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Materials Modelling for Energy Harvesting: From Conversion to Application through Storage
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.ORCID iD: 0000-0002-3548-133x
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this Ph.D. thesis, ab initio density functional theory along with molecular dynamics and global optimization methods are used to unveil and understand the structures and properties of energy relevant materials. In this connection, the following applications are considered: i. electrocatalyst for solar fuel production through water splitting, ii. hybrid perovskite solar cell for generation of electrical energy and iii. Battery materials to store the electrical energy. The water splitting mechanism in terms of hydrogen evolution and oxygen evolution reactions (HER and OER) on the catalytic surfaces has been envisaged based on the free energy diagram, named reaction coordinate, of the reaction intermediates. The Ti-functionalized two-dimensional (2D) borophene monolayer has been emerged as a promising material for HER and OER mechanisms as compared to the pristine borophene sheet. Further investigation in the series of this noble metal free monolayer catalyst is 2D Al2C monolayer both in form of pristine and functionalized with nitrogen (N), phosphorous (P), boron (B), and sulphur (S). It has been observed that only B substituted Al2C shows very close to thermoneutral, that could be the most promising candidate for HER on functionalized Al2C monolayer. The adsorption of O* intermediate is stronger in S-substituted Al2C, whereas it is less strongly adsorbed on N-substituted Al2C. The subsequent consideration is being the case of n-type doping (W) along with Ti codoped in BiVO4 to enhance the efficiency of BiVO4 photoanode for water splitting. The determined adsorption energy and corresponding Gibbs free energies depict that the Ti site is energetically more favorable for water splitting. Moreover, the Ti site possesses a lower overpotential in the W–Ti codoped sample as compared to the mono-W doped sample. We have also explored the effect of mixed cation and mixed anion substitution in the hybrid perovskite in terms of structural stability, electronic properties and optical response of hybrid perovskite crystal structures. It has been found that the insertion of bromine (Br) into the system could modulate the stability of the Guanidinium lead iodide (GAPbI3) hybrid perovskite.  Moreover, the band gap of the mixed hybrid perovskite is increased with the inclusion of smaller Br anion while replacing partially the larger iodine (I) anion. Finally the electrochemical storage mechanism for Sodium (Na) and lithium (Li) ion insertion has been envisaged in inorganic electrode (eldfellite, NaFe(SO4)2) as well as in more sustainable organic electrode (di-lithium terephthalate, Li2TP). The full desodiation capability of the eldfellite enhances the capacity while the activation energies (higher than 1 eV) for the Na+ ion diffusion for the charged state lower the ionic insertion rate. The key factor as the variation of Li-O coordination in the terephthalate, for the disproportionation redox reaction in Li2TP is also identified.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 96
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1760
Keywords [en]
Materials Modelling, DFT, Energy Materials, Photocatalysis, HER and OER, Hybrid Perovskite Solar Cells, Stability, Thermodynamics and Kinetics in Na-ion battery, Organic Crystal Battery
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:uu:diva-369695ISBN: 978-91-513-0544-8 (print)OAI: oai:DiVA.org:uu-369695DiVA, id: diva2:1272793
Public defence
2019-02-15, 80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2019-01-24 Created: 2018-12-19 Last updated: 2019-02-18
List of papers
1. Scrupulous Probing of Bifunctional Catalytic Activity of Borophene Monolayer: Mapping Reaction Coordinate with Charge Transfer
Open this publication in new window or tab >>Scrupulous Probing of Bifunctional Catalytic Activity of Borophene Monolayer: Mapping Reaction Coordinate with Charge Transfer
2018 (English)In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 8, p. 3571-3576Article in journal (Refereed) Published
Abstract [en]

We have envisaged the hydrogen evolution and oxygen evolution reactions (HER and OER) on two-dimensional (2D) noble metal free borophene monolayer based on first-principles electronic structure calculations. We have investigated the effect of Ti functionalization on borophene monolayer from the perspective of HER and OER activities enhancement. We have probed the activities based on the reaction coordinate, which is conceptually related to the adsorption free energies of the intermediates of HER and OER, as well as from the vibrational frequency analysis with the corresponding charge transfer mechanism between the surface and the adsorbate. Ti-functionalized borophene has emerged as a promising material for HER and OER mechanisms. We believe that our probing method, based on reaction coordinate coupled with vibrational analysis that has been validated by the charge transfer mechanism, would certainly become as a robust prediction route for HER and OER mechanisms in coming days.

