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Patel BB, Feng H, Loo WS, Snyder CR, Eom C, Murphy J, Sunday DF, Nealey PF, DeLongchamp DM. Self-Assembly of Hierarchical High-χ Fluorinated Block Copolymers with an Orthogonal Smectic-within-Lamellae 3 nm Sublattice and Vertical Surface Orientation. ACS Nano 2024; 18:11311-11322. [PMID: 38623826 DOI: 10.1021/acsnano.4c00664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Hierarchical structure-within-structure assemblies offer a route toward increasingly complex and multifunctional materials while pushing the limits of block copolymer self-assembly. We present a detailed study of the self-assembly of a series of fluorinated high-χ block copolymers (BCPs) prepared via postmodification of a single poly(styrene)-block-poly(glycidyl methacrylate) (S-b-G) parent polymer with the fluorinated alkylthiol pendent groups containing 1, 6, or 8 fluorinated carbons (termed trifluoro-ethanethiol (TFET), perfluoro-octylthiol (PFOT), and perfluoro-decylthiol (PFDT), respectively). Bulk X-ray scattering of thermally annealed samples demonstrates hierarchical molecular assembly with phase separation between the two blocks and within the fluorinated block. The degree of ordering within the fluorinated block is highly sensitive to synthetic variation; a lamellar sublattice was formed for S-b-GPFOT and S-b-GPFDT. Thermal analyses of S-b-GPFOT reveal that the fluorinated block exhibits liquid crystal-like ordering. The complex thin-film self-assembly behavior of an S-b-GPFOT polymer was investigated using real-space (atomic force microscopy and scanning electron microscopy) and reciprocal-space (resonant soft X-ray scattering (RSoXS), grazing incidence small- and wide-angle scattering) measurements. After thermal annealing in nitrogen or vacuum, films thicker than 1.5 times the primary lattice spacing exhibit a 90-degree grain boundary, exposing a thin layer of vertical lamellae at the free interface, while exhibiting horizontal lamellae on the preferential (polystyrene brush) substrate. RSoXS measurements reveal the near-perfect orthogonality between the primary and sublattice orientations, demonstrating hierarchical patterning at the nanoscale.
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Affiliation(s)
- Bijal B Patel
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Hongbo Feng
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Whitney S Loo
- Department of Chemical and Biological Engineering, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Chad R Snyder
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Christopher Eom
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Julia Murphy
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Daniel F Sunday
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Paul F Nealey
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Dean M DeLongchamp
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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2
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Moehring NK, Naclerio AE, Chaturvedi P, Knight T, Kidambi PR. Ultra-thin proton conducting carrier layers for scalable integration of atomically thin 2D materials with proton exchange polymers for next-generation PEMs. Nanoscale 2024; 16:6973-6983. [PMID: 38353333 DOI: 10.1039/d3nr05202h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
Scalable approaches for synthesis and integration of proton selective atomically thin 2D materials with proton conducting polymers can enable next-generation proton exchange membranes (PEMs) with minimal crossover of reactants or undesired species while maintaining adequately high proton conductance for practical applications. Here, we systematically investigate facile and scalable approaches to interface monolayer graphene synthesized via scalable chemical vapor deposition (CVD) on Cu foil with the most widely used proton exchange polymer Nafion 211 (N211, ∼25 μm thick film) via (i) spin-coating a ∼700 nm thin Nafion carrier layer to transfer graphene (spin + scoop), (ii) casting a Nafion film and cold pressing (cold press), and (iii) hot pressing (hot press) while minimizing micron-scale defects to <0.3% area. Interfacing CVD graphene on Cu with N211 via cold press or hot press and subsequent removal of Cu via etching results in ∼50% lower areal proton conductance compared to membranes fabricated via the spin + scoop method. Notably, the areal proton conductance can be recovered by soaking the hot and cold press membranes in 0.1 M HCl, without significant damage to graphene. We rationalize our finding by the significantly smaller reservoir for cation uptake from Cu etching for the ∼700 nm thin carrier Nafion layer used for spin + scoop transfer compared to the ∼25 μm thick N211 film for hot and cold pressing. Finally, we demonstrate performance in H2 fuel cells with power densities of ∼0.23 W cm-2 and up to ∼41-54% reduction in H2 crossover for the N211|G|N211 sandwich membranes compared to the control N211|N211 indicating potential for our approach in enabling advanced PEMs for fuel cells, redox-flow batteries, isotope separations and beyond.
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Affiliation(s)
- Nicole K Moehring
- Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, TN 37235, USA.
- Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt Institute of Nanoscale Science and Engineering, Nashville, TN 37212, USA
| | - Andrew E Naclerio
- Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville, TN 37212, USA
| | - Pavan Chaturvedi
- Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt Institute of Nanoscale Science and Engineering, Nashville, TN 37212, USA
| | - Thomas Knight
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Piran R Kidambi
- Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, TN 37235, USA.
- Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt Institute of Nanoscale Science and Engineering, Nashville, TN 37212, USA
- Mechanical Engineering Department, Vanderbilt University, Nashville, TN, 37212, USA
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3
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Lee DW, Hyun J, Oh E, Seok K, Bae H, Park J, Kim HT. Potential-Dependent Ionomer Rearrangement on the Pt Surface in Polymer Electrolyte Membrane Fuel Cells. ACS Appl Mater Interfaces 2024; 16:4637-4647. [PMID: 38251952 DOI: 10.1021/acsami.3c15827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
The interface between the catalyst and the ionomer in the catalyst layer of polymer electrolyte membrane fuel cells (PEMFCs) has been a subject of keen interest, but its effect on durability has not been fully understood due to the complexity of the catalyst layer structure. Herein, we utilize a Pt nanoparticle (NP) array electrode fabricated using a block copolymer template as the platform for a focused investigation of the interfacial change between the Nafion thin film and the Pt NP under a constant potential. A set of analyses for the electrodes treated with various potentials reveals that the Nafion thin film becomes densely packed at the intermediate potentials (0.4 and 0.7 V), indicating an increased ionomer-catalyst interaction due to the positive charges formed at the Pt surface at these potentials. Even for a practical PEMFC single cell, we demonstrate that the potential holding at the intermediate potentials increases ionomer adsorption to the Pt surface and the oxygen transport resistance, negatively impacting its power performance. This work provides fresh insight into the mechanism behind the performance fade in PEMFCs caused by potential-dependent ionomer rearrangement.
