| 1. |
- Guo, Y., et al.
(author)
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Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation
- 2022
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:26, s. 11736-11747
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Journal article (peer-reviewed)abstract
- Photosynthetic water oxidation is catalyzed by a manganese-calcium oxide cluster, which experiences five "S-states" during a light-driven reaction cycle. The unique "distorted chair"-like geometry of the Mn4CaO5(6)cluster shows structural flexibility that has been frequently proposed to involve "open" and "closed"-cubane forms from the S1 to S3states. The isomers are interconvertible in the S1 and S2states, while in the S3state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yzstate to the S3nYz•→ S4+Yzstep, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yzstate, is fully recovered in the ensuing S3nYz•state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese-ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2formation, and exert a significant influence on the water oxidation mechanism in photosystem II.
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| 2. |
- Gamstedt, Helene, et al.
(author)
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Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes
- 2009
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In: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 28:4, s. 757-762
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Journal article (peer-reviewed)abstract
- The efficiency of dye-sensitized nanocryst. solar cells contg. ionic liqs., composed of org. sulfonium or imidazolium iodides, or a std. org.-liq.-based electrolyte was studied, while using sensitizers based on different polypyridyl-ruthenium complexes. The dyes N-719, [cis-Ru(II)(H2dcbpy)2(NCS)2(TBA)2] and Z-907, [cis-Ru(II)(H2dcbpy)(dnbpy)(NCS)2, Z-907 having a more hydrophobic character, as well as a bidentate beta -diketonato complex, [(dcbpy)2Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with the dye N-719 were more efficient than the Z-907 cells, for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells contg. an org.-liq. electrolyte resulted in increased overall light-to-electricity conversion efficiencies, from 3.7% to 4.0%, (100 W m-2, AM 1.5). Possibly, this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the org.-liq. electrolyte, the conversion efficiency was increased from 4.1% to 4.6% (100 W m-2, AM 1.5). In 1000 W m-2 illumination, the highest overall short-circuit c.d., 9.3 mA cm-2, was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-contg. org.-liq.-based electrolyte. For solar cells sensitized with N-719, Z-907 or the beta -diketonato complex, and contg. imidazolium or sulfonium iodide ionic liqs., no improvements of the overall conversion efficiency could be noticed at addn. of HDMA to the dye or nanoparticles to the electrolyte.
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| 3. |
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| 4. |
- Åkerstedt, Josefin, et al.
(author)
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Synthesis and characterization of binuclear palladium(I) compounds and the influence of competing arenes
- 2010
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In: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X .- 1872-8561. ; 695:10-11, s. 1513-1517
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Journal article (peer-reviewed)abstract
- The binuclear palladium(I) compounds, [Pd-2(Ga2Cl7)(2)(C7H8)(2)] (1), [Pd-2(GaCl4)(2)(C9H12)(2)]center dot C9H12 (2) and [Pd-2(Ga2Cl7)(2)(C6H5Cl)(2)] (3), have been prepared from palladium(II) chloride in gallium(III) chloride-arene reaction media. All isolated crystalline solids (1, 2 and 3) have been structurally characterized by single crystal X-ray diffraction and Raman spectroscopy. The results form quantum chemical calculations on the interaction energies of the arenes and the dipalladium unit of these compounds is also presented.
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| 5. |
- Yu, Ze, et al.
(author)
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Investigation of Iodine Concentration Effects in Electrolytes for Dye-Sensitized Solar Cells
- 2010
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:23, s. 10612-10620
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Journal article (peer-reviewed)abstract
- The present work describes the effects of different iodine concentrations and iodine-to-iodide ratios in electrolytes for dye-sensitized solar cells based on low-viscous, binary ionic liquid and organic liquid solvents. Current-voltage characteristics, photoelectrochemical measurements, electrochemical impedance spectroscopy, and Raman spectroscopy were used for characterization. Optimal short-circuit current and overall conversion efficiency were achieved using intermediate and low iodine concentration in ionic liquid-based and acetonitrile-based electrolytes, respectively. Results from photoelectrochemical and Raman-spectroscopic measurements reveal that both triiodide mobility and chemical availability affect the optimal iodine concentration required in these two types of electrolytes. The higher iodine concentrations required for the ionic liquid-based electrolytes partly compensate for these effects, although negative effects from higher recombination losses and light absorption of iodine-containing species start to become significant.
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| 6. |
- Privalov, Timofei, et al.
