| 1. |
- Araujo, Rafael B., et al.
(författare)
-
Designing strategies to tune reduction potential of organic molecules for sustainable high capacity batteries application
- 2017
-
Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 5:9, s. 4430-4454
-
Tidskriftsartikel (refereegranskat)abstract
- Organic compounds evolve as a promising alternative to the currently used inorganic materials in rechargeable batteries due to their low-cost, environmentally friendliness and flexibility. One of the strategies to reach acceptable energy densities and to deal with the high solubility of known organic compounds is to combine small redox active molecules, acting as capacity carrying centres, with conducting polymers. Following this strategy, it is important to achieve redox matching between the chosen molecule and the polymer backbone. Here, a synergetic approach combining theory and experiment has been employed to investigate this strategy. The framework of density functional theory connected with the reaction field method has been applied to predict the formal potential of 137 molecules and identify promising candidates for the referent application. The effects of including different ring types, e.g. fused rings or bonded rings, heteroatoms, [small pi] bonds, as well as carboxyl groups on the formal potential, has been rationalized. Finally, we have identified a number of molecules with acceptable theoretical capacities that show redox matching with thiophene-based conducting polymers which, hence, are suggested as pendent groups for the development of conducting redox polymer based electrode materials.
|
|
| 2. |
- Carvalho, Rodrigo P., et al.
(författare)
-
An evolutionary-driven AI model discovering redox-stable organic electrode materials for alkali-ion batteries
- 2023
-
Ingår i: Energy Storage Materials. - : Elsevier. - 2405-8289 .- 2405-8297. ; 61
-
Tidskriftsartikel (refereegranskat)abstract
- Data-driven approaches have been revolutionizing materials science and materials discovery in the past years. Especially when coupled with other computational physics methods, they can be applied in complex high-throughput schemes to discover novel materials, e.g. for batteries. In this direction, the present work provides a robust AI-driven framework, to accelerate the discovery of novel organic-based materials for Li-, Na- and K-ion batteries. This platform is able to predict the open-circuit voltage of the respective battery and provide an initial assessment of the materials redox stability. The model was employed to screen 45 million small molecules in the search for novel high-potential cathodes, resulting in a proposed shortlist of 3202, 689 and 702 novel compounds for Li-, Na- and K-ion batteries, respectively, considering only the redox stable candidates.
|
|
| 3. |
- Carvalho, Rodrigo P.
(författare)
-
Organic Electrode Battery Materials : A Journey from Quantum Mechanics to Artificial Intelligence
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Batteries have become an irreplaceable technology in human life as society becomes progressively more dependent on electricity. The demand for novel battery technologies has increased fast, especially with the popularisation of different portable devices. However, the current battery industry relies heavily on non-renewable resources that are also prone to provoke environmental harm. Among the possible candidates for the next generation of batteries, organic electroactive materials (OEMs) have become attractive due to a series of advantages: vastly accessible from renewable raw materials; highly versatile due to the possible functionalisation mechanisms; possibly lower production costs; reduced environmental impacts; etc. Nevertheless, some drawbacks need to be overcome before OEMs become competitive. Issues with energy density, rate capability and cycling stability hinder their final technological application. This thesis thereby discusses fundamental aspects of OEMs and proposes novel techniques to accelerate the materials discovery process.The first part of this thesis presents a pathway to systematically investigate organic materials by combining quantum mechanics calculations and crystal structure predictions. An evolutionary algorithm predicts the crystal structure of several OEMs, enabling an initial assessment of the electronic structure and the thermodynamics of the ionic insertion mechanism in these compounds. Furthermore, this first part also suggests an approach to tailor OEMs, identifying their charge storage limits and the possible occurrence of metastable phases during the ion insertion process. However, the presented strategy, while accurate, is seriously limited by its high computational demands, which are unrealistic for high-throughput screening of novel materials.Since organic materials represent a possibly limitless universe of compounds, alternative techniques are needed. Thus, the second part of this thesis combines quantum mechanics and artificial intelligence (AI), rendering a powerful platform to aid this task. An “AI-\textit{kernel}” was employed to analyse millions of organic compounds, discovering novel possible organic battery materials. Moreover, the AI accurately identified common functional groups associated with higher-voltage electrodes and suggested features that may aid future materials design. Furthermore, the kernel can also identify materials suitable for Na- and K-ion batteries and anticipate their redox stability.In conclusion, this thesis has focused on investigating fundamental properties of organic electroactive materials, particularly the ionic insertion process in batteries. Furthermore, AI-driven methodologies have also been proposed, accurately evaluating OEMs and enabling fast access to the gigantic organic realm when searching for novel battery electrode materials.
|
|
| 4. |
- Carvalho, Rodrigo P., et al.
(författare)
-
Understanding the lithiation limits of high-capacity organic battery anodes by atomic charge derivative analysis
- 2022
-
Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 157:18
-
Tidskriftsartikel (refereegranskat)abstract
- The superlithiation of organic anodes is a promising approach for developing the next generation of sustainable Li-ion batteries with high capacity. However, the lack of fundamental understanding hinders its faster development. Here, a systematic study of the lithiation processes in a set of dicarboxylate-based materials is carried out within the density functional theory formalism. It is demonstrated that a combined analysis of the Li insertion reaction thermodynamics and the conjugated-moiety charge derivative enables establishing the experimentally observed maximum storage, thus allowing an assessment of the structure-function relationships also.
|
|
| 5. |
- de Araujo, L. O., et al.
(författare)
-
A new CBD-CC-E spectral similarity scale for optimizing computer-simulated UV–vis spectra
- 2021
-
Ingår i: Computational and Theoretical Chemistry. - : Elsevier. - 2210-271X .- 2210-2728. ; 1197
-
Tidskriftsartikel (refereegranskat)abstract
- A new CBD-CC-E spectral similarity scale is proposed to optimize computer-simulated UV–vis spectra. The scale was tested using the S1←S0 spectrum of the dithienyl-diketopyrrolopyrrole molecule (DPP2T), an important building block for manufacturing materials for optoelectronic applications. Our results indicate that the spectrum calculated at M06/6-311++G(d,p) level was the one that best reproduced the intensity and shape features of the experimental spectrum, while CAM-B3LYP/6-311++G(d,p) was the one that best reproduced the energy. The CBD-CC-E scale makes the comparison between computer-simulated and experimental spectra statistically based, allowing a systematic and automated choice of the theory level whose calculated spectrum best reproduces the shape, intensity or energy of the experimental UV–vis spectrum.
|
|
| 6. |
- Ebadi, Mahsa, et al.
(författare)
-
Density Functional Theory Modeling the Interfacial Chemistry of the LiNO3 Additive for Lithium-Sulfur Batteries by Means of Simulated Photoelectron Spectroscopy
- 2017
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:42, s. 23324-23332
-
Tidskriftsartikel (refereegranskat)abstract
- Lithium-sulfur (Li-S) batteries are considered candidates for next-generation energy storage systems due to their high theoretical specific energy. There exist, however, some shortcomings of these batteries, not least the solubility of intermediate polysulfides into the electrolyte generating a so-called "redox shuttle", which gives rise to self-discharge. LiNO3 is therefore frequently used as an electrolyte additive to help suppress this mechanism, but the exact nature of the LiNO3 functionality is still unclear. Here, density functional theory calculations are used to investigate the electronic structure of LiNO3 and a number of likely species (N-2, N2O, LiNO2, Li3N, and Li2N2O2) resulting from the reduction of this additive on the surface of Li metal anode. The N is X-ray photoelectron spectroscopy core level binding energies of these molecules on the surface are calculated in order to compare the results with experimentally reported values. The core level shifts (CLS) of the binding energies are studied to identify possible factors responsible for the position of the peaks. Moreover, solid phases of (cubic) c-Li3N and (hexagonal) alpha-Li3N on the surface of Li metal are considered. The N is binding energies for the bulk phases of Li3N and at the Li3N/Li interfaces display higher values as compared to the Li3N molecule, indicating a clear correlation between the coordination number and the CLS of the solid phases of Li3N.
|
|
| 7. |
- Franco, Leandro R., et al.