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Affiliation(s)
- Dong Wook Lee
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Jonghyun Hyun
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Euntaek Oh
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Kyunghwa Seok
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Hanmin Bae
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Jeesoo Park
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Hee-Tak Kim
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
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Zelovich T, Dekel DR, Tuckerman ME. Electrostatic Potential of Functional Cations as a Predictor of Hydroxide Diffusion Pathways in Nanoconfined Environments of Anion Exchange Membranes. J Phys Chem Lett 2024; 15:408-415. [PMID: 38179916 PMCID: PMC10801687 DOI: 10.1021/acs.jpclett.3c02800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/16/2023] [Accepted: 12/18/2023] [Indexed: 01/06/2024]
Abstract
Nanoconfined anion exchange membranes (AEMs) play a vital role in emerging electrochemical technologies. The ability to control dominant hydroxide diffusion pathways is an important goal in the design of nanoconfined AEMs. Such control can shorten hydroxide transport pathways between electrodes, reduce transport resistance, and enhance device performance. In this work, we propose an electrostatic potential (ESP) approach to explore the effect of the polymer electrolyte cation spacing on hydroxide diffusion pathways from a molecular perspective. By exploring cation ESP energy surfaces and validating outcomes through prior ab initio molecular dynamics simulations of nanoconfined AEMs, we find that we can achieve control over preferred hydroxide diffusion pathways by adjusting the cation spacing. The results presented in this work provide a unique and straightforward approach to predict preferential hydroxide diffusion pathways, enabling efficient design of highly conductive nanoconfined AEM materials for electrochemical technologies.
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Affiliation(s)
- Tamar Zelovich
- Department
of Chemistry, New York University (NYU), New York, New York 10003, United States
| | - Dario R. Dekel
- Wolfson
Department of Chemical Engineering, Technion
− Israel Institute of Technology, Haifa, 3200003, Israel
- Nancy
& Stephen Grand Technion Energy Program, Technion − Israel Institute of Technology, Haifa, 3200003, Israel
| | - Mark E. Tuckerman
- Department
of Chemistry, New York University (NYU), New York, New York 10003, United States
- Courant
Institute of Mathematical Sciences, New
York University (NYU), New York, New York 10012, United States
- NYU-ECNU
Center for Computational Chemistry at NYU Shanghai, 3663 Zhongshan Rd. North, Shanghai 200062, China
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5
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Hoffman JM, Thompson NB, Borkiewicz O, He X, Amsterdam S, Xie ZL, Taggart A, Mulfort KL, Martinson ABF, Chen LX, Ruett U, Tiede DM. Orientational analysis of atomic pair correlations in nanocrystalline indium oxide thin films. IUCrJ 2024; 11:120-128. [PMID: 38133556 PMCID: PMC10833382 DOI: 10.1107/s2052252523010357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023]
Abstract
The application of grazing-incidence total X-ray scattering (GITXS) for pair distribution function (PDF) analysis using >50 keV X-rays from synchrotron light sources has created new opportunities for structural characterization of supported thin films with high resolution. Compared with grazing-incidence wide-angle X-ray scattering, which is only useful for highly ordered materials, GITXS/PDFs expand such analysis to largely disordered or nanostructured materials by examining the atomic pair correlations dependent on the direction relative to the surface of the supporting substrate. A characterization of nanocrystalline In2O3-derived thin films is presented here with in-plane-isotropic and out-of-plane-anisotropic orientational ordering of the atomic structure, each synthesized using different techniques. The atomic orientations of such films are known to vary based on the synthetic conditions. Here, an azimuthal orientational analysis of these films using GITXS with a single incident angle is shown to resolve the markedly different orientations of the atomic structures with respect to the planar support and the different degrees of long-range order, and hence, the terminal surface chemistries. It is anticipated that orientational analysis of GITXS/PDF data will offer opportunities to extend structural analyses of thin films by providing a means to qualitatively determine the major atomic orientation within nanocrystalline and, eventually, non-crystalline films.
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Affiliation(s)
- Justin M. Hoffman
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Niklas B. Thompson
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Olaf Borkiewicz
- X-ray Science, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Xiang He
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Samuel Amsterdam
- Materials Science Divisions, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Zhu-lin Xie
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Aaron Taggart
- Materials Science Divisions, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Karen L. Mulfort
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Alex B. F. Martinson
- Materials Science Divisions, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Lin X. Chen
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Uta Ruett
- X-ray Science, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - David M. Tiede
- Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
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Kuebler J, Loosbrock T, Strzalka J, Fernandez-Ballester L. Direct Observation of Two-Step, Stratified Crystallization and Morphology in Conjugated Polymer Thin Films. Macromolecules 2023. [DOI: 10.1021/acs.macromol.2c02439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Affiliation(s)
- Jesse Kuebler
- Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska at Lincoln, Lincoln, Nebraska 68588, United States
| | - Tucker Loosbrock
- Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska at Lincoln, Lincoln, Nebraska 68588, United States
| | - Joseph Strzalka
- X-Ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Lucia Fernandez-Ballester
- Department of Mechanical and Materials Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska at Lincoln, Lincoln, Nebraska 68588, United States
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7
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Pang S, Chen Z, Li J, Chen Y, Liu Z, Wu H, Duan C, Huang F, Cao Y. High-efficiency organic solar cells processed from a real green solvent. Mater Horiz 2023; 10:473-482. [PMID: 36468609 DOI: 10.1039/d2mh01314b] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The fabrication of organic solar cells (OSCs) depends heavily on the use of highly toxic chlorinated solvents, which are incompatible with industrial manufacturing. The reported alternative solvents such as non-halogenated aromatic hydrocarbons and cyclic ethers are also not really "green" according to the "Globally Harmonized System of Classification and Labelling of Chemicals" of the United Nations. Therefore, processing from real green solvents such as water, alcohols, or anisole will constitute a big breakthrough for OSCs. However, it is fundamentally challenging to obtain high-performance photovoltaic materials processable from these solvents. Herein, we propose the incorporation of a B-N covalent bond, which has a dipole moment of 1.84 Debye, into the conjugated backbone of polymer donors to fabricate high-efficiency OSCs from anisole, a real green and eco-compatible solvent recommended by the United Nations. Based on a newly developed B-N-based polymer, the OSCs with a record-high efficiency of 15.65% in the 0.04 cm2 device and 14.01% in the 1.10 cm2 device have thus been realized via real green processing.
