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Mijangos, Edgar
Publications (10 of 10) Show all publications
Föhlinger, J., Maji, S., Brown, A. M., Mijangos, E., Ott, S. & Hammarström, L. (2018). Self-quenching and Slow Hole Injection May Limit the Efficiency in NiO-based Dye-Sensitized Solar Cells. The Journal of Physical Chemistry C, 122(25), 13902-13910
Open this publication in new window or tab >>Self-quenching and Slow Hole Injection May Limit the Efficiency in NiO-based Dye-Sensitized Solar Cells
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 25, p. 13902-13910Article in journal (Refereed) Published
Abstract [en]

A series of bis-tridentate ruthenium complexes was designed to feature opposite localizations of their lowest metal-to-ligand charge transfer (MLCT) excited states, relative to a carboxylic acid that served as a binding group to mesoporous NiO. The purpose was to study the effect of MLCT direction on the rates of hole injection into NiO and subsequent charge recombination. Surprisingly, femtosecond-transient absorption spectroscopy showed that the two heteroleptic, cyclometalated complexes of this series did not inject holes into NiO, but their excited states were nevertheless quenched in a rapid process (on the time scale of hundreds of picoseconds). An identical result was obtained for the dyes on nonreactive ZrO2 and we therefore attribute the short MLCT lifetime to self-quenching, due the high surface concentrations of the dyes. We further show that self-quenching on this time scale can potentially compete with hole injection also for functional NiO sensitizers. A ruthenium polypyridine complex, which has previously been used for NiO-based solar cells, was shown to inject holes only very slowly (τ ≈ 5 ns), in contrast to the common notion that hole injection in dye-NiO systems is ultrafast (predominantly subpicosecond time scale). The hole injection yield was estimated to only ca. 20%, which matches the reported APCE value of the corresponding device [Freys, J. C.; Gardner, J. M.; D’Amario, L.; Brown, A. M.; Hammarström, L. Dalton Trans. 2012, 41, 13105]. Therefore, we suggest that slow injection and self-quenching might be a reason for the low photovoltaic performance of some p-type dye-sensitized solar cells.

National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-343442 (URN)10.1021/acs.jpcc.8b01016 (DOI)000437811500078 ()
Funder
Swedish Research Council, 2014-5921Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-09-21Bibliographically approved
Mijangos, E., Roy, S., Pullen, S., Lomoth, R. & Ott, S. (2017). Evaluation of two- and three-dimensional electrode platforms for the electrochemical characterization of organometallic catalysts incorporated in non-conducting metal-organic frameworks. Dalton Transactions, 46(15), 4907-4911
Open this publication in new window or tab >>Evaluation of two- and three-dimensional electrode platforms for the electrochemical characterization of organometallic catalysts incorporated in non-conducting metal-organic frameworks
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2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 15, p. 4907-4911Article in journal (Refereed) Published
Abstract [en]

The development of a reliable platform for the electrochemical characterization of a redox-active molecular diiron complex, [FeFe], immobilized in a non-conducting metal organic framework (MOF), UiO-66, based on glassy-carbon electrodes is reported. Voltammetric data with appreciable current responses can be obtained by the use of multiwalled carbon nanotubes (MWCNT) or mesoporous carbon (CB) additives that function as conductive scaffolds to interface the MOF crystals in "three-dimensional" electrodes. In the investigated UiO-66-[FeFe] sample, the low abundance of [FeFe] in the MOF and the intrinsic insulating properties of UiO-66 prevent charge transport through the framework, and consequently, only [FeFe] units that are in direct physical contact with the electrode material are electrochemically addressable.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Inorganic Chemistry Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-321800 (URN)10.1039/c7dt00578d (DOI)000398888700006 ()28345708 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationWenner-Gren FoundationsEU, European Research Council, ERC-CoG2015-681895_MOFcat
Available from: 2017-05-11 Created: 2017-05-11 Last updated: 2017-05-11Bibliographically approved
Morales Salazar, D., Mijangos, E., Pullen, S., Gao, M. & Orthaber, A. (2017). Functional small-molecules & polymers containing P[double bond, length as m-dash]C and As[double bond, length as m-dash]C bonds as hybrid π-conjugated materials. Chemical Communications, 53(6), 1120-1123
Open this publication in new window or tab >>Functional small-molecules & polymers containing P[double bond, length as m-dash]C and As[double bond, length as m-dash]C bonds as hybrid π-conjugated materials
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2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 6, p. 1120-1123Article in journal (Refereed) Published
Abstract [en]

Stable phospha- and arsaalkenes were used to synthesize polymers containing unsaturated P[double bond, length as m-dash]C and As[double bond, length as m-dash]C moieties. The composition, chemical environment, structure, optical, and electronic properties of the monomers and polymers were elucidated. The incorporation of the heteroatom-carbon double bonded units efficiently perturbs the optoelectronics and solid state features of both monomeric and polymeric scaffolds. Proof-of principle work supports their responsive character through post-functionalisation and electrochromic behaviour. To the best of our knowledge, this is the first example of a polymer containing arsenic-carbon double bonds.