(författare)
-
Theoretical investigation of solvent and oxidation/deprotonation effects on the electronic structure of a mononuclear Ru-aqua-polypyridine complex in aqueous solution
- 2023
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:36, s. 24475-24494
-
Tidskriftsartikel (refereegranskat)abstract
- Mononuclear polypyridine ruthenium (Ru) complexes can catalyze various reactions, including water splitting, and can also serve as photosensitizers in solar cells. Despite recent progress in their synthesis, accurately modeling their physicochemical properties, particularly in solution, remains challenging. Herein, we conduct a theoretical investigation of the structural and electronic properties of a mononuclear Ru-aqua polypyridine complex in aqueous solution, considering five of its possible oxidation/protonation states species: [RuII(H2O)(py)(bpy)2]2+, [RuII(OH)(py)(bpy)2]+, [RuIII(H2O)(py)(bpy)2]3+, [RuIII(OH)(py)(bpy)2]2+ and [RuIV(O)(py)(bpy)2]2+, where py = pyridine and bpy = 2,2 & PRIME;-bipyridine. At first, we investigate the impact of proton-coupled and non-coupled electron transfer reactions on the geometry and electronic structure of the complexes in vacuum and in solution, using an implicit solvent model. Then, using a sequential multiscale approach that combines quantum mechanics and molecular mechanics (S-QM/MM), we examine the explicit solvent effects on the electronic excitations of the complexes, and compare them with the experimental results. The complexes were synthesized, and their absorption spectra measured in aqueous solution. To accurately describe the QM interactions between the metal center and the aqueous ligand in the MM simulations, we developed new force field parameters for the Ru atom. We analyze the solvent structure around the complexes and account for its explicit influence on the polarization and electronic excitations of the complexes. Notably, accounting for the explicit solvent polarization effects of the first solvation shells is essential to correctly describe the energy of the electronic transitions, and the explicit treatment of the hydrogen bonds at the QM level in the excitation calculations improves the accuracy of the description of the metal-to-ligand charge-transfer bands. Transition density matrix analysis is used to characterize all electronic transitions in the visible and ultraviolet ranges according to their charge-transfer (CT) character. This study elucidates the electronic structure of those ruthenium polypyridyl complexes in aqueous solution and underscores the importance of precisely describing solvent effects, which can be achieved employing the S-QM/MM method. Ru-aqua complex in water, showcasing Ru atom, coordinated water, and hydrogen bonds on left; UV-Vis spectrum and comparison to experiment on right. QM/MM approach emphasized.
|
|
| 8. |
- Franco, Leandro Rezende, et al.
(författare)
-
Theoretical investigation of solvent and oxidation/deprotonation effects on the electronic structure of a mononuclear Ru-aqua-polypyridine complex in aqueous solution
- 2023
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:36, s. 24475-24494
-
Tidskriftsartikel (refereegranskat)abstract
- Mononuclear polypyridine ruthenium (Ru) complexes can catalyze various reactions, including water splitting, and can also serve as photosensitizers in solar cells. Despite recent progress in their synthesis, accurately modeling their physicochemical properties, particularly in solution, remains challenging. Herein, we conduct a theoretical investigation of the structural and electronic properties of a mononuclear Ru-aqua polypyridine complex in aqueous solution, considering five of its possible oxidation/protonation states species: [RuII(H2O)(py)(bpy)2]2+, [RuII(OH)(py)(bpy)2]+, [RuIII(H2O)(py)(bpy)2]3+, [RuIII(OH)(py)(bpy)2]2+ and [RuIV(O)(py)(bpy)2]2+, where py = pyridine and bpy = 2,2 & PRIME;-bipyridine. At first, we investigate the impact of proton-coupled and non-coupled electron transfer reactions on the geometry and electronic structure of the complexes in vacuum and in solution, using an implicit solvent model. Then, using a sequential multiscale approach that combines quantum mechanics and molecular mechanics (S-QM/MM), we examine the explicit solvent effects on the electronic excitations of the complexes, and compare them with the experimental results. The complexes were synthesized, and their absorption spectra measured in aqueous solution. To accurately describe the QM interactions between the metal center and the aqueous ligand in the MM simulations, we developed new force field parameters for the Ru atom. We analyze the solvent structure around the complexes and account for its explicit influence on the polarization and electronic excitations of the complexes. Notably, accounting for the explicit solvent polarization effects of the first solvation shells is essential to correctly describe the energy of the electronic transitions, and the explicit treatment of the hydrogen bonds at the QM level in the excitation calculations improves the accuracy of the description of the metal-to-ligand charge-transfer bands. Transition density matrix analysis is used to characterize all electronic transitions in the visible and ultraviolet ranges according to their charge-transfer (CT) character. This study elucidates the electronic structure of those ruthenium polypyridyl complexes in aqueous solution and underscores the importance of precisely describing solvent effects, which can be achieved employing the S-QM/MM method.
|
|
| 9. |
- Franco, Leandro R., et al.
(författare)
-
Unraveling the acid-base characterization and solvent effects on the structural and electronic properties of a bis-bidentate bridging ligand
- 2022
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:17, s. 10222-10240
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the interactions and the solvent effects on the distribution of several species in equilibrium and how it can influence the 1H-NMR properties, spectroscopy (UV-vis absorption), and the acid–base equilibria can be especially challenging. This is the case of a bis-bidentate bridging ligand bis(2-pyridyl)-benzo-bis(imidazole), where the two pyridyl and four imidazolyl nitrogen atoms can be protonated in different ways, depending on the solvent, generating many isomeric/tautomeric species. Herein, we report a combined theoretical–experimental approach based on a sequential quantum mechanics/molecular mechanics procedure that was successfully applied to describe in detail the acid–base characterization and its effects on the electronic properties of such a molecule in solution. The calculated free-energies allowed the identification of the main species present in solution as a function of the solvent polarity, and its effects on the magnetic shielding of protons (1H-NMR chemical shifts), the UV-vis absorption spectra, and the acid–base equilibrium constants (pKas) in aqueous solution. Three acid–base equilibrium constants were experimentally/theoretically determined (pKa1 = 1.3/1.2, pKa2 = 2.1/2.2 and pKa5 = 10.1/11.3) involving mono-deprotonated and mono-protonated cis and trans species. Interestingly, other processes with pKa3 = 3.7 and pKa4 = 6.0 were also experimentally determined and assigned to the protonation and deprotonation of dimeric species. The dimerization of the most stable neutral species was investigated by Monte Carlo simulations and its electronic effects were considered for the elucidation of the UV-vis absorption bands, revealing transitions mainly with the charge-transfer characteristic and involving both the monomeric species and the dimeric species. The good matching of the theoretical and experimental results provides an atomistic insight into the solvent effects on the electronic properties of this bis-bidentate bridging ligand.
|
|
| 10. |
- Marchiori, Cleber, et al.
(författare)
-
Understanding the Electrochemical Stability Window of Polymer Electrolytes in Solid-State Batteries from Atomic-Scale Modeling : The Role of Li-Ion Salts
- 2020
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 32:17, s. 7237-7246
-
Tidskriftsartikel (refereegranskat)abstract
- After decades of development in Li-ion batteries, solid polymer electrolytes (SPEs) are currently experiencing a renaissance as a promising category of materials to be used in all-solid-state batteries. However, a fundamental understanding of their electrochemical properties in the battery environment is still lacking, which in turn limits the implementation of this prospective solution. With the aim of bridging this knowledge gap, we have assessed, through first-principles thermodynamics calculations based on atomic-scale modeling, the electrochemistry of a range of relevant polymer electrolyte hosts in their pristine form and also when doped with commonly used Li-ion salts. A significant change of the electrochemical stability window upon formation of the polymer/salt complexes was found. The mechanisms of the reduction and oxidation reactions are unveiled and correlated to the electronic structures and molecular structural relaxations. In the reduction process, the salt anions control the potentials due to bond cleavage that stabilize the reduced state. In the oxidation process, the mechanism is different with the charge being stabilized either on the polymer or on the salt anion depending on the complex formed. This assessment of the electrochemical stability of the polymer/salt complexes could serve as a guide for electrolyte design in SPE-based all-solid-state batteries.
|
|
| 11. |
- Pereira de Carvalho, Rodrigo, et al.
(författare)
-
An AI-kernel discovering redox-stable organic electrode materials for alkali-ion batteries
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Data-driven approaches have been revolutionizing materials science and materials discovery in the past years. Especially when coupled with other computational physics methods, it can be applied in complex high-throughput schemes to discover novel materials, for example for batteries. In this direction, this work presents a robust AI-driven framework, the AI-kernel, working as a platform to accelerate the discovery of novel organic-based materials for Li-, Na- and K-ion batteries. This platform was able to predict the open-circuit voltage of the respective battery and provide an initial assessment of the material’s redox stability. The kernel was employed to screen 45 million small molecules in the search for novel high-potential cathodes, resulting in a proposed shortlist of 3202, 689 and 702 novel compounds for Li-, Na- and K-ion batteries, respectively, when only considering the redox-stable candidates.
|
|
| 12. |
- Pereira de Carvalho, Rodrigo, et al.
(författare)
-
Artificial intelligence driven in-silico discovery of novel organic lithium-ion battery cathodes
- 2022
-
Ingår i: Energy Storage Materials. - : Elsevier. - 2405-8289 .- 2405-8297. ; 44, s. 313-325
-
Tidskriftsartikel (refereegranskat)abstract
- Organic electrode materials (OEMs) combine key sustainability and versatility properties with the potential to enable the realisation of the next generation of truly green battery technologies. However, for OEMs to become a competitive alternative, challenging issues related to energy density, rate capability and cycling stability need to be overcome. In this work, we have developed and applied an alternative yet systematic methodology to accelerate the discovery of suitable cathode-active OEMs by interplaying artificial intelligence (AI) and quantum mechanics. This AI-kernel has allowed a high-throughput screening of a huge library of organic molecules, leading to the discovery of 459 novel promising OEMs with candidates offering the potential to achieve theoretical energy densities superior to 1000 W h kg(1). Moreover, the machinery accurately identified common molecular functionalities that lead to such higher-voltage electrodes and pointed out an interesting donor-accepter-like effect that may drive the future design of cathode-active OEMs.
|
|
| 13. |
- Pereira de Carvalho, Rodrigo, et al.
