1
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Ludlam GH, Gnaniah SJP, Degl’Innocenti R, Gupta G, Wain AJ, Lin H. Measurement of Water Uptake and States in Nafion Membranes Using Humidity-Controlled Terahertz Time-Domain Spectroscopy. ACS SUSTAINABLE CHEMISTRY & ENGINEERING 2024; 12:7924-7934. [PMID: 38783844 PMCID: PMC11110106 DOI: 10.1021/acssuschemeng.4c01820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/18/2024] [Accepted: 04/22/2024] [Indexed: 05/25/2024]
Abstract
Perfluorinated sulfonic acid ionomers are well known for their unique water uptake properties and chemical/mechanical stability. Understanding their performance-stability trade-offs is key to realizing membranes with optimal properties. Terahertz time-domain spectroscopy has been demonstrated to resolve water states inside industrially relevant membranes, producing qualitatively agreeable results to conventional gravimetric analysis and prior demonstrations. Using the proposed humidity-controlled terahertz time-domain spectroscopy, here we quantify this detailed water information inside commercially available Nafion membranes at various humidities for direct comparison against literature values from dynamic vapor sorption, differential scanning calorimetry, and Fourier transform infrared spectroscopy on selected samples. Using this technique therefore opens up opportunities for rapid future parameter space investigation for membrane optimization.
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Affiliation(s)
| | - Sam J. P. Gnaniah
- National
Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, U.K.
| | - Riccardo Degl’Innocenti
- Department
of Engineering, Lancaster University, Lancaster LA1 4YW, U.K.
- School
of Electronic Engineering and Computer Science, Queen Mary University of London, London, E1 4NS, U.K.
| | - Gaurav Gupta
- Department
of Engineering, Lancaster University, Lancaster LA1 4YW, U.K.
| | - Andrew J. Wain
- National
Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, U.K.
| | - Hungyen Lin
- Department
of Engineering, Lancaster University, Lancaster LA1 4YW, U.K.
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2
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Stine JM, Ruland KL, Beardslee LA, Levy JA, Abianeh H, Botasini S, Pasricha PJ, Ghodssi R. Miniaturized Capsule System Toward Real-Time Electrochemical Detection of H 2 S in the Gastrointestinal Tract. Adv Healthc Mater 2024; 13:e2302897. [PMID: 38035728 DOI: 10.1002/adhm.202302897] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 11/20/2023] [Indexed: 12/02/2023]
Abstract
Hydrogen sulfide (H2 S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H2 S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H2 S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas-sensing ingestible capsule is developed to enable real-time, wireless amperometric measurement of H2 S in GI conditions. A gold (Au) three-electrode sensor is modified with a Nafion solid-polymer electrolyte (Nafion-Au) to enhance selectivity toward H2 S in humid environments. The Nafion-Au sensor-integrated capsule shows a linear current response in H2 S concentration ranging from 0.21 to 4.5 ppm (R2 = 0.954) with a normalized sensitivity of 12.4% ppm-1 when evaluated in a benchtop setting. The sensor proves highly selective toward H2 S in the presence of known interferent gases, such as hydrogen (H2 ), with a selectivity ratio of H2 S:H2 = 1340, as well as toward methane (CH4 ) and carbon dioxide (CO2 ). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold-based notification is investigated, showing potential for in vivo application. Thus, the developed H2 S capsule platform provides an analytical tool to uncover the complex biology-modulating effects of intraluminal H2 S.