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Affiliation(s)
- Shuting Pang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
| | - Zhili Chen
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
- Institute of Materials for Optoelectronics and New Energy, School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430205, P. R. China
| | - Junyu Li
- Molecular Materials and Nanosystems & Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - Yuting Chen
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
| | - Zhitian Liu
- Institute of Materials for Optoelectronics and New Energy, School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430205, P. R. China
| | - Hongbin Wu
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
| | - Chunhui Duan
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
- Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou 510640, P. R. China
| | - Fei Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
- Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou 510640, P. R. China
| | - Yong Cao
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
- Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou 510640, P. R. China
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8
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Xian K, Zhang S, Xu Y, Liu J, Zhou K, Peng Z, Li M, Zhao W, Chen Y, Fei Z, Hou J, Geng Y, Ye L. Refining acceptor aggregation in nonfullerene organic solar cells to achieve high efficiency and superior thermal stability. Sci China Chem 2022. [DOI: 10.1007/s11426-022-1394-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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9
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Eskandari H, Paul DK, Young AP, Karan K. Humidity-Dependent Hydration and Proton Conductivity of PFSA Ionomer Thin Films at Fuel-Cell-Relevant Temperatures: Effect of Ionomer Equivalent Weight and Side-Chain Characteristics. ACS Appl Mater Interfaces 2022; 14:50762-50772. [PMID: 36342365 DOI: 10.1021/acsami.2c12667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Studies on the hydration properties, proton conductivity, and water content of perfluorinated ionomer thin films at temperatures relevant to fuel cell operation temperatures (around 80 °C) and the effect of ionomer chemistry are scarce. In this work, we report the water content and proton conductivity properties of thin-film ionomers (30 nm) at 80 °C over a wide range of relative humidity (0-90%) for seven different ionomers differing in the side-chain structure, including the number of protogenic groups, with the equivalent weight ranging from 620 to 1100 g/mol of sulfonic acid. The results show that the acid content or equivalent weight of the ionomer is the strongest determinant of both the swelling and the proton conductivity of ionomer films at a given relative humidity. The molar water content (λ) of ionomer films normalized to the molar protogenic group is observed to be equivalent-weight-dependent, implying that the affinity for water is acid-content-dependent. At high relative humidity conditions (>70%) pertinent to fuel cell operations, the proton conductivity of low-equivalent-weight ionomers was higher than that of higher-equivalent-weight ionomers. However, upon correlating the proton conductivity with molar water content (λ), the differences reduce dramatically, highlighting that water content is the controlling factor for proton conduction. Significantly higher values of both water content and proton conductivity are observed at 80 °C compared to those at 30 °C, implying that room temperature data are not reliable for estimating ionomer properties in the fuel cell catalyst layer.
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Affiliation(s)
- Hamideh Eskandari
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AlbertaT2N 1N4, Canada
| | - Devproshad K Paul
- Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, British ColumbiaV5J 5J8, Canada
| | - Alan P Young
- Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, British ColumbiaV5J 5J8, Canada
| | - Kunal Karan
- Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AlbertaT2N 1N4, Canada
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Saito M, Ito K, Yokoyama H. Film thickness and strain rate dependences of the mechanical properties of polystyrene-b-polyisoprene-b-polystyrene block copolymer ultrathin films forming a spherical domain. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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11
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Lucero AM, Orozco M, Navarro N, Collins V, Szekely G. Sensitivity of Nafion Films to Organic Substances, Especially Ketones. Advances in Polymer Technology 2022; 2022:1-8. [DOI: 10.1155/2022/1025653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This work shows the possibility to employ sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, commercially known as Nafion, as a sensible layer on sensors to detect organic solvents such as ketones. The detection and evaluation of ketone corpuses is very important for multiple applications on medicine, specially to detect and evaluate diabetes mellitus from the breath of patients. Nafion is a very stable copolymer, easily available and relatively inexpensive. This allows us to envision the possibility of having cheap and reliable sensors to detect vapors of these substances based on this copolymer. The main result of the present work is that Nafion can protonate gaseous ions from organic solvents, such as acetone and similar substances, which modify its electrical properties, presenting a differentiated behavior according to the chemical nature of these substances, which could lead to their identification, designing an electrical nose, because each behavior is a fingerprint of the substance to detect. Then, this material can be used in the design of electrical sensors, which can be inexpensive, reliable, and chemically stable, representing an excellent alternative to ceramic sensors.
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12
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Di Sacco F, de Jong L, Pelras T, Portale G. Confined crystallization and polymorphism in iPP thin films. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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13
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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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14
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Wang G, Najafi F, Ho K, Hamidinejad M, Cui T, Walker GC, Singh CV, Filleter T. Mechanical Size Effect of Freestanding Nanoconfined Polymer Films. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02270] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guorui Wang
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
| | - Farzin Najafi
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
| | - Kevin Ho
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Mahdi Hamidinejad
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
| | - Teng Cui
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
| | - Gilbert C. Walker
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Chandra Veer Singh
- Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada
| | - Tobin Filleter
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
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15
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Reshetenko TV, Kulikovsky A. Impedance Spectroscopy Measurements of Ionomer Film Oxygen Transport Resistivity in Operating Low-Pt PEM Fuel Cell. Membranes (Basel) 2021; 11:985. [PMID: 34940486 PMCID: PMC8703679 DOI: 10.3390/membranes11120985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/10/2021] [Accepted: 12/12/2021] [Indexed: 11/16/2022]
Abstract
The work presents a model for local impedance of low-Pt proton exchange membrane fuel cells (PEMFCs), including cathode pore size distribution and O2 transport along pores and through a thin ionomer film covering Pt/C agglomerates. The model was applied to fit the local impedance spectra of low-Pt fuel cells operated at current densities from 100 to 800 mA cm-2 and recorded by a segmented cell system. Assuming an ionomer film thickness of 10 nm, the fitting returned the product of the dimensionless Henry's constant of oxygen dissolution in ionomer KH by the oxygen diffusivity DN in the ionomer (KHDN). This parameter allowed us to determine the fundamental O2 transport resistivity RN through the ionomer film in the working electrode under conditions relevant to the realistic operation of PEMFCs. The results show that variation of the operating current density does not affect RN, which remains nearly constant at ≃0.4 s cm-1.
