The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Yuhou Wu - One of the best experts on this subject based on the ideXlab platform.
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Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene
International Journal of Hydrogen Energy, 2012Co-Authors: Yuhou WuAbstract:Abstract The Proton exchange membrane (PEM) fuel cell is one of the most promising fuel cells for wide applications, and the Proton exchange membrane is one of its key components. However, the Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene remains unclear for the research on PEM fuel cells. In this paper, the model of the Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene is developed based on the fundamentals of the molecular dynamics, particularly the principle of energy and radial distribution function. The Proton Transfer process in perfluorinated sulfonic acid polytetrafluoroethylene is simulated, whereas the effects driven by the water content in the membrane and fuel cell temperature are analyzed. The results show that the water bridges developed by free water are the passage for Proton Transfer from one sulfonic group to its adjacent sulfonic group in perfluorinated sulfonic acid polytetrafluoroethylene. The Proton Transfers along the water bridge by the formation and cleavage of the H–O bond between the water from the water bridge and the Proton; the increases in the water content in the membrane and the fuel cell temperature speed up the Proton Transfer, causing the decrease in the resistance of Proton Transfer. These findings are remarkably helpful to understand the working mechanism of PEM fuel cells.
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Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene
International Journal of Hydrogen Energy, 2012Co-Authors: Hong Sun, Zhe Sun, Yuhou WuAbstract:The Proton exchange membrane (PEM) fuel cell is one of the most promising fuel cells for wide applications, and the Proton exchange membrane is one of its key components. However, the Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene remains unclear for the research on PEM fuel cells. In this paper, the model of the Proton Transfer mechanism in perfluorinated sulfonic acid polytetrafluoroethylene is developed based on the fundamentals of the molecular dynamics, particularly the principle of energy and radial distribution function. The Proton Transfer process in perfluorinated sulfonic acid polytetrafluoroethylene is simulated, whereas the effects driven by the water content in the membrane and fuel cell temperature are analyzed. The results show that the water bridges developed by free water are the passage for Proton Transfer from one sulfonic group to its adjacent sulfonic group in perfluorinated sulfonic acid polytetrafluoroethylene. The Proton Transfers along the water bridge by the formation and cleavage of the H-O bond between the water from the water bridge and the Proton; the increases in the water content in the membrane and the fuel cell temperature speed up the Proton Transfer, causing the decrease in the resistance of Proton Transfer. These findings are remarkably helpful to understand the working mechanism of PEM fuel cells. © 2012 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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Proton Transfer in Proton Exchange Membrane Based on RDF
Advanced Materials Research, 2011Co-Authors: Yu Lan Tang, Yuhou WuAbstract:PEM fuel cell is the most promising application as an automotive power. Proton Transfer in PEM is one of important factors to understand the performance of PEM fuel cell. In this paper, the Proton Transfer mechanisms are analyzed by the molecular simulation based on the basic principle of molecular dynamics. Effects of water content in the Proton exchange membrane and cell temperature on the Proton Transfer in the membrane are studied by the radial distribution function (RDF). Results show that Proton Transfers in the Nafion polymer by water bridges between two sulfonic groups of adjacent side chains. There are more water bridges supporting Proton Transfer with the increase of water content in membrane. The increase of cell temperature speeds up the form and break of O-H bond, which promotes the Proton Transfer. The research results are very helpful to understanding the Proton Transfer mechanism in Proton exchange membrane and promoting the applications of PEM fuel cell.
Kyril M Solntsev - One of the best experts on this subject based on the ideXlab platform.
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excited state Proton Transfer from constrained systems to super photoacids to superfast Proton Transfer
Accounts of Chemical Research, 2002Co-Authors: Laren M. Tolbert, Kyril M SolntsevAbstract:We have used knowledge of the electronic structure of excited states of acids to design molecules that exhibit enhanced excited-state acidity. Such “super” photoacids are the strongest reversible photoacids known and allow the time evolution of Proton Transfer to be examined in a wide array of organic solvents. This includes breaking/formation of the hydrogen bonds in hundreds of femtoseconds, solvent reorientation and relaxation in picoseconds, Proton dissociation, and, finally, diffusion and geminate recombination of the dissociated Proton, observed in nanoseconds.
Laren M. Tolbert - One of the best experts on this subject based on the ideXlab platform.
