| 1. |
- Gao, Weiming, et al.
(författare)
-
Attachment of a Hydrogen-Bonding Carboxylate Side Chain to an FeFe -Hydrogenase Model Complex : Influence on the Catalytic Mechanism
- 2010
-
Ingår i: Chemistry - A European Journal. - Weinheim : Wiley. - 0947-6539 .- 1521-3765. ; 16:8, s. 2537-2546
-
Tidskriftsartikel (refereegranskat)abstract
- Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4-6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the Fe Fe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of [Ru(bpy)(3)](2+), complex 1, 2, or 3, and ascorbic acid in CH3CN/D2O solution by on-line mass spectrometry.
|
|
| 2. |
- Lin, Shuangzheng, et al.
(författare)
-
Dynamic One-Pot Three-Component Catalytic Asymmetric Transformation by Combination of Hydrogen-Bond-Donating and Amine Catalysts
- 2011
-
Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 50:33, s. 7624-7630
-
Tidskriftsartikel (refereegranskat)abstract
- In control: The first dynamic one-pot three-component asymmetric transformation between aldehydes, protected α-cyanoglycine esters, and enals catalyzed by a combination of a simple hydrogen-bond-donating catalyst and a chiral amine catalyst is disclosed. Polysubstituted proline derivatives, which have a quaternary α stereocenter, were synthesized with high endo-, diastereo-, and enantioselectivities (93-99 ee). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
|
|
| 3. |
- Zhao, Gui-Ling, et al.
(författare)
-
Dynamic Kinetic Asymmetric Transformation (DYKAT) by Combined Amine- and Transition-Metal-Catalyzed Enantioselective Cycloisomerization
- 2010
-
Ingår i: Chemistry - A European Journal. - Weinheim : Wiley. - 0947-6539 .- 1521-3765. ; 16:5, s. 1585-1591
-
Tidskriftsartikel (refereegranskat)abstract
- The first examples of one-pot highly chemo- and enantioselective dynamic kinetic asymmetric transformations (DYKATs) involving alpha,beta-unsaturated aldehydes and proparaylated carbon acids are presented. These DYKATs, which proceed by a combination of catalytic iminium activation, enamine activation, and Pd-0-catalyzed enyne cycloisomerization, give access to functionalized cyclopentenes wit. It up to. 99% ee and can be used for the generation of all-carbon quaternary stereocenters
|
|
| 4. |
- Zhu, Mingzhao, et al.
(författare)
-
Organocatalytic diastereoselective dibromination of alkenes
- 2010
-
Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 51:20, s. 2708-2712
-
Tidskriftsartikel (refereegranskat)abstract
- A highly diastereoselective pyrrolidine-promoted dibromination of alkenes by combination of NBS and succinimide is presented. The pyrrolidine-mediated dibromination of alkenes is higly anti-selective and gives the corresponding products in moderate to high yields and up to >25:1 dr.
|
|
| 5. |
- Wang, Lei, et al.
(författare)
-
A nickel (II) PY5 complex as an electrocatalyst for water oxidation
- 2016
-
Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 335, s. 72-78
-
Tidskriftsartikel (refereegranskat)abstract
- A Ni-PY5 [PY5 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine)] complex has been found to act as an electrocatalyst for oxidizing water to dioxygen in aqueous phosphate buffer solutions. The rate of water oxidation catalyzed by the Ni-PY5 is remarkably enhanced by the proton acceptor base HPO42-, with rate constant of 1820 M-1 s(-1). Controlled potential bulk electrolysis with Ni-PY5 at pH 10.8 under an applied potential of 1.5 V vs. normal hydrogen electrode (NHE) resulted in dioxygen formation with a high faradaic efficiency over 90%. A detailed mechanistic study identifies the water nucleophilic attack pathway for water oxidation catalysis.
|
|
| 6. |
- Etman, Ahmed S., et al.
(författare)
-
Insights into the Exfoliation Process of V2O5· nH2O Nanosheet Formation Using Real-Time 51V NMR
- 2019
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:6, s. 10899-10905
-
Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2019 American Chemical Society. Nanostructured hydrated vanadium oxides (V2O5·nH2O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V2O5·nH2O nanosheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V2O5·nH2O nanosheets from the V2O5 and VO2 precursors in real time using solution- and solid-state 51V NMR. Solution-state 51V NMR showed that the aqueous solution contained mostly the decavanadate anion [H2V10O28]4- and the hydrated dioxovanadate cation [VO2·4H2O]+, and during the exfoliation process, decavanadate was formed, while the amount of [VO2·4H2O]+ remained constant. The conversion of the solid precursor V2O5, which was monitored with solid-state 51V NMR, was initiated when VO2 was in its monoclinic forms. The dried V2O5·nH2O nanosheets were weakly paramagnetic because of a minor content of isolated V4+. Its solid-state 51V signal was less than 20% of V2O5 and arose from diamagnetic V4+ or V5+.This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials. ©
|
|
| 7. |
- Etman, Ahmed S., et al.
