| 1. |
- Kaur, A., et al.
(författare)
-
Correlation between reduced dielectric loss and charge migration kinetics in NdFeO3-modified Ba0.7Sr0.3TiO3 ceramics
- 2021
-
Ingår i: Journal of materials science. Materials in electronics. - : Springer Nature. - 0957-4522 .- 1573-482X. ; 32:20, s. 24910-24929
-
Tidskriftsartikel (refereegranskat)abstract
- The present study demonstrates the reduction in the dielectric loss at room temperature from 0.149 to 0.027 in the composite of (NdFeO3)0.1−(Ba0.7Sr0.3TiO3)0.9 as compared to the undoped Ba0.7Sr0.3TiO3 and correlates with the charge compensation due to the ionic substitutions for both A site (NdBa) and B (FeTi) site generated excess electrons, localized hole states and robust oxygen vacancies (VO) along with different cationic oxidation states. The VO mediated F center charge transfer mechanism i.e., bound magnetic polaronic behaviour and defect complex generated between acceptors and ionized VO reduce electrical conductivity and loss factor. The presence of weak ferromagnetism in the M-H loop reconfirms the F center exchange mechanism in mixed phase symmetry. The activation energy calculated from impedance spectroscopy, electrical modulus and electrical conductivity analysis supports the presence of doubly ionized VO. Further, density functional theory based first principle calculation manifests that the impurity induced depopulation of valence band edge electrons into a single spin up channel which distorts TiO6 octahedra with fluctuating bond length and Ti 3deg orbital splitting observed in decomposed density of states for accommodating excess electrons. These trapped and accommodated electrons reduce the effective electron concentration which in turn decreases the electrical conductivity and loss factor.
|
|
| 2. |
- Haman, Zakaryae, et al.
(författare)
-
Computational identification of efficient 2D Aluminium chalcogenides monolayers for optoelectronics and photocatalysts applications
- 2021
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 556
-
Tidskriftsartikel (refereegranskat)abstract
- The massive consumption of traditional fossil fuel like oil, coal and natural gas has led to serious environmental issues, which drove the search for cleaner renewable energy sources. One such option is photocatalytic water splitting that has attracted much attention as a viable process for the large scale production of hydrogen as a renewable fuel. Within this perspective, we methodically studied the structural, optoelectronic, and photocatalytic properties of two-dimensional aluminum monochalcogenide monolayers with the chemical formula AlX (X = O, S, Se, and Te) based on the framework of Density Functional Theory (DFT). All considered structures are full relaxed and their thermodynamic stabilities are confirmed by computing the phonon spectrum and Ab Initio Molecular Dynamics (AIMD) simulations. The electronic characteristics are also performed on the basis of both exchange correlation functional GGA-PBE and HSE06 in order to obtain the accurate electronic band gap. According to our calculations, all the four monolayers posses indirect band gaps ranging between 1.937 and 2.46 eV. Furthermore, based on desirable electronic band gaps, the optical performance features were further explored including complex refractive index, absorption coefficient and energy loss function by means of the complex dielectric function. It is found that all the four materials present a high absorption coefficient in the visible and Ultra-Violet regions. Finally, the band edge positions of our monolayers straddle the reduction potential of H2 and the oxidation potential H2O. Also, it was found that the Gibbs free energy of 2D AlO monolayer is 0.02 eV at certain applied external electric field and very close to ideal catalysts which suggest that the AlO monolayer is better candidate for hydrogen production. Our findings demonstrate that AlX monolayers are suitable materials for optoelectronics and hydrogen production via photocatalytic water splitting.
|
|
| 3. |
- Kaewmaraya, T., et al.
(författare)
-
Novel green phosphorene as a superior chemical gas sensing material
- 2021
-
Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 401
-
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.
|
|
| 4. |
- Khossossi, Nabil, et al.
