Torben Lund - Academia.edu (original) (raw)
Papers by Torben Lund
Journal of Electroanalytical Chemistry, 2018
Modification of fluorine-doped tin oxide-electrodes by electrochemical reduction of di(4-nitrophe... more Modification of fluorine-doped tin oxide-electrodes by electrochemical reduction of di(4-nitrophenyl)iodonium tetrafluoroborate -And its application as a photo-anode in dye-sensitized solar cells.
Applied Surface Science, Apr 1, 2020
Direct experimental evidence for the adsorption of 4-tert-butylpyridine and 2,2′-bipyridine on Ti... more Direct experimental evidence for the adsorption of 4-tert-butylpyridine and 2,2′-bipyridine on TiO 2 surface and their influence on dye-sensitized solar cells' performance
Differences in the structure of anthocyanins from the two amphibious plants, Lobelia cardinalis and Nesaea crassicaulis
Natural Product Research, Jun 13, 2012
The foliar anthocyanin profiles of two amphibious plants, Nesaea crassicaulis and Lobelia cardina... more The foliar anthocyanin profiles of two amphibious plants, Nesaea crassicaulis and Lobelia cardinalis were analysed for the first time. N. crassicaulis produced very simple anthocyanins, achieving the highest concentrations when grown submerged. In contrast, L. cardinalis produced leaves with a high content of very complex, acylated anthocyanins, especially when growing emergent. Anthocyanins were separated by high performance liquid chromatography. Nesaea crassicaulis anthocyanins were identified according to their fragment mass spectra and ultra-visible-violet spectral characteristics and 1D and 2D NMR spectra as -3,5-di-O-β-glucosides of delphinidin, cyanidin, petunidin, malvidin and peonidin as well as cyanidine and peonidin-3-O-β-glucoside. In L. cardinalis cyanidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside was the major anthocyanin and contributed more than 98% of total anthocyanin content. The remaining 2% was made up by cyanidin-3-O-[6-O-(4-O-E-caffeoyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside and pelargonidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside.
Journal of Physical Chemistry B, Oct 21, 2016
The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing... more The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing the compounds in the ratio 1:1 leads to a phase separation in which the upper phase is DIPEA and the lower phase is the "ionic liquid" named DIPEF. A combined NMR and DFT study shows that the lower phase primarily is formic acid:formate and diisopropylammonium ions in the ratio 2:1 (acid:base) plus the formic acid dimer. Addition of more acid leads to more and more of the acid dimer. The proton transfer in the system is 65−80%. The structural picture presented in this paper is very different from that presented elsewhere. However, the present picture should be considered using acids and bases with a pK a difference less than 8. The formic acid content in the DIPEF ionic liquid causes desorption of the dye-sensitized solar cell (DSC) dye N719 from the photo anode, and DIPEF is therefore not a suitable electrolyte for DSCs.
Solar Energy, Sep 1, 2019
Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and p... more Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and pyridines: Why the dye-sensitized solar cell electrolyte should be dry.
![Research paper thumbnail of Photovoltaic Performance and Characteristics of Dye‐Sensitized Solar Cells Prepared with the N719 Thermal Degradation Products [Ru(LH) <sub>2</sub> (NCS)(4‐ <i>tert</i> ‐butylpyridine)][N(Bu) <sub>4</sub> ] and [Ru(LH) <sub>2</sub> (NCS)(1‐methylbenzimidazole)][N(Bu) <sub>4</sub> ]](https://attachments.academia-assets.com/106840187/thumbnails/1.jpg)
](European Journal of Inorganic Chemistry, Apr 26, 2011
Photovoltaic performance and characteristics of dye sensitized solar cells prepared with the N719... more Photovoltaic performance and characteristics of dye sensitized solar cells prepared with the N719 thermal degradation products [Ru(L-H)2(NCS)(4-tert-butylpyridine)]-, +N(Bu)4 and [Ru(L-H)2(NCS)(1-methylbenzimidazole)]-, +N(Bu)4
Structure of protic ionic liquids studies by NMR, IR and DFT calculations. An isotope effect study
Dye-sensitized solar cells and complexes between pyridines and iodines. A NMR, IR and DFT study
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Dec 1, 2012
Interactions between triiodide (I(3)(-)) and 4-tert-butylpyridine (4TBP) as postulated in dye-sen... more Interactions between triiodide (I(3)(-)) and 4-tert-butylpyridine (4TBP) as postulated in dye-sensitized solar cells (DSC) are investigated by means of (13)C NMR and IR spectroscopy supported by DFT calculations. The charge transfer (CT) complex 4TBP·I(2) and potential salts such as (4TBP)(2)I(+), I(3)(-) were synthesized and characterized by IR and (13)C NMR spectroscopy. However, mixing (butyl)(4)N(+), I(3)(-) and 4TBP at concentrations comparable to those of the DSC solar cell did not lead to any reaction. Neither CT complexes nor cationic species like (4TBP)(2)I(+) were observed, judging from the (13)C NMR spectroscopic evidence. This questions the previously proposed formation of (4TBP)(2)I(+) in DSC cells.