(författare)
-
Exploring Metastable Phases During Lithiation of Organic Battery Electrode Materials
- 2022
-
Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; :2
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the Li-ion insertion mechanism in organic electrode materials is investigated through the lens of atomic-scale models based on first-principles theory. Starting with a structural analysis, the interplay of density functional theory with evolutionary and potential-mapping algorithms is used to resolve the crystal structure of the different (de)lithiated phases. These methods elucidate different lithiation reaction pathways and help to explore the formation of metastable phases and predict one- or multi-electron reactions, which are still poorly understood for organic intercalation electrodes. The cathode material dilithium 2,5-oxyterephthalate (operating at 2.6 V vs. Li/Li+) is investigated in depth as a case study, owing to its rich redox chemistry. When compared with recent experimental results, it is demonstrated that metastable phases with peculiar ring-ring molecular interactions are more likely to be controlling the redox reactions thermodynamics and consequently the battery voltage.
|
|
| 14. |
- Pereira de Carvalho, Rodrigo, et al.
(författare)
-
Structure-property relationships in organic battery anode materials : exploring redox reactions in crystalline Na- and Li-benzene diacrylate using combined crystallography and density functional theory calculations
- 2021
-
Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 2:3, s. 1024-1034
-
Tidskriftsartikel (refereegranskat)abstract
- Organic-based materials are potential candidates for a new generation of sustainable and environmentally friendly battery technologies, but insights into the structural, kinetic and thermodynamic properties of how these compounds lithiate or sodiate are currently missing. In this regard, benzenediacrylates (BDAs) are here investigated for application as low-potential electrodes in Na-ion and Li-ion batteries. Aided by a joint effort of theoretical and experimental frameworks, we unveil the structural, electronic and electrochemical properties of the Na(2)BDA and Li(2)BDA compounds. The crystal structure of these systems in their different sodiated and lithiated phases have been predicted by an evolutionary algorithm interplayed with density functional theory calculations. Due to difficulties in obtaining useful single crystals for the BDA salts, other methods have been explored in combination with the computational approach. While the predicted structure of the pristine Na(2)BDA compound has been experimentally confirmed through the 3D Electron Diffraction (3DED) technique, the hydrated version of Li(2)BDA is analysed through single crystal X-ray diffraction. The calculated cell voltages for the sodiation (0.63 V vs. Na/Na+) and lithiation (1.12 V vs. Li/Li+) processes display excellent quantitative agreement with experimental findings. These results validate the developed theoretical methodology. Moreover, fundamental aspects of the electronic structures and their relationship with the reaction thermodynamics are discussed. The results suggest a possible disproportionation between the sodiated phases of Na(2)BDA, supporting a two-electron process, and also unveil major differences for the two employed cations: Na+ and Li+.
|
|
| 15. |
- Scalon, Lucas, et al.
(författare)
-
Assessing the Donor-Acceptor Nature and the Electrochemical Stability of a Fluorene-Diketopyrrolopyrrole-Thiophene-Based Copolymer
- 2021
-
Ingår i: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 3:8, s. 4223-4233
-
Tidskriftsartikel (refereegranskat)abstract
- Organic dyes have been studied for applications in large-area, flexible, cheap, and efficient organic electronic devices. Among them, diketopyrrolopyrrole (DPP) has gained attention thanks to its planar structure, photochemical and thermal stability, and easy processability. Also, the electron-withdrawing nature of DPP makes its application attractive in the synthesis of donor-acceptor (D-A) copolymers, with appealing features such as the tunable energy levels and photophysical and electrochemical properties. Inspired by these exciting characteristics, a copolymer was developed based on DPP, thiophene, and fluorene (PFDPP2T). Photophysical and electrochemical studies using both experimental and theoretical approaches were performed aiming to understand the properties of this material, such as, for instance, the D-A characteristic and the outstanding electrochemical stability upon oxidation that enables more than 400 cycles of p-doping. The outcomes unveil fundamental aspects of this class of copolymers, reinforcing their suitability for photo-electrochemical and optoelectronic applications.
|
|
| 16. |
- Zhang, Chao, et al.
(författare)
-
2023 Roadmap on molecular modelling of electrochemical energy materials
- 2023
-
Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7655. ; 5:4
-
Tidskriftsartikel (refereegranskat)abstract
- New materials for electrochemical energy storage and conversion are the key to the electrification and sustainable development of our modern societies. Molecular modelling based on the principles of quantum mechanics and statistical mechanics as well as empowered by machine learning techniques can help us to understand, control and design electrochemical energy materials at atomistic precision. Therefore, this roadmap, which is a collection of authoritative opinions, serves as a gateway for both the experts and the beginners to have a quick overview of the current status and corresponding challenges in molecular modelling of electrochemical energy materials for batteries, supercapacitors, CO2 reduction reaction, and fuel cell applications.
|
|
| 17. |
- Aderne, Rian E., et al.
(författare)
-
On the energy gap determination of organic optoelectronic materials : the case of porphyrin derivatives
- 2022
-
Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; :3, s. 1791-1803
-
Tidskriftsartikel (refereegranskat)abstract
- The correct determination of the ionization potential (IP) and electron affinity (EA) as well as the energy gap is essential to properly characterize a series of key phenomena related to the applications of organic semiconductors. For example, energy offsets play an essential role in charge separation in organic photovoltaics. Yet there has been a lot of confusion involving the real physical meaning behind those quantities. Experimentally the energy gap can be measured by direct techniques such as UV-Vis absorption, or indirect techniques such as cyclic voltammetry (CV). Another spectroscopic method is the Reflection Electron Energy Loss Spectroscopy (REELS). Regarding data correlation, there is little consensus on how the REELS' energy gap can be interpreted in light of the energies obtained from other methodologies such as CV, UV-Vis, or photoemission. In addition, even data acquired using those traditional techniques has been misinterpreted or applied to derive conclusions beyond the limits imposed by the physics of the measurement. A similar situation also happens when different theoretical approaches are used to assess the energy gap or employed to explain outcomes from experiments. By using a set of porphyrin derivatives as model molecules, we discuss some key aspects of those important issues. The peculiar properties of these porphyrins demonstrate that even straightforward measurements or calculations performed in a group of very similar molecules need a careful interpretation of the outcomes. Differences up to 660 meV (similar to 190 meV) are found comparing REELS (electrochemical) measurements with UV-Vis energy gaps, for instance. From the theoretical point of view, a reasonable agreement with electrochemical measurements of the IP, EA, and the gap of the porphyrins is only obtained when the calculations involve the full thermodynamics of the redox processes. The purpose of this work is to shed light on the differences and similarities of those aforementioned characterization methods and provide some insight that might help one to develop a critical analysis of the different experimental and theoretical methodologies.
|
|
| 18. |
- Axelsson, Martin, et al.
(författare)
-
Small Organic Molecule Based on Benzothiadiazole for Electrocatalytic Hydrogen Production
- 2021
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:50, s. 21229-21233
-
Tidskriftsartikel (refereegranskat)abstract
- A small organic molecule 2,1,3-benzothiadiazole-4, 7-dicarbonitrile (BTDN) is assessed for electrocatalytic hydrogen evolution on glassy carbon electrode and shows a hydrogen production Faradaic efficiency of 82% in the presence of salicylic acid. The key catalytic intermediates of reduced species BTDN-. and protonated intermediates are characterized or hypothesized by using various spectroscopic methods and density functional theory (DFT)-based calculations. With the experimental and theoretical results, a catalytic mechanism of BTDN for electrocatalytic H-2 evolution is proposed.
|
|
| 19. |
- Carvalho, Rodrigo P, et al.
(författare)
-
Atomic-scale Modelling of Redox-active Organic Molecules and Polymers for Energy Applications
- 2020
-
Ingår i: Redox Polymers for Energy and Nanomedicine. - : Royal Society of Chemistry. - 9781788018715 ; , s. 93-136
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The use of computational techniques in materials science is currently expanding rapidly due to the better capabilities of computer infrastructure and increasing user friendliness of relevant software. This growth is also experienced for redox-active organic matter aimed at utilization in energy storage and conversion devices. We here cover a range of material modelling technologies – focused on electronic structure calculations and force field methods – which have been applied for these organic materials, targeting a broad range of materials categories and possible applications. We also take a look at how novel computational tools are likely to make an even greater impact on the field in the near future, where they can be used as predictive tools for finding novel relevant molecular systems for electronic applications. It is argued that the versatility of organic materials, possessing relevant properties over very different length scales, make computational tools particularly useful for achieving better performance of their devices.
|
|
| 20. |
- Cavallo, Carmen, 1986, et al.