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Affiliation(s)
| | - Andrei Kulikovsky
- Theory and Computation of Energy Materials (IEK-13), Institute of Energy and Climate Research Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany;
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16
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Ciftcioglu GA, Frank CW. Influence of Mixed Imide Composition and Thermal Annealing on Ionic Liquid Uptake and Conductivity of Polyimide-Poly(ethylene glycol) Segmented Block Copolymer Membranes. Molecules 2021; 26:7450. [PMID: 34946531 PMCID: PMC8705581 DOI: 10.3390/molecules26247450] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 10/29/2021] [Accepted: 11/01/2021] [Indexed: 11/29/2022] Open
Abstract
Understanding the impact of different bridging groups in the two-step polymerization of poly(ethylene glycol) (PEG)-incorporated polyimide (PI) materials is significant. It is known that the proton exchange membranes (PEMs) used in industry today can experience performance degradation under rising temperature conditions. Many efforts have been devoted to overcoming this problem by improving the physical and mechanical properties that extend the hygrothermal life of a PEM. This work examines the effect of oxygenated and fluorinated bridging anhydrides in the production of PI-PEG PEMs. It is shown that the dianhydride identity and the amount incorporated in the synthesis influences the properties of the segmented block copolymer (SBC) membranes, such as increased ionic liquid uptake (ILU), enhanced conductivity and higher Young's modulus favoring stiffness comparable to Nafion 115, an industrial standard. Investigations on the ionic conductivity of PI-PEG membranes were carried out to determine how thermal annealing would affect the material's performance as an ion-exchange membrane. By applying a thermal annealing process at 60 °C for one hour, the conductivities of synthesized segmented block copolymer membranes values were increased. The effect of thermal annealing on the mechanical properties was also shown for the undoped SBC via measuring the change in the Young's modulus. These higher ILU abilities and mechanical behavior changes are thought to arise from the interaction between PEG molecules and ethylammonium nitrate (EAN) ionic liquid (IL). In addition, higher interconnected routes provide a better ion-transfer environment within the membrane. It was found that the conductivity was increased by a factor of ten for undoped and a factor of two to seven for IL-doped membranes after thermal annealing.
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Affiliation(s)
- Gokcen A. Ciftcioglu
- Department of Chemical Engineering, Marmara University, Istanbul 34722, Turkey
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA;
| | - Curtis W. Frank
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA;
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17
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Yang HR, Chen YY, Sun HS, Tung SH, Huang SL, Huang PC, Lee JJ, Lai YY. Strengthening the Intrachain Interconnection of Polymers by the Naphthalene Diimide–Pyrene Complementary Interactions. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hau-Ren Yang
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Yen-Yu Chen
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Han-Sheng Sun
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Shih-Huang Tung
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Shou-Ling Huang
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Po-Chia Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Jey-Jau Lee
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yu-Ying Lai
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
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18
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Zelovich T, Tuckerman ME. OH - and H 3O + Diffusion in Model AEMs and PEMs at Low Hydration: Insights from Ab Initio Molecular Dynamics. Membranes (Basel) 2021; 11:355. [PMID: 34066142 PMCID: PMC8151131 DOI: 10.3390/membranes11050355] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/25/2021] [Accepted: 05/06/2021] [Indexed: 11/27/2022]
Abstract
Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing challenge. In this work, we aim to identify the fundamental atomistic steps governing hydroxide and hydronium transport phenomena. The motivation of this work lies in the fact that elucidating the key design differences between the hydroxide and hydronium diffusion mechanisms will play an important role in the discovery and determination of key design principles for the synthesis of new membrane materials with high ion conductivity for use in emerging fuel cell technologies. To this end, ab initio molecular dynamics simulations are presented to explore hydroxide and hydronium ion solvation complexes and diffusion mechanisms in the model AEM and PEM systems at low hydration in confined environments. We find that hydroxide diffusion in AEMs is mostly vehicular, while hydronium diffusion in model PEMs is structural. Furthermore, we find that the region between each pair of cations in AEMs creates a bottleneck for hydroxide diffusion, leading to a suppression of diffusivity, while the anions in PEMs become active participants in the hydronium diffusion, suggesting that the presence of the anions in model PEMs could potentially promote hydronium diffusion.
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Affiliation(s)
- Tamar Zelovich
- Department of Chemistry, New York University (NYU), New York 10003, NY, USA
| | - Mark E. Tuckerman
- Department of Chemistry, New York University (NYU), New York 10003, NY, USA
- Courant Institute of Mathematical Sciences, New York University (NYU), New York, NY 10012, USA
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, 3663 Zhongshan Rd. North, Shanghai 200062, China
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19
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Wang W, Qu Z, Wang X, Zhang J. A Molecular Model of PEMFC Catalyst Layer: Simulation on Reactant Transport and Thermal Conduction. Membranes (Basel) 2021; 11:membranes11020148. [PMID: 33672648 PMCID: PMC7924188 DOI: 10.3390/membranes11020148] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 02/18/2021] [Accepted: 02/18/2021] [Indexed: 11/16/2022]
Abstract
Minimizing platinum (Pt) loading while reserving high reaction efficiency in the catalyst layer (CL) has been confirmed as one of the key issues in improving the performance and application of proton exchange membrane fuel cells (PEMFCs). To enhance the reaction efficiency of Pt catalyst in CL, the interfacial interactions in the three-phase interface, i.e., carbon, Pt, and ionomer should be first clarified. In this study, a molecular model containing carbon, Pt, and ionomer compositions is built and the radial distribution functions (RDFs), diffusion coefficient, water cluster morphology, and thermal conductivity are investigated after the equilibrium molecular dynamics (MD) and nonequilibrium MD simulations. The results indicate that increasing water content improves water aggregation and cluster interconnection, both of which benefit the transport of oxygen and proton in the CL. The growing amount of ionomer promotes proton transport but generates additional resistance to oxygen. Both the increase of water and ionomer improve the thermal conductivity of the C. The above-mentioned findings are expected to help design catalyst layers with optimized Pt content and enhanced reaction efficiency, and further improve the performance of PEMFCs.
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20
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Katzenberg A, Mukherjee D, Dudenas PJ, Okamoto Y, Kusoglu A, Modestino MA. Dynamic Emergence of Nanostructure and Transport Properties in Perfluorinated Sulfonic Acid Ionomers. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01213] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Adlai Katzenberg
- Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Debdyuti Mukherjee
- Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
| | - Peter J. Dudenas
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Yoshiyuki Okamoto
- Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
| | - Ahmet Kusoglu
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Miguel A. Modestino
- Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
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21
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Abstract
In functionalized nanoconfined environments of the type employed in the study of anion exchange membranes (AEMs), a unique set of water layers forms as a result of the presence of cations and the proximity of the waters to the edges of the confining volume. In this work, we employ fully atomistic ab initio molecular dynamics in order to provide a clear picture of the solvation patterns and diffusion mechanisms of the hydroxide ion within each water layer. We find that each water layer supports a particular dominant coordination pattern for the hydroxide ion and that these solvation complexes differ among the layers. As these solvation structures affect the rate of hydroxide diffusion, it is suggested that different water layers can either promote or suppress diffusion. We believe the results presented in this work elucidate water layer features that influence hydroxide transport and can provide a guide for engineering AEMs with high hydroxide conductivity.
