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Water Splitting Mechanism on 2D Catalytic Materials: DFT based Theoretical Investigations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we have envisaged systematic investigation to predict the water splitting mechanism on ultra-thin two-dimensional (2D) materials using cutting edge computation. Three different families of materials are considered as the case studies - i.MX2 (where M= W and Pt) based transition metal dichalcogenides, ii. lightest 2D material as Boron monolayer and iii. Mg3N2 monolayer. The catalytic reaction mechanism of water dissociation consists of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), both of which are required to be investigated thoroughly in order to perceive the complete picture of water splitting. This is because of the fact that the fundamental understanding of how and why the improved solar hydrogenproduction properties could be developed for such 2D materials is also of great technological importance. We have performed rigorous electronic structure calculations based on density functional theory (DFT) to find the optimum catalytic activity of the considered monolayer nanostructures. Hydrogen and oxygen evolution reaction activity are determined from the surface-adsorbate interaction based on the adsorption energy of the major intermediates of HER and OER mechanism. Our DFT based investigations will be the intuitive way to theoretically rationalize HER and OER activity for a series of functionalized different two-dimensional systems and can guide the actual experiment in the laboratory with a preconceived framework.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 57
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1804
National Category
Natural Sciences
Research subject
Physics and Astronomy specializing in Theoretical Physics; Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-381720ISBN: 978-91-513-0646-9 (print)OAI: oai:DiVA.org:uu-381720DiVA, id: diva2:1304750
Public defence
2019-05-27, Room Å80101, Ångströmlaboratoriet, Lägerhyddsvägen 2, 13:15 (English)
Opponent
Supervisors
Available from: 2019-04-29 Created: 2019-04-13 Last updated: 2019-06-18Bibliographically approved
List of papers
1. A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory
Open this publication in new window or tab >>A comparative study of hydrogen evolution reaction on pseudo-monolayer WS2 and PtS2: insights based on the density functional theory
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2017 (English)In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 7, no 3, p. 687-692Article in journal (Refereed) Published
Abstract [en]

In this study, we investigated the catalytic activity of ultrathin PtS2 and WS2 nanostructures for the hydrogen evolution reaction by electronic structure calculations based on the spin-polarised density functional theory. We also explored the effect of van der Waals interactions on the surface-adsorbate interactions. Using the adsorption free energy of H-2 as an activity descriptor, we tuned the photocatalytic water splitting activity of PtS2 and WS2 by functionalizing the individual systems with different transition metals such as Ru, Rh, Pd, Ag, Ir, Au, and Hg. The density of states was calculated along with the band structure to find the effect of different dopants on the fundamental band gap, which is one of the primary parameters in the photocatalytic water splitting.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-320468 (URN)10.1039/c6cy02426b (DOI)000398053000017 ()
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2019-04-13Bibliographically approved
2. Two-dimensional boron: Lightest catalyst for hydrogen and oxygen evolution reaction
Open this publication in new window or tab >>Two-dimensional boron: Lightest catalyst for hydrogen and oxygen evolution reaction
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2016 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 109, no 5, article id 053903Article in journal (Refereed) Published
Abstract [en]

The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) have been envisaged on a two-dimensional (2D) boron sheet through electronic structure calculations based on a density functional theory framework. To date, boron sheets are the lightest 2D material and, therefore, exploring the catalytic activity of such a monolayer system would be quite intuitive both from fundamental and application perspectives. We have functionalized the boron sheet (BS) with different elemental dopants like carbon, nitrogen, phosphorous, sulphur, and lithium and determined the adsorption energy for each case while hydrogen and oxygen are on top of the doping site of the boron sheet. The free energy calculated from the individual adsorption energy for each functionalized BS subsequently guides us to predict which case of functionalization serves better for the HER or the OER.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-305577 (URN)10.1063/1.4960102 (DOI)000383091400055 ()
Available from: 2016-10-19 Created: 2016-10-19 Last updated: 2019-04-13Bibliographically approved
3. Toward the Realization of 2D Borophene Based Gas Sensor
Open this publication in new window or tab >>Toward the Realization of 2D Borophene Based Gas Sensor
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 48, p. 26869-26876Article in journal (Refereed) Published
Abstract [en]

To the league of rapidly expanding 2D materials, borophene is a recent addition. Herein, a combination of ab initio density functional theory (DFT) and nonequilibrium Green's function (NEGF) based methods is used to estimate the prospects of this promising elemental 2D material for gas sensing applications. We note that the binding of target gas molecules such as CO, NO, NO2, NH3, and CO2 is quite strong on the borophene surface. Interestingly, our computed binding energies are far stronger than several other reported 2D materials like graphene, MoS2, and phosphorene. Further rationalization of stronger binding is made with the help of charge transfer analysis. The sensitivity of the borophene for these gases is also interpreted in terms of computing the vibrational spectra of the adsorbed gases on top of borophene, which show dramatic shift from their gas phase reference values. The metallic nature of borophene enables us to devise a setup considering the same substrate as electrodes. From the computation of the transmission function of system (gas + borophene), appreciable changes in the transmission functions are noted compared to pristine borophene surface. The measurements of current-voltage (I-V) characteristics unambiguously demonstrate the presence and absence of gas molecules (acting as ON and OFF states), strengthening the plausibility of a borophene based gas sensing device. As we extol the extraordinary sensitivity of borophene, we assert that this elemental 2D material is likely to attract subsequent interest.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-340255 (URN)10.1021/acs.jpcc.7b09552 (DOI)000417671500032 ()
Funder
Swedish National Infrastructure for Computing (SNIC)Swedish Research CouncilCarl Tryggers foundation StandUp
Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2019-04-13Bibliographically approved
4. Reaction Coordinate Mapping of Hydrogen Evolution Mechanism on Mg3N2Monolayer
Open this publication in new window or tab >>Reaction Coordinate Mapping of Hydrogen Evolution Mechanism on Mg3N2Monolayer
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-381723 (URN)
Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-04-13

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