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Design of Water Splitting Devices via Molecular Engineering
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Licheng Sun)ORCID iD: 0000-0003-3455-0855
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Converting solar energyto fuels such as hydrogen by the reaction of water splitting is a promising solution for the future sustainable energy systems. The theme of this thesis is to design water splitting devices via molecular engineering; it concerns the studies of both electrochemical-driven and photo-electrochemical driven molecular functional devices for water splitting.

The first chapter presents a general introduction about Solar Fuel Conversion. It concerns molecular water splitting catalysts, light harvesting materials and fabrication methods of water splitting devices.

The second chapter describes an electrode by immobilizing a molecular water oxidation catalyston carbon nanotubes through the hydrophobic interaction. This fabrication method is corresponding to the question: “How to employ catalysts in functional devices without affecting their performances?”

In the third chapter, molecular water oxidation catalysts were successfully immobilized on glassy carbon electrode surface via electrochemical polymerization method. The O-O bond formation pathways of catalysts on electrode surfaces were studied. This kinetic studyis corresponding to the question: “How to get kinetic information of RDS whena catalyst is immobilized on the electrode surface?”

Chapter four explores molecular water oxidation catalysts immobilized on dye-sensitized TiO2 electrodeand Fe2O3 semiconductor electrode via different fabrication methods. The reasons of photocurrent decay are discussed and two potential solutions are provided. These studies are corresponding to the question: “How to improvethe stability of photo-electrodes?”

Finally, in the last chapter, two novel Pt-free Z-schemed molecular photo-electrochemical cells with both photoactive cathode and photoactive anode for visible light driven water splitting driven were demonstrated. These studies are corresponding to the question: “How to utilizethe concept of Z-schemein photosynthesis to fabricate Pt-free molecular based PEC cells?

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 92 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:6
Keyword [en]
electrochemical-driven water splitting, artificial photosynthesis, molecular catalysts
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-181107ISBN: 978-91-7595-841-5OAI: oai:DiVA.org:kth-181107DiVA: diva2:898695
Public defence
2016-02-26, F3, Lindstedtsvägen 26, KTH, Stockholm., 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20160129

Available from: 2016-01-29 Created: 2016-01-29 Last updated: 2016-01-29Bibliographically approved
List of papers
1. Immobilization of a molecular catalyst on carbon nanotubes for highly efficient electro-catalytic water oxidation
Open this publication in new window or tab >>Immobilization of a molecular catalyst on carbon nanotubes for highly efficient electro-catalytic water oxidation
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2014 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 90, 13948-13951 p.Article in journal (Refereed) Published
Abstract [en]

Electrochemically driven water oxidation has been performed using a molecular water oxidation catalyst immobilized on hybrid carbon nanotubes and nano-material electrodes. A high turnover frequency (TOF) of 7.6 s(-1) together with a high catalytic current density of 2.2 mA cm(-2) was successfully obtained at an overpotential of 480 mV after 1 h of bulk electrolysis.

Keyword
multi walled nanotube, ruthenium, water
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-157248 (URN)10.1039/c4cc06959e (DOI)000343985600019 ()25265253 (PubMedID)2-s2.0-84907998300 (ScopusID)
Note

QC 20141208

Available from: 2014-12-08 Created: 2014-12-08 Last updated: 2016-01-29Bibliographically approved
2. Control the O-O bond formation pathways by immobilizing molecular catalysts on glassy carbon via electrochemical polymerization
Open this publication in new window or tab >>Control the O-O bond formation pathways by immobilizing molecular catalysts on glassy carbon via electrochemical polymerization
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Molecular water oxidation catalysts Ru-bda (1) and Ru-pda (2) are electrochemically polymerized on glassy carbon (GC) electrodes. Reaction orders and kinetic isotope effects (KIE) of the corresponding electrodes are studied. Results indicate that poly-1@GC goes through a radical coupling pathway. By adding poly-styrene (PSt) as a “blocking unit” in the poly-1, the radical coupling process of Ru-bda is blocked, and poly-1+PSt@GC catalyzes water oxidation through the water nucleophilic attack pathway. In comparison, catalyst 2, which oxidizes water via water nucleophilic attack path in homogeneous systems, goes through a radical coupling pathway as well when 2 is polymerized on glassy carbon (poly-2@GC).

