| 1. |
- Cano, Israel, et al.
(författare)
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Blurring the boundary between homogenous and heterogeneous catalysis using palladium nanoclusters with dynamic surfaces
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Using a magnetron sputtering approach that allows size-controlled formation of nanoclusters, we have created palladium nanoclusters that combine the features of both heterogeneous and homogeneous catalysts. Here we report the atomic structures and electronic environments of a series of metal nanoclusters in ionic liquids at different stages of formation, leading to the discovery of Pd nanoclusters with a core of ca. 2 nm surrounded by a diffuse dynamic shell of atoms in [C4C1Im][NTf2]. Comparison of the catalytic activity of Pd nanoclusters in alkene cyclopropanation reveals that the atomically dynamic surface is critically important, increasing the activity by a factor of ca. 2 when compared to compact nanoclusters of similar size. Catalyst poisoning tests using mercury and dibenzo[a,e]cyclooctene show that dynamic Pd nanoclusters maintain their catalytic activity, which demonstrate their combined features of homogeneous and heterogeneous catalysts within the same material. Additionally, kinetic studies of cyclopropanation of alkenes mediated by the dynamic Pd nanoclusters reveal an observed catalyst order of 1, underpinning the pseudo-homogeneous character of the dynamic Pd nanoclusters.
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| 2. |
- Garcia-Quintana, Laura, et al.
(författare)
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Stabilisation of the superoxide anion in bis(fluorosulfonyl)imide (FSI) ionic liquid by small chain length phosphonium cations: Voltammetric, DFT modelling and spectroscopic perspectives
- 2021
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids (ILs) containing the bis(fluorosulfonyl)imide anion, FSI, have been investigated as electrolytes for metal-air batteries. Full chemical reversibility is found for the reduction of oxygen to superoxide at 60 degrees C under short time scale conditions of cyclic voltammetry at a glassy carbon electrode when the IL contains the small chain length triisobutyl(methyl)phosphonium rather than a pyrrolidinium cation. DFT calculations suggest that this is a consequence of the higher ion pair association energy and shorter intermolecular distance associated with the interaction of the superoxide anion with the phosphonium cation. Stabilization on longer timescales was also established by spectroscopic techniques when the phosphonium based ILs were exposed to KO2. Studies on superoxide stability in related ionic liquids containing the triisobutyl(methyl)phosphonium cation with the fluorosulfonyl(trifluoromethanesulfonyl)imide, FTFSI, or bis(trifluoromethanesulfonyl)imide, TFSI, anions are also reported.Y
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| 3. |
- Halat, David M., et al.
(författare)
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Natural abundance solid-state S-33 NMR study of NbS3: applications for battery conversion electrodes
- 2019
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 55:84, s. 12687-12690
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Tidskriftsartikel (refereegranskat)abstract
- We report ultra-wideline, high-field natural abundance solid-state S-33 NMR spectra of the Li-ion battery conversion electrode NbS3, the first S-33 NMR study of a compound containing disulfide (S-2(2-)) units. The large quadrupolar coupling parameters (C-Q approximate to 31 MHz) are consistent with values obtained from DFT calculations, and the spectra provide evidence for the linear Peierls distortion that doubles the number of S-33 sites.
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| 4. |
- Han, S. D., et al.
(författare)
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Solvate Structures and Computational/Spectroscopic Characterization of Lithium Difluoro(oxalato)borate (LiDFOB) Electrolytes
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:11, s. 5521-5531
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Tidskriftsartikel (refereegranskat)abstract
- Lithium difluoro(oxalato)borate (LiDFOB) is a relatively new salt designed for battery electrolyte usage. Limited information is currently available, however, regarding the ionic interactions of this salt (i.e., solvate formation) when it is dissolved in aprotic solvents. Vibrational spectroscopy is a particularly useful tool for identifying these interactions, but only if the vibrational bands can be correctly linked to specific forms of anion coordination. Single crystal structures of LiDFOB solvates have therefore been used to both explore the DFOB-center dot center dot center dot Li+ cation coordination interactions and serve as unambiguous models for the assignment of the Raman vibrational bands. The solvate crystal structures determined indude (monoglyme)(2):LiDFOB, (1,2-diethoxyethane)(3/2):LiDFOB, (acetonitrile)(3):LiDFOB, (acetonitrile)(1):LiDFOB, (dimethyl carbonate)(3/2):LiDFOB, (succinonitrile)(1):LiDFOB, (adiponitrile)(1):LiDFOB, (PMDETA)(1):LiDFOB, (CRYPT-222)(2/3):LiDFOB, and (propylene carbonate)(1):LiDFOB. DFT calculations have been incorporated to provide additional insight into the origin (i.e., vibrational modes) of the Raman vibrational bands to aid in the interpretation of the experimental analysis.