Journal of Technology Innovations in Renewable Energy, 2016
The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of... more The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of the dye itself and on the microscopic structure of the dye-semiconductor interface. Previous experimental studies of DSCs based on ruthenium dye with bipyridine ligands (N719) adsorbed to the TiO2substrate applied FTIR,un-polarized Raman (RS) and un-polarized resonance Raman (RRS) spectroscopy. In the un-polarized RRS studies of N719/TiO2-DSCs the discussion of the adsorption of N719 was based on the rather weak carbonyl or carboxyl group stretching vibrations and on minor spectral changes of overlapping Raman modes, whereas conclusions about the dye-stability was based on the observation that fresh and aged DSCs had almost identical RRS spectra. In the present paper we address the problems mentioned above, by utilizing the unique property of Raman scattering that the polarization of the scattered light is generally different from the polarization of the laser light. When the excitation is chosen within the visible absorption band of N719 only the skeleton ring-modes in N719 are enhanced and are observed as the most intense bands in the RRS spectra. We demonstrate by experimental results on N719/TiO2-DSCs that by combining an analysis of the wave number dependent polarization of these modes with the small shifts observed in the visible absorption spectra of adsorbed, non-adsorbed molecules and degradation products new and more reliable information about dye stability and about the adsorption of the dye on TiO2 can be obtained. Furthermore it is found that the polarization fluorescence anisotropy is very different for adsorbed and non-adsorbed dye molecules. This information is automatically obtained when processing the Raman data. The conclusion is that if the polarization properties of the resonance Raman spectra are analyzed instead of just analyzing the minute spectral changes of the (weaker) Raman bands the potential of RRS as an on-site tool for investigation of DSCs can be greatly improved.
Solar Energy, Feb 1, 2013
Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium ... more Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO 2 particles. The dye degradation was followed by the use of HPLC-coupled electrospray mass spectrometry. The longest half life of N719 of 84 h at 100°C was obtained in 3methoxypropionitrile based electrolytes containing 0.5 M 4-TBP, no Li + ions and 0.25 M I À 3. If 4-TBP was removed from the solution the degradation rate of N719 increased up to 3-15 times depending on the I À 3 concentration. If Li + ions were added to the electrolyte the degradation increased by a factor of 4-16 times and the thermal degradation product mixture became more complex. It is suggested that an adsorbed layer of 4-TBP on the TiO 2 protects the N719 dye against solvent substitution and oxidation processes. A complexation constant of Li + ions with 4-TBP equal to 9 M À1 was obtained by 13 C NMR. The Li + complexation with 4-TBP is thought to destroy the adsorbed protection layer of 4-TBP on the TiO 2 surface. It is concluded that addition of 4-TBP or other N-additives to the DSC electrolyte is important to enhance the dye life time at elevated temperatures. However, addition of Li + to the electrolyte should be avoided if the wish is to construct DSCs with high thermal stability.