Keyword
kinetics
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-181103 (URN)
Funder
Swedish Energy Agency, B61649
Note

QS 2016

Available from: 2016-01-29 Created: 2016-01-29 Last updated: 2016-02-01Bibliographically approved
3. Immobilizing Ru(bda) Catalyst on a Photoanode via Electrochemical Polymerization for Light-Driven Water Splitting
Open this publication in new window or tab >>Immobilizing Ru(bda) Catalyst on a Photoanode via Electrochemical Polymerization for Light-Driven Water Splitting
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2015 (English)In: ACS Catalysis, ISSN 2155-5435, Vol. 5, no 6, 3786-3790 p.Article in journal (Refereed) Published
Abstract [en]

The molecular water oxidation catalyst 1 was electrochemically polymerized on a dye-sensitized TiO2 electrode and an Fe2O3 nanorod electrode. High photocurrent densities of ca. 1.4 mA cm(-2) for poly-1+RuP@TiO2 and ca. 0.4 mA cm(-2) for poly-1@Fe2O3 were achieved under pH-neutral conditions. A kinetic isotope effect (KIE) study on poly-1+RuP@TiO2 shows that poly-1 catalyzes water oxidation on the surface of TiO2 via a radical coupling mechanism.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-170683 (URN)10.1021/cs502115f (DOI)000355964300067 ()2-s2.0-84930938630 (ScopusID)
Funder
Swedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish Research Council
Note

QC 20150707

Available from: 2015-07-07 Created: 2015-07-03 Last updated: 2016-01-29Bibliographically approved
4. Immobilization of a Molecular Ruthenium Catalyst on Hematite Nanorod Arrays for Water Oxidation with Stable Photocurrent
Open this publication in new window or tab >>Immobilization of a Molecular Ruthenium Catalyst on Hematite Nanorod Arrays for Water Oxidation with Stable Photocurrent
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2015 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 19, 3242-3247 p.Article in journal (Refereed) Published
Abstract [en]

Photoelectrochemical (PEC) cells for light-driven water splitting are prepared using hematite nanorod arrays on conductive glass as the photoanode. These devices improve the photocurrent of the hematite-based photoanode for water splitting, owing to fewer surface traps and decreased electron recombination resulting from the one-dimensional structure. By employing a molecular ruthenium co-catalyst, which contains a strong 2,6-pyridine-dicarboxylic acid anchoring group at the hematite photoanode, the photocurrent of the PEC cell is enhanced with high stability for over 10000s in a 1M KOH solution. This approach can pave a route for combining one-dimensional nanomaterials and molecular catalysts to split water with high efficiency and stability.

Keyword
hematite, heterogeneous catalysis, nanorods, ruthenium, water oxidation
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-174709 (URN)10.1002/cssc.201500730 (DOI)000362729800009 ()2-s2.0-84943583520 (ScopusID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Energy Agency
Note

QC 20151111

Available from: 2015-11-11 Created: 2015-10-07 Last updated: 2016-01-29Bibliographically approved
5. Pt-free tandem molecular photoelectrochemical cells for water splitting driven by visible light
Open this publication in new window or tab >>Pt-free tandem molecular photoelectrochemical cells for water splitting driven by visible light
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2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 46, 25234-25240 p.Article in journal (Refereed) Published
Abstract [en]

Photoelectrochemical (PEC) cells using molecular catalysts to split water into hydrogen and oxygen have been investigated intensively during the past years. However, the high-cost of Pt counter electrodes and instability of molecular PEC cells hinder the practical applications. We describe in this article a Pt-free tandem molecular PEC cell, for the first time, employing molecular ruthenium- and cobalt-catalysts with strong dipicolinic acid anchoring groups on the respective photoanode and photocathode for total water splitting. The Pt-free tandem molecular PEC cell showed an effective and steady photocurrent density of ca. 25 mu A cm(-2) for water splitting driven by visible light without external bias. This study indicates that tandem molecular PEC cells can provide great potential to the Pt-free devices for light driven total water splitting.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-158855 (URN)10.1039/c4cp04489d (DOI)000344989500003 ()2-s2.0-84908568729 (ScopusID)
Note

QC 20150120

Available from: 2015-01-20 Created: 2015-01-12 Last updated: 2016-01-29Bibliographically approved
6. Organic Dye-Sensitized Tandem Photoelectrochemical Cell for Light Driven Total Water Splitting
Open this publication in new window or tab >>Organic Dye-Sensitized Tandem Photoelectrochemical Cell for Light Driven Total Water Splitting
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2015 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, no 28, 9153-9159 p.Article in journal (Refereed) Published
Abstract [en]

Light driven water splitting was achieved by a tandem dye-sensitized photoelectrochemical cell with two photoactive electrodes. The photoanode is constituted by an organic dye L0 as photosensitizer and a molecular complex Ru1 as water oxidation catalyst on meso-porous TiO2, while the photocathode is constructed with an organic dye P1 as photoabsorber and a molecular complex Col as hydrogen generation catalyst on nanostructured NiO. By combining the photocathode and the photoanode, this tandem DS-PEC cell can split water by visible light under neutral pH conditions without applying any bias.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-172717 (URN)10.1021/jacs.5b04856 (DOI)000358556200043 ()26132113 (PubMedID)2-s2.0-84937697932 (ScopusID)
Funder
Swedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish Research Council
Note

QC 20150831

Available from: 2015-08-31 Created: 2015-08-27 Last updated: 2016-01-29Bibliographically approved

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The full text will be freely available from 2017-06-01 10:09
Available from 2017-06-01 10:09

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