(författare)
-
Effect of the Niobium Doping Concentration on the Charge Storage Mechanism of Mesoporous Anatase Beads as an Anode for High-Rate Li-Ion Batteries
- 2021
-
Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:1, s. 215-225
-
Tidskriftsartikel (refereegranskat)abstract
- A promising strategy to improve the rate performance of Li-ion batteries is to enhance and facilitate the insertion of Li ions into nanostructured oxides like TiO2. In this work, we present a systematic study of pentavalent-doped anatase TiO2 materials for third-generation high-rate Li-ion batteries. Mesoporous niobium-doped anatase beads (Nb-doped TiO2) with different Nb5+ doping (n-type) concentrations (0.1, 1.0, and 10% at.) were synthesized via an improved template approach followed by hydrothermal treatment. The formation of intrinsic n-type defects and oxygen vacancies under RT conditions gives rise to a metallic-type conduction due to a shift of the Fermi energy level. The increase in the metallic character, confirmed by electrochemical impedance spectroscopy, enhances the performance of the anatase bead electrodes in terms of rate capability and provides higher capacities both at low and fast charging rates. The experimental data were supported by density functional theory (DFT) calculations showing how a different n-type doping can be correlated to the same electrochemical effect on the final device. The Nb-doped TiO2 electrode materials exhibit an improved cycling stability at all the doping concentrations by overcoming the capacity fade shown in the case of pure TiO2 beads. The 0.1% Nb-doped TiO2-based electrodes exhibit the highest reversible capacities of 180 mAh g-1 at 1C (330 mA g-1) after 500 cycles and 110 mAh g-1 at 10C (3300 mA g-1) after 1000 cycles. Our experimental and computational results highlight the possibility of using n-type doped TiO2 materials as anodes in high-rate Li-ion batteries.
|
|
| 21. |
- Chen, Qiaonan, 1992, et al.
(författare)
-
Effects of Flexible Conjugation-Break Spacers of Non-Conjugated Polymer Acceptors on Photovoltaic and Mechanical Properties of All-Polymer Solar Cells
- 2022
-
Ingår i: Nano-Micro Letters. - : Springer Science and Business Media LLC. - 2311-6706 .- 2150-5551. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Highlights: A series of non-conjugated acceptor polymers with flexible conjugation-break spacers (FCBSs) of different lengths were synthesized.The effect of FCBSs length on solubility of the acceptor polymers, and their photovoltaic and mechanical properties in all-polymer solar cells were explored.This work provides useful guidelines for the design of semiconducting polymers by introducing FCBS with proper length, which can giantly improved properties that are not possible to be achieved by the state-of-the-art fully conjugated polymers. Abstract: All-polymer solar cells (all-PSCs) possess attractive merits including superior thermal stability and mechanical flexibility for large-area roll-to-roll processing. Introducing flexible conjugation-break spacers (FCBSs) into backbones of polymer donor (PD) or polymer acceptor (PA) has been demonstrated as an efficient approach to enhance both the photovoltaic (PV) and mechanical properties of the all-PSCs. However, length dependency of FCBS on certain all-PSC related properties has not been systematically explored. In this regard, we report a series of new non-conjugated PAs by incorporating FCBS with various lengths (2, 4, and 8 carbon atoms in thioalkyl segments). Unlike common studies on so-called side-chain engineering, where longer side chains would lead to better solubility of those resulting polymers, in this work, we observe that the solubilities and the resulting photovoltaic/mechanical properties are optimized by a proper FCBS length (i.e., C2) in PA named PYTS-C2. Its all-PSC achieves a high efficiency of 11.37%, and excellent mechanical robustness with a crack onset strain of 12.39%, significantly superior to those of the other PAs. These results firstly demonstrate the effects of FCBS lengths on the PV performance and mechanical properties of the all-PSCs, providing an effective strategy to fine-tune the structures of PAs for highly efficient and mechanically robust PSCs.[Figure not available: see fulltext.]
|
|
| 22. |
- Choi, Young Won, et al.
(författare)
-
Amorphisation-induced electrochemical stability of solid-electrolytes in Li-metal batteries : The case of Li3ClO
- 2022
-
Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 521
-
Tidskriftsartikel (refereegranskat)abstract
- Energy storage technologies that can meet the unprecedented demands of a sustainable energy system based on intermittent energy sources require new battery materials. In recent years, new superionic conducting glasses have been discovered that have captured the attention of the community due to their potential use as solid electrolytes for all-solid-state Li-ion batteries. New research is needed to understand the correlations between the non-crystalline structure of glasses and their advanced properties. Here we investigate the structural properties, the electronic structure and the electrochemical stability against Li metal of the high ionic conducting Li3ClO glass. We use the stochastic quenching method based on first principles theory to model the amorphous structure of the glass. We characterise the structure by means of radial distribution functions, angle distributions functions, bond lengths and coordination numbers. Our calculations of the electronic structure of Li3ClO for both phases, crystalline and amorphous, demonstrate that both materials are good insulators. We assess the electrochemical stability of the electrolyte against Li metal electrode and in particular we analyse the role of amorphisation. Our results show that crystalline Li3ClO is not stable against Li metal electrode and that the glass can be made stable if less oxygen is supplied, for instance, by producing an substoichiometric glass.
|
|
| 23. |
- Damas, Giane Benvinda, et al.
(författare)
-
Carbon dioxide reduction mechanism on Ru-based electrocatalysts [Ru(bpy)(2)(CO)(2)](2+) : insights from first-principles theory
- 2021
-
Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 5:23, s. 6066-6076
-
Tidskriftsartikel (refereegranskat)abstract
- Solar fuel production through the so-called artificial photosynthesis has attracted a great deal of attention to the development of a new world energy matrix that is renewable and environmentally friendly. This process is characterized by light absorption with enough photon energy to generate conduction electrons, which drive the carbon dioxide reduction to produce organic fuels. It is also common to couple Ru-complex electrocatalysts to form a more efficient and selective hybrid system for this application. In this work, we have undertaken a thorough investigation of the redox reaction mechanism of Ru-based electrocatalysts by means of density functional theory (DFT) methods under the experimental conditions that have been previously reported. More specifically, we have studied the electrochemistry and catalytic activity of the [Ru(bpy)(2)(CO)(2)](2+) coordination complex. Our theoretical assessment supports the following catalytic cycle: (i) [Ru(bpy)(2)(CO)(2)](2+) is transformed into [Ru(bpy)(2)(CO)](0) upon two-electron reduction and CO release; (ii) [Ru(bpy)(2)(CO)](0) is protonated to form the [Ru(bpy)(2)(CO)H](+) hydride complex; (iii) CO2 is activated by the hydride complex through an electrophilic addition to form the [Ru(bpy)(2)(CO)(OCHO)](+) intermediate; (iv) the resulting formic acid ligand is released in solution; and, finally, (v) the CO ligand is reattached to the complex to recover the initial [Ru(bpy)(2)(CO)(2)](2+) catalyst.
|
|
| 24. |
- Ebadi, Mahsa, et al.
(författare)
-
Assessing structure and stability of polymer/lithium-metal interfaces from first-principles calculations
- 2019
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:14, s. 8394-8404
-
Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes (SPEs) are promising candidates for Li metal battery applications, but the interface between these two categories of materials has so far been studied only to a limited degree. A better understanding of interfacial phenomena, primarily polymer degradation, is essential for improving battery performance. The aim of this study is to get insights into atomistic surface interaction and the early stages of solid electrolyte interphase formation between ionically conductive SPE host polymers and the Li metal electrode. A range of SPE candidates are studied, representative of major host material classes: polyethers, polyalcohols, polyesters, polycarbonates, polyamines and polynitriles. Density functional theory (DFT) calculations are carried out to study the stability and the electronic structure of such polymer/Li interfaces. The adsorption energies indicated a stronger adhesion to Li metal of polymers with ester/carbonate and nitrile functional groups. Together with a higher charge redistribution, a higher reactivity of these polymers is predicted as compared to the other electrolyte hosts. Products such as alkoxides and CO are obtained from the degradation of ester- and carbonate-based polymers by AIMD simulations, in agreement with experimental studies. Analogous to low-molecular-weight organic carbonates, decomposition pathways through C-carbonyl-O-ethereal and C-ethereal-O-ethereal bond cleavage can be assumed, with carbonate-containing fragments being thermodynamically favorable.
|
|
| 25. |
- Ebadi, Mahsa, et al.
(författare)
-
Electrolyte decomposition on Li-metal surfaces from first-principles theory
- 2016
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 145:20, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Animportant feature in Li batteries is the formation of a solid electrolyte interphase (SEI) on the surface of the anode. This film can have a profound effect on the stability and the performance of the device. In this work, we have employed density functional theory combined with implicit solvation models to study the inner layer of SEI formation from the reduction of common organic carbonate electrolyte solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate) on a Li metal anode surface. Their stability and electronic structure on the Li surface have been investigated. It is found that the CO producing route is energetically more favorable for ethylene and propylene carbonate decomposition. For the two linear solvents, dimethyl and diethyl carbonates, no significant differences are observed between the two considered reduction pathways. Bader charge analyses indicate that 2 e(-) reductions take place in the decomposition of all studied solvents. The density of states calculations demonstrate correlations between the degrees of hybridization between the oxygen of adsorbed solvents and the upper Li atoms on the surface with the trend of the solvent adsorption energies.
|
|
| 26. |
- Ebadi, Mahsa, et al.
