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Popov I, Zhu Z, Young-Gonzales AR, Sacci RL, Mamontov E, Gainaru C, Paddison SJ, Sokolov AP. Search for a Grotthuss mechanism through the observation of proton transfer. Commun Chem 2023; 6:77. [PMID: 37087505 PMCID: PMC10122652 DOI: 10.1038/s42004-023-00878-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/04/2023] [Indexed: 04/24/2023] Open
Abstract
The transport of protons is critical in a variety of bio- and electro-chemical processes and technologies. The Grotthuss mechanism is considered to be the most efficient proton transport mechanism, generally implying a transfer of protons between 'chains' of host molecules via elementary reactions within the hydrogen bonds. Although Grotthuss proposed this concept more than 200 years ago, only indirect experimental evidence of the mechanism has been observed. Here we report the first experimental observation of proton transfer between the molecules in pure and 85% aqueous phosphoric acid. Employing dielectric spectroscopy, quasielastic neutron, and light scattering, and ab initio molecular dynamic simulations we determined that protons move by surprisingly short jumps of only ~0.5-0.7 Å, much smaller than the typical ion jump length in ionic liquids. Our analysis confirms the existence of correlations in these proton jumps. However, these correlations actually reduce the conductivity, in contrast to a desirable enhancement, as is usually assumed by a Grotthuss mechanism. Furthermore, our analysis suggests that the expected Grotthuss-like enhancement of conductivity cannot be realized in bulk liquids where ionic correlations always decrease conductivity.
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Affiliation(s)
- Ivan Popov
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Chemistry, University of Tennessee, Knoxville, TN, USA
| | - Zhenghao Zhu
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN, USA
| | | | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Eugene Mamontov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Catalin Gainaru
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Stephen J Paddison
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN, USA.
| | - Alexei P Sokolov
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
- Department of Chemistry, University of Tennessee, Knoxville, TN, USA.
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2
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Cai L, Yang J, Lai Y, Liang Y, Zhang R, Gu C, Kitagawa S, Yin P. Dynamics and Proton Conduction of Heterogeneously Confined Imidazole in Porous Coordination Polymers. Angew Chem Int Ed Engl 2023; 62:e202211741. [PMID: 36583606 DOI: 10.1002/anie.202211741] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 12/31/2022]
Abstract
The nanoconfinement of proton carrier molecules may contribute to the lowing of their proton dissociation energy. However, the free proton transportation does not occur as easily as in liquid due to the restricted molecular motion from surface attraction. To resolve the puzzle, herein, imidazole is confined in the channels of porous coordination polymers with tunable geometries, and their electric/structural relaxations are quantified. Imidazole confined in a square-shape channels exhibits dynamics heterogeneity of core-shell-cylinder model. The core and shell layer possess faster and slower structural dynamics, respectively, when compared to the bulk imidazole. The dimensions and geometry of the nanochannels play an important role in both the shielding of the blocking effect from attractive surfaces and the frustration filling of the internal proton carrier molecules, ultimately contributing to the fast dynamics and enhanced proton conductivity.
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Affiliation(s)
- Linkun Cai
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Junsheng Yang
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Yuyan Lai
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Yuling Liang
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Rongchun Zhang
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Cheng Gu
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
| | - Susumu Kitagawa
- Institute for Integrated Cell-Material Sciences, Institute for Advanced Study, Kyoto University, Kyoto, 606-8501, Japan
| | - Panchao Yin
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou, 510640, China
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3
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Ahlmann S, Hoffmann L, Keppler M, Münzner P, Tonauer CM, Loerting T, Gainaru C, Böhmer R. Isotope effects on the dynamics of amorphous ices and aqueous phosphoric acid solutions. Phys Chem Chem Phys 2022; 24:14846-14856. [PMID: 35697341 DOI: 10.1039/d2cp01455f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The glass transitions of amorphous ices as well as of aqueous phosphoric acid solutions were reported to display very large 1H/2H isotope effects. Using dielectric spectroscopy, in both types of glassformers for equimolar protonated/deuterated mixtures an almost ideal isotope-mixing behavior rather than a bimodal relaxation is found. For the amorphous ices this finding is interpreted in terms of a glass-to-liquid rather than an orientational glass transition scenario. Based on calorimetric results revealing that major 16O/18O isotope effects are missing, the latter scenario was previously favored for the amorphous ices. Considering the dielectric results on 18O substituted amorphous ices and by comparison with corresponding results for the aqueous phosphoric acid solutions, it is argued that the present findings are compatible with the glass-to-liquid scenario. To provide additional information regarding the deeply supercooled state of 1H/2H isotopically mixed and 18O substituted glassformers, the aqueous phosphoric acid solutions are studied using shear mechanical spectroscopy as well, a technique which so far could not successfully be applied to characterize the glass transitions of the amorphous ices.
