High Temperature Polymer Electrolyte Membrane Fuel Cells

Preface Chapter 1 Introduction Chapter 2. Modifications of sulfonic acid-based membranes 2.1 Introduction 2.2 Composites membranes containing inorganic fillers 2.2.1 Composite PFSA membranes for direct methanol fuel cells (DMFC)s 2.2.2 Composite hydrocarbon membranes for DMFCs 2.2.3 Short-side chain PFSA membranes for DMFCs 2.4 Composite PFSA membranes for direct ethanol fuel cells 2.3 Composite and modified PFSA membranes for intermediate temperature PEM electrolysis 2.3.1 General aspect of PEM electrolysis 2.3.2 Intermediate temperature PEM electrolysis 2.3.3 Short side chain membranes for PEM water electrolysis 2.4 Short side chain PFSA membranes 2.5 Conclusions References Chapter 3 Acid-base chemistry and proton conductivity 3.1 Introduction 3.2 Thermodynamics of acid-base chemistry 3.3 Hydrogen bonds 3.3.1 Hydrogen bonds and their correlation with pKa 3.3.2 Degree of proton transfer of carboxylic acid and N-base systems 3.4 Ionicity of protic liquids and solids 3.4.1 Protic ionic liquids 3.4.2 Protic solid crystals 3.4.3 1H NMR chemical shift 3.4.4 The Walden rule and Grotthuss mechanism 3.5 Acid-base polymer membranes 3.5.1 Acid doped polybase membranes 3.5.2 Base-doped acidic polymer membranes 3.5.3 Polyacid-polybase membranes 3.5.4 Malfunction of phosphoric acid doped perfluorinated sulfonic acid membranes 3.6 Acid-base interactions in inorganic solid acids 3.7 Conclusive remarks Acknowledgements References Chapter 4. Applications of acid-base blend concepts to intermediate temperature membranes 4.1 Introduction 4.2 State of the art of the application of acid-base blend concepts 4.3 Short comparative study of the stability and properties of PBI-type membranes 4.3.1 Thermal stability of the blend membranes 4.3.2 Cross-linking degree/insoluble fraction by immersion in 90 DegreesC hot DMAc 4.3.4 Proton conductivity of H3PO4-doped membranes 4.4 Conclusions References Chapter 5: Pyridine Containing Aromatic Polyether Membranes 5.1 Introduction 5.2 Synthesis of linear aromatic polyethers containing main chain pyridine units 5.3 Side group functionalized linear aromatic polyethers containing main chain pyridine units 5.4 Cross-linked aromatic polyethers bearing pyridine main chain units 5.5 Interaction of phosphoric acid and water with the polymer membranes 5.5.1 Equilibrium hydration levels of water in the H3PO4 imbibed membranes 5.5.2 Stability and volatility of H3PO4 in the imbibed membranes 5.5.3 Steam permeability through the membrane 5.6 Application in HT-PEMFCs operating up to 220 DegreesC 5.6.1 Linear polymeric membranes 5.6.2 Cross-linked membranes 5.7 Conclusions Acknowledgements References Chapter 6 Techniques for PBI membrane characterization 6.1 Introduction 6.2 Molecular weight of PBI 6.2.1. Definitions 6.2.2 Viscosity 6.2.3 Size exclusion chromatography 6.3 Water and phosphoric acid uptake 6.3.1 Water uptake of pristine PBI membranes 6.3.2 Phosphoric acid uptake 6.3.3 Dimensional changes 6.4 Conductivity 6.4.1 Definitions and equations 6.4.2 Conductivity cells 6.4.3 Temperature dependence and activation energy 6.5 Solubility and gel contents 6.5.1 Solubility 6.5.2 Filtration of PBI solutions 6.5.3 Gel content 6.6 Mechanical properties 6.6.1 Tensile stress and strain 6.6.2 Tensile testing 6.6.3 Indentation, compression and creep 6.6.4 Dynamic mechanical analysis 6.7 Permeability, methanol crossover and electro-osmotic drag 6.7.1 Gas permeabilities 6.7.2 Electrochemical stripping method for hydrogen permeability measurements 6.7.3 Methanol crossover 6.7.4 Electro-osmotic drag of water 6.8 Thermal and oxidative stability 6.8.1 Thermal stability 6.8.2 Oxidative stability by Fenton test 6.9 Humidity definition and control 6.9.1 Saturated water vapor pressure, relative humidity and dew