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Accumulative Charge Separation in Photocatalysis: From Molecules to Nanoparticles
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. (Physical Chemistry)
2019 (English)Doctoral thesis, comprehensive summary (Other academic) [Artistic work]
Abstract [en]

Photochemical energy conversion into solar fuel involves steps of light absorption, charge separation and catalysis. Nature has taught us that the effective accumulation of redox equivalents and charge separation are the key steps in sunlight conversion. The focus of this thesis is to unveil photophysical and photochemical processes that lead to accumulative charge separation. The optimization of electron transfer process will be held by minimization of losses via recombination, and extension of the lifetime of the charge separated state by usage of the electron relay.

The goal is to couple light induced electron transfer process with the multi-electron catalytic process of hydrogen evolution. In this regard, light harvesters (molecules, metal nanostructures) that generate at least two electrons per absorbed photon will be studied. Additionally, semiconductors that generate long-lived charge separated states are utilized to accumulate several redox equivalents necessary for hydrogen evolution.

The hybrid systems produced by the combination of the advantageous properties of molecules, semiconductors, and metal nanoparticles are under the scope of investigation. Metal nanoparticles are advantageous because of their high absorption cross-section. The molecular linkers provide control and flexibility in tuning the connection between the light absorber and the electron relay. Semiconductor nanoparticles offer the desired charge separation properties via prolonging the lifetime sufficiently to perform photocatalysis.

The detailed understanding, investigation and development of the hybrid systems is at the heart of the progress of photochemical solar fuel production.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 88
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1759
Keywords [en]
Accumulative charge separation, Electron transfer, Plasmon dynamics, Time-resolved spectroscopy, Photocatalysis.
National Category
Chemical Sciences
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-369930ISBN: 978-91-513-0543-1 (print)OAI: oai:DiVA.org:uu-369930DiVA, id: diva2:1271643
Public defence
2019-02-22, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2019-01-23 Created: 2018-12-17 Last updated: 2019-02-18
List of papers
1. Ultra long-lived electron-hole separation within water-soluble colloidal ZnO nanocrystals: Prospective Applications For Solar Energy Production
Open this publication in new window or tab >>Ultra long-lived electron-hole separation within water-soluble colloidal ZnO nanocrystals: Prospective Applications For Solar Energy Production
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2016 (English)In: Nano Energy, ISSN 2211-2855, Vol. 30, p. 187-192Article in journal (Refereed) Published
Abstract [en]

Zinc oxide was one of the first semiconductors used in dye-sensitized solar cells but its instability in aqueous media precludes its use for large-scale applications. Herein, we report on a novel ZnO nanocrystal material derived by an organometallic approach that is simultaneously stable and soluble in water due to its carboxylate oligoethylene glycol shell strongly anchored to the inorganic core by the head groups. The resulting unique inorganic core-organic shell interface also stabilizes the photo-generated hole, leading to a dramatic slowing down of charge recombination, which otherwise is a major hurdle in using nanostructured ZnO.

Keywords
Water-soluble colloidal ZnO nanocrystals, Ultra long-lived electron-hole separation, Advanced laser based spectroscopy, Solar energy production prospectus
National Category
Nano Technology Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-314050 (URN)10.1016/j.nanoen.2016.09.045 (DOI)000390636100023 ()
Funder
Knut and Alice Wallenberg FoundationEU, European Research Council, 687008Swedish Research Council, 2015-03764
Available from: 2017-02-06 Created: 2017-01-26 Last updated: 2018-12-17Bibliographically approved
2. Hydrogen evolution with nanoengineered ZnO interfaces decorated using a beetroot extract and a hydrogenase mimic
Open this publication in new window or tab >>Hydrogen evolution with nanoengineered ZnO interfaces decorated using a beetroot extract and a hydrogenase mimic
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2017 (English)In: Sustainable Energy & Fuels, ISSN 2398-4902, Vol. 1, p. 69-73Article in journal (Refereed) Published
Abstract [en]

Herein, we report a nano-hybrid photo-system based on abundant elements for H2 production with visible light. The photo-system's proficiency relates to the novel ZnO nanocrystals employed. The ZnO carboxylate oligoethylene glycol shell enhances charge separation and accumulates reactive electrons for the photocatalytic process. 