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Affiliation(s)
- Tamar Zelovich
- Department of Chemistry, New York University (NYU), New York, New York 10003, United States
| | - Mark E Tuckerman
- Department of Chemistry, New York University (NYU), New York, New York 10003, United States
- Courant Institute of Mathematical Sciences, New York University (NYU), New York, New York 10003, United States
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, 3663 Zhongshan Rd. North, Shanghai 200062, China
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22
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Affiliation(s)
- Yawei Li
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Saad Intikhab
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Arnav Malkani
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Bingjun Xu
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Joshua Snyder
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
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23
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24
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Shrivastava UN, Suetsugu K, Nagano S, Fritzsche H, Nagao Y, Karan K. Cross-correlated humidity-dependent structural evolution of Nafion thin films confined on a platinum substrate. Soft Matter 2020; 16:1190-1200. [PMID: 31898714 DOI: 10.1039/c9sm01731c] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanometer thin films of Nafion ionomer interfaced with platinum form the functional electrodes in many electrochemical devices including fuel cells and electrolyzers. To impart facile proton conduction in a Nafion ionomer, sufficient hydration of the Nafion ionomer is necessary to create a percolating network of water-filled nanometer-sized hydrophilic domains that manifest as macroscopic swelling. This hydration behavior of the ionomer thin films is poorly understood especially for films confined on electrochemically relevant Pt substrates. In this work, we present the evolution of hydration-dependent microscopic hydrophilic domains and macroscopic expansion of a 55 nm thin Nafion film on a Pt substrate. The cross-correlation among the film macro-expansion from ellipsometry, the micro-expansion from GISAXS, and the water distribution from neutron reflectometry (NR) explains the observed non-affine behavior of the film which can be attributed to the randomly and spatially non-uniform distribution of water domains. A correlation between the macroscopic factor (ε/τ) for protonic conductivity, and the domain size and swelling is presented for the first time. In addition, interfacial water between Pt and the ionomer interface is estimated at 75% and 84% RH, and an increase in domain size with RH is discussed to explain the increased activity and oxygen diffusivity with RH.
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Affiliation(s)
- Udit N Shrivastava
- Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB, Canada.
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25
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Zhang Z, Ding J, Ocko BM, Fluerasu A, Wiegart L, Zhang Y, Kobrak M, Tian Y, Zhang H, Lhermitte J, Choi CH, Fisher FT, Yager KG, Black CT. Nanoscale viscosity of confined polyethylene oxide. Phys Rev E 2020; 100:062503. [PMID: 31962430 DOI: 10.1103/physreve.100.062503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Indexed: 11/07/2022]
Abstract
Complex fluids near interfaces or confined within nanoscale volumes can exhibit substantial shifts in physical properties compared to bulk, including glass transition temperature, phase separation, and crystallization. Because studies of these effects typically use thin film samples with one dimension of confinement, it is generally unclear how more extreme spatial confinement may influence these properties. In this work, we used x-ray photon correlation spectroscopy and gold nanoprobes to characterize polyethylene oxide confined by nanostructured gratings (<100nm width) and measured the viscosity in this nanoconfinement regime to be ∼500 times the bulk viscosity. This enhanced viscosity occurs even when the scale of confinement is several times the polymer's radius of gyration, consistent with previous reports of polymer viscosity near flat interfaces.
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Affiliation(s)
- Zheng Zhang
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
| | - Junjun Ding
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
| | - Benjamin M Ocko
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, USA
| | - Andrei Fluerasu
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, USA
| | - Lutz Wiegart
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, USA
| | - Yugang Zhang
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York, USA
| | - Mark Kobrak
- Brooklyn College and the Graduate Center of the City University of New York, Brooklyn, New York, USA
| | - Ye Tian
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
| | - Honghu Zhang
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
| | - Julien Lhermitte
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
| | - Chang-Hwan Choi
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
| | - Frank T Fisher
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
| | - Kevin G Yager
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
| | - Charles T Black
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, USA
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26
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Van Cleve T, Khandavalli S, Chowdhury A, Medina S, Pylypenko S, Wang M, More KL, Kariuki N, Myers DJ, Weber AZ, Mauger SA, Ulsh M, Neyerlin KC. Dictating Pt-Based Electrocatalyst Performance in Polymer Electrolyte Fuel Cells, from Formulation to Application. ACS Appl Mater Interfaces 2019; 11:46953-46964. [PMID: 31742376 DOI: 10.1021/acsami.9b17614] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In situ electrochemical diagnostics designed to probe ionomer interactions with platinum and carbon were applied to relate ionomer coverage and conformation, gleaned from anion adsorption data, with O2 transport resistance for low-loaded (0.05 mgPt cm-2) platinum-supported Vulcan carbon (Pt/Vu)-based electrodes in a polymer electrolyte fuel cell. Coupling the in situ diagnostic data with ex situ characterization of catalyst inks and electrode structures, the effect of ink composition is explained by both ink-level interactions that dictate the electrode microstructure during fabrication and the resulting local ionomer distribution near catalyst sites. Electrochemical techniques (CO displacement and ac impedance) show that catalyst inks with higher water content increase ionomer (sulfonate) interactions with Pt sites without significantly affecting ionomer coverage on the carbon support. Surprisingly, the higher anion adsorption is shown to have a minor impact on specific activity, while exhibiting a complex relationship with oxygen transport. Ex situ characterization of ionomer suspensions and catalyst/ionomer inks indicates that the lower ionomer coverage can be correlated with the formation of large ionomer aggregates and weaker ionomer/catalyst interactions in low-water content inks. These larger ionomer aggregates resulted in increased local oxygen transport resistance, namely, through the ionomer film, and reduced performance at high current density. In the water-rich inks, the ionomer aggregate size decreases, while stronger ionomer/Pt interactions are observed. The reduced ionomer aggregation improves transport resistance through the ionomer film, while the increased adsorption leads to the emergence of resistance at the ionomer/Pt interface. Overall, the high current density performance is shown to be a nonmonotonic function of ink water content, scaling with the local gas (H2, O2) transport resistance resulting from pore, thin film, and interfacial phenomena.