point 6.9.2 Control of water content Acknowledgements References Chapter 7 Synthesis of Polybenzimidazoles 7.1 Introduction to polybenzimidazoles 7.2 Procedures for synthesis of PBIs 7.2.1 Solvent free synthesis 7.2.2 Homogeneous solution polymerization 7.2.3 Microwave assisted synthesis 7.3 Characterization of PBIs 7.3.1 Viscosity 7.3.2 Structure identification 7.3.3 Solubility in organic solvents 7.4 Design and synthesis of PBI variants 7.4.1 Main chain modifications 7.4.2 Copolymers with polybenzimidazole blocks 7.4.3 Side-chain grafting via N-substitution 7.5 Summary Acknowledgements References Chapter 8 Phosphoric acid and its interactions with polybenzimidazole type polymers 8.1 Introduction 8.2 Basic chemical properties of phosphoric acid 8.2.1 The anhydride of phosphoric acid 8.2.2 Acidity and protolytic equilibria of orthophosphoric acid 8.2.3 Equilibria between the polyphosphoric acid species 8.3 Basic physical properties of phosphoric acid 8.3.1 Vapour pressure of phosphoric acid between 25 DegreesC and 170 DegreesC 8.3.2 Protonic conductivity in phosphoric acid in the range between 0 DegreesC and 170 DegreesC 8.3.3 Dynamic viscosity of aqueous phosphoric acid in range between 23 DegreesC and 170 DegreesC 8.3.4 Non-Arrhenius behaviour for the ionic transport 8.4 Interaction of phosphoric acid with polybenzimidazole 8.4.1 Adsorption model for a protic electrolyte by an ionogene basic polymer 8.4.2 Experimental studies on the doping behaviour of PBI-type polymers with protic electrolytes 8.5 Summary and conclusions 8.5.1 Bulk phosphoric acid 8.5.2 PBI-type polymers and protic (acidic) electrolyte References Chapter 9 Polybenzimidazole membranes by post acid doping 9.1 Introduction 9.2 Membrane preparation 9.2.1 Solvents 9.2.2 Membrane casting from organic solvents 9.2.3 Work-up 9.2.4 Doping 9.3 Structure and morphology 9.3.1 Structural features on a larger scale 9.3.2 Nanomorphology 9.4 Stability and mechanical strength 9.4.1 Chemical and thermal stability 9.4.2 Mechanical strength 9.5 Electrochemical and transport properties 9.5.1 Conductivity 9.5.2 Electro-osmotic drag 9.5.3 Solubility, diffusivity and permeability of gases 9.6 Structure modifications, polymer blends and composite systems 9.6.1 Composite systems 9.6.2 Polymer modifications and blends 9.7 Aspects on fuel cell performance and durability Acknowledgements References Chapter 10 PBI membranes via the PPA process 10.1 Introduction 10.2 The sol-gel process 10.3 Direct acid casting 10.4 Conductivities and acid content 10.5 Variations in PBI chemistry 10.5.1 Para-PBI (p-PBI) 10.5.2 Sulfonated-PBI 10.5.3 AB-PBI & isomeric AB-PBI (i-PBI) 10.5.4 Pyridine-based PBIs 10.5.5 Meta-PBI 10.5.6 Dihydroxy-PBI 10.6 Copolymers through the PPA process 10.6.1 Sulfonated para-PBI 10.6.2 Segmented block AB-para-PBI 10.6.3 Dihydroxy para-PBI 10.7 Membrane electrode assemblies (MEAs) and fuel cell testing 10.8 Conclusions References Chapter 11 Polybenzimidazoles with enhanced basicity: a chemical approach for durable membranes 11.1 The leaching of free phosphoric acid and membrane permanent proton conductivity 11.2 Novel benzimidazole monomers with additional basic heterocycles 11.3 Silica with basic functionalities as active fillers for stable PBI composite membranes 11.4 Conclusions References Chapter 12. Polybenzimidazole/porous poly(tetrafluoro ethylene) composite membranes 12.1 Reinforced Nafion membranes 12.2 Reinforcement of polybenzimidazole with porous poly(tetrafluoro ethylene) 12.2.1 Introduction 12.2.2 PBI solution properties 12.3.3 Preparation and characterizations of PBI/porous PTFE composite membranes 12.2.4 Applications of PBI/porous PTFE composite membranes 12.3 Other reinforced polymer composite membranes 12.3.1 Crosslinked polybenzimidazole-polybenzoxazine electrospun nano fibers 12.3.2 Other