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keywords
H2 evolution
National Category
Physical Chemistry Engineering and Technology
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-335979 (URN)10.1039/c6se00066e (DOI)000422769100006 ()
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-12-17Bibliographically approved
3. Magnetic Manipulation of Spontaneous Emission from Inorganic CsPbBr3 Perovskites Nanocrystals
Open this publication in new window or tab >>Magnetic Manipulation of Spontaneous Emission from Inorganic CsPbBr3 Perovskites Nanocrystals
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2016 (English)In: ADVANCED OPTICAL MATERIALS, ISSN 2195-1071, Vol. 4, no 12, p. 2004-2008Article in journal (Refereed) Published
Abstract [en]

Metal halide perovskites have shown great potential for both light-absorbing and light-emitting devices. It is demonstrated that the presence of a low-magnetic field decreases dramatically the photoluminescence of CsPbBr3. This is found to be due to a decrease in charge separated state lifetime. The effect is fully reversible, and can be exploited for simple and remote modulation of the output of light-emitting devices.

National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-315916 (URN)10.1002/adom.201600611 (DOI)000392405100014 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 2015-03764EU, FP7, Seventh Framework Programme, 306733
Available from: 2017-02-23 Created: 2017-02-23 Last updated: 2018-12-17Bibliographically approved
4. Hydrogen evolution with CsPbBr3 perovskite nanocrystals under visible light in solution
Open this publication in new window or tab >>Hydrogen evolution with CsPbBr3 perovskite nanocrystals under visible light in solution
2018 (English)In: MATERIALS TODAY COMMUNICATIONS, ISSN 2352-4928, Vol. 16, p. 90-96Article in journal (Refereed) Published
Abstract [en]

Direct proton photo-reduction to molecular hydrogen with a lead-halide perovskite photosystem is presented. The concept uses CsPbBr3 nanocrystals and Ru@TiO2 nanoparticles as light harvesters and catalyst, respectively. The photo-system attains charge transfer from donor to acceptor via collision events, established via static and ultrafast spectroscopy. The photo-system exhibits a photon-to-hydrogen efficiency of ca. 0.4%, a respectable efficiency for a system relying on effective collisions for the transference of electrons.

Keywords
Inorganic perovskites nanocrystals, H-2 evolution, Ultrafast spectroscopy, Charge transfer via collision
National Category
Materials Chemistry Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-364171 (URN)10.1016/j.mtcomm.2018.05.001 (DOI)000443035000012 ()
Funder
Swedish Research CouncilStiftelsen Olle Engkvist Byggmästare
Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-12-17Bibliographically approved
5. Nano-hybrid plasmonic photocatalyst for hydrogen production at 20% efficiency
Open this publication in new window or tab >>Nano-hybrid plasmonic photocatalyst for hydrogen production at 20% efficiency
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 8670Article in journal (Refereed) Published
Abstract [en]

The efficient conversion of light energy into chemical energy is key for sustainable human development. Several photocatalytic systems based on photovoltaic electrolysis have been used to produce hydrogen via water reduction. However, in such devices, light harvesting and proton reduction are carried separately, showing quantum efficiency of about 10–12%. Here, we report a nano-hybrid photocatalytic assembly that enables concomitant reductive hydrogen production and pollutant oxidation with solar-to-fuel efficiencies up to 20%. The modular architecture of this plasmonic material allows the fine-tuning of its photocatalytic properties by simple manipulation of a reduced number of basic components.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-328630 (URN)10.1038/s41598-017-09261-7 (DOI)000407864400051 ()
Funder
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IB2015-6474
Available from: 2017-08-28 Created: 2017-08-28 Last updated: 2018-12-17Bibliographically approved
6. Hydrated Electron Generation by Excitation of Localized Surface Plasmons in Copper Nanoparticles
Open this publication in new window or tab >>Hydrated Electron Generation by Excitation of Localized Surface Plasmons in Copper Nanoparticles
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(English)In: Science Advances, E-ISSN 2375-2548Article in journal (Refereed) Submitted
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-369929 (URN)
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-03-20

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