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Affiliation(s)
- Justin M Stine
- Department of Electrical and Computer Engineering, University of Maryland, College Park, MD, 20742, USA
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
- Fischell Institute for Biomedical Devices, University of Maryland, College Park, MD, 20742, USA
| | - Katie L Ruland
- Department of Electrical and Computer Engineering, University of Maryland, College Park, MD, 20742, USA
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
- Fischell Institute for Biomedical Devices, University of Maryland, College Park, MD, 20742, USA
| | - Luke A Beardslee
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
| | - Joshua A Levy
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
- Fischell Institute for Biomedical Devices, University of Maryland, College Park, MD, 20742, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA
| | - Hossein Abianeh
- Department of Electrical and Computer Engineering, University of Maryland, College Park, MD, 20742, USA
| | - Santiago Botasini
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
| | - Pankaj J Pasricha
- Department of Internal Medicine, Mayo Clinic Hospital, Phoenix, AZ, 85054, USA
| | - Reza Ghodssi
- Department of Electrical and Computer Engineering, University of Maryland, College Park, MD, 20742, USA
- Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA
- Fischell Institute for Biomedical Devices, University of Maryland, College Park, MD, 20742, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA
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3
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Achar SK, Bernasconi L, DeMaio RI, Howard KR, Johnson JK. In Silico Demonstration of Fast Anhydrous Proton Conduction on Graphanol. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37192530 DOI: 10.1021/acsami.3c04022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Development of new materials capable of conducting protons in the absence of water is crucial for improving the performance, reducing the cost, and extending the operating conditions for proton exchange membrane fuel cells. We present detailed atomistic simulations showing that graphanol (hydroxylated graphane) will conduct protons anhydrously with very low diffusion barriers. We developed a deep learning potential (DP) for graphanol that has near-density functional theory accuracy but requires a very small fraction of the computational cost. We used our DP to calculate proton self-diffusion coefficients as a function of temperature, to estimate the overall barrier to proton diffusion, and to characterize the impact of thermal fluctuations as a function of system size. We propose and test a detailed mechanism for proton conduction on the surface of graphanol. We show that protons can rapidly hop along Grotthuss chains containing several hydroxyl groups aligned such that hydrogen bonds allow for conduction of protons forward and backward along the chain without hydroxyl group rotation. Long-range proton transport only takes place as new Grotthuss chains are formed by rotation of one or more hydroxyl groups in the chain. Thus, the overall diffusion barrier consists of a convolution of the intrinsic proton hopping barrier and the intrinsic hydroxyl rotation barrier. Our results provide a set of design rules for developing new anhydrous proton conducting membranes with even lower diffusion barriers.
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Affiliation(s)
- Siddarth K Achar
- Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Leonardo Bernasconi
- Center for Research Computing and Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Ruby I DeMaio
- Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Katlyn R Howard
- Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - J Karl Johnson
- Department of Chemical & Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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4
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Siwy ZS, Bruening ML, Howorka S. Nanopores: synergy from DNA sequencing to industrial filtration - small holes with big impact. Chem Soc Rev 2023; 52:1983-1994. [PMID: 36794856 DOI: 10.1039/d2cs00894g] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Nanopores in thin membranes play important roles in science and industry. Single nanopores have provided a step-change in portable DNA sequencing and understanding nanoscale transport while multipore membranes facilitate food processing and purification of water and medicine. Despite the unifying use of nanopores, the fields of single nanopores and multipore membranes differ - to varying degrees - in terms of materials, fabrication, analysis, and applications. Such a partial disconnect hinders scientific progress as important challenges are best resolved together. This Viewpoint suggests how synergistic crosstalk between the two fields can provide considerable mutual benefits in fundamental understanding and the development of advanced membranes. We first describe the main differences including the atomistic definition of single pores compared to the less defined conduits in multipore membranes. We then outline steps to improve communication between the two fields such as harmonizing measurements and modelling of transport and selectivity. The resulting insight is expected to improve the rational design of porous membranes. The Viewpoint concludes with an outlook of other developments that can be best achieved by collaboration across the two fields to advance the understanding of transport in nanopores and create next-generation porous membranes tailored for sensing, filtration, and other applications.
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Affiliation(s)
- Zuzanna S Siwy
- Department of Physics and Astronomy, University of California, Irvine, USA.
| | - Merlin L Bruening
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, USA.
| | - Stefan Howorka
- Department of Chemistry, Institute of Structural Molecular Biology, University College London, UK.