polyelectrolytes reinforced with porous PTFE film support 12.4 Summary References Chapter 13 PBI-based composite membranes 13.1 Introduction 13.2 PBI-based composite membranes with hygroscopic oxides 13.2.1 Introduction 13.2.2 Preparation of PBI composite membranes with hygroscopic oxides 13.2.3 Physicochemical characterization 13.2.4 Proton conductivity 13.2.5 Fuel cell results 13.3 PBI-based composite membranes with solid acids and salts 13.3.1 Introduction 13.3.2 Preparation of the inorganic component 13.3.3 Physico-chemical characterization 13.3.4 Proton conductivity 13.3.5 Fuel cell results 13.4. PBI's modified with ionic liquids 13.4.1 Introduction 13.4.2 Membrane preparation 13.4.3 Physico-chemical characterization 13.4.4 Proton conductivity 13.4.5 Fuel cell results 13.5 PBI-based composite membrane with carbon based materials 13.5.1 Carbon nanotube composites 13.5.2 Graphite oxide composites 13.6 Summary Acknowledgments References Chapter 14 Catalysts and Catalyst-Layers in HT-PEFCs 14. 1 Introduction 14.2 Catalyst and catalyst layer characterization 14.3 Mitigating carbon corrosion during start-up and shut-down 14.4 Carbon support and alloy catalysts 14.5 Conclusion and outlook Acknowledgement Appendix: MEA specifications and Abbreviations References Chapter 15 Catalyst support material and electrode fabrication 15.1 Introduction 15.2 Electrode construction 15.2.1 Catalyst support material 15.3 Mechanism of degradation 15.3.1 Carbon corrosion 15.3.2 Electrolyte loss 15.3.3 Platinum agglomeration 15.3.4 Conclusion 15.4 Manufacturing of inks, electrodes and MEAs 15.4.1 Electrode inks 15.4.2 Manufacturing of gas diffusion electrodes 15.4.3 MEA production techniques 15.4.4 Differences between PBI and PFSA based MEA production techniques List of abbreviations References Chapter 16 Design and Optimization of HT-PEMFC-MEAs 16.1 Cost and durability targets for HT-PEMFC MEAs 16.1.1 Cost target 16.1.2. Durability target 16.2 Developments in HT-PEMFC MEA 16.2.1 Components of HT-PEMFC MEA 16.2.2 Durability of HT-PEMFC MEAs 16.3 Design of optimum MEA structure 16.3.1 Improvement of cell voltage 16.3.2 Improvement of MEA durability 16.4 Conclusions References Chapter 17 Characterization of HT-PEM Membrane-Electrode-Assemblies 17.1 General introduction to characterization techniques 17.2 Standard electrochemical techniques for HT-PEM fuel cells characterization 17.2.1 Polarization curve 17.2.2 Electrochemical impedance spectroscopy 17.2.3 Linear sweep voltammetry 17.2.4 Cyclic voltammetry 17.2.5 MEA characterization test procedure 17.3 Micro computed tomography technique for Post-mortem analysis 17.4 The role of membrane-electrode-assembly contact pressure 17.5 Long-term testing in HT-PEM single fuel cells 17.6 Conclusion remarks Acknowledgements References Chapter 18 Approaches for the modeling of PBI/H3PO4 based HT-PEM fuel cells 18.1 Introduction 18.2 State of the art technologies 18.2.1 Phosohoric acid fuel cell (PAFC) 18.2.2 HT-PEM fuel cells 18.3 Literature review 18.3.1 PAFC modeling and simulation 18.3.2 HT-PEM fuel cell modeling and simulation 18.4 Mathematical modeling of fuel cells 18.4.1 Introduction 18.4.2 Model equations and their origin 18.4.3 Fundamental fuel cell modeling equations 18.4.4 Dedicated PAFC and HT-PEM fuel cell modeling equations 18.5 Electrolyte modeling 18.5.1 Physicochemical properties of phosphoric acid 18.5.2 Modeling of the vapor-liquid equilibrium 18.5.3 Non-equilibrium effects at the interphase 18.5.4 Coupling of the vapor-liquid equilibrium to electrochemistry and mass transport properties 18.6 Numerical aspects 18.6.1 Overview 18.6.2 Examples of practical implications 18.7 Input parameters and experimental data for model validation 18.8 Conclusions References Chapter 19 Bipolar plates and gaskets: Different materials and