Keywords: borophene; hydrogen evolution reaction; oxygen evolution reaction; reaction coordinate; vibrational frequency

Keywords
borophene; hydrogen evolution reaction; oxygen evolution reaction; reaction coordinate; vibrational frequency
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-369691 (URN)10.1021/acsaem.8b00813 (DOI)000458706400007 ()
Funder
Carl Tryggers foundation StandUpSwedish Research Council
Available from: 2018-12-16 Created: 2018-12-16 Last updated: 2019-03-07Bibliographically approved
2. Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers
Open this publication in new window or tab >>Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers
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2018 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 1, p. 148-152Article in journal (Refereed) Published
Abstract [en]

First principles electronic structure calculations based on the density functional theory (DFT) framework are performed to investigate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on two-dimensional Al2C monolayers. In addition to the pristine Al2C monolayer, monolayers doped with Nitrogen (N), Phosphorous (P), Boron (B), and Sulphur (S) are also investigated. After determining the individual adsorption energy of hydrogen and oxygen on the different functionalized Al2C monolayers, the adsorption free energies are predicted for each of the functionalized monolayers in order to assess their suitability for HER or OER. The density of states and optical absorption spectra calculations along with the work function of the functionalized Al2C monolayers enable us to gain a profound understanding of the electronic structure for the individual system and their relation to the water splitting mechanism.

Keywords
adsorption free energy, Al2C monolayer, bifunctional catalysis, density functional calculations, doping
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-341495 (URN)10.1002/cphc.201700768 (DOI)000419338600020 ()28925531 (PubMedID)
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-12-19Bibliographically approved
3. Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W-Ti codoping
Open this publication in new window or tab >>Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W-Ti codoping
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2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 35, p. 16965-16974Article in journal (Refereed) Published
Abstract [en]

Efficient charge separation of photo-generated electrons and holes is critical to achieve high solar to hydrogen conversion efficiency in photoelectrochemical (PEC) water splitting. N-type doping is generally used to improve the conductivity by increasing the majority carrier density and enhance the charge separation in the photoanode. However, minority carrier transport is also very important in the process of charge separation, especially in materials that possess inadequate minority carrier mobility. Herein, we take a BiVO4 PEC water splitting cell as an example to demonstrate how to analyze the limiting factor and to formulate the corresponding solutions to improve the hole mobility. The benefits and problems caused by n-type doping (W-doping here) of BiVO4 are analyzed. Codoping with Ti further enhances the charge separation by improving the hole transport and leads to a cathodic shift of the photocurrent onset potential. A high charge separation efficiency (79% at 1.23 V-RHE) in a compact BiVO4 photoanode has been achieved without any nanostructure formation. Theoretical results show that W-Ti codoping has decreased the hole polaron hopping activation energy by 11.5% compared with mono-W doping, and this has resulted in a hole mobility increase by 29%. The calculated adsorption energy and reaction Gibbs free energies indicate that the Ti site is energetically more favorable for water splitting. Moreover, the Ti site possesses a lower overpotential in the W-Ti codoped sample compared with the mono-W doped sample. The current study indicates that in order to improve the solar energy conversion efficiency, there should be a balanced charge transport of both majority and minority charge carriers. This can be achieved by simply choosing appropriate codoping elements.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-366730 (URN)10.1039/c8ta05491f (DOI)000445218000025 ()
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-19Bibliographically approved
4. Bromination-induced stability enhancement with a multivalley optical response signature in guanidinium [C(NH2)(3)](+)-based hybrid perovskite solar cells
Open this publication in new window or tab >>Bromination-induced stability enhancement with a multivalley optical response signature in guanidinium [C(NH2)(3)](+)-based hybrid perovskite solar cells
2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 35, p. 18561-18568Article in journal (Refereed) Published
Abstract [en]