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5
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Cui R, Li S, Yu C, Zhou Y. The Evolution of Hydrogen Bond Network in Nafion via Molecular Dynamics Simulation. Macromolecules 2023. [DOI: 10.1021/acs.macromol.2c02106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- Rui Cui
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Shanlong Li
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Chunyang Yu
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yongfeng Zhou
- School of Chemistry & Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory of Electrical Insulation and Thermal Aging, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
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6
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Rezayani M, Sharif F, Netz RR, Makki H. Insight into the relationship between molecular morphology and water/ion diffusion in cation exchange membranes: Case of partially sulfonated polyether sulfone. J Memb Sci 2022. [DOI: 10.1016/j.memsci.2022.120561] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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7
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Rahbari A, Hartkamp R, Moultos OA, Bos A, van den Broeke LJP, Ramdin M, Dubbeldam D, Lyulin AV, Vlugt TJH. Electro-osmotic Drag and Thermodynamic Properties of Water in Hydrated Nafion Membranes from Molecular Dynamics. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:8121-8133. [PMID: 35592735 PMCID: PMC9109139 DOI: 10.1021/acs.jpcc.2c01226] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/18/2022] [Indexed: 06/15/2023]
Abstract
One of the important parameters in water management of proton exchange membranes is the electro-osmotic drag (EOD) coefficient of water. The value of the EOD coefficient is difficult to justify, and available literature data on this for Nafion membranes show scattering from in experiments and simulations. Here, we use a classical all-atom model to compute the EOD coefficient and thermodynamic properties of water from molecular dynamics simulations for temperatures between 330 and 420 K, and for different water contents between λ = 5 and λ = 20. λ is the ratio between the moles of water molecules to the moles of sulfonic acid sites. This classical model does not capture the Grotthuss mechanism; however, it is shown that it can predict the EOD coefficient within the range of experimental values for λ = 5 where the vehicular mechanism dominates proton transfer. For λ > 5, the Grotthuss mechanism becomes dominant. To obtain the EOD coefficient, average velocities of water and ions are computed by imposing different electric fields to the system. Our results show that the velocities of water and hydronium scale linearly with the electric field, resulting in a constant ratio of ca. 0.4 within the error bars. We find that the EOD coefficient of water linearly increases from 2 at λ = 5 to 8 at λ = 20 and the results are not sensitive to temperature. The EOD coefficient at λ = 5 is within the range of experimental values, confirming that the model can capture the vehicular transport of protons well. At λ = 20, due to the absence of proton hopping in the model, the EOD coefficient is overestimated by a factor of 3 compared to experimental values. To analyze the interactions between water and Nafion, the partial molar enthalpies and partial molar volumes of water are computed from molecular dynamics simulations. At different water uptakes, multiple linear regression is used on raw simulation data within a narrow composition range of water inside the Nafion membrane. The partial molar volumes and partial molar excess enthalpies of water asymptotically approach the molar volumes and molar excess enthalpies of pure water for water uptakes above 5. This confirms the model can capture the bulklike behavior of water in the Nafion at high water uptakes.
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Affiliation(s)
- Ahmadreza Rahbari
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
- XINTC
global, Wesselseweg 134, 3774 RL Kootwijkerbroek, The
Netherlands
| | - Remco Hartkamp
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - Othonas A. Moultos
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - Albert Bos
- XINTC
global, Wesselseweg 134, 3774 RL Kootwijkerbroek, The
Netherlands
| | - Leo J. P. van den Broeke
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - Mahinder Ramdin
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - David Dubbeldam
- Van’t
Hoff Institute for Molecular Sciences, University
of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
| | - Alexey V. Lyulin
- Soft
Matter and Biological Physics, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Center
for Computational Energy Research, P.O.
Box 6336, 5600 HH Eindhoven, The Netherlands
| | - Thijs J. H. Vlugt
- Engineering
Thermodynamics, Process & Energy Department, Faculty of Mechanical,
Maritime and Materials Engineering, Delft
University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
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8
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Bentley CL, Kang M, Bukola S, Creager SE, Unwin PR. High-Resolution Ion-Flux Imaging of Proton Transport through Graphene|Nafion Membranes. ACS NANO 2022; 16:5233-5245. [PMID: 35286810 PMCID: PMC9047657 DOI: 10.1021/acsnano.1c05872] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Accepted: 11/29/2021] [Indexed: 05/18/2023]
Abstract
In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This intrinsic proton conductivity of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is impermeable to atoms, ions, and molecules. More recent evidence points to a defect-facilitated transport mechanism, analogous to transport through conventional ion-selective membranes based on graphene and h-BN. Herein, local ion-flux imaging is performed on chemical vapor deposition (CVD) graphene|Nafion membranes using an "electrochemical ion (proton) pump cell" mode of scanning electrochemical cell microscopy (SECCM). Targeting regions that are free from visible macroscopic defects (e.g., cracks, holes, etc.) and assessing hundreds to thousands of different sites across the graphene surfaces in a typical experiment, we find that most of the CVD graphene|Nafion membrane is impermeable to proton transport, with transmission typically occurring at ≈20-60 localized sites across a ≈0.003 mm2 area of the membrane (>5000 measurements total). When localized proton transport occurs, it can be a highly dynamic process, with additional transmission sites "opening" and a small number of sites "closing" under an applied electric field on the seconds time scale. Applying a simple equivalent circuit model of ion transport through a cylindrical nanopore, the local transmission sites are estimated to possess dimensions (radii) on the (sub)nanometer scale, implying that rare atomic defects are responsible for proton conductance. Overall, this work reinforces SECCM as a premier tool for the structure-property mapping of microscopically complex (electro)materials, with the local ion-flux mapping configuration introduced herein being widely applicable for functional membrane characterization and beyond, for example in diagnosing the failure mechanisms of protective surface coatings.
