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Dynamics and Photochemical H-2 Evolution of Dye-NiO Photocathodes with a Biomimetic FeFe-Catalyst
Department of Chemistry—Ångström Laboratory, Uppsala University.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
Department of Chemistry—Ångström Laboratory, Uppsala University.
Department of Chemistry—Ångström Laboratory, Uppsala University.
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Number of Authors: 6
2016 (English)In: ACS Energy Letters, ISSN 2380-8195, Vol. 1, no 6, 1106-1111 p.Article in journal (Refereed) Published
Abstract [en]

Mesoporous NiO films were cosensitized with a coumarin 343 dye and a proton reduction catalyst of the [Fe-2(CO)(6)(bdt)] (bdt = benzene-1,2-dithiolate) family. Femtosecond ultraviolet visible transient absorption experiments directly demonstrated subpicosecond hole injection into NiO from excited dyes followed by rapid (t(50%) similar to 6 ps) reduction of the catalyst on the surface with similar to 70% yield. The reduced catalyst was long-lived (2 mu s to 20 ms), which may allow protonation and a second reduction step of the catalyst to occur. A photo electrochemical device based on this photocathode produced H-2 with a Faradaic efficiency of similar to 50%. Fourier transform infrared spectroscopy and gas chromatography experiments demonstrated that the observed device deterioration with time was mainly due to catalyst degradation and desorption from the NiO surface. The insights gained from these mechanistic studies, regarding development of dye-catalyst cosensitized photocathodes, are discussed.

Place, publisher, year, edition, pages
2016. Vol. 1, no 6, 1106-1111 p.
National Category
Other Physics Topics
Research subject
Experimental physics
Identifiers
URN: urn:nbn:se:ltu:diva-61410DOI: 10.1021/acsenergylett.6b00506ISI: 000390086400005OAI: oai:DiVA.org:ltu-61410DiVA: diva2:1064602
Note

Validerad; 2017; Nivå 2; 2017-01-12 (andbra)

Available from: 2017-01-12 Created: 2017-01-12 Last updated: 2017-11-24Bibliographically approved
In thesis
1. Advanced Metal Oxide Semiconductors for Solar Energy Harvesting and Solar Fuel Production
Open this publication in new window or tab >>Advanced Metal Oxide Semiconductors for Solar Energy Harvesting and Solar Fuel Production
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing energy consumption and its environmental impacts make it necessary to look for alternative energy sources. Solar energy as huge energy source which is able to cover the terms sustainability is considered as a favorable alternative. Solar cells and solar fuels are two kinds of technologies, which make us able to harness solar energy and convert it to electricity and/or store it chemically.

Metal oxide semiconductors (MOSs) have a major role in these devices and optimization of their properties (composition, morphology, dimensions, crystal structure) makes it possible to increase the performance of the devices. The light absorption, charge carriers mobility, the time scale between charge injection, regeneration and recombination processes are some of the properties critical to exploitation of MOSs in solar cells and solar fuel technology.

In this thesis, we explore two different systems. The first one is a NiO mesoporous semiconductor photocathode sensitized with a biomimetic Fe-Fe catalyst and a coumarin C343 dye, which was tested in a solar fuel device to produce hydrogen. This system is the first solar fuel device based on a biomimetic Fe-Fe catalyst and it shows a Faradic efficiency of 50% in hydrogen production. Cobalt catalysts have higher Faradic efficiency but their performance due to hydrolysis in low pH condition is limited. The second one is a photoanode based on the nanostructured hematite/magnetite film, which was tested in a photoelectrochemical cell. This hybrid electrode improved the photoactivity of the photoelectrochemical cell for water splitting. The main mechanism for the improvement of the functional properties relies with the role of the magnetite phase, which improves the charge carrier mobility of the composite system, compared to pure hematite, which acts as good light absorber semiconductor.

By optimizing the charge separation and mobility of charge carriers of MOSs, they can be a promising active material in solar cells and solar fuel devices due to their abundance, stability, non-toxicity, and low-cost. The future work will be focused on the use of nanostructured MOSs in all-oxide solar cell devices. We have already obtained some preliminary results on 1-dimensional heterojunctions, which we report in Chapter 3.3. While they are not conclusive, they give an idea about the future direction of the present research. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keyword
Photovoltaic, Semiconductors, Photoelectrochemical cell, Solar fuel, Water splitting, Hydrogen evolution, Oxygen evolution
National Category
Engineering and Technology
Research subject
Experimental physics
Identifiers
urn:nbn:se:ltu:diva-64922 (URN)978-91-7583-979-0 (ISBN)978-91-7583-980-6 (ISBN)
Presentation
2017-11-08, E231, Luleå, 10:00 (English)
Opponent
Supervisors
Funder
VINNOVA, 224320
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2017-11-24Bibliographically approved

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