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Affiliation(s)
- Tim Van Cleve
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Sunilkumar Khandavalli
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Anamika Chowdhury
- Energy Conversion Group, Energy Technologies Area , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Chemical and Biomolecular Engineering , University of California , Berkeley , California 94720 , United States
| | - Samantha Medina
- Colorado School of Mines , Golden , Colorado 80401 , United States
| | - Svitlana Pylypenko
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
- Colorado School of Mines , Golden , Colorado 80401 , United States
| | - Min Wang
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Karren L More
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37830 , United States
| | - Nancy Kariuki
- Argonne National Laboratory , Lemont , Illinois 60439 , United States
| | - Deborah J Myers
- Argonne National Laboratory , Lemont , Illinois 60439 , United States
| | - Adam Z Weber
- Energy Conversion Group, Energy Technologies Area , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Scott A Mauger
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Michael Ulsh
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - K C Neyerlin
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
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27
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Abstract
Ion-containing perfluorinated polymers possess unique viscoelastic properties, excellent proton conductivity, and nanophase-segregated structure all arising from the clustering of hydrophilic sulfonic acid groups within a matrix of hydrophobic fluorocarbons. When these ionomers are confined to nanothin films, a broad swathe of structural organization imparting a rich variety of surface, interfacial, and bulk characteristics can be expected. However, our understanding of perfluorinated ionomer thin film behavior is still in a rudimentary stage, and much of the research focus to date has been on its hydration-related structure and properties pertinent to electrochemical applications. Thus, many hidden gems-their interesting surface and interfacial properties-have been overlooked. In this Invited Feature Article, which is a summary of the key contributions by the author's group, including several collaborative publications on ionomer thin films, we unravel many of these facets. In addition, the article attempts to integrate knowledge acquired from a variety of investigations of different aspects of the ionomer thin films to refine and develop a consistent picture of their structure and behavior. First, we focus on the self-assembly of ionomers and show that dispersion media and hydrophobicity/hydrophilicity of the substrate can result in partial or even no coverage of substrates, shedding light on the complexity of polymer-substrate, polymer-solvent, and polymer-polymer interactions, an insight completely obscured when the spin-coating method is adopted for film creation. We demonstrate that the same ionomer can be used to create a variety of surfaces ranging from superhydrophilic to highly hydrophobic by controlling the film thickness or through the choice of substrate material. The ultrathin, hydrophilic surfaces of self-assembled Nafion ionomer films exhibit wettability switching behavior which opens the door to creating stimuli-responsive smart surfaces. The thermoresponsive behavior of the films is discussed in the context of surface (wettability) and bulk (thermal expansion) characteristics as well as a newly discovered vibrational mode. The substrate- and film thickness-dependent thermal expansion coefficients reinforce the importance of interfacial interactions and confinement on the structure/properties of these films. They also open up the potential of tuning ionomer bulk properties via substrate chemistry. The discovery of a vibrational mode that becomes thermally activated at high temperature has provided new insights into the origins of the molecular motions responsible for the α-relaxation of the Nafion ionomer as well as the underlying reason for wettability switching. Our recent neutron reflectometry study of different ionomers varying in side-chain composition/length on a platinum substrate shows that the interfacial hydration level is correlated to the side-chain length, which opens up the possibility of the controlling the interfacial electrochemistry. Finally, a systematic analysis of factors affecting proton conduction is presented to elucidate the yet-unresolved origins of the suppressed conduction of nanothin ionomer films compared to that of the bulk membrane. By revealing these interesting yet poorly understood facets of ionomer thin films, the article aims to stimulate further scientific pursuit on this topic.
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Affiliation(s)
- Kunal Karan
- Department of Chemical & Petroleum Engineering , The University of Calgary , Calgary , Alberta T2N1N4 , Canada
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28
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Affiliation(s)
- Peter J. Dudenas
- Chemical and Biomolecular Engineering, University of California Berkeley, Berkeley, California 94720, United States
- Energy Conversion Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ahmet Kusoglu
- Energy Conversion Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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29
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Zhong X, Chen H, Wang M, Gan S, He Q, Chen W, He F. Synergistic Effect of Chlorination and Selenophene: Achieving Elevated Solar Conversion in Highly Aggregated Systems. Macromolecules 2019. [DOI: 10.1021/acs.macromol.8b02445] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Xiaowei Zhong
- Department of Chemistry and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Hui Chen
- Department of Chemistry and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Meijing Wang
- Department of Chemistry and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Shenglong Gan
- Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States
| | - Qiming He
- Institute for Molecular Engineering, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Wei Chen
- Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States
- Institute for Molecular Engineering, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Feng He
- Department of Chemistry and Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen 518055, P. R. China
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30
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Feng C, Li Y, Qu K, Zhang Z, He P. Mechanical behavior of a hydrated perfluorosulfonic acid membrane at meso and nano scales. RSC Adv 2019; 9:9594-9603. [PMID: 35520728 PMCID: PMC9062152 DOI: 10.1039/c9ra00745h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 03/15/2019] [Indexed: 01/13/2023] Open
Abstract
Perfluorosulfonic acid (PFSA) is widely used as the membrane material for proton-exchange membrane fuel cells, and its mechanical properties directly affect the stability and the life of the internal structure of the proton exchange membrane.
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Affiliation(s)
- Cong Feng
- College of Materials Science and Engineering
- Shanghai Key Lab of Metal Functional Materials
- Tongji University
- Shanghai 201804
- China
| | - Yan Li
- College of Materials Science and Engineering
- Shanghai Key Lab of Metal Functional Materials
- Tongji University
- Shanghai 201804
- China
| | - Kunnan Qu
- College of Materials Science and Engineering
- Shanghai Key Lab of Metal Functional Materials
- Tongji University
- Shanghai 201804
- China
| | - Zhiming Zhang
- School of Automotive Studies
- Tongji University
- Shanghai 201804
- China
| | - Pengfei He
- School of Aerospace Engineering and Applied Mechanics
- Tongji University
- Shanghai 200092
- China
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31
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Abstract
Thin perfluorosulfonated ion-conducting polymers (PFSI ionomers) in energy-conversion devices have limitations in functionality attributed to confinement-driven and surface-dependent interactions. This study highlights the effects of confinement and interface-dependent interactions of PFSI thin-films by exploring thin-film thermal transition temperature (TT). Change in TT in polymers is an indicator for chain relaxation and mobility with implications on properties like gas transport. This work demonstrates an increase in TT with decreasing PFSI film thickness in acid (H+) form (from 70 to 130 °C for 400 to 10 nm, respectively). In metal cation (M+) exchanged PFSI, TT remained constant with thickness. Results point to an interplay between increased chain mobility at the free surface and hindered motion near the rigid substrate interface, which is amplified upon further confinement. This balance is additionally impacted by ionomer intermolecular forces, as strong electrostatic networks within the PFSI-M+ matrix raises TT above the mainly hydrogen-bonded PFSI-H+ ionomer.
