| 1. |
- Singh, Deobrat, et al.
(författare)
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Harnessing the unique properties of MXenes for advanced rechargeable batteries
- 2021
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Ingår i: JPhys Energy. - : IOP Publishing. - 2515-7655. ; 3:1
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Forskningsöversikt (refereegranskat)abstract
- In recent years, two-dimensional MXenes have been emerged as potential electrode materials for rechargeable batteries due to their unique properties such as exceptional safety, significant interlayer spacing, environmental flexibility, large surface area, high electrical conductivity, and excellent thermal stability. This review examined all of the recent advances in the field of MXenes and their composites (hybrid structures), which are found to be useful for the electrochemical applications of advanced rechargeable batteries. The main focus of this review is on metal-ion batteries and lithium-sulfur (Li-S) batteries. It is intended to show that the combination of recent improvements in the synthesis and characterization, greater control of the interlayer distance, and new MXene composites, together serve as an emerging and potential way for energy storage applications.
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| 2. |
- Kaewmaraya, T., et al.
(författare)
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Novel green phosphorene as a superior chemical gas sensing material
- 2021
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 401
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Tidskriftsartikel (refereegranskat)abstract
- Green phosphorus and its monolayer variant, green phosphorene (GreenP), are the recent members of two-dimensional (2D) phosphorus polymorphs. The new polymorph possesses the high stability, tunable direct bandgap, exceptional electronic transport, and directionally anisotropic properties. All these unique features could reinforce it the new contender in a variety of electronic, optical, and sensing devices. Herein, we present gas-sensing characteristics of pristine and defected GreenP towards major environmental gases (i. e., NH3, NO, NO2, CO, CO2, and H2O) using combination of the density functional theory, statistical thermodynamic modeling, and the non-equilibrium Green's function approach (NEGF). The calculated adsorption energies, density of states (DOS), charge transfer, and Crystal Orbital Hamiltonian Population (COHP) reveal that NO, NO2, CO, CO2 are adsorbed on GreenP, stronger than both NH3 and H2O, which are weakly physisorbed via van der Waals interactions. Furthermore, substitutional doping by sulfur can selectively intensify the adsorption towards crucial NO2 gas because of the enhanced charge transfer between p orbitals of the dopant and the analyte. The statistical estimation of macroscopic measurable adsorption densities manifests that the significant amount of NO2 molecules can be practically adsorbed at ambient temperature even at the ultra-low concentration of part per billion (ppb). In addition, the current-voltage (I–V) characteristics of S-doped GreenP exhibit a variation upon NO2 exposure, indicating the superior sensitivity in sensing devices. Our work sheds light on the promising application of the novel GreenP as promising chemical gas sensors.
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| 3. |
- Li, Jibiao, et al.
(författare)
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Chemical Bonding of Unique CO on Fe(100)
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:16, s. 9062-9074
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Tidskriftsartikel (refereegranskat)abstract
- At low coverage, CO molecules are known to preferentially occupy the hollow sites of Fe(100) with considerably inclined molecular orientations. This CO configuration serves as the precursor state of CO dissociation, which is particularly important in several important catalytic reactions. In this study, we present a unique bonding picture of the precursor state from the spin, charge, and orbital perspectives. From the spin and orbital views, we show the antiferromagenetic nature of the adsorbate-metal coupling, where 2 pi magnetism prevails with a dominant spin-down channel. However, contrasting tendencies are found for the two 1 pi orbitals in two orthogonal directions: the 1 pi orbital in the vertical plane loses its symmetry, whereas the other 1 pi orbital remains intact with a preserved symmetry. The 1 pi symmetry in the vertical plane favors the 1 pi -> 2 pi* excitation mechanism owing to the partial opening up of the 1 pi symmetry. In the charge perspective, we have identified a charge transfer mechanism involving the local structural Fe-I(C)-C-O motif, in which the surface slightly charges the adsorbate with additional partial electrons located at the surface Fe atoms bonded to the carbon end, whereas the charges of the metallic atoms beneath the Fe-I(C)-C-O motif are found to be depleted. In both the adsorbate and metal sides, the depletion of s electrons serves as a good measure of orbital repulsion and delocalization. Interestingly, the carbon and oxygen ends exhibit contrasting electron affinity with the metal surface: the carbon end is attractive, whereas the oxygen end is repulsive in terms of the contrasting charge rearrangement in the bonded metallic atoms.
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| 4. |
- Magnuson, Martin, et al.