National Category
Organic Chemistry Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-312610 (URN)10.1039/c6cc08736a (DOI)000393978300026 ()28054056 (PubMedID)
Funder
Lars Hierta Memorial FoundationStiftelsen Olle Engkvist ByggmästareSwedish Research Council, 2013-4763
Available from: 2017-01-12 Created: 2017-01-12 Last updated: 2017-11-29Bibliographically approved
Hao, Y., Yang, W., Zhang, L., Jiang, R., Mijangos, E., Saygili, Y., . . . Boschloo, G. (2016). A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells. Nature Communications, 7, Article ID 13934.
Open this publication in new window or tab >>A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells
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2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 13934Article in journal (Refereed) Published
Abstract [en]

Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy-by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte-to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-310194 (URN)10.1038/ncomms13934 (DOI)000390223200001 ()
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationStiftelsen Olle Engkvist Byggmästare
Note

Yan Hao and Wenxing Yang contributed equally to this work.

Available from: 2016-12-12 Created: 2016-12-12 Last updated: 2018-08-16Bibliographically approved
Johnson, B. A., Maji, S., Agarwala, H., White, T. A., Mijangos, E. & Ott, S. (2016). Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst. Angewandte Chemie International Edition, 55(5)
Open this publication in new window or tab >>Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst
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2016 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 5Article in journal (Refereed) Published
Abstract [en]

The introduction of a simple methyl substituent on the bipyridine ligand of [Ru(tBu(3)tpy)(bpy)(NCCH3)](2+) (tBu(3)tpy = 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine; bpy = 2,2'-bipyridine) gives rise to a highly active electrocatalyst for the reduction of CO2 to CO. The methyl group enables CO2 binding already at the one-electron reduced state of the complex to enter a previously not accessible catalytic cycle that operates at the potential of the first reduction. The complex turns over with a Faradaic efficiency close to unity and at an overpotential that is amongst the lowest ever reported for homogenous CO2 reduction catalysts.

Keywords
carbon dioxide reduction, electrocatalysis, overpotential, reaction mechanisms, ruthenium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-280898 (URN)10.1002/anie.201508490 (DOI)000369854000042 ()26671836 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationWenner-Gren Foundations
Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2017-11-30Bibliographically approved
Pavliuk, M. V., Mijangos, E., Makhankova, V. G., Kokozay, V. N., Pullen, S., Liu, J., . . . Thapper, A. (2016). Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation. ChemSusChem, 9(20), 2957-2966
Open this publication in new window or tab >>Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation
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2016 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 20, p. 2957-2966Article in journal (Refereed) Published
Abstract [en]

The heterometallic complexes (NH4)2[Co(H2O)6]2[V10O28]·4H2O (1) and (NH4)2[Co(H2O)5(β-HAla)]2[V10O28]·4H2O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV2O6/V2O5 (3) and Co2V2O7/V2O5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm−2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.

Keywords
cobalt, heterogeneous catalysis, mixed oxides, synthesis design, water oxidation
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Molecular Biomimetics
Identifiers
urn:nbn:se:uu:diva-306375 (URN)10.1002/cssc.201600769 (DOI)000386953500011 ()
Funder
Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067Swedish Institute, 00284/2013
Available from: 2016-10-27 Created: 2016-10-27 Last updated: 2017-11-29Bibliographically approved
Finke, A. D., Jahn, B. O., Saithalavi, A., Dahlstrand, C., Nauroozi, D., Haberland, S., . . . Diederich, F. (2015). The 6,6-Dicyanopentafulvene Core: A Template for the Design of Electron-Acceptor Compounds. Chemistry - A European Journal, 21(22), 8168-8176
Open this publication in new window or tab >>The 6,6-Dicyanopentafulvene Core: A Template for the Design of Electron-Acceptor Compounds
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2015 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 22, p. 8168-8176Article in journal (Refereed) Published
Abstract [en]

The electron-accepting ability of 6,6-dicyanopentafulvenes (DCFs) can be varied extensively through substitution on the five-membered ring. The reduction potentials for a set of 2,3,4,5-tetraphenyl-substituted DCFs, with varying substituents at the para-position of the phenyl rings, strongly correlate with their Hammett sigma(p)-parameters. By combining cyclic voltammetry with DFT calculations ((U)B3LYP/6-311+G(d)), using the conductor-like polarizable continuum model (CPCM) for implicit solvation, the absolute reduction potentials of a set of twenty DCFs were reproduced with a mean absolute deviation of 0.10eV and a maximum deviation of 0.19eV. Our experimentally investigated DCFs have reduction potentials within 3.67-4.41eV, however, the computations reveal that DCFs with experimental reduction potentials as high as 5.3eV could be achieved, higher than that of F-4-TCNQ (5.02eV). Thus, the DCF core is a template that allows variation in the reduction potentials by about 1.6eV.