(författare)
-
V2O5·nH2O nanosheets and multi-walled carbon nanotube composite as a negative electrode for sodium-ion batteries
- 2019
-
Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956 .- 2096-885X. ; 30, s. 145-151
-
Tidskriftsartikel (refereegranskat)abstract
- Two dimensional (2D) transition metal oxides and chalcogenides demonstrate a promising performance in sodium-ion batteries (SIBs) application. In this study, we investigated the use of a composite of freeze dried V2O5·nH2O nanosheets and multi-walled carbon nanotube (MWCNT) as a negative electrode material for SIBs. Cyclic voltammetry (CV) results indicated that a reversible sodium-ion insertion/deinsertion into the composite electrode can be obtained in the potential window of 0.1–2.5 V vs. Na+/Na. The composite electrodes delivered sodium storage capacities of 140 and 45 mAh g−1 under applied current densities of 20 and 100 mA g−1, respectively. The pause test during constant current measurement showed a raise in the open circuit potential (OCP) of about 0.46 V, and a charge capacity loss of ∼10%. These values are comparable with those reported for hard carbon electrodes. For comparison, electrodes of freeze dried V2O5·nH2O nanosheets were prepared and tested for SIBs application. The results showed that the MWCNT plays a significant role in the electrochemical performance of the composite material.
|
|
| 8. |
- Shatskiy, Andrey, et al.
(författare)
-
Catalyst-solvent interactions in a dinuclear Ru-based water oxidation catalyst
- 2016
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 45:47, s. 19024-19033
-
Tidskriftsartikel (refereegranskat)abstract
- Photocatalytic water oxidation represents a key process in conversion of solar energy into fuels and can be facilitated by the use of molecular transition metal-based catalysts. A novel straightforward approach for covalent linking of the catalytic units to other moieties is demonstrated by preparation of a dinuclear complex containing two [Ru(pdc)(pic)(3)]-derived units (pdc = 2,6-pyridinedicarboxylate, pic = 4-picoline). The activity of this complex towards chemical and photochemical oxidation of water was evaluated and a detailed insight is given into the interactions between the catalyst and acetonitrile, a common co-solvent employed to increase solubility of water oxidation catalysts. The solvent-induced transformations were studied by electrochemical and spectroscopic techniques and the relevant quantitative parameters were extracted.
|
|
| 9. |
- Tian, Lei, et al.
(författare)
-
Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells
- 2018
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 54:30, s. 3739-3742
-
Tidskriftsartikel (refereegranskat)abstract
- Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells with an organic dye PB6 were successfully fabricated for the first time. With Al2O3 as an inner barrier layer, the recombination process between injected holes in NiO and injected electrons in TiO2 was significantly suppressed and the charge transport time was also improved.
|
|
| 10. |
- Xu, Bo, 1980-, et al.
(författare)
-
Solution-processed nanoporous NiO-dye-ZnO photocathodes : Toward efficient and stable solid-state p-type dye-sensitized solar cells and dye-sensitized photoelectrosynthesis cells
- 2019
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 55, s. 59-64
-
Tidskriftsartikel (refereegranskat)abstract
- A solution-processed NiO-dye-ZnO photocathode was developed for applications in both solid-state p-type dye-sensitized solar cells (p-ssDSCs) and p-type dye-sensitized photoelectrosynthesis cells (p-DSPECs). In p-ssDSCs, the solar cell using ZnO as electron transport material showed a short circuit current, up to 680 mu A cm(-2), which is 60-fold larger than that previously reported device using TiO2 as electron transport material with similar architecture. In the p-DSPECs, a remarkable photocurrent of 100 mu A cm(-2) was achieved in a pH = 5.0 acetate buffer solution under a bias potential at 0.05 V vs RHE with platinum as the proton reduction catalyst. A Faradaic efficiency approaching 100% for the H-2 evolution reaction was obtained after photoelectrolysis for 9 h. Importantly, the solution-processed NiO-dye-ZnO photocathode exhibited excellent long-term stability in both p-ssDSCs and p-DSPECs. To the best of our knowledge, this is the first study where a solution-processable, nanoporous NiO-dye-ZnO photocathode is used for both p-ssDSCs and p-DSPECs having both excellent device performance and stability.
|
|