(författare)
-
Insights into the Li-Metal/Organic Carbonate Interfacial Chemistry by Combined First-Principles Theory and X-ray Photoelectron Spectroscopy
- 2019
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:1, s. 347-355
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) is a widely used technique to study surfaces and interfaces. In complex chemical systems, however, interpretation of the XPS results and peak assignments is not straightforward. This is not least true for Li-batteries, where XPS yet remains a standard technique for interface characterization. In this work, a combined density functional theory (DFT) and experimental XPS study is carried out to obtain the C 1s and O 1s core-level binding energies of organic carbonate molecules on the surface of Li metal. Decomposition of organic carbonates is frequently encountered in electrochemical cells employing this electrode, contributing to the build up of a complex solid electrolyte interphase (SEI). The goal in this current study is to identify the XPS fingerprints of the formed compounds, degradation pathways, and thereby the early formation stages of the SEI. The contribution of partial atomic charges on the core-ionized atoms and the electrostatic potential due to the surrounding atoms on the core-level binding energies, which is decisive for interpretation of the XPS spectra, are addressed based on the DFT calculations. The results display strong correlations between these two terms and the binding energies, whereas electrostatic potential is found to be the dominating factor. The organic carbonate molecules, decomposed at the surface of the Li metal, are considered based on two different decomposition pathways. The trends of calculated binding energies for products from ethereal carbon-ethereal oxygen bond cleavage in the organic carbonates are better supported when compared to the experimental XPS results.
|
|
| 27. |
- Ebadi, Mahsa, et al.
(författare)
-
Modelling the Polymer Electrolyte/Li-Metal Interface by Molecular Dynamics simulations
- 2017
-
Ingår i: Electrochimica Acta. - : Pergamon-Elsevier. - 0013-4686 .- 1873-3859. ; 234, s. 43-51
-
Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes are considered promising candidates for application in Li-metal batteries due to their comparatively high mechanical strength, which can prevent dendrite formation. In this study, we have performed Molecular Dynamics simulations to investigate structural and dynamical properties of a common polymer electrolyte, poly(ethylene oxide) (PEO) doped with LiTFSI salt in the presence of a Li metal surface. Both a physical (solid wall) and a chemical (slab) model of the Li (100) surface have been applied, and the results are also compared with a model of the bulk electrolyte. The average coordination numbers for oxygen atoms around the Li ions are ca. 6 for all investigated systems. However, the calculated Radial Distribution Functions (RDFs) for Li+-(OPEO) and Li+-(OTFSI) show sharper peaks for the Li slab model, indicating a more well-defined coordination sphere for Li+ in this system. This is clearly a surface effect, since the RDF for Li+ in the interface region exhibits sharper peaks than in the bulk region of the same system. The simulations also display a high accumulation of TFSI anions and Li+ cations close to interface regions. This also leads to slower dynamics of the ionic transport in the systems, which have a Li-metal surface present, as seen from the calculated mean-square-displacement functions. The accumulation of ions close to the surface is thus likely to induce a polarization close to the electrode.
|
|
| 28. |
- Ebadi, Mahsa, et al.
(författare)
-
Restricted Ion Transport by Plasticizing Side Chains in Polycarbonate-Based Solid Electrolytes
- 2020
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 53:3, s. 764-774
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing the ionic conductivity has for decades been an overriding goal in the development of solid polymer electrolytes. According to fundamental theories on ion transport mechanisms in polymers, the ionic conductivity is strongly correlated to free volume and segmental mobility of the polymer for the conventional transport processes. Therefore, incorporating plasticizing side chains onto the main chain of the polymer host often appears as a clear-cut strategy to improve the ionic conductivity of the system through lowering of the glass transition temperature (T-g) This intended correlation between Tg and ionic conductivity is, however, not consistently observed in practice. The aim of this study is therefore to elucidate this interplay between segmental mobility and polymer structure in polymer electrolyte systems comprising plasticizing side chains. To this end, we utilize the synthetic versatility of the ion-conductive poly(trimethylene carbonate) (PTMC) platform. Two types of host polymers with side chains added to a PTMC backbone are employed, and the resulting electrolytes are investigated together with the side chain-free analogue both by experiment and with molecular dynamics (MD) simulations. The results show that while added side chains do indeed lead to a lower Tg, the total ionic conductivity is highest in the host matrix without side chains. It was seen in the MD simulations that while side chains promote ionic mobility associated with the polymer chain, the more efficient interchain hopping transport mechanism occurs with a higher probability in the system without side chains. This is connected to a significantly higher solvation site diversity for the Li+ ions in the side-chain-free system, providing better conduction paths. These results strongly indicate that the side chains in fact restrict the mobility of the Li+ ions in the polymer hosts.
|
|
| 29. |
- Filate, Tadele Tamenu, 1994, et al.
(författare)
-
Aqueous Processed All-Polymer Solar Cells with High Open-Circuit Voltage Based on Low-Cost Thiophene-Quinoxaline Polymers
- 2024
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 16:10, s. 12886-12896
-
Tidskriftsartikel (refereegranskat)abstract
- Eco-friendly solution processing and the low-cost synthesis of photoactive materials are important requirements for the commercialization of organic solar cells (OSCs). Although varieties of aqueous-soluble acceptors have been developed, the availability of aqueous-processable polymer donors remains quite limited. In particular, the generally shallow highest occupied molecular orbital (HOMO) energy levels of existing polymer donors limit further increases in the power conversion efficiency (PCE). Here, we design and synthesize two water/alcohol-processable polymer donors, poly[(thiophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-T)) and poly[(selenophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-Se)) with oligo(ethylene glycol) (OEG) side chains, having deep HOMO energy levels (∼−5.4 eV). The synthesis of the polymers is achieved in a few synthetic and purification steps at reduced cost. The theoretical calculations uncover that the dielectric environmental variations are responsible for the observed band gap lowering in OEG-based polymers compared to their alkylated counterparts. Notably, the aqueous-processed all-polymer solar cells (aq-APSCs) based on P(Qx8O-T) and poly[(N,N′-bis(3-(2-(2-(2-methoxyethoxy)-ethoxy)ethoxy)-2-((2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-methyl)propyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-(2,5-thiophene)] (P(NDIDEG-T)) active layer exhibit a PCE of 2.27% and high open-circuit voltage (VOC) approaching 0.8 V, which are among the highest values for aq-APSCs reported to date. This study provides important clues for the design of low-cost, aqueous-processable polymer donors and the fabrication of aqueous-processable OSCs with high VOC
|
|
| 30. |
- Franco, Leandro R., et al.
(författare)
-
Unveiling the impact of exchange-correlation functionals on the description of key electronic properties of non-fullerene acceptors in organic photovoltaics
- 2023
-
Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 159:20
-
Tidskriftsartikel (refereegranskat)abstract
- Non-fullerene electron acceptors have emerged as promising alternatives to traditional electron-acceptors in the active layers of organic photovoltaics. This is due to their tunable energy levels, optical response in the visible light spectrum, high electron mobility, and photochemical stability. In this study, the electronic properties of two representative non-fullerene acceptors, ITIC and Y5, have been calculated within the framework of density functional theory using a range of hybrid and non-hybrid density functionals. Screened range-separated hybrid (SRSH) approaches were also tested. The results are analyzed in light of the previously reported experimental outcomes. Specifically, we have calculated the oxidation and reduction potentials, fundamental and optical gaps, the highest occupied molecular orbital and lowest unoccupied molecular orbital energies, and exciton binding energies. Additionally, we have investigated the effects of the medium dielectric constant on these properties employing a universal implicit solvent model. It was found that hybrid functionals generally perform poorly in predicting oxidation potentials, while non-hybrid functionals tend to overestimate reduction potentials. The inclusion of a large Hartree-Fock contribution to the global or long range was identified as the source of inaccuracy for many hybrid functionals in predicting both redox potentials and the fundamental and optical gaps. Corroborating with the available literature, ∼50% of all tested functionals predicted very small exciton binding energies, within the range of ±0.1 eV, that become even smaller by increasing the dielectric constant of the material. Finally, the OHSE2PBE and tHCTHhyb functionals and the optimal tuning SRSH approach emerged as the best-performing methods, with good accuracy in the description of the electronic properties of interest.
|
|
| 31. |
- Graça Araújo, Carlos Moysés, 1975-
(författare)
-
Hydrogen Storage Materials : Design, Catalysis, Thermodynamics, Structure and Optics
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen is abundant, uniformly distributed throughout the Earth's surface and its oxidation product (water) is environmentally benign. Owing to these features, it is considered as an ideal synthetic fuel for a new world energetic matrix (renewable, secure and environmentally friendly) that could allow a sustainable future development. However, for this prospect to become a reality, efficient ways to produce, transport and store hydrogen still need to be developed. In the present thesis, theoretical studies of a number of potential hydrogen storage materials have been performed using density functional theory. In NaAlH4 doped with 3d transition metals (TM), the hypothesis of the formation of Ti-Al intermetallic alloy as the main catalytic mechanism for the hydrogen sorption reaction is supported. The gateway hypothesis for the catalysis mechanism in TM-doped MgH2 is confirmed through the investigation of MgH2 nano-clusters. Thermodynamics of Li-Mg-N-H systems are analyzed with good agreement between theory and experiments. Besides chemical hydrides, the metal-organic frameworks (MOFs) have also been investigated. Li-decorated MOF-5 is demonstrated to possess enhanced hydrogen gas uptake properties with a theoretically predicted storage capacity of 2 wt% at 300 K and low pressure.The metal-hydrogen systems undergo many structural and electronic phase transitions induced by changes in pressure and/or temperature and/or H-concentration. It is important both from a fundamental and applied viewpoint to understand the underlying physics of these phenomena. Here, the pressure-induced structural phase transformations of NaBH4 and ErH3 were investigated. In the latter, an electronic transition is shown to accompany the structural modification. The electronic and optical properties of the low and high-pressure phases of crystalline MgH2 were calculated. The temperature-induced order-disorder transition in Li2NH is demonstrated to be triggered by Li sub-lattice melting. This result may contribute to a better understanding of the important solid-solid hydrogen storage reactions that involve this compound.
|
|
| 32. |
- Jalan, Ishita, 1991-, et al.