Keywords
computational chemistry, density functional calculations, electron acceptors, molecular materials, reduction potentials
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-256225 (URN)10.1002/chem.201500379 (DOI)000354651300027 ()25917111 (PubMedID)
Available from: 2015-06-25 Created: 2015-06-22 Last updated: 2017-12-04Bibliographically approved
Wang, H., Lu, Y., Mijangos, E. & Thapper, A. (2014). Photo-Induced Water Oxidation Based on a Mononuclear Cobalt(II) Complex. Chinese journal of chemistry, 32(6), 467-473
Open this publication in new window or tab >>Photo-Induced Water Oxidation Based on a Mononuclear Cobalt(II) Complex
2014 (English)In: Chinese journal of chemistry, ISSN 1001-604X, E-ISSN 1614-7065, Vol. 32, no 6, p. 467-473Article in journal (Refereed) Published
Abstract [en]

Photo-induced water oxidation based on first row transition metal complexes has drawn much attention recently as a part of the efforts to design systems for solar fuel production. Here, the classic tetradentate ligand TPA (tris(2-pyridylmethyl)amine) is used together with cobalt(II) in CH3CN to form a mononuclear cobalt complex [Co(TPA)Cl]Cl. Single crystal X-ray diffraction shows that [Co(TPA) Cl] Cl is composed of discrete cationic units with a penta-coordinate cobalt center, along with chloride counter ions. In borate buffer, the Co complex acts as a water oxidation catalyst, as shown by the presence of a catalytic wave in electrochemistry. Under visible light irradiation, in the presence of photosensitizer and electron acceptor, the Co complex catalyzes O-2 evolution with a turnover frequency (TOF) of 1.0 mol(O-2)center dot mol(Co)(-1)center dot s(-1) and a turnover number (TON) of 55 mol(O-2)center dot mol(Co)(-1) in pH 8 borate buffer.

Keywords
water splitting, photosynthesis, cobalt, ligand design, electron transfer
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-229304 (URN)10.1002/cjoc.201300856 (DOI)000338041200002 ()
Available from: 2014-08-06 Created: 2014-08-05 Last updated: 2017-12-05Bibliographically approved
Arkhypchuk, A. I., Mijangos, E., Lomoth, R. & Ott, S. (2014). Redox Switching in Ethenyl- Bridged Bisphospholes. Chemistry - A European Journal, 20(49), 16083-16087
Open this publication in new window or tab >>Redox Switching in Ethenyl- Bridged Bisphospholes
2014 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 49, p. 16083-16087Article in journal (Refereed) Published
Abstract [en]

A 2e(-)/2H(+) redox platform has been implemented in the ethenyl-bridged bisphosphol-3-ol 1 to afford the first phospholes that feature chemically reversible oxidations. Oxidation of the title compounds to the corresponding bisphosphol-3-one 2 leads to a change in conjugation topology and a concomitant hypsochromic shift of the lowest-energy absorption maximum by 100nm. Electrochemical oxidation proceeds without any detectable intermediates, whereas the deprotonated form of 1 can be observed in an aprotic medium during the reduction of 2. This dianionic intermediate 3 is characterized by end absorptions that are bathochromically shifted by circa 200nm compared to those of 2.

Keywords
conjugation, cyclic voltammetry, electrochromism, phosphaorganic chemistry
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-240068 (URN)10.1002/chem.201405525 (DOI)000345515700008 ()25346007 (PubMedID)
Available from: 2015-01-05 Created: 2015-01-05 Last updated: 2017-12-05Bibliographically approved
Wang, H.-Y., Mijangos, E., Ott, S. & Thapper, A. (2014). Water Oxidation Catalyzed by a Dinuclear Cobalt–Polypyridine Complex. Angewandte Chemie International Edition, 53(52), 14499-14502
Open this publication in new window or tab >>Water Oxidation Catalyzed by a Dinuclear Cobalt–Polypyridine Complex
2014 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 52, p. 14499-14502Article in journal (Refereed) Published
Abstract [en]

The dinuclear Co complex [(TPA)Co(µ-OH)(µ-O2)Co(TPA)](ClO4)3 (1, TPA=tris(2-pyridylmethyl)amine) catalyzes the oxidation of water. In the presence of [Ru(bpy)3]2+ and S2O82-, photoinduced oxygen evolution can be observed with a turnover frequency (TOF) of 1.4±0.1 mol(O2) mol(1)-1 s-1 and a maximal turnover number (TON) of 585 mol(O2)mol(1)-1. The complex is shown to act as a molecular and homogeneous catalyst and a mechanismis proposed based on the combination of EPR data and light-driven O2 evolution kinetics.

Keywords
dinuclear cobalt complexes, homogeneous catalysis, photocatalysis, water oxidation
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-239839 (URN)10.1002/anie.201406540 (DOI)000346485800036 ()
Funder
Swedish Energy AgencyKnut and Alice Wallenberg Foundation
Available from: 2015-01-02 Created: 2015-01-02 Last updated: 2017-12-05Bibliographically approved
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