(author)
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A Study of the Interactions between I−/I3− Redox Mediators and Organometallic Sensitizing Dyes in Solar Cells
- 2009
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:2, s. 783-790
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Journal article (peer-reviewed)abstract
- Specific interactions of the I−/I3− redox mediators with the reduced and oxidized dye, Ru(4,4′-dicarboxy-2,2′-bipyridyl)2(NCS)2, referred to as N3 or Ru(dcbpy)2(NCS)2, have been studied by means of density functional theory (DFT) with the focus on the charge transfer process involving {dye+ I−} adducts; computations had been performed with a series of density functionals (gradient-corrected density functional BP86, and the hybrid density functionals B3LYP, MPW1K, B3PW1K, and MPW1PW91). Different pathways leading to {dye+ I−} adducts have been studied. First, mechanistic insights into the interaction of I− with RuIII(dcbpy)2(NCS)2 via an SCN− ligand directly giving rise to RuII(dcbpy)2(NCS)2I⌉0 have been obtained with the distinctive S−I bonding. Second, the binding of I− to the N3 dye cation via I−−dcbpy interactions has been analyzed. We also report experimental and computational evidence that sheds light on the interaction of the redox mediator with bipyridyl moieties. Evidence for a charge transfer process in the presence of only one I− anion in the outer coordination sphere of the ruthenium center has been identified. Finally, geometries and electronic structures of plausible intermediates have been computationally analyzed based on an inner-sphere interaction between the metal center and the redox mediator, including a two-step regeneration reaction: RuIII(dcbpy)2(NCS)2⌉+ + I− → RuIII(dcbpy)2(NCS)I⌉+ + SCN−, followed by the interaction of a second I− with the intermediate RuIII(dcbpy)2(NCS)I⌉+ complex. Conclusive evidence of a charge-transfer process that gives rise to the regenerated RuII complex, where I− interacts with the intermediate RuIII(dcbpy)2(NCS)I⌉+ complex has been identified.
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| 7. |
- Gao, Jiajia, et al.
(author)
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Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells
- 2019
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:33, s. 19495-19505
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Journal article (peer-reviewed)abstract
- Lithium-ion-free tris(2,2′-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)3]3+ and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)3]3+/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)3]3+ upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical Jsc-Voc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system.
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| 8. |
- Gao, Jiajia, et al.
(author)
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Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells : An Electrolyte Effect
- 2018
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:31, s. 26241-26247
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Journal article (peer-reviewed)abstract
- A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.
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| 9. |
- Paulsson, Heléne, et al.
(author)
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Molten and solid trialkylsulfonium iodides and their polyiodides as electrolytes in dye-sensitized nanocrystalline solar cells
- 2003
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 107:49, s. 13665-13670
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Journal article (peer-reviewed)abstract
- Potential new electrolytes for dye-sensitized nanocrystalline solar cells (DNSCs) of Gratzel type based on trialkylsulfonium iodides have been investigated. Room temperature molten salts of (Et2MeS)I, (Bu2MeS)I, and (Bu2EtS)I, with iodine in low concentrations, revealed good conducting abilities. DNSCs using iodine-doped (Bu2MeS)l as electrolyte achieved an overall light-to-electricity conversion efficiency of 3.7% in simulated AM 1.5 solar light at a light intensity of 0.1 Sun. The effects from varying the temperature during the IN measurements were studied, as well as the effects of 4-tert-butylpyridine treatment of the electrodes.
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| 10. |
- Tot, Aleksandar, et al.
(author)
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Tuning of Molecular Water Organization in Water-in-Salt Electrolytes by Addition of Chaotropic Ionic Liquids
- 2023
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In: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 127:50, s. 24065-24076
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Journal article (peer-reviewed)abstract
- Water-in-salt electrolytes (WISEs) have expanded the useful electrochemical stability of water, making the development of functional aqueous lithium-ion batteries more accessible. The implementation of additives in the formulation of WISEs can further improve the electrochemical stability of water and avoid potential lithium-ion salt solubility issues. Here, we have used Gemini-type ionic liquids to suppress water activity by designing the structure of ionic-liquid cations. The different water-organizing effects of ionic-liquid cations have been investigated and correlated to battery performance in LTO/LMO full cells. The champion device, containing the most chaotropic ionic liquid, retained at least 99% of its Coulombic efficiency after 500 charging cycles, associated with a final specific discharge capacity of 85 mA h·g-1. These results indicated that water-rich Li+ solvation shells significantly contribute to the excellent device performance and long-term stability of the LTO/LMO-based full battery cells. This work shows that the fine-tuning of the Li+ solvation shell and water structure by the addition of chaotropic cations represents a promising strategy for generating more stable and effective lithium-ion-containing rechargeable aqueous batteries.
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