(författare)
-
High-Specific-Capacity and High-Performing Post-Lithium-Ion Battery Anode over 2D Black Arsenic Phosphorus
- 2021
-
Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:8, s. 7900-7910
-
Tidskriftsartikel (refereegranskat)abstract
- Nowadays, secondary batteries based on sodium (Na), potassium (K), and magnesium (Mg) stimulate curiosity as eventually high-availability, nontoxic, and eco-friendly alternatives of lithium-ion batteries (LIBs). Against this background, a spate of studies has been carried out over the past few years on anode materials suitable for post-lithium-ion battery (PLIBs), in particular sodium-, potassium- and magnesium-ion batteries. Here, we have consistently studied the efficiency of a 2D alpha-phase arsenic phosphorus (alpha-AsP) as anodes through density functional theory (DFT) basin-hopping Monte Carlo algorithm (BHMC) and ab initio molecular dynamics (AIMD) calculations. Our findings show that alpha-AsP is an optimal anode material with very high stabilities, high binding strength, intrinsic metallic characteristic after (Na/K/Mg) adsorption, theoretical specific capacity, and ultralow ion diffusion barriers. The ultralow energy barriers are found to be 0.066 eV (Na), 0.043 eV (K), and 0.058 eV (Mg), inferior to that of the widely investigated MXene materials. During the charging process, a wide (Na+/K+/Mg2+) concentration storage from which a high specific capacity of 759.24/506.16/253.08 mAh/g for Na/K/Mg ions was achieved with average operating voltages of 0.84, 0.93, and 0.52 V, respectively. The above results provide valuable insights for the experimental setup of outstanding anode material for post-Li-ion battery.
|
|
| 5. |
- Mahida, H. R., et al.
(författare)
-
2D MgF2 nanosheet as a promising candidate for thermoelectric material
- 2021
-
Ingår i: Materials today. - : Elsevier. - 2214-7853. ; , s. 555-558
-
Konferensbidrag (refereegranskat)abstract
- The electronic and thermoelectric (TE) characteristics of MgF2 monolayer theoretically simulated by merging first-principles calculations with Boltzmann semi-classical approach. We have studied the thermopower, electrical conductivity, thermal conductivity, power factor (PF), and figure of merit (ZT) utilizingBoltzTraP code. Due to the ultralow thermal conductivity of T-phase of MgF2, monolayer is beneficial for superior TE materials. The maximum ZT values are of 0.93 at lower temperature and 0.70 at 800 K for T-phase of MgF2 monolayer. These theoretical investigations suggest that these materials have potential applications in better performance for thermoelectric (TE) devices at the room, as well as higher temperatures.
|
|
| 6. |
- Mahida, H. R., et al.
(författare)
-
Hydrogenation and oxidation enhances the thermoelectric performance of Si2BN monolayer
- 2021
-
Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 45:8, s. 3892-3900
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have investigated the structural, electronic, and charge transport properties of pristine, hydrogenated, and oxidized Si2BN monolayers via first-principles calculations based on density functional theory (DFT). Hydrogenation and oxidation of Si2BN monolayer display negative binding energy therefore these structures are energetically favorable. The electronic band structure engineered by the hydrogenation and oxidation of the Si2BN monolayer transformed from metallic to semiconducting nature. Due to the hydrogenation and oxidation of Si2BN, the monolayer also changes from a planar structure to a non-planar structure. The hydrogenated and oxidized structures led to high thermoelectric performance as compared to the pristine Si2BN monolayer. When the Si2BN monolayer is hydrogenated and oxidized, its electronic figure of merit (ZT(e)) significantly enhanced from 0.45 to 0.99. The investigation results suggest a practical approach for improving the performance of thermoelectric properties of the Si2BN monolayer.
|
|
| 7. |
- Murugesan, Chinnasamy, et al.
(författare)
-
Cobalt tetraphosphate as an efficient bifunctional electrocatalyst for hybrid sodium-air batteries
- 2021
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 89
-
Tidskriftsartikel (refereegranskat)abstract
- Economic and efficient bifunctional electrocatalysts are pivotal in realization of rechargeable (hybrid) metal-air batteries. It is ideal to employ noble-metal free bifunctional electrocatalysts that are not selective towards oxygen evolution and reduction (OER and ORR) activities. This work unveils cobalt-based tetraphosphate K2Co(PO3)(4) as an economic bifunctional electrocatalyst acting as cathode for rechargeable hybrid sodium-air batteries. Auto combustion route led to the development of homogeneous, carbon-coated, spherical K2Co(PO3)(4) nanoparticles enabling active site exposure to incoming guest molecules (O-2, OH-). This monoclinic compound exhibited superior oxygen evolution activity with low overpotential (ca. 0.32 V) surpassing the commercial RuO2 catalyst. Tetraphosphate K2Co(PO3)(4) was successfully implemented in hybrid Na-air batteries delivering reversible cycling with roundtrip efficiency over 70%. DFT study revealed this catalytic activity stem from the most active and stable surface (001) and half-metallic nature of Co in K2Co(PO3)(4). Cobalt tetraphosphates can be harnessed to design low cost electrocatalysts for hybrid sodium-air batteries.
|
|
| 8. |
- Negi, Devendra, et al.