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Affiliation(s)
- S Ahlmann
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - L Hoffmann
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - M Keppler
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - P Münzner
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - C M Tonauer
- Institute of Physical Chemistry, University of Innsbruck, Innrain 52c, A-6020 Innsbruck, Austria
| | - T Loerting
- Institute of Physical Chemistry, University of Innsbruck, Innrain 52c, A-6020 Innsbruck, Austria
| | - C Gainaru
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany.,Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R Böhmer
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
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4
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Ahlmann S, Münzner P, Moch K, Sokolov AP, Böhmer R, Gainaru C. The relationship between charge and molecular dynamics in viscous acid hydrates. J Chem Phys 2021; 155:014505. [PMID: 34241375 DOI: 10.1063/5.0055179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oscillatory shear rheology has been employed to access the structural rearrangements of deeply supercooled sulfuric acid tetrahydrate (SA4H) and phosphoric acid monohydrate, the latter in protonated (PA1H) and deuterated (PA1D) forms. Their viscoelastic responses are analyzed in relation to their previously investigated electric conductivity. The comparison of the also presently reported dielectric response of deuterated sulfuric acid tetrahydrate (SA4D) and that of its protonated analog SA4H reveals an absence of isotope effects for the charge transport in this hydrate. This finding clearly contrasts with the situation known for PA1H and PA1D. Our analyses also demonstrate that the conductivity relaxation profiles of acid hydrides closely resemble those exhibited by classical ionic electrolytes, even though the charge transport in phosphoric acid hydrates is dominated by proton transfer processes. At variance with this dielectric simplicity, the viscoelastic responses of these materials depend on their structural compositions. While SA4H displays a "simple liquid"-like viscoelastic behavior, the mechanical responses of PA1H and PA1D are more complex, revealing relaxation modes, which are faster than their ubiquitous structural rearrangements. Interestingly, the characteristic rates of these fast mechanical relaxations agree well with the characteristic frequencies of the charge rearrangements probed in the dielectric investigations, suggesting appearance of a proton transfer in mechanical relaxation of phosphoric acid hydrates. These findings open the exciting perspective of exploiting shear rheology to access not only the dynamics of the matrix but also that of the charge carriers in highly viscous decoupled conductors.
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Affiliation(s)
- S Ahlmann
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - P Münzner
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - K Moch
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - A P Sokolov
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - R Böhmer
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - C Gainaru
- Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany
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5
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Young-Gonzales AR, Paddison SJ, Sokolov AP. Tuning proton conductivity and energy barriers for proton transfer. J Chem Phys 2021; 154:014503. [PMID: 33412878 DOI: 10.1063/5.0032512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Proton transport is critical for many technologies and for a variety of biochemical and biophysical processes. Proton transfer between molecules (via structural diffusion) is considered to be an efficient mechanism in highly proton conducting materials. Yet, the mechanism and what controls energy barriers for this process remain poorly understood. It was shown that mixing phosphoric acid (PA) with lidocaine leads to an increase in proton conductivity at the same liquid viscosity. However, recent simulations of mixtures of PA with various bases, including lidocaine, suggested no decrease in the proton transfer energy barrier. To elucidate this surprising result, we have performed broadband dielectric spectroscopy to verify the predictions of the simulations for mixtures of PA with several bases. Our results reveal that adding bases to PA increases the energy barriers for proton transfer, and the observed increase in proton conductivity at a similar viscosity appears to be related to the increase in the glass transition temperature (Tg) of the mixture. Moreover, the energy barrier seems to increase with Tg of the mixtures, emphasizing the importance of molecular mobility or interactions in the proton transfer mechanism.
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Affiliation(s)
| | - Stephen J Paddison
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Alexei P Sokolov
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA
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6
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Kumar A, Pisula W, Müllen K. One Dimensional Enhanced Anhydrous Proton Conduction in Well Defined Molecular Columns Induced by Non-Covalent Interactions. Chemphyschem 2019; 20:651-654. [PMID: 30702798 DOI: 10.1002/cphc.201801017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/30/2019] [Indexed: 11/11/2022]
Abstract
1D anhydrous proton conduction is enhanced significantly in ionic channels created by self-assembly of functionalized organic phosphonic acid and aromatic heterocyclic 1,2,4-triazole molecules. This study reveals high proton conduction in one dimension through a well-defined supramolecular architecture in which two different molecules undergo host-guest synergy and self-assemble to provide two-fold advantages: 1) formation of the ionic channels and 2) higher proton conduction in the absence of water. A clear correlation is found between the phenomena of ionic channels and anhydrous conductivity in the absolute dry state and we demonstrate that the one-dimensional conductivity can be as high as that recorded for 3D channels in, for instance, Nafion.