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Affiliation(s)
- Cameron L. Bentley
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Minkyung Kang
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Saheed Bukola
- Department
of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Stephen E. Creager
- Department
of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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9
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Zelovich T, Tuckerman ME. Controlling Hydronium Diffusivity in Model Proton Exchange Membranes. J Phys Chem Lett 2022; 13:2245-2253. [PMID: 35238561 DOI: 10.1021/acs.jpclett.1c04071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Fuel-cell-based proton exchange membranes (PEMs) show great potential as cost-effective and clean energy conversion devices. In our recent work, we found that for the low-hydrated model PEMs with a inhomogeneous water distribution and a sulfonate anionic functional end group (SO3-), the H3O+ reacts with SO3- according to SO3- + H3O+ ↔ SO3H + H2O, indicating that the anions in PEMs become active participants in the hydronium diffusion. In this work, we use fully atomistic ab initio molecular dynamics simulations to elucidate the optimal conditions that would promote the participation of SO3- in the hydronium diffusion mechanism by increasing the H3O+/SO3- reactivity, thus increasing the hydronium diffusivity along the cell. The results presented in this work allow us to suggest a set of design rules for creating novel, highly conductive PEMs operating at high temperatures under a nonuniform water distribution using a linker/anion with a relatively high pKa such as (CH2)2SO3. We expect that the discovery of these key design principles will play an important role in the synthesis of high-performing materials for emerging PEM-based fuel cell technologies.
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Affiliation(s)
- Tamar Zelovich
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Mark E Tuckerman
- Department of Chemistry, New York University, New York, New York 10003, United States
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, United States
- NYU-ECNU Center for Computational Chemistry, New York University Shanghai, 3663 North Zhongshan Rd, Shanghai 200062, China
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10
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Jiménez-García JC, Olmos-Asar JA, Franceschini EA, Mariscal MM. Effect of Nafion content and hydration level on the electrochemical area of a Pt nanocatalyst in the triple-phase boundary. Phys Chem Chem Phys 2021; 23:27543-27551. [PMID: 34874379 DOI: 10.1039/d1cp03731e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Despite the great scientific effort, there are still some aspects of a polymeric membrane-based fuel cell (PEMFC) operation that are difficult to access experimentally. This is the case of the so-called triple-phase boundary (TPB), where the ionomer (commonly Nafion) interacts with the supported nanocatalyst (commonly Pt) and is key to the catalytic activity of the system. In this work, we use molecular dynamics simulations and electrochemical experiments on a Nafion/Pt/C system. We perform a systematic analysis, at an atomistic level, to evaluate the effect of several fundamental factors and their intercorrelation on the electrochemically active area (ECSA) of the catalysts. Our results reveal that at high Nafion contents, the catalyst utilization is affected due to the strong interaction between the sulfonic groups of the ionomer and the surface of the Pt nanoparticles (NPs). On the other hand, when the hydration level of the membrane decreases, the sulfonic groups have a greater occupation on the NP surface, covering the active area with hydrophobic Nafion chains and therefore increasing the inactive area. Voltammograms can corroborate our calculations. Overall, this investigation allows us to rationalize how the catalyst utilization is affected, which is an important step in establishing the relationship between the environment and the effectiveness and durability of the PEMFC system.
