UNDERSTANDING THE EFFECTS OF COMPRESSION AND CONSTRAINTS ON WATER UPTAKE OF FUEL-CELL MEMBRANES

Accurate characterization of polymer-electrolyte fuel cells (PEFCs) requires understanding the impact of mechanical and electrochemical loads on cell components. An essential aspect of this relationship is the effect of compression on the polymer membrane?s water-uptake behavior and transport properties. However, there is limited information on the impact of physical constraints on membrane properties. In this paper, we investigate both theoretically and experimentally how the water uptake of Nafion membrane changes under external compression loads. The swelling of a compressed membrane is modeled by modifying the swelling pressure in the polymer backbone which relies on the changes in the microscopic volume of the polymer. The model successfully predicts the water content of the compressed membrane measured through in-situ swelling-compression tests and neutron imaging. The results show that external mechanical loads could reduce the water content and conductivity of the membrane, especially at lower temperatures, higher humidities, and in liquid water. The modeling framework and experimental data provide valuable insight for the swelling and conductivity of constrained and compressed membranes, which are of interest in electrochemical devices such as batteries and fuel cells.

[1]  Moon Jeong Park,et al.  Increased water retention in polymer electrolyte membranes at elevated temperatures assisted by capillary condensation. , 2007, Nano letters.

[2]  T. He,et al.  Modeling on swelling behavior of a confined polymer network , 2008 .

[3]  G. Gebel,et al.  Distribution of the « micelles » in hydrated perfluorinated ionomer membranes from SANS experiments , 1990 .

[4]  Xiaodong Sun,et al.  Water-sorption and transport properties of Nafion 117 H , 1993 .

[5]  Adam Z. Weber,et al.  Transport in Polymer-Electrolyte Membranes I. Physical Model , 2004 .

[6]  Y. Benveniste.  On the Mori-Tanaka's method in cracked bodies , 1986 .

[7]  H.-G. Haubold,et al.  Nano structure of NAFION: a SAXS study , 2001 .

[8]  Alan A. Jones,et al.  Morphology of dry and swollen perfluorosulfonate ionomer by fluorine-19 MAS, NMR and xenon-129 NMR , 2001 .

[9]  J. Jorné,et al.  Investigation of Low-Temperature Proton Transport in Nafion Using Direct Current Conductivity and Differential Scanning Calorimetry , 2006 .

[10]  Keith Promislow,et al.  The Impact of Membrane Constraint on PEM Fuel Cell Water Management , 2007 .

[11]  Michael H. Santare,et al.  Numerical Investigation of Mechanical Durability in Polymer Electrolyte Membrane Fuel Cells , 2010 .

[12]  Steven Holdcroft,et al.  Effect of water on the low temperature conductivity of polymer electrolytes. , 2006, The journal of physical chemistry. B.

[13]  S. Grot,et al.  SANS Study of the Effects of Water Vapor Sorption on the Nanoscale Structure of Perfluorinated Sulfonic Acid (NAFION) Membranes , 2006 .

[14]  J. Hinatsu,et al.  Water Uptake of Perfluorosulfonic Acid Membranes from Liquid Water and Water Vapor , 1994 .

[15]  V. Freger.  Elastic energy in microscopically phase-separated swollen polymer networks , 2002 .

[16]  F. C. Wilson,et al.  The morphology in nafion† perfluorinated membrane products, as determined by wide- and small-angle x-ray studies , 1981 .

[17]  Michael H. Santare,et al.  Constitutive response and mechanical properties of PFSA membranes in liquid water , 2010 .

[18]  Moon Jeong Park,et al.  Confinement Effects on Watery Domains in Hydrated Block Copolymer Electrolyte Membranes , 2010 .

[19]  Jenn-Jiang Hwang,et al.  Effect of clamping pressure on the performance of a PEM fuel cell , 2007 .

[20]  A. Morin,et al.  Characterization of PEMFCs gas diffusion layers properties , 2006 .

[21]  K. Mauritz,et al.  A water sorption isotherm model for ionomer membranes with cluster morphologies , 1985 .