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excited state Proton Transfer from constrained systems to super photoacids to superfast Proton Transfer
Accounts of Chemical Research, 2002Co-Authors: Laren M. Tolbert, Kyril M SolntsevAbstract:We have used knowledge of the electronic structure of excited states of acids to design molecules that exhibit enhanced excited-state acidity. Such “super” photoacids are the strongest reversible photoacids known and allow the time evolution of Proton Transfer to be examined in a wide array of organic solvents. This includes breaking/formation of the hydrogen bonds in hundreds of femtoseconds, solvent reorientation and relaxation in picoseconds, Proton dissociation, and, finally, diffusion and geminate recombination of the dissociated Proton, observed in nanoseconds.
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Excited-state Proton Transfer from hydroxyalkylnaphthols
The Journal of Physical Chemistry, 1993Co-Authors: Laren M. Tolbert, Lilia Cuesta HarveyAbstract:The excited-state Proton-Transfer (ESPT) reactions of 1-propyl-2-naphthol (PN), 1-(3-hydroxypropyl)-2-naphthol (HPN), and 1-(2,3-dihydroxypropyl)-2-naphthol (DPN) in aqueous methanol solutions have been investigated. The hydroxypropyl and dihydroxypropyl side chains have a pronounced effect on the rate of the Proton Transfer and on the number of water molecules involved, indicating that Proton Transfer in alcoholic solvents is more complex than simple models of water clusters can accommodate. Alternative models in which a side chain facilitates the formation of the requisite geometry for Proton Transfer are discussed
Noam Agmon - One of the best experts on this subject based on the ideXlab platform.
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elementary steps in excited state Proton Transfer
Journal of Physical Chemistry A, 2005Co-Authors: Noam AgmonAbstract:The absorption of a photon by a hydroxy-aromatic photoacid triggers a cascade of events contributing to the overall phenomenon of intermolecular excited-state Proton Transfer. The fundamental steps involved were studied over the last 20 years using a combination of theoretical and experimental techniques. They are surveyed in this sequel in sequential order, from fast to slow. The excitation triggers an intramolecular charge Transfer to the ring system, which is more prominent for the anionic base than the acid. The charge redistribution, in turn, triggers changes in hydrogen-bond strengths that set the stage for the Proton-Transfer step itself. This step is strongly influenced by the solvent, resulting in unusual dependence of the dissociation rate coefficient on water content, temperature, and isotopic substitution. The photolyzed Proton can diffuse in the aqueous solution in a mechanism that involves collective changes in hydrogen-bonding. On longer times, it may recombine adiabatically with the excited base or quench it. The theory for these diffusion-influenced geminate reactions has been developed, showing nice agreement with experiment. Finally, the effect of inert salts, bases, and acids on these reactions is analyzed.
Jinfeng Zhao - One of the best experts on this subject based on the ideXlab platform.
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a questionable excited state double Proton Transfer mechanism for 3 hydroxyisoquinoline
Physical Chemistry Chemical Physics, 2015Co-Authors: Jinfeng Zhao, Junsheng Chen, Jing Wang, Peng SongAbstract:Two excited state Proton Transfer mechanisms of 3-hydroxyisoquinoline (3HIQ) in cyclohexane and acetic acid (ACID) were investigated based on the time-dependent density functional theory (TDDFT), suggesting a different double-Proton Transfer mechanism from the one proposed previously (J. Phys. Chem. B, 1998, 102, 1053). Instead of the formation of keto–enol complexes for 3HIQ self-association in cyclohexane, our theoretical results predicted that 3HIQ self-association exists in two forms: the normal form (enol/enol) and the tautomer form (keto/keto) in cyclohexane. A high barrier (37.023 kcal mol−1) between the 3HIQ enol monomer and 3HIQ keto monomer form indicated that the 3HIQ keto monomer in the ground state should not exist. In addition, the constructed potential energy surfaces of the ground state and excited state have been used to explain the Proton Transfer process. Upon optical excitation, the enol/enol form is excited to the first excited state, then Transfers one Proton, in turn, transition to the ground state to Transfer another Proton. A relatively low barrier (8.98 kcal mol−1) demonstrates two stable structures in the ground state. In view of the acetic acid solvent effect, two Protons of 3HIQ/ACID Transfer along the dihydrogen bonds in the first excited state, which is a different Transfer mechanism to 3HIQ self-association. In addition, the Proton Transfer process provides a possible explanation for the fluorescence quenching observed.