Solid State Ionics, 2018
In this work 2,2´-bipyridine (bipy) is introduced as a new nitrogen containing electrolyte additi... more In this work 2,2´-bipyridine (bipy) is introduced as a new nitrogen containing electrolyte additive in Dye-sensitized solar cells (DSCs) as an alternative to the commonly used 4-tertbutylpyridine (TBP). Bipy was shown to substitute the thiocyanate ligands in the N719 ruthenium dye ~4 times slower than TBP at elevated temperatures 80-85 ºC and therefore reduce the thermal degradation of N719 relative to TBP. The thermal stability experiments were performed in sealed glass ampules filled with a colloidal solution of N719 dyed TiO2 nano-particles in an ionic liquid electrolyte with either TBP or bipy as N-additive. The glass ampules were opened after various time intervals between 0-2000 hours of heating at either 80 or 85 ºC and the N719 and its degradation products were extracted from the TiO2 nano particles and analyzed by LC-UV/Vis-MS. After 1000 hours at 85 ºC in dark, 85 % of N719 was intact in an electrolyte containing 0.2 M bipy whereas the same number was 67% for TBP. DSCs prepared with bipy in the electrolyte was shown to perform equally well as 2 DSCs with TBP containing electrolytes with light to electricity performance of 4.5% for both N-additives. 2,2´-bipyridine may therefore be used as an alternative to TBP as N-additive in DSCs.
Solar Energy, 2013
Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium ... more Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO 2 particles. The dye degradation was followed by the use of HPLC-coupled electrospray mass spectrometry. The longest half life of N719 of 84 h at 100°C was obtained in 3methoxypropionitrile based electrolytes containing 0.5 M 4-TBP, no Li + ions and 0.25 M I À 3. If 4-TBP was removed from the solution the degradation rate of N719 increased up to 3-15 times depending on the I À 3 concentration. If Li + ions were added to the electrolyte the degradation increased by a factor of 4-16 times and the thermal degradation product mixture became more complex. It is suggested that an adsorbed layer of 4-TBP on the TiO 2 protects the N719 dye against solvent substitution and oxidation processes. A complexation constant of Li + ions with 4-TBP equal to 9 M À1 was obtained by 13 C NMR. The Li + complexation with 4-TBP is thought to destroy the adsorbed protection layer of 4-TBP on the TiO 2 surface. It is concluded that addition of 4-TBP or other N-additives to the DSC electrolyte is important to enhance the dye life time at elevated temperatures. However, addition of Li + to the electrolyte should be avoided if the wish is to construct DSCs with high thermal stability.
Solar Energy, 2019
Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and p... more Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and pyridines: Why the dye-sensitized solar cell electrolyte should be dry.
In the last decades dye-sensitized solar cells (DSCs) have extensively been studied. From an econ... more In the last decades dye-sensitized solar cells (DSCs) have extensively been studied. From an economical point of view, DSCs are of high interest because the manufacturing costs of DSCs devices are significantly lower compared with other solar devices such as silicon cells. One of the success criteria required for commercial use of DSCs is high stability under light soaking and thermal stress conditions. The dye sensitizer is one of the key components of a DSC device. Consequently, the stability of DSCs is directly linked to the dye stability, which is in turn linked to its degradation on the surface of a semiconductor anode (TiO2). In my lecture, I will present and overview of our degradation investigations of the ruthenium dyes N719, Z907 and C106 with the general structure RuLL ́(NCS)2 and show how detailed degradation mechanistic knowledge is important in the developing of DSC cells with improved thermal dye stability [1,2]. In my talk, I will also include a brief account of our ...
The Journal of Physical Chemistry B, 2016
Experimental determination of the reorganization energy of the NO2+/NO2 redox couple. Comparison with theory
Journal of the Chemical Society, Perkin Transactions 2
... Chem. Soc., 1965, 87, 2529 Article CAS . 24, C. Amatore, M. Azzabi, P. Calas, A. Jutand, C. L... more ... Chem. Soc., 1965, 87, 2529 Article CAS . 24, C. Amatore, M. Azzabi, P. Calas, A. Jutand, C. Lefrou and Y. Rollin, J. Electroanal. Chem., 1990, 288, 45 Article CAS . ... Chem., 1996, 100, 5303 Article CAS . 31, N. Gatti, SU Pedersen and H. Lund, Acta Chem. Scand., Ser. ...