processing methods 19.1 Introduction 19.2 Technical requirements of bipolar plates and gaskets 19.3 General concepts of bipolar plate manufacturing 19.3.1 Compounding 19.3.2 Binder polymers 19.3.3 Graphite materials and fillers 19.4 Characterization data of HT-PEM bipolar plate materials 19.4.1 General remarks 19.4.2 Thermogravimetric analysis (TGA) 19.4.3 Electrical conductivity measurements (in-plane) 19.4.4 Electrical conductivity measurements (through-plane) 19.4.5 Phosphoric acid uptake of bipolar plates 19.5 Gaskets Acknowledgement List of abbreviations References Chapter 20 Stack concepts for high temperature polymer electrolyte membrane fuel cells 20.1 Introduction 20.2 Basic stack concepts 20.3 Energy balance for a HT-PEMFC stack 20.4 Thermal management of a HT-PEMFC stack 20.4.1 Passive cooling of HT-PEMFC stacks 20.4.2 Active cooling of HT-PEMFC stacks 20.5 Alternative cooling concepts and conclusions Acknowledgments References Chapter 21 High Temperature PEM Fuel Cell Systems, Control and Diagnostics 21.1 Introduction 21.2 Methanol reformer systems 21.3 Air cooled systems 21.4 Liquid cooled systems 21.5 Hydrogen vs. reformer systems 21.6 Control of HTPEM FC systems 21.6.1 System start-up state 21.6.2 Power delivery state 21.6.3 System shutdown 21.7 Advanced control strategies using ANFIS modelling 21.8 HTPEM fuel cell system diagnostics 21.9 Applying diagnostic procedures References Chapter 22 Durability Issues and Status of PBI Based Fuel Cells 22.1 Introduction 22.2 Polymer membrane degradation 22.2.1 Mechanical failure 22.2.2 Thermal degradation of PBI 22.2.3 Oxidative degradation 22.2.4 Effect of phosphoric acid 22.2.5 Radical oxidation degradation of PBI and its variants 22.3 Acid loss 22.3.1 Mechanisms of acid loss 22.3.2 Acid loss by evaporation 22.3.3 Phosphoric acid transfer in MEAs 22.4 Catalyst Degradation 22.4.1 Platinum dissolution 22.4.2 Carbon support corrosion 22.4.3 Catalyst focused protocols 22.4.4 Durable catalysts and supports 22.5 Other stack components 22.5.1 Bipolar plates 22.5.2 Gas Diffusion Layers 22.6 Lifetime Demonstration 22.6.1 Steady state operation 22.6.2 Dynamic test 22.6.3 Effect of fuel impurities 22.7 Conclusive remarks References Chapter 23 High Temperature Polymer Electrolyte Fuel Cell Systems for Aircraft Applications 23.1 Introduction 23.2 Specific aircraft considerations 23.3 Basic considerations on fuels and fuel cell technology in aviation 23.3.1 Temperature of the reforming process 23.3.2 Heat integration and system efficiency 23.3.3 Fuel quality and water 23.4 Development of an HT-PEFC system for aircraft propulsion 23.4.1 HT-PEFC cooling concept 23.4.2 HT-PEFC system layout with reformate supply from methanol steam reforming 23.4.3 Dimensioning the HT-PEFC stack for maximum flight endurance 23.4.4 Determining mean power for propulsion during flight 23.5 System integration into the wing pod 23.5.1 Startup procedure before flight 23.5.2 Shutdown procedure after landing 23.5.3 Dynamic requirements during flight operation 23.5.4 Outlook toward HT-PEFC/battery hybridization 23.5.5 Outlook toward water recycling 23.6 Conclusions List of symbols and abbreviations References Chapter 24 Electrochemical Hydrogen Pumping 24.1 Introduction 24.2 Electrochemistry 24.3 Low and high temperature devices 24.4 High-temperature membrane hydrogen pumping 24.4.1 Para-PBI 24.4.2 Other PBI's 24.5 Low-temperature hydrogen pumping 24.5.1 Perfluorosulfonic acid-based membranes 24.5.2 Poly(ether ether ketone)-based membranes 24.6 Applications 24.6.1 Electrochemical industrial hydrogen recycling 24.6.2 Fuel cell applications 24.6.3 Electro-analytical methods 24.6.4 Compression 24.6.5 Hydrogen purification 24.6.6 Limitations of the technology 24.6.7 Comparison to fuel cells - Lifetime/MEA Stability 24.7 Conclusions References.