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Affiliation(s)
- Juan C Jiménez-García
- Instituto de Investigaciones en Fisico-Química de Córdoba (INFIQC) - CONICET, Córdoba, Argentina. .,Departamento de Química Teórica y Computacional, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Jimena A Olmos-Asar
- Instituto de Investigaciones en Fisico-Química de Córdoba (INFIQC) - CONICET, Córdoba, Argentina. .,Departamento de Química Teórica y Computacional, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Esteban A Franceschini
- Instituto de Investigaciones en Fisico-Química de Córdoba (INFIQC) - CONICET, Córdoba, Argentina. .,Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Marcelo M Mariscal
- Instituto de Investigaciones en Fisico-Química de Córdoba (INFIQC) - CONICET, Córdoba, Argentina. .,Departamento de Química Teórica y Computacional, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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11
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Michelarakis N, Franz F, Gkagkas K, Gräter F. Longitudinal strand ordering leads to shear thinning in Nafion. Phys Chem Chem Phys 2021; 23:25901-25910. [PMID: 34779459 DOI: 10.1039/d1cp02024b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Proton-exchange membrane fuel cells (PEMFC) offer a promising energy generation alternative for a wide range of technologies thanks to their ecological friendliness and unparalleled efficiency. At the heart of these electrochemical cells lies the membrane electrode assembly with its most important energy conversion components, the Proton Exchange Membrane. This component is created through the use of printing techniques and Nafion inks. The physicochemical properties of the ink, such as its viscosity under shear, are critical for the finished product. In this work we present non-equilibrium Molecular Dynamics simulations using a MARTINI based coarse-grained model for Nafion to understand the mechanism governing the shear viscosity of Nafion solutions. By simulating a Couette flow and calculating density maps of the Nafion chains in these simulations we shed light on the process that leads to the experimentally observed shear thinning effects of Nafion solutions under flow. We observe rod-shaped Nafion microstructures, 3 nm in size on average, when shear flow is absent or low. Higher shear rates instead break these structures and align Nafion strands along the direction of the flow, resulting in lower shear viscosities. Our work paves the way for a deeper understanding of the dynamic and mechanical properties of Nafion including studies of more complex CL and PEM inks.
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Affiliation(s)
- Nicholas Michelarakis
- Molecular Biomechanics Group, Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
| | - Florian Franz
- Molecular Biomechanics Group, Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
| | - Konstantinos Gkagkas
- Toyota Motor Europe, Technical Center, Toyota Motor Europe NVSA, Zavente, Belgium
| | - Frauke Gräter
- Molecular Biomechanics Group, Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany.,Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120 Heidelberg, Germany
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12
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Zhang G, Yang G, Li S, Shen Q, Wang H, Li Z, Zhou Y, Ye W. Effects of Hydration and Temperature on the Microstructure and Transport Properties of Nafion Polyelectrolyte Membrane: A Molecular Dynamics Simulation. MEMBRANES 2021; 11:695. [PMID: 34564512 PMCID: PMC8467011 DOI: 10.3390/membranes11090695] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/05/2021] [Accepted: 09/06/2021] [Indexed: 11/16/2022]
Abstract
To investigate the effects of temperature and hydration on the microstructure of polymer electrolyte membrane and the transport of water molecules and hydronium ions, molecular dynamics simulations are performed on Nafion 117 for a series of water contents at different temperatures. The interactions among the sulfonate groups, hydronium ions, and water molecules are studied according to the analysis of radial distribution functions and coordination numbers. The sizes and connectivity of water clusters are also discussed, and it is found that the hydration level plays a key role in the phase separation of the membrane. However, the effect of the temperature is slight. When the water content increases from 3.5 to 16, the size of water clusters in the membrane increases, and the clusters connect to each other to form continuous channels for diffusion of water molecules and hydronium ions. The diffusion coefficients are estimated by studying the mean square displacements. The results show that the diffusion of water molecules and hydronium ions are both enhanced by the increase of the temperature and hydration level. Furthermore, the diffusion coefficient of water molecules is always much larger than that of hydronium ions. However, the ratio of the diffusion coefficient of water molecules to that of hydronium ions decreases with the increase of water content.