(författare)
-
Coexisting commensurate and incommensurate charge ordered phases in CoO
- 2021
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- The subtle interplay of strong electronic correlations in a distorted crystal lattice often leads to the evolution of novel emergent functionalities in the strongly correlated materials (SCM). Here, we unravel such unprecedented commensurate (COM) and incommensurate (ICOM) charge ordered (CO) phases at room temperature in a simple transition-metal mono-oxide, namely CoO. The electron diffraction pattern unveils a COM (q(1) = 1/2 (1, 1, (1) over bar) and ICOM (q(2) = 0.213(1, 1, (1) over bar)) periodic lattice distortion. Transmission electron microscopy (TEM) captures unidirectional and bidirectional stripe patterns of charge density modulations. The widespread phase singularities in the phase-field of the order parameter (OP) affirms the abundant topological disorder. Using, density functional theory (DFT) calculations, we demystify the underlying electronic mechanism. The DFT study shows that a cation disordering (Co1-x O, with x = 4.17%) stabilizes Jahn-Teller (JT) distortion and localized aliovalent Co3+ states in CoO. Therefore, the lattice distortion accompanied with mixed valence states (Co3+, Co2+) states introduces CO in CoO. Our findings offer an electronic paradigm to engineer CO to exploit the associated electronic functionalities in widely available transition-metal mono-oxides.
|
|
| 9. |
- Patel, Abhishek, et al.
(författare)
-
Impact of stacking on the optoelectronic properties of 2D ZrS2/GaS heterostructure
- 2021
-
Ingår i: Materials today. - : Elsevier. - 2214-7853. ; , s. 526-528
-
Konferensbidrag (refereegranskat)abstract
- In the present study, we have systematically investigated the structural, electronic and optical properties of 2D ZrS2/GaS (with van der Waals interaction) heterostructure by using first-principles calculations. The pristine ZrS2 and GaS monolayers have semiconducting behavior with band gap of 0.99 eV and 2.39 eV, respectively. It is found that the ZrS2 and GaS monolayers interact with each other through strong van der Waals interactions due to that the band gap significantly reduces 0.88 eV. Our results indicate that the considered three stacking configurations AA, AB and AC shows semiconducting behavior. Promisingly, the optical properties display that the ZrS2/GaS heterostructures strongly absorbs light with energies from visible to ultraviolet (UV) regions. From the result, considered heterostructures may be utilized for optoelectronic devices applications.
|
|
| 10. |
- Singh, Deobrat, et al.
(författare)
-
Antimonene Allotropes alpha- and beta-Phases as Promising Anchoring Materials for Lithium-Sulfur Batteries
- 2021
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 35:10, s. 9001-9009
-
Tidskriftsartikel (refereegranskat)abstract
- In a quest to mitigate the undesirable shuttling effect that hampers the performance of Li-S batteries, we adopted first-principles calculations to study the anchoring mechanism of lithium polysulfides on antimonene phases, i.e., alpha-Sb and beta-Sb. The anchoring mechanisms of LiPSs on alpha-Sb and beta-Sb were studied through calculations of binding energy, charge transfer, and vertical binding distances from the monolayer to LiPSs. The results indicated that pristine alpha-Sb and beta-Sb showed significant physisorption/chemisorption interactions toward LiPSs due to the considerable E-b, values (0.71-1.68 and 0.96-2.07 eV, respectively). Meanwhile, with single Sb vacancy, the binding strength was enhanced (0.83-2.91 eV) for the beta-Sb monolayer. Furthermore, we substituted the Sb atom with the Sn/Te atom and found stronger E-b (1.32 5.69 and 0.45-4.81 eV). All these bindings of LiPSs were much stronger than their interactions with those of electrolytes (DME/DOL) (E-b values: 0.20-1.16 and 0.17-1.07 eV). Also, we investigated the redistribution of electrons and the influence of electronic states near the Fermi level in DOS for LiPSs on alpha-Sb and beta-Sb. Our findings suggest that pristine and defected beta-Sb monolayers could be an excellent anchoring material for Li-S batteries.
|
|
