Solid State Proton Conductors

Proton conduction can be found in many different solid materials, from organic polymers at room temperature to inorganic oxides at high temperature. Solid state proton conductors are of central interest for many technological innovations, including hydrogen and humidity sensors, membranes for water electrolyzers and, most importantly, for high-efficiency electrochemical energy conversion in fuel cells.

Focusing on fundamentals and physico-chemical properties of solid state proton conductors, topics covered include:

• Morphology and Structure of Solid Acids

• Diffusion in Solid Proton Conductors by Nuclear Magnetic Resonance Spectroscopy

• Structure and Diffusivity by Quasielastic Neutron Scattering

• Broadband Dielectric Spectroscopy

• Mechanical and Dynamic Mechanical Analysis of Proton-Conducting Polymers

• Ab initio Modeling of Transport and Structure

• Perfluorinated Sulfonic Acids

• Proton-Conducting Aromatic Polymers

• Inorganic Solid Proton Conductors

Uniquely combining both organic (polymeric) and inorganic proton conductors, Solid State Proton Conductors: Properties and Applications in Fuel Cells provides a complete treatment of research on proton-conducting materials.

Autorentext

Philippe Knauth is Professor and Director of the Laboratoire Chimie Provence, University of Provence, Marseille, France.
He has published 6 books, 2 European and 2 US patents, 200 publications, including 95 papers in international journals and 35 invited/plenary talks at international conferences.

Maria Luisa Di Vona is Assistant Professor in Chemistry at the Dipartimento di Scienze e Tecnologie Chimiche, Universita Degli Studi di RomaTor Veragata, Rome, Italy. She is also Visiting Professor at the University of Provence.
Author of 100 publications, including 67 in international journals, 2 book chapters , 1 book (Electroceramics VIII-2002).
Di Vona and Knauth were organizers of the 2009 E-MRS symposium "Materials for Polymer Electrolyte Membrane Fuel Cells".

Inhalt
Preface xi About the Editors xiii

Contributing Authors xv

**1 Introduction and Overview: Protons, the Nonconformist Ions 1
Maria Luisa Di Vona and Philippe Knauth

1.1 Brief History of the Field 2

1.2 Structure of This Book 2

References 4

**2 Morphology and Structure of Solid Acids 5
Habib Ghobarkar, Philippe Knauth and Oliver Schaf

2.1 Introduction 5

2.1.1 Preparation Technique of Solid Acids 5

2.1.2 Imaging Technique with the Scanning Electron Microscope 6

2.2 Crystal Morphology and Structure of Solid Acids 8

2.2.1 Hydrohalic Acids 8

2.2.2 Main Group Element Oxoacids 10

2.2.3 Transition Metal Oxoacids 20

2.2.4 Carboxylic Acids 22

References 24

**3 Diffusion in Solid Proton Conductors: Theoretical Aspects and Nuclear Magnetic Resonance Analysis 25
Maria Luisa Di Vona, Emanuela Sgreccia and Sebastiano Tosto

3.1 Fundamentals of Diffusion 25

3.1.1 Phenomenology of Diffusion 26

3.1.2 Solutions of the Diffusion Equation 35

3.1.3 Diffusion Coefficients and Proton Conduction 37

3.1.4 Measurement of the Diffusion Coefficient 38

3.2 Basic Principles of NMR 40

3.2.1 Description of the Main NMR Techniques Used in Measuring Diffusion Coefficients 42

3.3 Application of NMR Techniques 47

3.3.1 Polymeric Proton Conductors 47

3.3.2 Inorganic Proton Conductors 58

3.4 Liquid Water Visualization in Proton-Conducting Membranes by Nuclear Magnetic Resonance Imaging 62

3.5 Conclusions 66

References 67

**4 Structure and Diffusivity in Proton-Conducting Membranes Studied by Quasielastic Neutron Scattering 71
Rolf Hempelmann

4.1 Survey 71

4.2 Diffusion in Solids and Liquids 73

4.3 Quasielastic Neutron Scattering: A Brief Introduction 76

4.4 Proton Diffusion in Membranes 82

4.4.1 Microstructure by Means of SAXS and SANS 82

4.4.2 Proton Conductivity and Water Diffusion 89

4.4.3 QENS Studies 90

4.5 Solid State Proton Conductors 95

4.5.1 Aliovalently Doped Perovskites 96

4.5.2 Hydrogen-Bonded Systems 101

4.6 Concluding Remarks 104

References 104

**5 Broadband Dielectric Spectroscopy: A Powerful Tool for the Determination of Charge Transfer Mechanisms in Ion Conductors 109
Vito Di Noto, Guinevere A. Giffin, Keti Vezzu`, Matteo Piga and Sandra Lavina

5.1 Basic Principles 110

5.1.1 The Interaction of Matter with Electromagnetic Fields: The Maxwell Equations 110

5.1.2 Electric Response in Terms of e*m ðoÞ, s*m ðoÞ, and Z*mðoÞ 111

5.2 Phenomenological Background of Electric Properties in a Time-Dependent Field 114

5.2.1 Polarization Events 114

5.3 Theory of Dielectric Relaxation 127

5.3.1 Dielectric Relaxation Modes of Macromolecular Systems 129

5.3.2 A General Equation for the Analysis in the Frequency Domain of s(o) and e(o) 132

5.4 Analysis of Electric Spectra 132

5.5 Broadband Dielectric Spectroscopy Measurement Techniques 141

5.5.1 Measurement Systems 142

5.5.2 Contacts 158

5.5.3 Calibration 165

5.5.4 Calibration in Parallel Plate Methods 165

5.5.5 Measurement Accuracy 172

5.6 Concluding Remarks 180

References 180

**6 Mechanical and Dynamic Mechanical Analysis of Proton-Conducting Polymers 185
Jean-Franc¸ois Chailan, Mustapha Khadhraoui and Philippe Knauth

6.1 Introduction 185

6.1.1 Molecular Configurations: The Morphology and Microstructure of Polymers 185

6.1.2 Molecular Motions 187

6.1.3 Glass Transition and Other Molecular Relaxations 188

6.2 Methodology of Uniaxial Tensile Tests 191

6.2.1 Elasticity and Young's Modulus E 192 6.2.2 Elasticity and Shear Modulus G 195&lt...