[22]  Ravindra Datta,et al.  Sorption in Proton-Exchange Membranes An Explanation of Schroeder’s Paradox , 2003 .

[23]  S. Hanna,et al.  Hydration of Nafion® studied by AFM and X-ray scattering , 2000 .

[24]  G. Gebel,et al.  Small-Angle Scattering Study of Water-Swollen Perfluorinated Ionomer Membranes , 1997 .

[25]  Zhigang Suo,et al.  A theory of constrained swelling of a pH-sensitive hydrogel†‡ , 2010 .

[26]  M. Santare,et al.  Structure-Property Relationship in Ionomer Membranes , 2010 .

[27]  W. Marsden.  I and J , 2012 .

[28]  O. Kamishima,et al.  Investigation of proton diffusion in Nafion®117 membrane by electrical conductivity and NMR , 2009 .

[29]  T. Springer,et al.  Water Uptake by and Transport Through Nafion® 117 Membranes , 1993 .

[30]  M. Pegoraro,et al.  Perfluorosulfonated membrane (Nafion): FT-IR study of the state of water with increasing humidity , 1999 .

[31]  F. Horkay,et al.  Polymer Networks and Gels , 2007 .

[32]  M. Santare,et al.  Mechanics-based model for non-affine swelling in perfluorosulfonic acid (PFSA) membranes , 2009 .

[33]  J. Jorné,et al.  PEM Fuel Cell Operation at − 20 ° C . I. Electrode and Membrane Water (Charge) Storage , 2008 .

[34]  R. Yeo.  Dual cohesive energy densities of perfluorosulphonic acid (Nafion) membrane , 1980 .

[35]  Qiang Chen,et al.  Parallel cylindrical water nanochannels in Nafion fuel-cell membranes. , 2008, Nature materials.

[36]  E. Robens,et al.  Application of coupled thermal analysis techniques to thermodynamic studies of water interactions with a compressible ionic polymer matrix , 1984 .

[37]  Qing Wang,et al.  Dynamic Water Uptake of Flexible Ion‐Containing Polymer Networks , 2009 .

[38]  W. B. Johnson,et al.  Micromechanics Model Based on the Nanostructure of PFSA Membranes , 2008 .

[39]  David A. Dillard,et al.  Viscoelastic Stress Analysis of Constrained Proton Exchange Membranes Under Humidity Cycling , 2009 .

[40]  R. Iyer,et al.  Thermodynamics of water sorption by perfluorosulphonate (Nafion-117) and polystyrene–divinylbenzene sulphonate (Dowex 50W) ion-exchange resins at 298 ± 1 K , 1988 .

[41]  Z. Suo,et al.  Inhomogeneous swelling of a gel in equilibrium with a solvent and mechanical load , 2009 .

[42]  A. Eisenberg.  Clustering of Ions in Organic Polymers. A Theoretical Approach , 1970 .

[43]  Nikhil H. Jalani,et al.  The effect of equivalent weight, temperature, cationic forms, sorbates, and nanoinorganic additives on the sorption behavior of Nafion ® , 2005 .

[44]  K. Mauritz,et al.  Anisotropic Ionic-Conductivity in Uniaxially Oriented Perfluorosulfonate Ionomers , 1995 .

[45]  C. Lorentz,et al.  Hygrothermal aging of Nafion , 2009 .

[46]  John Newman,et al.  A theoretical study of membrane constraint in polymer-electrolyte fuel cells , 2004 .

[47]  P. Colomban,et al.  Nanostructure of Nafion® membranes at different states of hydration , 2001 .

[48]  P. Flory.  Principles of polymer chemistry , 1953 .

[49]  R. Duplessix,et al.  Small‐angle scattering studies of nafion membranes , 1981 .

[50]  R. Duplessix,et al.  Phase separation in perfluorosulfonate ionomer membranes , 1982 .

[51]  J. Newman,et al.  Equilibrium and diffusion of methanol and water in a nafion 117 membrane , 2000 .

[52]  S. Hanna,et al.  Interpretation of the Small-Angle X-ray Scattering from Swollen and Oriented Perfluorinated Ionomer Membranes , 2000 .