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Affiliation(s)
- Meron Tesfaye
- Chemical and Biomolecular Engineering, University of California−Berkeley, Berkeley, California 94720, United States
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Douglas I. Kushner
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Bryan D. McCloskey
- Chemical and Biomolecular Engineering, University of California−Berkeley, Berkeley, California 94720, United States
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Adam Z. Weber
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ahmet Kusoglu
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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32
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Affiliation(s)
| | | | - Joseph D. Paulsen
- Department of Physics and Soft and Living Matter Program, Syracuse University, Syracuse, New York 13244, United States
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Korzeniewski C, Liang Y, Zhang P, Sharif I, Kitt JP, Harris JM, Hamrock SJ, Creager SE, DesMarteau DD. Vibrational Spectroscopy for the Determination of Ionizable Group Content in Ionomer Materials. Appl Spectrosc 2018; 72:141-150. [PMID: 28782369 DOI: 10.1177/0003702817728243] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An approach based on vibrational spectral measurements is described for determining the ionizable group content of ion conducting polymer membrane materials. Aimed at supporting the assessment of membrane stability and wear characteristics, performance is evaluated for attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, confocal Raman microscopy, and ATR FT-IR microscopy using perfluorinated ionomer membrane standards. One set of ionomer standards contained a sulfonic acid ionizable group and the other a sulfonyl imide group. The average number of backbone tetrafluoroethylene (TFE) units separating the ionizable-group containing side chains was in the range of 7.2-2.1 (sulfonic acid set) and 10.5-4.6 (sulfonyl imide set). A poly(tetrafluoroethylene) (PTFE) sample was included as a blank, representing the limit of zero ionizable group (and maximum TFE) content. Calibration relationships were derived from area-normalized vibrational spectra. For all three methods, calibration models applied to independent spectral measurements of samples predicted the ratio of backbone TFE groups to ionizable groups in the repeat unit ( m) with a standard error of ≤ ±0.3. The confocal Raman and ATR FT-IR microscopy techniques achieved ideal blank responses and the lowest prediction errors, down to m ± 0.1 at the 90% confidence level. With its relative simplicity, low sample size requirements, and potential for quantitative micron-scale spatial mapping of the ionizable group content within a membrane, the approach has application to advancing materials development, including exploratory synthesis, durability and wear assessment, and in situ studies of membrane process.
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Affiliation(s)
- Carol Korzeniewski
- 1 6177 Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Ying Liang
- 1 6177 Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Pei Zhang
- 1 6177 Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, USA
| | - Iqbal Sharif
- 2 Department of Chemistry, Clemson University, Hunter Laboratories, Clemson, SC, USA
| | - Jay P Kitt
- 3 Department of Chemistry, University of Utah, Salt Lake City, UT, USA
| | - Joel M Harris
- 3 Department of Chemistry, University of Utah, Salt Lake City, UT, USA
| | - Steven J Hamrock
- 4 3M Energy Components Group, 3M Center, St Paul, MN, USA (retired)
| | - Stephen E Creager
- 2 Department of Chemistry, Clemson University, Hunter Laboratories, Clemson, SC, USA
| | - Darryl D DesMarteau
- 2 Department of Chemistry, Clemson University, Hunter Laboratories, Clemson, SC, USA
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Huq AF, Zvonkina I, Al-enizi AM, Karim A. Controlling nanoparticle crystallinity and surface enrichment in polymer (P3HT)/Nanoparticle(PCBM) blend films with tunable soft confinement. POLYMER 2018; 136:37-46. [DOI: 10.1016/j.polymer.2017.12.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Affiliation(s)
- Heedong Yoon
- Department of Chemical Engineering,
Whitacre College of Engineering, Texas Tech University, Lubbock, Texas 79409-4121, United States
| | - Gregory B. McKenna
- Department of Chemical Engineering,
Whitacre College of Engineering, Texas Tech University, Lubbock, Texas 79409-4121, United States
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Abstract
Highly proton conductive polymers have long attracted the attention of researchers for use in energy conversion, sensors, catalysts, and other applications. From the viewpoint of the scientific history of the creation of highly proton conductive polymers, one fundamental approach is based on the strategy of phase-segregated structures with strong acid groups. This Feature Article presents a new approach to enhancing the proton conductivity of the polymer thin films using an interface that can modify the degrees of freedom for a polymer structure through interaction between the substrate surface and polymers. I introduce suppressed proton conductivity into Nafion thin films and then specifically examine the enhancement in proton conductivity by the molecular orientation of the polymers. As the last topic, a highly proton conductive organized polyimide thin film is demonstrated using the lyotropic liquid-crystal property. Both molecular ordering and the in-plane oriented structure can enhance proton conductivity. Moreover, the optical domain and degree of molecular ordering derived from the molecular weight can contribute strongly to the proton transport property.
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Affiliation(s)
- Yuki Nagao
- School of Materials Science, Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan
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Chae S, Yi A, Park C, Chang WS, Lee HH, Choi J, Kim HJ. Using Femtosecond Laser Irradiation to Enhance the Vertical Electrical Properties and Tailor the Morphology of a Conducting Polymer Blend Film. ACS Appl Mater Interfaces 2017; 9:24422-24427. [PMID: 28691483 DOI: 10.1021/acsami.7b05937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report femtosecond infrared laser-induced selective tailoring of carrier transport as well as surface morphology on a conducting polymer blend thin film. Maximal 2.4 times enhancement on vertical current transport in poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester, was achieved by this irradiation. The laser irradiation induced a photo expansion without deteriorating its molecular structure and the film morphology could be customized in the micron scale by adjusting the laser writing parameters. In the photoexpanded region, the face-on populations were about 2.2 times larger in comparison with the pristine region, which was a major contributor to the enhanced carrier transport.
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Affiliation(s)
- Sangmin Chae
- Department of Organic Material Science and Engineering, Pusan National University , Busan 46241, South Korea
- Korea Institute of Machinery and Materials (KIMM) , 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, South Korea
| | - Ahra Yi
- Department of Organic Material Science and Engineering, Pusan National University , Busan 46241, South Korea
| | - Cheolmin Park
- Korea Institute of Machinery and Materials (KIMM) , 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, South Korea
| | - Won Seok Chang
- Korea Institute of Machinery and Materials (KIMM) , 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, South Korea
| | - Hyun Hwi Lee
- Pohang Accelerator Laboratory, POSTECH , Pohang 37673, South Korea
| | - Jiyeon Choi
- Korea Institute of Machinery and Materials (KIMM) , 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, South Korea
| | - Hyo Jung Kim
- Department of Organic Material Science and Engineering, Pusan National University , Busan 46241, South Korea
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Abstract
In this comprehensive review, recent progress and developments on perfluorinated sulfonic-acid (PFSA) membranes have been summarized on many key topics. Although quite well investigated for decades, PFSA ionomers' complex behavior, along with their key role in many emerging technologies, have presented significant scientific challenges but also helped create a unique cross-disciplinary research field to overcome such challenges. Research and progress on PFSAs, especially when considered with their applications, are at the forefront of bridging electrochemistry and polymer (physics), which have also opened up development of state-of-the-art in situ characterization techniques as well as multiphysics computation models. Topics reviewed stem from correlating the various physical (e.g., mechanical) and transport properties with morphology and structure across time and length scales. In addition, topics of recent interest such as structure/transport correlations and modeling, composite PFSA membranes, degradation phenomena, and PFSA thin films are presented. Throughout, the impact of PFSA chemistry and side-chain is also discussed to present a broader perspective.