(författare)
-
Donor-acceptor polymer complex formation in solution confirmed by spectroscopy and atomic-scale modelling
- 2023
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 11:27, s. 9316-9326
-
Tidskriftsartikel (refereegranskat)abstract
- In all-polymer solar cells, high performance is attributed to the fine-grained morphology of the film in the active layer. However, the mechanism by which this fine-grained morphology is achieved remains unknown. Polymeric non-fullerene acceptors have the potential to restrict the self-aggregation, typical of non-fullerene small molecule acceptors. Here we employed a blend of the polymeric acceptor PF5-Y5 and the donor polymer PBDB-T to investigate the balance between molecular interactions in solution. Temperature-dependent absorption spectra show evidence of temperature-induced disaggregation of both donor and acceptor polymers, where the donor polymer disaggregation depends on the solvent polarity. Concentration-dependent fluorescence spectra of blend solutions display blue-shifted acceptor emission upon dilution, similar to that observed in acceptor solutions, and a decreased tendency for charge transfer from donor to acceptor upon dilution. Excitation spectra of dilute blend solutions contain an increased contribution to the long-wavelength acceptor emission, as compared to pure acceptor solutions, from a chromophore that absorbs in a region where the donor does not absorb. These observations can be explained by donor-acceptor complexation in dilute blend solutions, that is stabilized in more polar solvents. Moreover, the near IR-region of the absorption spectrum could be matched with the calculated electronic excitations of donor-acceptor complexes of PBDB-T and PF5-Y5 oligomers. The results corroborate that the interaction between segments of the donor and acceptor polymer chains favours the formation of donor-acceptor charge transfer complexes, stabilized by hybridization of the molecular orbitals, which reduces the electronic energy. The proposed donor-acceptor complex formation competes with the donor and acceptor self-aggregation and is influenced by the solvent environment. These pre-formed donor-acceptor complexes in low-concentration solutions can be expected to have important consequences on the film morphology of all-polymer blends. The results from this joint experimental-theoretical spectroscopy study provide insights that can guide the design of compatible donor and acceptor polymers for future high-performance organic solar cells.
|
|
| 33. |
- Jin, Wentao, et al.
(författare)
-
Absolute surface energies of wurtzite (10 1 over bar 1) surfaces and the instability of the cation-adsorbed surfaces of II-VI semiconductors
- 2021
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 119:20, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the wurtzite (10 1 over bar 1) planes of five semiconductors, AlN, GaN, GaAs, ZnO, and ZnS. The absolute surface energies are obtained by using a series of wedge nanowire structures. A cation-adsorbed surface reconstruction, (1 x 1)X (X is the electropositive element of the semiconductor) adlayer, is found to have dramatically low energy under the cation-rich condition for AlN and GaN. A p electron draining mechanism is proposed to explain these results. We also developed a framework to analyze the stabilization mechanism of the unneutral surfaces. It suggests that the cation-adsorbed surfaces of II-VI semiconductors should be more unstable than the anion-adsorbed surfaces.
|
|
| 34. |
- Jin, Wentao, et al.
(författare)
-
Absolute surface energies of wurtzite (101‾1) surfaces and the instability of the cation-adsorbed surfaces of II-VI semiconductors
- 2021
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 119:20
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the wurtzite (101‾1) planes of five semiconductors, AlN, GaN, GaAs, ZnO, and ZnS. The absolute surface energies are obtained by using a series of wedge nanowire structures. A cation-adsorbed surface reconstruction, (1 × 1)X (X is the electropositive element of the semiconductor) adlayer, is found to have dramatically low energy under the cation-rich condition for AlN and GaN. A p electron draining mechanism is proposed to explain these results. We also developed a framework to analyze the stabilization mechanism of the unneutral surfaces. It suggests that the cation-adsorbed surfaces of II–VI semiconductors should be more unstable than the anion-adsorbed surfaces.
|
|
| 35. |
- Khan, Ziyauddin, et al.
(författare)
-
Mass Transport in “Water-in-Polymer Salt” Electrolytes
- 2023
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 35, s. 6382-6395
-
Tidskriftsartikel (refereegranskat)abstract
- “Water-in-polymer salt” electrolytes (WiPSEs) based on potassium polyacrylate (PAAK) belong to a new family of “water-in-salt” electrolytes that is envisioned as a potential solution for large-scale supercapacitors to balance the electric grid at short time scales. The WiPSEs display a broad electrochemical stability window up to 3 V, yet they are nonflammable and provide high ionic conductivity (100 mS/cm) as required in high-power devices. However, the transport of matter in PAAK-based WiPSEs has not been studied. In this work, we have extensively characterized PAAK by spectroscopic methods such as Raman spectroscopy and NMR diffusometry to determine the state of water and elucidate the mechanism of ionic transport as well as its interplay with water and polymer chain dynamics, which reveals that a significant proportion of the transport in WiPSEs is attributed to hydrated cations. The results are further supported by molecular dynamics (MD) simulations. Finally, the potential of WiPSEs based on PAAK is demonstrated in an activated carbon-based supercapacitor operating up to 2 V with reasonable self-discharge. This proof of concept shows promise for low-cost and large-scale supercapacitors.
|
|
| 36. |
- Kozdra, Melania, et al.
(författare)
-
The sensitive aspects of modelling polymer-ceramic composite solid-state electrolytes using molecular dynamics simulations
- 2024
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 26:7, s. 6216-6227
-
Tidskriftsartikel (refereegranskat)abstract
- Solid-state composite electrolytes have arisen as one of the most promising materials classes for next-generation Li-ion battery technology. These composites mix ceramic and solid-polymer ion conductors with the aim of combining the advantages of each material. The ion-transport mechanisms within such materials, however, remain elusive. This knowledge gap can to a large part be attributed to difficulties in studying processes at the ceramic-polymer interface, which are expected to play a major role in the overall ion transport through the electrolyte. Computational efforts have the potential of providing significant insight into these processes. One of the main challenges to overcome is then to understand how a sufficiently robust model can be constructed in order to provide reliable results. To this end, a series of molecular dynamics simulations are here carried out with a variation of certain structural (surface termination and polymer length) and pair potential (van der Waals parameters and partial charges) models of the Li7La3Zr2O12 (LLZO) poly(ethylene oxide) (PEO) system, in order to test how sensitive the outcome is to each variation. The study shows that the static and dynamic properties of Li-ion are significantly affected by van der Waals parameters as well as the surface terminations, while the thickness of the interfacial region - where the structure-dynamic properties are different as compared to the bulk-like regime - is the same irrespective of the simulation setup.
|
|
| 37. |
- Kumar, Divyaratan, et al.
(författare)
-
Water-in-Polymer Salt Electrolyte for Long-Life Rechargeable Aqueous Zinc-Lignin Battery
- 2024
-
Ingår i: Energy & Environmental Materials. - : John Wiley & Sons. - 2575-0356 .- 2575-0348.
-
Tidskriftsartikel (refereegranskat)abstract
- Zinc metal batteries (ZnBs) are poised as the next-generation energy storage solution, complementing lithium-ion batteries, thanks to their cost-effectiveness and safety advantages. These benefits originate from the abundance of zinc and its compatibility with non-flammable aqueous electrolytes. However, the inherent instability of zinc in aqueous environments, manifested through hydrogen evolution reactions (HER) and dendritic growth, has hindered commercialization due to poor cycling stability. Enter potassium polyacrylate (PAAK)-based water-in-polymer salt electrolyte (WiPSE), a novel variant of water-in-salt electrolytes (WiSE), designed to mitigate side reactions associated with water redox processes, thereby enhancing the cyclic stability of ZnBs. In this study, WiPSE was employed in ZnBs featuring lignin and carbon composites as cathode materials. Our research highlights the crucial function of acrylate groups from WiPSE in stabilizing the ionic flux on the surface of the Zn electrode. This stabilization promotes the parallel deposition of Zn along the (002) plane, resulting in a significant reduction in dendritic growth. Notably, our sustainable Zn-lignin battery showcases remarkable cyclic stability, retaining 80% of its initial capacity after 8000 cycles at a high current rate (1 A g-1) and maintaining over 75% capacity retention up to 2000 cycles at a low current rate (0.2 A g-1). This study showcases the practical application of WiPSE for the development of low-cost, dendrite-free, and scalable ZnBs. A dendrite-free and long-life cycle Zn-lignin battery was demonstrated using water-in-polymer salt electrolyte.
