximum of 1.29 eV per H2 becoming too high in value for room temperature reversible applications. Boron doping improves the situations: in this case, after Ni decoration desorption temperature estimation is ~300–500 K. Overall, each Ni adatom on B-doped GDY can bind only one H2 molecule within the needed energy range, which gives low hydrogen uptake (~1.2 wt%). However, doping with boron led to the decrease in the value of hydrogen adsorption energy and good desorption temperature estimations, therefore, codoping of metal atoms and boron could be an effective strategy for other transition metals.
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| 3. |
- Banerjee, Amitava, et al.
(författare)
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Reaction Coordinate Mapping of Hydrogen Evolution Mechanism on Mg3N2Monolayer
- 2020
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199 .- 1879-3487.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this work, we have envisaged the hydrogen evolution reaction (HER) mechanism on Mg3N2 monolayer based on electronic structure calculations within the framework of density functional theory (DFT) formalism. The semiconducting nature of Mg3N2 monolayer motivates us to investigate the HER mechanism on this sheet. We have constructed the reaction coordinate associated with HER mechanism after determining the hydrogen adsorption energy on Mg3N2 monolayer, while investigating all possible adsorption sites. After obtaining the adsorption energy, we subsequently obtain the adsorption free energy while adding zero point energy difference (Delta ZPE) and entropic contribution (T Delta S). We have not only confined our investigations to a single hydrogen, but have thoroughly observed the adsorption phenomena for increasing number of hydrogen atoms on the surface. We have determined the projected density of states (DOS) in order to find the elemental contribution in the valence band and conduction band regime for all the considered cases. We have also compared the work function value among all the cases, which quantifies the amount of energy required for taking an electron out of the surface. The charge transfer mechanism is also being investigated in order to correlate with the HER mechanism with amount of charge transfer. This is the first attempt on this material to the best of our knowledge, where theoretical investigation has been done to mapping the reaction coordinate of HER mechanism with the associated charge transfer process and the work function values, not only for single hydrogen adsorption, but also for increasing number of adsorbed hydrogen.
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| 4. |
- Birkeland, Kåre I., et al.
(författare)
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Heart failure and chronic kidney disease manifestation and mortality risk associations in type 2 diabetes : A large multinational cohort study
- 2020
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Ingår i: Diabetes, obesity and metabolism. - : John Wiley & Sons. - 1462-8902 .- 1463-1326. ; 22:9, s. 1607-1618
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Tidskriftsartikel (refereegranskat)abstract
- Aims To examine the manifestation of cardiovascular or renal disease (CVRD) in patients with type 2 diabetes (T2D) initially free from CVRD as well as the mortality risks associated with these diseases.Methods Patients free from CVRD were identified from healthcare records in England, Germany, Japan, the Netherlands, Norway and Sweden at a fixed date. CVRD manifestation was defined by first diagnosis of cardiorenal disease, or a stroke, myocardial infarction (MI) or peripheral artery disease (PAD) event. The mortality risk associated with single CVRD history of heart failure (HF), chronic kidney disease (CKD), MI, stroke or PAD was compared with that associated with CVRD-free status.Results Of 1 177 896 patients with T2D, 772 336 (66%) were CVRD-free and followed for a mean of 4.5 years. A total of 137 081 patients (18%) developed a first CVRD manifestation, represented by CKD (36%), HF (24%), stroke (16%), MI (14%) and PAD (10%). HF or CKD was associated with increased cardiovascular and all-cause mortality risk: hazard ratio (HR) 2.02 (95% confidence interval [CI] 1.75-2.33) and HR 2.05 (95% CI 1.82-2.32), respectively. HF and CKD were separately associated with significantly increased mortality risks, and the combination was associated with the highest cardiovascular and all-cause mortality risk: HRs 3.91 (95% CI 3.02-5.07) and 3.14 (95% CI 2.90-3.40), respectively.Conclusion In a large multinational study of >750 000 CVRD-free patients with T2D, HF and CKD were consistently the most frequent first cardiovascular disease manifestations and were also associated with increased mortality risks. These novel findings show these cardiorenal diseases to be important and serious complications requiring improved preventive strategies.