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| 5. |
- Jin, Yanting, et al.
(författare)
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Understanding Fluoroethylene Carbonate and Vinylene Carbonate Based Electrolytes for Si Anodes in Lithium Ion Batteries with NMR Spectroscopy
- 2018
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 140:31, s. 9854-9867
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Tidskriftsartikel (refereegranskat)abstract
- Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are widely used as electrolyte additives in lithium ion batteries. Here we analyze the solid electrolyte interphase (SEI) formed on binder-free silicon nanowire (SiNW) electrodes in pure FEC or VC electrolytes containing 1 M LiPF6by solid-state NMR with and without dynamic nuclear polarization (DNP) enhancement. We find that the polymeric SEIs formed in pure FEC or VC electrolytes consist mainly of cross-linked poly(ethylene oxide) (PEO) and aliphatic chain functionalities along with additional carbonate and carboxylate species. The formation of branched fragments is further confirmed by13C-13C correlation NMR experiments. The presence of cross-linked PEO-type polymers in FEC and VC correlates with good capacity retention and high Coulombic efficiencies of the SiNWs. Using29Si DNP NMR, we are able to probe the interfacial region between SEI and the Si surface for the first time with NMR spectroscopy. Organosiloxanes form upon cycling, confirming that some of the organic SEI is covalently bonded to the Si surface. We suggest that both the polymeric structure of the SEI and the nature of its adhesion to the redox-active materials are important for electrochemical performance.
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| 6. |
- Jonsson, Erlendur, 1983
(författare)
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Ab initio modelling of alkali-ion battery electrolyte properties
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries are omnipresent in modern electronics. They can be found in laptops, mobile phones and electric vehicles. However, there is room for both improvement, as the thermal instability of the dominant lithium salt used in batteries today, LiPF6, causes safety concerns, and more fundamental changes, as there is a limited amount of lithium available – resulting in sodium-ion batteries being a nascent field of study.This thesis looks in detail at some underlying fundamental features affecting properties ofelectrolytes of both lithium-ion and sodium-ion batteries. These properties include the oxidative stability of the anions of the lithium and sodium salts (important for voltage and safety); the cation-anion interaction strength (important for conductivity); the solvation of the lithium and sodium cations in the common carbonate solvents (important for conductivity and the (de-)solvation at the anodes/cathodes); and the thermal stability of the anions and the possible decomposition reactions (important for safety).The properties are mainly studied for a number of both novel and well established anions. Some of the novel anions involve completely new concepts for anion design for alkali-ion battery electrolytes. The systems are studied with a number of ab initio methods, most based on density functional theory (DFT).These include high level calculations of benchmark quality. The applicability of DFT and the selection of DFT functionals is also studied. Novel calculation strategies were employed to understand thermal decomposition.
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| 7. |
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| 8. |
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| 9. |
- Jonsson, Erlendur, 1983, et al.
(författare)
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Electrochemical oxidation stability of anions for modern battery electrolytes: a CBS and DFT study
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:5, s. 3697-3703
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical stability vs. oxidation is a crucial property of anions in order to be suitable as components in lithium-ion batteries. Here the applicability of a number of computational approaches and methods to assess this property, employing a wide selection of DFT functionals, has been studied using the CCSD(T)/CBS method as the reference. In all, the vertical anion oxidation potential, Delta E-v, is a fair way to calculate the stability vs. oxidation, however, a functional of at least hybrid quality is recommended. In addition, the chemical hardness, eta, is identified as a novel approach to calculate the stability vs. oxidation.
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| 10. |
- Jonsson, Erlendur, 1983
(författare)
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Ionic liquids as electrolytes for energy storage applications – A modelling perspective
- 2020
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8297. ; 25, s. 827-835
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Forskningsöversikt (refereegranskat)abstract
- Ionic liquids as electrolytes for energy storage devices is a promising field. Here, the various approaches of how ionic liquids can be modelled are discussed along with how the modelling connects to experimental results. Recent theoretical developments are highlighted along with extended discussion of what molecular dynamics simulation options are now available and what key results can be extracted. Ab initio work is also discussed, this includes some of the spectral properties, both of ionic liquids and their electrolyte formulations.
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