[53]  Yue Zou,et al.  On mechanical behavior and in-plane modeling of constrained PEM fuel cell membranes subjected to hydration and temperature cycles , 2007 .

[54]  Hubert A. Gasteiger,et al.  Handbook of fuel cells : fundamentals technology and applications , 2003 .

[55]  P. Mukherjee,et al.  Measurement of Water Content in Polymer Electrolyte Membranes Using High Resolution Neutron Imaging , 2010 .

[56]  G. Alberti,et al.  Evolution of Permanent Deformations (or Memory) in Nafion 117 Membranes with Changes in Temperature, Relative Humidity and Time, and Its Importance in the Development of Medium Temperature PEMFCs , 2009 .

[57]  John M Prausnitz,et al.  Water-Nafion equilibria. absence of Schroeder's paradox. , 2007, The journal of physical chemistry. B.

[58]  Gérard Gebel,et al.  Evidence of elongated polymeric aggregates in Nafion , 2002 .

[59]  W. B. Johnson,et al.  Mechanical response of fuel cell membranes subjected to a hygro-thermal cycle , 2006 .

[60]  J. E. Mark,et al.  Physical properties of polymers handbook , 2007 .

[61]  M. Budinski,et al.  Osmotic Pressure of Water in Nafion , 2010 .

[62]  H. Kawai,et al.  Small-angle x-ray scattering study of perfluorinated ionomer membranes. 2. Models for ionic scattering maximum , 1982 .

[63]  Nikhil H. Jalani,et al.  Thermodynamics and Proton Transport in Nafion II. Proton Diffusion Mechanisms and Conductivity , 2005 .

[64]  Michael H. Santare,et al.  Mechanical properties of a reinforced composite polymer electrolyte membrane and its simulated performance in PEM fuel cells , 2008 .

[65]  Jing Li,et al.  Linear coupling of alignment with transport in a polymer electrolyte membrane. , 2011, Nature materials.

[66]  H. Kawai,et al.  Small-angle x-ray scattering study of perfluorinated ionomer membranes. 1. Origin of two scattering maxima , 1981 .

[67]  Y. Termonia.  Nanoscale modeling of the structure of perfluorosulfonated ionomer membranes at varying degrees of swelling , 2007 .

[68]  G. Gebel,et al.  Structural evolution of water swollen perfluorosulfonated ionomers from dry membrane to solution , 2000 .

[69]  M. Yoshitake,et al.  Adsorption properties of water vapor on sulfonated perfluoropolymer membranes , 2007 .

[70]  I-Ming Hsing,et al.  Thermodynamics of water vapor uptake in perfluorosulfonic acid membranes , 1999 .

[71]  V. Freger,et al.  An experimental study of Schroeder's paradox in Nafion and Dowex polymer electrolytes , 2006 .

[72]  T. Gierke,et al.  Elastic theory for ionic clustering in perfluorinated ionomers , 1982 .

[73]  A. Weber,et al.  Transport in Polymer-Electrolyte Membranes II. Mathematical Model , 2004 .

[74]  T. Gierke,et al.  Ion transport and clustering in nafion perfluorinated membranes , 1983 .

[75]  N. Djilali,et al.  Effect of compression on liquid water transport and microstructure of PEMFC gas diffusion layers , 2007 .

[76]  C. Gittleman,et al.  Through-Plane Proton Transport Resistance of Membrane and Ohmic Resistance Distribution in Fuel Cells , 2009 .

[77]  G. Alberti,et al.  Effects of hydrothermal/thermal treatments on the water-uptake of Nafion membranes and relations with changes of conformation, counter-elastic force and tensile modulus of the matrix , 2008 .

[78]  D. A. Bograchev,et al.  Stress and plastic deformation of MEA in fuel cells: Stresses generated during cell assembly , 2008 .

[79]  Kikuko Hayamizu,et al.  Temperature dependence of ion and water transport in perfluorinated ionomer membranes for fuel cells. , 2005, The journal of physical chemistry. B.