|
|
| 38. |
- Lima de Jesus Silva, Jose Luis, 1987-
(författare)
-
Modelling and Simulation of Electro-catalysts for Green Energy : From Solvated Complexes to Solid-Liquid Interfaces
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I have worked with solid-liquid interfaces, adsorbed molecules on the surface, and solvated complexes using Density Functional Theory (DFT) calculations to find possible signatures that could help design suitable energy materials. More specifically, I have explored hybrid electrocatalysts for hydrogen evolution reaction (HER), XPS fingerprints of gas-phase melamine (monomer, dimer, trimer, and hexagonal packed arrangement), hexagonally packed melamine adsorbed on the Au(111) surface, and high-valence Ruthenium complexes along a reaction pathway in aqueous solution through a joint theory-experiment approach. First, I have explored single layer and hybrid-type systems as micro-reactors (current collector/catalysts) for HER with site-dependent calculations of the hydrogen binding free energy ΔGH to estimate the HER activity, electronic structure, and Schottky Barrier Height (SBH) to measure the resis-tance for charge injection across the interface. Furthermore, we have predicted a new hybrid electrocatalyst Td-WTe2/2H-MoS2 employing DFT-based trends. Additionally, we have built carbon-based hybrid systems from a bilayer of g-C3N4 coupled with Td-WTe2, 2H-MoS2, and Graphene, and used an implicit solvation model to obtain more realistic signatures. The results show that g-C3N4/Td-WTe2 has filled states in the Fermi level, which is a good indication of higher charge mobility. The SBH was evaluated with both GGA and HSE06, and Td-WTe2/g-C3N4 has shown lower resistance for charge injection across the interface. Further, the induced dipole (driving force for electron injection) increases under higher hydrogen coverages, enhanc-ing the catalytic activity. Finally, our results indicate that Td-WTe2/g-C3N4 could be classified as an efficient electrocatalyst for HER. In the last two papers, we have estimated XPS finger-prints of molecular and solid-state systems by calculating the core-level binding energy shifts using the Janak-Slater transition state approximation. Also, we have developed a new methodology by combing DFT calculations with Monte Carlo Simulations using explicit solvation to resolve the XPS and understand the chemical shifts of the [RuII -OH2]2+ species, as well as of multiple PCET oxidation states. This work also shows that the chemical shift of [RuIV =O]2+ is affected by the polarization of the explicit solvation model, and that we could only capture the experimental trend by using the complete first solvation shell and an XPS averaged spectra over a certain amount of snapshots from the Monte Carlo simulation. To the end, we also show that the nearest-neighbor potential contributions to the Ru 3d binding energies arising from atoms around the metallic center explain the higher 3d-state shifts of the oxo complex.
|
|
| 39. |
- Liu, Huanji, et al.
(författare)
-
3D Lattice-Matching Layered Hydroxide Heterostructure with Improved Interfacial Charge Transfer and Ion Diffusion for High Energy Density Supercapacitor
- 2021
-
Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 8:14, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochemical charge storage mostly relies on the electrical properties of complex interfaces and electrode materials as well as the dynamic ions diffusion in the electrolytes. Nickel-cobalt layered double hydroxides (LDHs) with tunable chemical composition are promising for electrochemical supercapacitors, where the theoretical performance could be up to 3000 F g(-1). However, the experimental performances of NiCo-LDHs are still limited by low charge transfer rate and slow dynamic ions diffusion. Here, a 3D lattice matching Ni0.85Co0.15(OH)(2)@alpha-Co(OH)(2) heterostructure is epitaxially grown. The experimental results and theoretical calculation confirm that such a 3D heterostructure could improve charge transfer abilities and accelerated ions diffusion. The specific capacitance of 2480 F g(-1) and retained 71% of the initial capacitance at high current density of 30 A g(-1) have been achieved by optimal Co(OH)(2) amount of 20 mg (NCC-20). Asymmetric button devices and soft-pack devices have been demonstrated with exceptional energy densities of 69.2 and 65.7 Wh kg(-1) at power densities of 0.79 and 0.78 kW kg(-1), and maintained 88% and 80% initial capacitance under 10 000 cycles, respectively. The general design principles clearly demonstrate the importance of electrochemical interface and dynamic process, paving the way to push forward the application capability of electrochemical devices.
|
|
| 40. |
- Marchiori, Cleber F.N., et al.
(författare)
-
Predicting Structure and Electrochemistry of Dilithium Thiophene-2,5-Dicarboxylate Electrodes by Density Functional Theory and Evolutionary Algorithms
- 2019
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:8, s. 4691-4700
-
Tidskriftsartikel (refereegranskat)abstract
- Organic electroactive materials are promising candidates to be TUC used as lithium insertion electrodes in the next generation of environmentally friendly battery technologies. In this work, evolutionary algorithms at interplay with density functional theory calculations have been employed to predict the crystal structure for both delithiated and lithiated phases of dilithium thiophene dicarboxylate (Li2TDC). On the basis of the resulting crystals, electronic structure modifications and voltage profiles for the lithiation process have been calculated. The obtained structure for the delithiated phase showed a well-defined salt layer intercalating the organic components, forming a so-called lithium organic framework (LOF). Upon lithiation, new structures appear which deviate from the LOF as a consequence of the reduction of the S atoms, which coordinate with the additional Li ions. The calculated average potential of similar to 1.00 V vs Li/Li+ is found to be in good agreement with experimental findings. An additional study at the molecular level has also been conducted aiming at gaining insight into the importance of the crystallographic environment on the structural and thermodynamics properties. This strategy is suitable for an initial assessment of the electrochemical process that underlies the lithiation mechanism of electrode materials. Moreover, the employed evolutionary algorithm emerges as a promising tool to predict crystal structures during lithiation, which are otherwise difficult to resolve experimentally.
|
|
| 41. |
- Marchiori, Cleber F.N., et al.
(författare)
-
Tuning the photocatalytic properties of porphyrins for hydrogen evolution reaction : An in-silico design strategy
- 2022
-
Ingår i: Journal of Power Sources Advances. - Amsterdam, Netherlands : Elsevier. - 2666-2485. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Porphyrins constitute a class of attractive materials for harvesting sunlight and promote chemical reactions following their natural activity for the photosynthetic process in plants. In this work, we employ an in-silico design strategy to propose novel porphyrin-based materials as photocatalysts for hydrogen evolution reaction (HER). More specifically, a set of meso-substituted porphyrins with donor-acceptor architecture are evaluated within the density functional theory (DFT) framework, according to these screening criteria: i) broad absorption spectrum in the ultraviolet–visible (UV–Vis) and near infrared (NIR) range, ii) suitable redox potentials to drive the uphill reaction that lead to molecular hydrogen formation, iii) low exciton binding free energy (Eb), and iv) low hydrogen binding free energy (ΔGH), a quantity that should present low HER overpotentials, ideally ΔGH = 0. The outcomes indicate that the Se-containing compound, where the donor ligands are attached to the porphyrin core by the spacer, outstands as the most promising candidate that is presented in this work. It displays a broad absorption in the visible and NIR regions to up to 1000 nm, suitable catalytic power, low Eb (in special in high dielectric constant environment, such as water) and the lowest ΔGH = +0.082 eV. This is comparable, in absolute values, to the value exhibited by platinum (ΔGH = −0.10 eV), one of the most efficient catalysts for HER.
|
|
| 42. |
- Mirsakiyeva, Amina, et al.
(författare)
-
Initial Steps in PEO Decomposition on a Li Metal Electrode
- 2019
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:37, s. 22851-22857
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(ethylene oxide) (PEO) is the most widely used compound as a solid-state (solvent-free) polymer electrolyte for Li batteries, mainly due to its low glass transition temperature (T-g) and ability to dissolve Li salts. It is also frequently suggested that its cathodic stability renders it possible to operate with Li metal anodes in the design of high energy density storage devices. However, little is still known about the true interfacial chemistry between Li metal and PEO and how these two materials interact with each other. We are here exploring this relationship by the means of density functional theory (DFT)-based modeling. Using bulk structures and isolated PEO chains, we have found that there is a strong thermodynamic driving force to oxidize Li metal into lithium oxide (Li2O) when PEO is decomposed into C2H4 and H-2, irrespectively of the PEO oligomer length. Explicit modeling of PEO on a Li(100) surface reveals that all steps in the decomposition are exothermic and that the PEO/Li metal system should have a layer of Li2O between the polymer electrolyte and the metal surface. These insights and the computational strategy adopted here could be highly useful to better tailor polymer electrolytes with favorable interfacial properties.
|
|
| 43. |
- Osorio-Guillen, J. M., et al.