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Affiliation(s)
- Avneesh Kumar
- Institute of Organic Chemistry, L2-02, Room No. 554, TU Darmstadt, Alarich-Weiss-Str. 4, 64287, Darmstadt, Germany.,International Center for Materials Science, JNCASR, Jakkur, Bangalore, 650064, India
| | - Wojciech Pisula
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.,Department of Molecular Physics, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924, Lodz, Poland
| | - Klaus Müllen
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
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7
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Zhang H, Hu Q, Zheng X, Yin Y, Wu H, Jiang Z. Incorporating phosphoric acid-functionalized polydopamine into Nafion polymer by in situ sol-gel method for enhanced proton conductivity. J Memb Sci 2019. [DOI: 10.1016/j.memsci.2018.10.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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8
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Cheng X, Jin H, Shen C, Gao S, Wang J, Zhu X. Preparation and characterization of proton exchange membrane based on polyphosphoric acid modified by PVDF-HFP. J Appl Polym Sci 2018. [DOI: 10.1002/app.46737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Xiangze Cheng
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
| | - Huaiyang Jin
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
| | - Chunhui Shen
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
| | - Shanjun Gao
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
| | - Jiang Wang
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
| | - Xi Zhu
- Department of Polymer Materials and Engineering, School of Material Science and Engineering; Wuhan University of Technology; Wuhan 430070 People's Republic of China
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9
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In Operando Neutron Radiography Analysis of a High-Temperature Polymer Electrolyte Fuel Cell Based on a Phosphoric Acid-Doped Polybenzimidazole Membrane Using the Hydrogen-Deuterium Contrast Method. ENERGIES 2018. [DOI: 10.3390/en11092214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In order to characterize high temperature polymer electrolyte fuel cells (HT-PEFCs) in operando, neutron radiography imaging, in combination with the deuterium contrast method, was used to analyze the hydrogen distribution and proton exchange processes in operando. These measurements were then combined with the electrochemical impedance spectroscopy measurements. The cell was operated under different current densities and stoichiometries. Neutron images of the active area of the cell were captured in order to study the changeover times when the fuel supply was switched between hydrogen and deuterium, as well as to analyze the cell during steady state conditions. This work demonstrates that the changeover from proton to deuteron (and vice versa) leads to local varying media distributions in the electrolyte, independent of the overall exchange dynamics. A faster proton-to-deuteron exchange was re-discovered when switching the gas supply from H2 to D2 than that from D2 to H2. Furthermore, the D2 uptake and discharge were faster at a higher current density. Specifically, the changeover from H to D takes 5–6 min at 200 mA cm−2, 2–3 min at 400 mA cm−2 and 1–2 min at 600 mA cm−2. An effect on the transmittance changes is apparent when the stoichiometry changes.
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11
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Griffin PJ, Freyer JL, Han N, Geller N, Yin X, Gheewala CD, Lambert TH, Campos LM, Winey KI. Ion Transport in Cyclopropenium-Based Polymerized Ionic Liquids. Macromolecules 2018. [DOI: 10.1021/acs.macromol.7b02546] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Philip J. Griffin
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jessica L. Freyer
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Nicholas Han
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Noah Geller
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Xiaodong Yin
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Chirag D. Gheewala
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Tristan H. Lambert
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Luis M. Campos
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Karen I. Winey
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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12
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Novikov VN, Sokolov AP. Quantum effects in dynamics of water and other liquids of light molecules. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2017; 40:57. [PMID: 28510231 DOI: 10.1140/epje/i2017-11546-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Accepted: 05/04/2017] [Indexed: 06/07/2023]
Abstract
Nuclear quantum effects in atomic motions are well known at low temperatures [Formula: see text] K, but analyses of structural relaxation in liquids and description of the glass transition traditionally neglect quantum effects at higher temperatures, [Formula: see text] K. Recent studies, however, suggested that nuclear quantum effects in systems of light molecules (e.g., water) might play an important role in structural dynamics and provide non-negligible contributions at such temperatures, and even up to ambient temperature. In this article, we discuss experimental evidences of the quantum effects in glass transition in liquids of light molecules and possible theoretical descriptions of these effects. We show that quantum effects may qualitatively change the temperature behavior of the structural relaxation time in supercooled liquids leading to deviations of some well-established properties of the glass transition when it happens at low temperatures. We also demonstrate that unusual behavior of water dynamics at low temperatures, including apparent fragile-to-strong crossover, can be ascribed to nuclear quantum effects.
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Affiliation(s)
- V N Novikov
- Department of Chemistry, University of Tennessee, 37996, Knoxville, TN, USA.
- Shull Wollan Center - Joint-Institute for Neutron Sciences, Oak Ridge National Laboratory and University of Tennessee, 37831, Oak Ridge, TN, USA.
- Institute of Automation and Electrometry, Russian Academy of Sciences, 630090, Novosibirsk, Russia.
| | - A P Sokolov
- Department of Chemistry, University of Tennessee, 37996, Knoxville, TN, USA
- Shull Wollan Center - Joint-Institute for Neutron Sciences, Oak Ridge National Laboratory and University of Tennessee, 37831, Oak Ridge, TN, USA
- Chemical Sciences Division, Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA
- Department of Physics and Astronomy, University of Tennessee, 37996, Knoxville, TN, USA
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13
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Melchior JP, Frick B. On the nanosecond proton dynamics in phosphoric acid–benzimidazole and phosphoric acid–water mixtures. Phys Chem Chem Phys 2017; 19:28540-28554. [DOI: 10.1039/c7cp04116k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Combining 1H-NMR, 17O-NMR, and high-resolution backscattering QENS hydrodynamic and structural proton transport in phosphoric acid is separated. The rate limiting steps for structural proton diffusion in mixtures of acid with Brønsted bases are found to occur below the nanosecond timescale.
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