Acta Chemica Scandinavica, 1997
Electrochim Acta, 2005
The electrochemical oxidation of 2,4-dimethyl-3-ethylpyrrole in acetonitrile has been studied usi... more The electrochemical oxidation of 2,4-dimethyl-3-ethylpyrrole in acetonitrile has been studied using cyclic voltammetry, constant current coulometry, preparative electrolyses and ab initio calculations. The product analysis after the preparative electrolyses was carried out by HPLC combined with UV-vis and electrospray ionization MS detection. The aim of the work was to address some of the unresolved problems in the oxidative oligomerization and polymerization of alkylpyrroles. The title compound was chosen as a model for studies of pyrroles that are more basic than the solvent-supporting electrolyte system and for that reason are forced to serve as the base accepting the protons released during the coupling steps. The voltammograms obtained by cyclic voltammetry at a substrate concentration of 2 mM and voltage scan rates between 0.02 and 2 V s −1 showed a characteristic trace-crossing phenomenon that could be demonstrated by digital simulation to be related to that fact that the deprotonations of the initially formed dimer dication are slow with second order rate constants in the range 10 3 -10 4 M −1 s −1 . The relative stability of the different tautomers of the protonated pyrrole monomer and the corresponding 2,2 -dimer was determined by ab initio calculations at the RHF 6-31G(d) level. The studies also included investigations of the effects resulting from addition of a non-nucleophilic base, 2,6-di-tertbutylpyridine, to the voltammetry solutions. The major product observed after preparative electrolyses was a trimer the structure of which is proposed to include a central 2H-pyrrole unit. Since 2H-pyrroles are stronger bases than the corresponding 1H-pyrroles, the trimer is effectively protected against further oxidation by protonation. Two other trimers were observed as minor or trace products as well as a 1H,2H-dimer and several tetramers, also in trace amounts. In addition to the dimer, the trimers and the tetramers, a number of other minor products could be detected. These could all be traced back to the nucleophilic attack by residual water on the radical cations or dications of the 2,2 -dimer and the trimers. The results obtained by constant current coulometry are in agreement with the formation of a 2H-pyrrole based trimer as the major product.
Correlation between inner-sphere stabilization and stereo-chemistry for the aliphatic nucleophilic substitution
Tetrahedron Letters, 1991
Journal of Electroanalytical Chemistry, 2018
Modification of fluorine-doped tin oxide-electrodes by electrochemical reduction of di(4-nitrophe... more Modification of fluorine-doped tin oxide-electrodes by electrochemical reduction of di(4-nitrophenyl)iodonium tetrafluoroborate -And its application as a photo-anode in dye-sensitized solar cells.
Applied Surface Science, Apr 1, 2020
Direct experimental evidence for the adsorption of 4-tert-butylpyridine and 2,2′-bipyridine on Ti... more Direct experimental evidence for the adsorption of 4-tert-butylpyridine and 2,2′-bipyridine on TiO 2 surface and their influence on dye-sensitized solar cells' performance
Differences in the structure of anthocyanins from the two amphibious plants, Lobelia cardinalis and Nesaea crassicaulis
Natural Product Research, Jun 13, 2012
The foliar anthocyanin profiles of two amphibious plants, Nesaea crassicaulis and Lobelia cardina... more The foliar anthocyanin profiles of two amphibious plants, Nesaea crassicaulis and Lobelia cardinalis were analysed for the first time. N. crassicaulis produced very simple anthocyanins, achieving the highest concentrations when grown submerged. In contrast, L. cardinalis produced leaves with a high content of very complex, acylated anthocyanins, especially when growing emergent. Anthocyanins were separated by high performance liquid chromatography. Nesaea crassicaulis anthocyanins were identified according to their fragment mass spectra and ultra-visible-violet spectral characteristics and 1D and 2D NMR spectra as -3,5-di-O-β-glucosides of delphinidin, cyanidin, petunidin, malvidin and peonidin as well as cyanidine and peonidin-3-O-β-glucoside. In L. cardinalis cyanidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside was the major anthocyanin and contributed more than 98% of total anthocyanin content. The remaining 2% was made up by cyanidin-3-O-[6-O-(4-O-E-caffeoyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside and pelargonidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-β-glucopyrano]-5-O-β-glucopyranoside.