Guanidinium lead iodide (GAPbI(3)) has been synthesized experimentally, but stability remains an issue, which can be modulated by the insertion of bromine (Br) into the system. We have performed a systematic theoretical investigation to see how bromination can tune the stability of GAPbI(3). The optical properties were also determined, and we have found formation enthalpy-based stability in the perovskite systems, which are active in the visible and IR region even after bromine insertion and additionally more active in the IR range with the transition from GAPbI(3) to GAPbBr(3). The spin orbit coupling effect is considered throughout the band structure calculations. The ensemble of the primary and secondary gaps in the half and fully brominated hybrid perovskites leads to the phenomenon of a multipeak response in the optical spectra, which can be subsequently attributed as multivalley optical response behaviour. This multivalley optical behaviour enables the brominated guanidinium-based hybrid perovskites to exhibit broad light harvesting abilities, and this can be perceived as an idea for natural multi-junction solar cells.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-336031 (URN)10.1039/c7ta03114a (DOI)000410597200026 ()
Funder
Carl Tryggers foundation Swedish Research CouncilSwedish Energy AgencyStandUp
Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2018-12-19Bibliographically approved
5. Rashba Triggered Electronic and Optical Properties in De Novo Designed Mixed Halide Hybrid Perovskites
Open this publication in new window or tab >>Rashba Triggered Electronic and Optical Properties in De Novo Designed Mixed Halide Hybrid Perovskites
(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-369693 (URN)
Available from: 2018-12-16 Created: 2018-12-16 Last updated: 2018-12-19
6. Cesium bismuth iodide, CsxBiyIz, solar cell compounds from systematic molar ratio variation
Open this publication in new window or tab >>Cesium bismuth iodide, CsxBiyIz, solar cell compounds from systematic molar ratio variation
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-369694 (URN)
Available from: 2018-12-16 Created: 2018-12-16 Last updated: 2018-12-19
7. Unveiling the thermodynamic and kinetic properties of NaxFe(SO4)2 (x = 0–2): toward a high-capacity and low-cost cathode material
Open this publication in new window or tab >>Unveiling the thermodynamic and kinetic properties of NaxFe(SO4)2 (x = 0–2): toward a high-capacity and low-cost cathode material
2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, p. 17960-17969Article in journal (Refereed) Published
Abstract [en]

The mineral eldfellite, NaFe(SO4)2, was recently proposed as an inexpensive candidate for the next generation of cathode application in Na-based batteries. Employing the density functional theory framework, we have investigated the phase stability, electrochemical properties and ionic diffusion of this eldfellite cathode material. We showed that the crystal structure undergoes a volume shrinkage of ≈8% upon full removal of Na ions with no imaginary frequencies at the Γ point of phonon dispersion. This evokes the stability of the host structure. According to this result, we proposed structural changes to get higher specific energy by inserting two Na ions per redox-active metal. Our calculations indicate NaV(SO4)2 as the best candidate with the capability of reversibly inserting two Na ions per redox center and producing an excellent specific energy. The main bottleneck for the application of eldfellite as a cathode is the high activation energies for the Na+ ion hop, which can reach values even higher than 1 eV for the charged state. This effect produces a low ionic insertion rate.

National Category
Physical Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-311345 (URN)10.1039/C6TA05330K (DOI)000388505400007 ()
Funder
Swedish Research CouncilSwedish Energy AgencyStandUp
Available from: 2016-12-23 Created: 2016-12-23 Last updated: 2018-12-19Bibliographically approved
8. Designing strategies to tune reduction potential of organic molecules for sustainable high capacity batteries application
Open this publication in new window or tab >>Designing strategies to tune reduction potential of organic molecules for sustainable high capacity batteries application
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2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 9, p. 4430-4454Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-314502 (URN)10.1039/C6TA09760J (DOI)000395926100022 ()
Funder
Swedish Foundation for Strategic Research Swedish Energy AgencyStandUpSwedish Research Council
Available from: 2017-02-02 Created: 2017-02-02 Last updated: 2018-12-19Bibliographically approved
9. Assessing Electrochemical Properties of Polypyridine and Polythiophene for Prospective Application in Sustainable Organic Batteries
Open this publication in new window or tab >>Assessing Electrochemical Properties of Polypyridine and Polythiophene for Prospective Application in Sustainable Organic Batteries
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2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 4, p. 3307-3314Article in journal (Refereed) Published
Abstract [en]