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| 5. |
- Wang, Huan, et al.
(författare)
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Effect of Cycling Ion and Solvent on the Redox Chemistry of Substituted Quinones and Solvent-Induced Breakdown of the Correlation between Redox Potential and Electron-Withdrawing Power of Substituents
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:25, s. 13609-13617
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Tidskriftsartikel (refereegranskat)abstract
- Quinones have a capacity for high energy storage and exhibit facile and reversible electrochemistry in several widely different electrolytes. They are, therefore, one of the most popular compounds currently used in organic materials based electrical energy storage. Quinone electrochemistry is, however, strongly affected by the composition of the electrolyte. This report summarizes our systematic investigation of the redox chemistry of a series of quinones with electron-withdrawing and electron-donating substituents in aqueous solution and in acetonitrile (MeCN) with tetrabutylammonium (TBA+)-, Li+-, and H+-based electrolytes. As a general trend, proton cycling, TBA+ cycling, and Li+ cycling resulted in the highest, the lowest, and intermediate redox potentials, respectively. We attribute this trend to stabilization of the reduced state, namely benzene-1,4-bis(olate) (Q2–), by the different counterions. Density functional theory (DFT) calculations showed that, in the fully reduced state, two Li+ counterions accommodated 35% of the injected electron charges while proton counterions accommodated 69% of the injected charge, thus significantly stabilizing the reduced state. However, with the bulky TBA+ as the cycling ion, this stabilization was not possible and the reduction potential was decreased. In addition, we showed that stabilization of the counterion also affected the Coulombic interaction between the successively injected charges, resulting in the well-known disproportionation of the semiquinone radical intermediate state with proton cycling, while Li+ and TBA+ cycling generally resulted in two consecutive redox reactions. Finally, we showed that the electrolyte strongly influences the effects of substitution with electron-donating and electron-withdrawing substituents. A strong relationship between the redox potential and the electron-withdrawing power of the substituent was observed in the MeCN solution. However, this relationship was completely lost in aqueous solution. The reason for the loss of the relationship was addressed using a DFT explicit-solvent model and is discussed.
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| 6. |
- Yang, X., et al.
(författare)
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Structural Insight of the Frailty of 2D Janus NbSeTe as an Active Photocatalyst
- 2020
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 12:23, s. 6013-6023
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Tidskriftsartikel (refereegranskat)abstract
- A new family of 2D materials, Janus MTeSe (M=Nb, Mo, or W) pristine and defective monolayers have been investigated in this work as promising catalysts for hydrogen evolution reaction (HER) based on first-principles calculations. It has been observed that these Janus monolayers are dynamically and thermodynamically stable. Hybrid exchange-correlation functional (HSE06) based electronic structures reveal Janus NbTeSe is a polarized semiconductor with an indirect bandgap of 1.478 eV with excellent optical absorption capability near infra-red region. While MoTeSe and WTeSe monolayers are direct bandgap semiconductors with a suitable bandgap of 1.859 and 1.898 eV. The carrier effective masses and mobilities in MTeSe monolayer are also calculated. Subsequently, the catalytic activity of pristine as well as defective MTeSe for HER has been identified from the reaction coordinate based on the adsorption free energy ((Formula presented.)). It is noticed that the Nb based Janus layer has comparatively weak HER activity than its peers, group VIB transition metals, Mo, W based Janus layer. The Coulomb attraction between the hydrogen and the monolayer decreases with the increase of the inner atomic radius from Nb, Mo to W, which is one of the structural frailties of 2D Janus NbSeTe as an active photocatalyst. We have further analyzed electronic structures and charge density distributions of pristine and defective MTeSe with/without H adatom to unveil the reason of the catalytic inferiority for Nb based Janus layer over W and Mo based systems. This comparative study of Janus MTeSe monolayers with HSE06 would provide a deep understanding of Janus based HER catalyst.
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