Journal of Physical Chemistry B, Oct 21, 2016
The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing... more The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing the compounds in the ratio 1:1 leads to a phase separation in which the upper phase is DIPEA and the lower phase is the "ionic liquid" named DIPEF. A combined NMR and DFT study shows that the lower phase primarily is formic acid:formate and diisopropylammonium ions in the ratio 2:1 (acid:base) plus the formic acid dimer. Addition of more acid leads to more and more of the acid dimer. The proton transfer in the system is 65−80%. The structural picture presented in this paper is very different from that presented elsewhere. However, the present picture should be considered using acids and bases with a pK a difference less than 8. The formic acid content in the DIPEF ionic liquid causes desorption of the dye-sensitized solar cell (DSC) dye N719 from the photo anode, and DIPEF is therefore not a suitable electrolyte for DSCs.
Solar Energy, Sep 1, 2019
Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and p... more Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and pyridines: Why the dye-sensitized solar cell electrolyte should be dry.
European Journal of Inorganic Chemistry, Apr 26, 2011
Photovoltaic performance and characteristics of dye sensitized solar cells prepared with the N719... more Photovoltaic performance and characteristics of dye sensitized solar cells prepared with the N719 thermal degradation products [Ru(L-H)2(NCS)(4-tert-butylpyridine)]-, +N(Bu)4 and [Ru(L-H)2(NCS)(1-methylbenzimidazole)]-, +N(Bu)4
Structure of protic ionic liquids studies by NMR, IR and DFT calculations. An isotope effect study
Dye-sensitized solar cells and complexes between pyridines and iodines. A NMR, IR and DFT study
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Dec 1, 2012
Interactions between triiodide (I(3)(-)) and 4-tert-butylpyridine (4TBP) as postulated in dye-sen... more Interactions between triiodide (I(3)(-)) and 4-tert-butylpyridine (4TBP) as postulated in dye-sensitized solar cells (DSC) are investigated by means of (13)C NMR and IR spectroscopy supported by DFT calculations. The charge transfer (CT) complex 4TBP·I(2) and potential salts such as (4TBP)(2)I(+), I(3)(-) were synthesized and characterized by IR and (13)C NMR spectroscopy. However, mixing (butyl)(4)N(+), I(3)(-) and 4TBP at concentrations comparable to those of the DSC solar cell did not lead to any reaction. Neither CT complexes nor cationic species like (4TBP)(2)I(+) were observed, judging from the (13)C NMR spectroscopic evidence. This questions the previously proposed formation of (4TBP)(2)I(+) in DSC cells.
Journal of Technology Innovations in Renewable Energy, 2016
The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of... more The working efficiency of dye-sensitized solar cells (DSCs) depends on the long-term stability of the dye itself and on the microscopic structure of the dye-semiconductor interface. Previous experimental studies of DSCs based on ruthenium dye with bipyridine ligands (N719) adsorbed to the TiO2substrate applied FTIR,un-polarized Raman (RS) and un-polarized resonance Raman (RRS) spectroscopy. In the un-polarized RRS studies of N719/TiO2-DSCs the discussion of the adsorption of N719 was based on the rather weak carbonyl or carboxyl group stretching vibrations and on minor spectral changes of overlapping Raman modes, whereas conclusions about the dye-stability was based on the observation that fresh and aged DSCs had almost identical RRS spectra. In the present paper we address the problems mentioned above, by utilizing the unique property of Raman scattering that the polarization of the scattered light is generally different from the polarization of the laser light. When the excitation is chosen within the visible absorption band of N719 only the skeleton ring-modes in N719 are enhanced and are observed as the most intense bands in the RRS spectra. We demonstrate by experimental results on N719/TiO2-DSCs that by combining an analysis of the wave number dependent polarization of these modes with the small shifts observed in the visible absorption spectra of adsorbed, non-adsorbed molecules and degradation products new and more reliable information about dye stability and about the adsorption of the dye on TiO2 can be obtained. Furthermore it is found that the polarization fluorescence anisotropy is very different for adsorbed and non-adsorbed dye molecules. This information is automatically obtained when processing the Raman data. The conclusion is that if the polarization properties of the resonance Raman spectra are analyzed instead of just analyzing the minute spectral changes of the (weaker) Raman bands the potential of RRS as an on-site tool for investigation of DSCs can be greatly improved.