(författare)
-
Assessing photocatalytic power of g-C3N4 for solar fuel production : A first-principles study involving quasi-particle theory and dispersive forces
- 2015
-
Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 143:9
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles quasi-particle theory has been employed to assess catalytic power of graphitic carbon nitride, g-C3N4, for solar fuel production. A comparative study between g-h-triazine and g-h-heptazine has been carried out taking also into account van der Waals dispersive forces. The band edge potentials have been calculated using a recently developed approach where quasi-particle effects are taken into account through the OW approximation First, it was found that the description of ground state properties such as cohesive and surface formation energies requires the proper treatment of dispersive interaction. Furthermore, through the analysis of calculated band-edge potentials, it is shown that g-h-triazine has high reductive power reaching the potential to reduce CO2 to formic acid, coplanar g-h-heptazine displays the highest thermodynamics force toward H2O/O-2 oxidation reaction, and corrugated g-h-heptazine exhibits a good capacity for both reactions. This rigorous theoretical study shows a route to further improve the catalytic performance of g-C3N4. (C) 2015 AIP Publishing LLC.
|
|
| 44. |
- Pereira, Cassia Ferreira Coutinho, et al.
(författare)
-
Inducing molecular orientation in solution-processed thin films of fluorene-bithiophene-based copolymer : thermal annealing vs. solvent additive
- 2024
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 14:13, s. 9051-9061
-
Tidskriftsartikel (refereegranskat)abstract
- A deep understanding of the factors influencing the morphology of thin films based on conjugated polymers is essential to boost their performance in optoelectronic devices. Herein, we investigated the electronic structure and morphology of thin films of the copolymer poly(9,9-dioctyl-fluorenyl-co-bithiophene) (F8T2) in its pristine form as well as samples processed with the solvent additive 1,8-diiodooctane (DIO) or post-processed through thermal annealing treatment. Measurements were carried out using angle-resolved S K-edge NEXAFS (near-edge X-ray absorption fine structure) in total electron yield (TEY) and fluorescence yield (FY) detection modes. Two main transitions were observed at the S 1s NEXAFS spectra: S 1s -> pi* and S 1s -> sigma* (S-C). The observed dichroism pointed to a face-on orientation of the conjugated backbone, which was significantly increased for F8T2 films processed with DIO. Resonant Auger decay spectra were obtained and analyzed using the core-hole clock (CHC) method. An enhancement in the charge transfer process was observed for thermally annealed films, especially for samples processed with DIO, corresponding to an increase in film ordering. Furthermore, the investigated films were characterized using X-ray photoelectron spectroscopy, attesting to the presence of the thiophene unit in the samples and demonstrating that some of its sulfur atoms were positively polarized in the F8T2 films. All these experimental findings were compared with molecular dynamics (MD) simulations of film evaporation with and without DIO. The use of MD, together with mathematical modeling, was able to explain the major effects found in the experiments, including the polarization of sulfur atoms. The simultaneous use of powerful spectroscopic techniques and theoretical methods shed light on key aspects linking film morphology with fabrication procedures.
|
|
| 45. |
- Pereira de Carvalho, Rodrigo, et al.
(författare)
-
Tuning the Electrochemical Properties of Organic Battery Cathode Materials : Insights from Evolutionary Algorithm DFT Calculations
- 2020
-
Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 13:9, s. 2402-2409
-
Tidskriftsartikel (refereegranskat)abstract
- Several forms of organic materials have arisen as promising candidates for future active electrode materials for Li-ion and post-Li-ion batteries, owing to a series of key features that encompasses sustainability, accessibility, and tunable electrochemical properties by molecular modifications. In this context, a series of organic electrode materials (OEMs) are investigated to further understand their thermodynamic and electronic properties. Through an evolutionary algorithm approach combined with first-principles calculations, the crystal structure of lithiated and delithiated phases of these OEMs and their respective NO2-substituted analogues are predicted. This framework allows a first assessment of their electrochemical and electronic properties and further understanding on the effects of the nitro group in the substituted compounds. NO2 is found to strongly affect structural and thermodynamic aspects during the electrochemical reaction with the reducing equivalents (Li++e(-)), changing the OEM's character from a low-potential anode to a high-potential cathode by creating a localization of the additional electrons, thus resulting in a better-defined redox-active center and leading to a shift in the potential from 0.92 V to 2.66 V vs. Li/Li+.
|
|
| 46. |
- Prasad, Suraj, et al.
(författare)
-
Photostability of Y-type electron acceptor molecules and related copolymer
- 2023
-
Ingår i: Proceedings Volume 12660, Organic, Hybrid, and Perovskite Photovoltaics XXIV. - : SPIE - The International Society for Optics and Photonics. ; 12660
-
Konferensbidrag (refereegranskat)abstract
- The lifetime of organic solar cells critically depends on the photochemical stability of the materials. To shed light on the photostability of novel Y-series electron acceptors, we investigate the evolution of optical properties and composition during one-sun illumination in ambient atmosphere of thin films of the small-molecule acceptor Y5 and its copolymers PF5-Y5 and PYT. We employ UV-vis, Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS), to assess changes in these properties as a function of illumination time. UV-Vis spectra show that PF5-Y5 undergoes rapid photobleaching, while the Y5 spectrum remains essentially unaffected even after 30 hours of exposure. The absorption spectrum of PYT, which contains a different co-mer than PF5-Y5, is only weakly affected. XPS C1s spectra of the PF5- Y5 film show a decreasing main peak and the development of a new component after 30 hours exposure, while the Y5 film surface composition remained intact. The photodegradation products of PF5-Y5 are characterized by the presence of new carbonyl groups, emerging as absorption bands in the FTIR spectra, while such spectral changes are absent for the Y5 film, indicating that Y5 is resistant to photooxidation, while PF5-Y5 undergoes photochemical reactions. The faster photodegradation of PF5-Y5 compared to Y5 and PYT raises the question about the role of the copolymer’s BDT moiety in the photooxidation. These new insights on the dependence of the photostability of acceptor molecules on their molecular structure are expected to contribute to the design of stable acceptor copolymers for organic solar cells with long operational lifetimes.
|
|
| 47. |
|
|
| 48. |
|
|
| 49. |
- Ronchi, Rodrigo M., et al.
(författare)
-
Thermoplastic polyurethane - Ti3C2(T-x) MXene nanocomposite : The influence of functional groups upon the matrix-reinforcement interaction
- 2020
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 528
-
Tidskriftsartikel (refereegranskat)abstract
- The recently discovered MXenes are promising candidates as reinforcements for nanocomposites due to their high mechanical properties, thermal and electrical conductivities. These properties are strongly affected by the presence of surface functional groups (-O, -F or -OH), which are related to the synthesis route employed. However, there is a lack of scientific investigations concerning the influence of such functional groups on the MXene/polymer matrix interaction. Therefore, we performed density functional theory calculations to simulate the interaction between Ti3C2 MXenes with different functional groups and thermoplastic polyurethane (TPU) based molecules. It was found that the main interaction mechanisms involved were the formation of hydrogen bonds and pi-pi stacking (in the aromatic ring). Moreover, while fluorine and hydroxyl terminations favored the interaction with TPU, oxygen-terminated MXene has hindered it in three of the four configurations tested. These findings indicate the relevance of controlling the MXenes surface chemistry for improving MXenes/polymer matrixes interactions in nanocomposites.
|
|
| 50. |
- Sousa, O. M., et al.
(författare)
-
Charging behavior of ZnMn2O4 and LiMn2O4 in a zinc- and lithium-ion battery : an ab initio study
- 2024
-
Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 2515-7655. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- In the field of sustainable energy storage systems, zinc-ion batteries (ZIB) employing aqueous electrolytes have emerged as viable successors to the widely used lithium-ion batteries, attributed to their cost-effectiveness, environmental friendliness, and intrinsic safety features. Despite these advantages, the performance of ZIBs is significantly hindered by the scarcity of suitable cathode materials, positioning manganese zinc oxide (ZnMn2O4) as a potential solution. In this study, we describe the ZnMn2O4 (ZMO) compound focusing on its properties variations during Zn extraction and potential battery applications. For the sake of comparison, we also analyze the same properties of the LiMn2O4 in its tetragonal phase (TLMO), for the first time, motivated by a recent discovery that the substitution of Zn ions by Li in ZMO forms isostructural TLMO compound at room temperature. The study was conducted within the density functional theory (DFT) framework, where the structural, electronic, magnetic, electrochemical, and spectroscopic properties of ZMO and TLMO are investigated under various conditions. Although both systems crystallize in tetragonal structures, they demonstrate distinct electronic and magnetic properties due to different oxidation states of the Mn. Computationally optimized lattice parameters align closely with experimental values. The TLMO exhibits a narrower band gap compared to ZMO, indicating enhanced electrical conductivity. In addition, TLMO presented a lower diffusion energy barrier than ZMO, indicating better ionic conductivity. To evaluate the potential application of these materials in battery technologies, we further explored their volume changes during charging/discharging cycles, simulating Zn or Li ions extraction. TLMO underwent a significant volume contraction of 5.8% upon complete Li removal, while ZMO experienced a more pronounced contraction of 12.5% with full Zn removal. By adjusting ion extraction levels, it is possible to reduce these contractions, thereby approaching more viable battery applications. Voltage profiles, constructed from DFT-based simulation results, unveiled an average voltage of 4.05 V for TLMO, closely matching experimental values. Furthermore, spectroscopy results provide insights into the electronic transitions and validate the computational findings, consolidating our understanding of the intrinsic properties of ZMO and TLMO.
|
|