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Affiliation(s)
- Ahmet Kusoglu
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
| | - Adam Z Weber
- Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS70-108B, Berkeley, California 94720, United States
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Frieberg BR, Page KA, Graybill JR, Walker ML, Stafford CM, Stafford GR, Soles CL. Mechanical Response of Thermally Annealed Nafion Thin Films. ACS Appl Mater Interfaces 2016; 8:33240-33249. [PMID: 27934151 DOI: 10.1021/acsami.6b12423] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Perfluorinated ionomers, in particular, Nafion, are a critical component in hydrogen fuel cells as the ion conducting binder within the catalyst layer in which it can be confined to thicknesses on the order of 10 nm or less. It is well reported that many physical properties, such as the Young's modulus, are thickness dependent when the film thickness is less than 100 nm. Here we utilize a cantilever bending methodology to quantify the swelling-induced stresses and relevant mechanical properties of Nafion films as a function of film thickness exposed to cyclic humidity. We observe a factor of 5 increase in the Young's modulus in films thinner than 50 nm and show how this increased stiffness translates to reduced swelling or hydration. The swelling stress was found to increase by a factor of 2 for films approximately 40 nm thick. We demonstrate that thermal annealing enhances the modulus at all film thicknesses and correlate these mechanical changes to chemical changes in the infrared absorption spectra.
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Affiliation(s)
- Bradley R Frieberg
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Kirt A Page
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Joshua R Graybill
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Marlon L Walker
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Christopher M Stafford
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Gery R Stafford
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Christopher L Soles
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
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Kushner DI, Zhu L, Kusoglu A, Hickner MA. Side Chain Influence on the Mechanical Properties and Water Uptake of Confined Comb-Shaped Cationic Polymer Thin Films. MACROMOL CHEM PHYS 2016; 217:2442-51. [DOI: 10.1002/macp.201600254] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Singhal N, Mishra A, Datta A. Excited-State Proton Transfer and Conformational Relaxation of 2-(4′-Pyridyl)benzimidazole in Nafion Films. Chemphyschem 2016; 17:3004-9. [DOI: 10.1002/cphc.201600546] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Indexed: 11/07/2022]
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Affiliation(s)
- Nancy Singhal
- Department of Chemistry; Indian Institute of Technology Bombay; Powai Mumbai 400 076 India
| | - Anindya Datta
- Department of Chemistry; Indian Institute of Technology Bombay; Powai Mumbai 400 076 India
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Abstract
Substantial progress has been made in reducing proton-exchange membrane fuel cell (PEMFC) cathode platinum loadings from 0.4-0.8 mgPt/cm(2) to about 0.1 mgPt/cm(2). However, at this level of cathode Pt loading, large performance loss is observed at high-current density (>1 A/cm(2)), preventing a reduction in the overall stack cost. This next developmental step is being limited by the presence of a resistance term exhibited at these lower Pt loadings and apparently due to a phenomenon at or near the catalyst surface. This issue can be addressed through the design of catalysts with high and stable Pt dispersion as well as through development and implementation of ionomers designed to interact with Pt in a way that does not constrain oxygen reduction reaction rates. Extrapolating from progress made in past decades, we are optimistic that the concerted efforts of materials and electrode designers can resolve this issue, thus enabling a large step toward fuel cell vehicles that are affordable for the mass market.
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Affiliation(s)
- Anusorn Kongkanand
- Fuel Cell Activities, General Motors Global Product Development , Pontiac, Michigan 48340, United States
| | - Mark F Mathias
- Fuel Cell Activities, General Motors Global Product Development , Pontiac, Michigan 48340, United States
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Paul DK, Shim HKK, Giorgi JB, Karan K. Thickness dependence of thermally induced changes in surface and bulk properties of Nafion®
nanofilms. ACTA ACUST UNITED AC 2016. [DOI: 10.1002/polb.24034] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Devproshad K. Paul
- Department of Chemical and Petroleum Engineering; University of Calgary; Calgary Alberta Canada
- Department of Chemical Engineering; Queen's University; Kingston Ontario Canada
| | - Hyun Ki Key Shim
- Department of Chemical Engineering; Queen's University; Kingston Ontario Canada
| | - Javier B. Giorgi
- Centre for Catalysis Research and Innovation, University of Ottawa; Ottawa Ontario Canada
| | - Kunal Karan
- Department of Chemical and Petroleum Engineering; University of Calgary; Calgary Alberta Canada
- Department of Chemical Engineering; Queen's University; Kingston Ontario Canada
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Jinnouchi R, Kudo K, Kitano N, Morimoto Y. Molecular Dynamics Simulations on O 2 Permeation through Nafion Ionomer on Platinum Surface. Electrochim Acta 2016; 188:767-76. [DOI: 10.1016/j.electacta.2015.12.031] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Novitski D, Holdcroft S. Determination of O₂ Mass Transport at the Pt | PFSA Ionomer Interface under Reduced Relative Humidity. ACS Appl Mater Interfaces 2015; 7:27314-27323. [PMID: 26583742 DOI: 10.1021/acsami.5b08720] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Oxygen mass transport resistance through the ionomer component in the cathode catalyst layer is considered to contribute overpotential losses in polymer electrolyte membrane fuel cells. Whereas it is known that water uptake, water transport, and proton conductivity are reduced upon reducing relative humidity, the effect on oxygen mass transport remains unknown. We report a two-electrode approach to determine mass transport coefficients for the oxygen reduction reaction in air at the Pt/perfluorosulfonic acid ionomer membrane interface between 90 and 30% RH at 70 °C using a Pt microdisk in a solid state electrochemical cell. Potential-step chronoamperometry was performed at specific mass-transport limiting potentials to allow for the elucidation of the oxygen diffusion coefficient (D(bO2)) and oxygen concentration (c(bO2)). In our efforts, novel approaches in data acquisition, as well as analysis, were examined because of the dynamic nature of the membrane under lowered hydration conditions. Linear regression analysis reveals a decrease in oxygen permeability (D(bO2c(bO2)) by a factor of 1.7 and 3.4 from 90 to 30% RH for Nafion 211 membrane and membranes cast from Nafion DE2020 ionomer solutions, respectively. Additionally, nonlinear curve fitting by way of the Shoup-Szabo equation is employed to analyze the entire current transient during potential step controlled ORR. We also report on the presence of an RH dependence of our previously reported time-dependency measurements for O2 mass transport coefficients.
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Affiliation(s)
- David Novitski
- Department of Chemistry, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada
| | - Steven Holdcroft
- Department of Chemistry, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada
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