Solar Energy, Feb 1, 2013
Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium ... more Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO 2 particles. The dye degradation was followed by the use of HPLC-coupled electrospray mass spectrometry. The longest half life of N719 of 84 h at 100°C was obtained in 3methoxypropionitrile based electrolytes containing 0.5 M 4-TBP, no Li + ions and 0.25 M I À 3. If 4-TBP was removed from the solution the degradation rate of N719 increased up to 3-15 times depending on the I À 3 concentration. If Li + ions were added to the electrolyte the degradation increased by a factor of 4-16 times and the thermal degradation product mixture became more complex. It is suggested that an adsorbed layer of 4-TBP on the TiO 2 protects the N719 dye against solvent substitution and oxidation processes. A complexation constant of Li + ions with 4-TBP equal to 9 M À1 was obtained by 13 C NMR. The Li + complexation with 4-TBP is thought to destroy the adsorbed protection layer of 4-TBP on the TiO 2 surface. It is concluded that addition of 4-TBP or other N-additives to the DSC electrolyte is important to enhance the dye life time at elevated temperatures. However, addition of Li + to the electrolyte should be avoided if the wish is to construct DSCs with high thermal stability.
Solid State Ionics, 2018
In this work 2,2´-bipyridine (bipy) is introduced as a new nitrogen containing electrolyte additi... more In this work 2,2´-bipyridine (bipy) is introduced as a new nitrogen containing electrolyte additive in Dye-sensitized solar cells (DSCs) as an alternative to the commonly used 4-tertbutylpyridine (TBP). Bipy was shown to substitute the thiocyanate ligands in the N719 ruthenium dye ~4 times slower than TBP at elevated temperatures 80-85 ºC and therefore reduce the thermal degradation of N719 relative to TBP. The thermal stability experiments were performed in sealed glass ampules filled with a colloidal solution of N719 dyed TiO2 nano-particles in an ionic liquid electrolyte with either TBP or bipy as N-additive. The glass ampules were opened after various time intervals between 0-2000 hours of heating at either 80 or 85 ºC and the N719 and its degradation products were extracted from the TiO2 nano particles and analyzed by LC-UV/Vis-MS. After 1000 hours at 85 ºC in dark, 85 % of N719 was intact in an electrolyte containing 0.2 M bipy whereas the same number was 67% for TBP. DSCs prepared with bipy in the electrolyte was shown to perform equally well as 2 DSCs with TBP containing electrolytes with light to electricity performance of 4.5% for both N-additives. 2,2´-bipyridine may therefore be used as an alternative to TBP as N-additive in DSCs.
Solar Energy, 2013
Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium ... more Thermal stability experiments were performed at 100°C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO 2 particles. The dye degradation was followed by the use of HPLC-coupled electrospray mass spectrometry. The longest half life of N719 of 84 h at 100°C was obtained in 3methoxypropionitrile based electrolytes containing 0.5 M 4-TBP, no Li + ions and 0.25 M I À 3. If 4-TBP was removed from the solution the degradation rate of N719 increased up to 3-15 times depending on the I À 3 concentration. If Li + ions were added to the electrolyte the degradation increased by a factor of 4-16 times and the thermal degradation product mixture became more complex. It is suggested that an adsorbed layer of 4-TBP on the TiO 2 protects the N719 dye against solvent substitution and oxidation processes. A complexation constant of Li + ions with 4-TBP equal to 9 M À1 was obtained by 13 C NMR. The Li + complexation with 4-TBP is thought to destroy the adsorbed protection layer of 4-TBP on the TiO 2 surface. It is concluded that addition of 4-TBP or other N-additives to the DSC electrolyte is important to enhance the dye life time at elevated temperatures. However, addition of Li + to the electrolyte should be avoided if the wish is to construct DSCs with high thermal stability.