(författare)
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Anisotropy in the electronic structure of V2GeC investigated by soft x-ray emission spectroscopy and first-principles theory
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:035117
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Tidskriftsartikel (refereegranskat)abstract
- Theanisotropy of the electronic structure of ternary nanolaminate V2GeC isinvestigated by bulk-sensitive soft x-ray emission spectroscopy. The measured polarization-dependentemission spectra of V L2,3, C K, Ge M1, and Ge M2,3 in V2GeCare compared with those from monocarbide VC and pure Ge.The experimental emission spectra are interpreted with calculated spectra usingab initio density-functional theory including dipole transition matrix elements. Differenttypes of covalent chemical bond regions are revealed: V 3d-C 2p bondingat −3.8 eV, Ge 4p-C 2p bonding at −6 eV, and Ge 4p-C 2s interaction mediatedvia the V 3d orbitals at −11 eV below the Fermi level.We find that the anisotropic effects are high for the4p valence states and the shallow 3d core levels ofGe, while relatively small anisotropy is detected for the V 3dstates. The macroscopic properties of the V2GeC nanolaminate result fromthe chemical bonds with the anisotropic pattern as shown inthis work.
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| 5. |
- Singh, Deobrat, et al.
(författare)
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Carbon-phosphide monolayer with high carrier mobility and perceptible: I - V response for superior gas sensing
- 2020
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1369-9261 .- 1144-0546. ; 44:9, s. 3777-3785
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Tidskriftsartikel (refereegranskat)abstract
- Monolayered carbon phosphide (CP), with semi-metallic electrical conductivity and graphene-like Dirac cone responses, has attracted significant attention from the advanced nanoelectronics community, for use in gas sensing devices. The CP monolayer exhibits semi-metallic behavior in the x-direction and semi-conducting behavior in the y-direction. With the presence of graphene-like Dirac cones, it holds highly anisotropic carrier mobility characteristics. Here, we introduce the first-principle theoretical calculations for understanding the adsorption mechanism of different gas molecules-CO, CO2, NH3, NO and NO2-on the monolayer for electronic sensing devices. The binding strengths of these gas molecules adsorbed on the CP layer are much stronger than for other reported two-dimensional materials, such as graphene, blue phosphorene, germanene, etc. Additionally, the charge transfer analysis also supported an enhanced binding strength due to the sufficient amount of charge sharing between the CP monolayer and gas molecules. We further present an extensive study about the transport properties of CP monolayer sensor devices with electrodes made out of identical materials. The transmission characteristics, the density of states, and I-V response are supported by analysis of the charge distribution of the CP monolayer upon adsorption of CO, CO2, NH3, NO and NO2. Molecules have been calculated using density functional theory and non-equilibrium Green's function. The presented theoretical investigations reveal that the CP monolayer-based device exhibits improved characteristics and could be the foundation towards constructing highly sensitive nanosensor devices.
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| 6. |
- Philippe, Bertrand, Dr. 1986-, et al.
(författare)
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Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy : Variation with Photon Energy
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:48, s. 26655-26666
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Tidskriftsartikel (refereegranskat)abstract
- A better understanding of the electronic structure of perovskite materials used in photovoltaic devices is essential for their development and optimization. In this investigation, synchrotron-based photoelectron spectroscopy (PES) was used to experimentally delineate the character and energy position of the valence band structures of a mixed perovskite. The valence band was measured using PES with photon energies ranging from ultraviolet photoelectron spectroscopy (21.2 eV) to hard X-rays (up to 4000 eV), and by taking the variation of the photoionization cross sections into account, we could experimentally determine the inorganic and organic contributions. The experiments were compared to theoretical calculations to further distinguish the role of the different anions in the electronic structure. This work also includes a thorough study of the valence band maximum and its position in relation to the Fermi level, which is crucial for the design and optimization of complete solar cells and their functional properties.
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| 7. |
- Khossossi, Nabil, et al.