Conducting polymers are being considered promising candidates for sustainable organic batteries mainly due to their fast electron transport properties and high recyclability. In this work, key properties of polythiophene and polypyridine have been assessed through a combined theoretical and experimental study focusing on such applications. A theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation models. Here, the evolution of the electrochemical properties of solvated oligomers as a function of the length of the chain is analyzed and then the polymer properties are estimated via linear regressions using ordinary least square. The predicted values were verified against our electrochemical experiments. This protocol can now be employed to screen a large database of compounds in order to identify organic electrodes with superior properties.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-311276 (URN)10.1039/C6CP07435A (DOI)000394940400071 ()28091636 (PubMedID)
Funder
Swedish Foundation for Strategic Research Swedish Energy AgencyStandUpSwedish Research Council
Available from: 2016-12-22 Created: 2016-12-22 Last updated: 2018-12-19Bibliographically approved
10. Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries
Open this publication in new window or tab >>Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 26, p. 14027-14036Article in journal (Refereed) Published
Abstract [en]

In the current emerging sustainable organic battery field, quinones are seen as one of the prime candidates for application in rechargeable battery electrodes. Recently, C6Cl4O2, a modified quinone, has been proposed as a high voltage organic cathode. However, the sodium insertion mechanism behind the cell reaction remained unclear due to the nescience of the right crystal structure. Here, the framework of the density functional theory (DFT) together with an evolutionary algorithm was employed to elucidate the crystal structures of the compounds NaxC6Cl4O2 (x = 0.5, 1.0, 1.5 and 2). Along with the usefulness of PBE functional to reflect the experimental potential, also the importance of the hybrid functional to divulge the hidden theoretical capacity is evaluated. We showed that the experimentally observed lower specific capacity is a result of the great stabilization of the intermediate phase Na1.5C6Cl4O2. The calculated activation barriers for the ionic hops are 0.68, 0.40, and 0.31 eV, respectively, for NaC6Cl4O2, Na1.5C6Cl4O2, and Na2C6Cl4O2. These results indicate that the kinetic process must not be a limiting factor upon Na insertion. Finally, the correct prediction of the specific capacity has confirmed that the theoretical strategy used, employing evolutionary simulations together with the hybrid functional framework, can rightly model the thermodynamic process in organic electrode compounds.

National Category
Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:uu:diva-329995 (URN)10.1021/acs.jpcc.7b03621 (DOI)000405252800007 ()
Funder
Swedish Energy AgencySwedish Research CouncilStandUp
Note

Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2018-12-19Bibliographically approved
11. Identifying the tuning key of disproportionation redox reaction in terephthalate: A Li-based anode for sustainable organic batteries
Open this publication in new window or tab >>Identifying the tuning key of disproportionation redox reaction in terephthalate: A Li-based anode for sustainable organic batteries
2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 47, p. 301-308Article in journal (Refereed) Published
Abstract [en]

The ever-increasing consumption of energy storage devices has pushed the scientific community to realize strategies toward organic electrodes with superior properties. This is owed to advantages such as economic viability and eco-friendliness. In this context, the family of conjugated dicarboxylates has emerged as an interesting candidate for the application as negative electrodes in advanced Li-ion batteries due to the revealed thermal stability, rate capability, high capacity and high cyclability. This work aims to rationalize the effects of small molecular modifications on the electrochemical properties of the terephthalate anode by means of first principles calculations. The crystal structure prediction of the investigated host compounds dilithium terephthalate (Li2TP) and diethyl terephthalate (Et2Li0TP) together with their crystal modification upon battery cycling enable us to calculate the potential profile of these materials. Distinct underlying mechanisms of the redox reactions were obtained where Li2TP comes with a disproportionation reaction while Et2Li0TP displays sequential redox reactions. This effect proved to be strongly correlated to the Li coordination number evolution upon the Li insertion into the host structures. Finally, the calculations of sublimation enthalpy inferred that polymerization techniques could easily be employed in Et2Li0TP as compared to Li2TP. Similar results are observed with methyl, propyl, and vinyl capped groups. That could be a strategy to enhance the properties of this compound placing it into the gallery of the new anode materials for state of art Li-batteries.

Keywords
Li-ion organic battery, Lithium terephthalate, Disproportionation, Redox potential
National Category
Physical Chemistry Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-354095 (URN)10.1016/j.nanoen.2018.02.038 (DOI)000430057000031 ()
Funder
Swedish Research Council, 2016-06014
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2018-12-19Bibliographically approved

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