Solar Energy, 2019
Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and p... more Stability of the oxidized form of RuLL´(NCS)2 dyes in acetonitrile in the presence of water and pyridines: Why the dye-sensitized solar cell electrolyte should be dry.
In the last decades dye-sensitized solar cells (DSCs) have extensively been studied. From an econ... more In the last decades dye-sensitized solar cells (DSCs) have extensively been studied. From an economical point of view, DSCs are of high interest because the manufacturing costs of DSCs devices are significantly lower compared with other solar devices such as silicon cells. One of the success criteria required for commercial use of DSCs is high stability under light soaking and thermal stress conditions. The dye sensitizer is one of the key components of a DSC device. Consequently, the stability of DSCs is directly linked to the dye stability, which is in turn linked to its degradation on the surface of a semiconductor anode (TiO2). In my lecture, I will present and overview of our degradation investigations of the ruthenium dyes N719, Z907 and C106 with the general structure RuLL ́(NCS)2 and show how detailed degradation mechanistic knowledge is important in the developing of DSC cells with improved thermal dye stability [1,2]. In my talk, I will also include a brief account of our ...
The Journal of Physical Chemistry B, 2016
Experimental determination of the reorganization energy of the NO2+/NO2 redox couple. Comparison with theory
Journal of the Chemical Society, Perkin Transactions 2
... Chem. Soc., 1965, 87, 2529 Article CAS . 24, C. Amatore, M. Azzabi, P. Calas, A. Jutand, C. L... more ... Chem. Soc., 1965, 87, 2529 Article CAS . 24, C. Amatore, M. Azzabi, P. Calas, A. Jutand, C. Lefrou and Y. Rollin, J. Electroanal. Chem., 1990, 288, 45 Article CAS . ... Chem., 1996, 100, 5303 Article CAS . 31, N. Gatti, SU Pedersen and H. Lund, Acta Chem. Scand., Ser. ...
Acta Chemica Scandinavica, 1997
Electrochim Acta, 2005
The electrochemical oxidation of 2,4-dimethyl-3-ethylpyrrole in acetonitrile has been studied usi... more The electrochemical oxidation of 2,4-dimethyl-3-ethylpyrrole in acetonitrile has been studied using cyclic voltammetry, constant current coulometry, preparative electrolyses and ab initio calculations. The product analysis after the preparative electrolyses was carried out by HPLC combined with UV-vis and electrospray ionization MS detection. The aim of the work was to address some of the unresolved problems in the oxidative oligomerization and polymerization of alkylpyrroles. The title compound was chosen as a model for studies of pyrroles that are more basic than the solvent-supporting electrolyte system and for that reason are forced to serve as the base accepting the protons released during the coupling steps. The voltammograms obtained by cyclic voltammetry at a substrate concentration of 2 mM and voltage scan rates between 0.02 and 2 V s −1 showed a characteristic trace-crossing phenomenon that could be demonstrated by digital simulation to be related to that fact that the deprotonations of the initially formed dimer dication are slow with second order rate constants in the range 10 3 -10 4 M −1 s −1 . The relative stability of the different tautomers of the protonated pyrrole monomer and the corresponding 2,2 -dimer was determined by ab initio calculations at the RHF 6-31G(d) level. The studies also included investigations of the effects resulting from addition of a non-nucleophilic base, 2,6-di-tertbutylpyridine, to the voltammetry solutions. The major product observed after preparative electrolyses was a trimer the structure of which is proposed to include a central 2H-pyrrole unit. Since 2H-pyrroles are stronger bases than the corresponding 1H-pyrroles, the trimer is effectively protected against further oxidation by protonation. Two other trimers were observed as minor or trace products as well as a 1H,2H-dimer and several tetramers, also in trace amounts. In addition to the dimer, the trimers and the tetramers, a number of other minor products could be detected. These could all be traced back to the nucleophilic attack by residual water on the radical cations or dications of the 2,2 -dimer and the trimers. The results obtained by constant current coulometry are in agreement with the formation of a 2H-pyrrole based trimer as the major product.
Correlation between inner-sphere stabilization and stereo-chemistry for the aliphatic nucleophilic substitution
Tetrahedron Letters, 1991