(författare)
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Exploring the Possibility of beta-Phase Arsenic-Phosphorus Polymorph Monolayer as Anode Materials for Sodium-Ion Batteries
- 2020
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Ingår i: Advanced Theory and Simulations. - : Wiley-VCH Verlag. - 2513-0390. ; 3:8
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Tidskriftsartikel (refereegranskat)abstract
- Graphite anode have shown commercial success for over two decades, since the start of their use in commercial Li-ion batteries, due to their high practical specific capacity, conductivity, and low lithiation potential. Graphite is to a large extent thermodynamically unfavorable for sodium-ion intercalation and thus limits advancement in Na-ion batteries. In this work, a beta-phase arsenic-phosphorus monolayer is studied, which has recently been predicted to have semiconducting behavior and to be dynamically stable. First-principles calculations based on density functional theory are used to explore the role of beta-AsP monolayer as a negative electrode for Na-ion batteries. Cohesive energy, phonon spectrum, and molecule dynamics simulations confirm the thermodynamic stability and the possibility of experimentally synthesizing this material. The Na-ion adsorption-energies are found to be high (>-1.2 eV) on both sides (As- and P-side). The ultra-fast energy barriers for Na (0.046/0.053 V) over both sides imply high diffusion of Na-ions on the surfaces of beta-AsP. During the evaluation of Na-ion anode performance, the fully sodiated state is found to be Na2AsP, which yields a high theoretical-specific capacity of 506.16 mAh g(-1)and low average sodiation potential of 0.43 V versus Na/Na+.
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| 8. |
- Mishra, Pushkar, et al.
(författare)
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Metal-functionalized 2D boron sulfide monolayer material enhancing hydrogen storage capacities
- 2020
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 127:18
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we have systematically investigated the structural, electronic, vibrational, and H2 storage properties of a layered 2H boron sulfide (2H-BS) monolayer using spin-polarized density functional theory (DFT). The pristine BS monolayer shows semiconducting behavior with an indirect bandgap of 2.83 eV. Spin-polarized DFT with van der Waals correction suggests that the pristine BS monolayer has weak binding strength with H2 molecules, but the binding energy can be significantly improved by alkali metal functionalization. A system energy study indicates the strong bonding of alkali metals with the BS monolayer. The Bader charge analysis also concludes that a considerable charge is transferred from the metal to the BS monolayer surface, which was further confirmed by the iso-surface charge density profile. All functionalized alkali metals form cations that can bond multiple H2 molecules with sufficient binding energies, which are excellent for H2 storage applications. An ideal range of adsorption energy and practicable desorption temperature promises the ability of the alkali metal functionalized BS monolayer as an efficient material for hydrogen storage.
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| 9. |
- Nair, Akhil S., et al.
(författare)
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Unraveling the single-atom electrocatalytic activity of transition metal-doped phosphorene
- 2020
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 2:6, s. 2410-2421
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Tidskriftsartikel (refereegranskat)abstract
- The development of single-atom catalysts (SACs) for chemical reactions of vital importance in the renewable energy sector has emerged as an urgent priority. In this perspective, transition metal-based SACs with monolayer phosphorous (phosphorene) as the supporting material are scrutinized for their electrocatalytic activity towards the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) from first-principle calculations. The detailed screening study has confirmed a breaking of the scaling relationship between the ORR/OER intermediates, resulting in various activity trends across the transition metal series. Groups 9 and 10 transition metal-based SACs are identified as potential catalyst candidates with the platinum single atom offering bifunctional activity for OER and HER with diminished overpotentials. Ambient condition stability analysis of SACs confirmed a different extent of interaction towards oxygen and water compared to pristine phosphorene, suggesting room for improving the stability of phosphoreneviachemical functionalization.
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| 10. |
- Singh, Deobrat, et al.
(författare)
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Van der Waals induced molecular recognition of canonical DNA nucleobases on a 2D GaS monolayer
- 2020
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 22:12, s. 6706-6715
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we systematically investigated the adsorption mechanism of canonical DNA nucleobases and their two nucleobase pairs on a single-layer gallium sulfide (GaS) substrate using DFT+D3 methods. The GaS substrate has chemical interactions with molecules 0.02 |e| 0.11 |e| from molecules to the monolayer GaS surface. Due to the chemical interactions of adenine, cytosine, guanine, and thymine on the monolayer GaS surface, the work function is decreased by 0.69, 0.60, 0.97, and 0.20 eV, respectively. It is displayed that the bandgap of the monolayer GaS sheet can be significantly affected as induced molecular electronic states tend to appear near the Fermi level region due to chemical and physisorption mechanism. We have also investigated the transport properties of DNA nucleobases, namely, AT and GC pair molecules on the GaS surface, which shows significant reduction in the zero-bias transmission spectra. Moreover, with and without DNA nucleobases, namely, AT and GC pair molecules' absorptions on the GaS surface, clearly expressed in terms of distinct current signals, can be observed as ON and OFF states for this device. The distinctive nucleobase adsorption energies and different I-V responses may serve as potential probes for the selective detection of nucleobase molecules in imminent DNA sequencing applications based on a monolayer GaS surface.
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