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Affiliation(s)
- Guoling Zhang
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Guogang Yang
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Shian Li
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Qiuwan Shen
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Hao Wang
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Zheng Li
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Yang Zhou
- Marine Engineering College, Dalian Maritime University, Dalian 116026, China; (G.Z.); (Q.S.); (H.W.); (Z.L.); (Y.Z.)
| | - Weiqiang Ye
- School of Marine Engineering, Guangzhou Maritime University, Guangzhou 510725, China;
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Simari C, Prejanò M, Lufrano E, Sicilia E, Nicotera I. Exploring the Structure-Performance Relationship of Sulfonated Polysulfone Proton Exchange Membrane by a Combined Computational and Experimental Approach. Polymers (Basel) 2021; 13:959. [PMID: 33804763 PMCID: PMC8003876 DOI: 10.3390/polym13060959] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/16/2021] [Accepted: 03/19/2021] [Indexed: 01/01/2023] Open
Abstract
Sulfonated Polysulfone (sPSU) is emerging as a concrete alternative to Nafion ionomer for the development of proton exchange electrolytic membranes for low cost, environmentally friendly and high-performance PEM fuel cells. This ionomer has recently gained great consideration since it can effectively combine large availability on the market, excellent film-forming ability and remarkable thermo-mechanical resistance with interesting proton conductive properties. Despite the great potential, however, the morphological architecture of hydrated sPSU is still unknown. In this study, computational and experimental advanced tools are combined to preliminary describe the relationship between the microstructure of highly sulfonated sPSU (DS = 80%) and its physico-chemical, mechanical and electrochemical features. Computer simulations allowed for describing the architecture and to estimate the structural parameters of the sPSU membrane. Molecular dynamics revealed an interconnected lamellar-like structure for hydrated sPSU, with ionic clusters of about 14-18 Å in diameter corresponding to the hydrophilic sulfonic-acid-containing phase. Water dynamics were investigated by 1H Pulsed Field Gradient (PFG) NMR spectroscopy in a wide temperature range (20-120 °C) and the self-diffusion coefficients data were analyzed by a "two-sites" model. It allows to estimate the hydration number in excellent agreement with the theoretical simulation (e.g., about 8 mol H2O/mol SO3- @ 80 °C). The PEM performance was assessed in terms of dimensional, thermo-mechanical and electrochemical properties by swelling tests, DMA and EIS, respectively. The peculiar microstructure of sPSU provides a wider thermo-mechanical stability in comparison to Nafion, but lower dimensional and conductive features. Nonetheless, the single H2/O2 fuel cell assembled with sPSU exhibited better features than any earlier published hydrocarbon ionomers, thus opening interesting perspectives toward the design and preparation of high-performing sPSU-based PEMs.
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Affiliation(s)
- Cataldo Simari
- Department of Chemistry and Chemical Technologies—CTC, University of Calabria, Via Pietro Bucci, 87036 Rende, Italy; (E.L.); (E.S.); (I.N.)
| | - Mario Prejanò
- Department of Chemistry and Chemical Technologies—CTC, University of Calabria, Via Pietro Bucci, 87036 Rende, Italy; (E.L.); (E.S.); (I.N.)
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Dissipative Particle Dynamics Modeling of Polyelectrolyte Membrane-Water Interfaces. Polymers (Basel) 2020; 12:polym12040907. [PMID: 32295222 PMCID: PMC7240515 DOI: 10.3390/polym12040907] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/10/2020] [Accepted: 04/11/2020] [Indexed: 12/03/2022] Open
Abstract
Previous experiments of water vapor penetration into polyelectrolyte membrane (PEM) thin films have indicated the influence of the water concentration gradient and polymer chemistry on the interface evolution, which will eventually affect the efficiency of the fuel cell operation. Moreover, PEMs of different side chains have shown differences in water cluster structure and diffusion. The evolution of the interface between water and polyelectrolyte membranes (PEMs), which are used in fuel cells and flow batteries, of three different side-chain lengths has been studied using dissipative particle dynamics (DPD) simulations. Higher and faster water uptake is usually beneficial in the operation of fuel cells and flow batteries. The simulated water uptake increased with the increasing side chain length. In addition, the water uptake was rapid initially and slowed down afterwards, which is in agreement with the experimental observations. The water cluster formation rate was also found to increase with the increasing side-chain length, whereas the water cluster shapes were unaffected. Water diffusion in the membranes, which affects proton mobility in the PEMs, increased with the side-chain length at all distances from the interface. In conclusion, side-chain length was found to have a strong influence on the interface water structure and water penetration rates, which can be harnessed for the better design of PEMs. Since the PEM can undergo cycles of dehydration and rehydration, faster water uptake increases the efficiency of these devices. We show that the longer side chains with backbone structure similar to Nafion should be more suitable for fuel cell/flow battery usage.
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