Fuel Cell Fundamentals

RYAN O'HAYRE, PhD, is a Professor of Metallurgical and Materials Engineering at the Colorado School of Mines where his Advanced Energy Materials Laboratory develops new materials and devices to enable alternative energy technologies. SUK-WON CHA, PhD, is a Professor in the School of Mechanical and Aerospace Engineering at Seoul National University, Seoul, South Korea. WHITNEY G. COLELLA, PhD, is Faculty with the G.W.C. Whiting School of Engineering at The Johns Hopkins University in Baltimore, Maryland and Principal Research Engineer with Gaia Energy Research Institute. FRITZ B. PRINZ, PhD, is the Finmeccanica Professor in the School of Engineering, Professor of Mechanical Engineering and Professor of Materials Science and Engineering at Stanford University.

PREFACE xi ACKNOWLEDGMENTS xiii NOMENCLATURE xvii I FUEL CELL PRINCIPLES 1 Introduction 3 1.1 What Is a Fuel Cell? / 3 1.2 A Simple Fuel Cell / 6 1.3 Fuel Cell Advantages / 8 1.4 Fuel Cell Disadvantages / 11 1.5 Fuel Cell Types / 12 1.6 Basic Fuel Cell Operation / 14 1.7 Fuel Cell Performance / 18 1.8 Characterization and Modeling / 20 1.9 Fuel Cell Technology / 21 1.10 Fuel Cells and the Environment / 21 1.11 Chapter Summary / 22 Chapter Exercises / 23 2 Fuel Cell Thermodynamics 25 2.1 Thermodynamics Review / 25 2.2 Heat Potential of a Fuel: Enthalpy of Reaction / 34 2.3 Work Potential of a Fuel: Gibbs Free Energy / 37 2.4 Predicting Reversible Voltage of a Fuel Cell under Non-Standard-State Conditions / 47 2.5 Fuel Cell Efficiency / 60 2.6 Thermal and Mass Balances in Fuel Cells / 65 2.7 Thermodynamics of Reversible Fuel Cells / 67 2.8 Chapter Summary / 71 Chapter Exercises / 72 3 Fuel Cell Reaction Kinetics 77 3.1 Introduction to Electrode Kinetics / 77 3.2 Why Charge Transfer Reactions Have an Activation Energy / 82 3.3 Activation Energy Determines Reaction Rate / 84 3.4 Calculating Net Rate of a Reaction / 85 3.5 Rate of Reaction at Equilibrium: Exchange Current Density / 86 3.6 Potential of a Reaction at Equilibrium: Galvani Potential / 87 3.7 Potential and Rate: ButlerVolmer Equation / 89 3.8 Exchange Currents and Electrocatalysis: How to Improve Kinetic Performance / 94 3.9 Simplified Activation Kinetics: Tafel Equation / 97 3.10 Different Fuel Cell Reactions Produce Different Kinetics / 100 3.11 CatalystElectrode Design / 103 3.12 Quantum Mechanics: Framework for Understanding Catalysis in Fuel Cells / 104 3.13 The Sabatier Principle for Catalyst Selection / 107 3.14 Connecting the ButlerVolmer and Nernst Equations (Optional) / 108 3.15 Chapter Summary / 112 Chapter Exercises / 113 4 Fuel Cell Charge Transport 117 4.1 Charges Move in Response to Forces / 117 4.2 Charge Transport Results in a Voltage Loss / 121 4.3 Characteristics of Fuel Cell Charge Transport Resistance / 124 4.4 Physical Meaning of Conductivity / 128 4.5 Review of Fuel Cell Electrolyte Classes / 132 4.6 More on Diffusivity and Conductivity (Optional) / 153 4.7 Why Electrical Driving Forces Dominate Charge Transport (Optional) / 160 4.8 Quantum MechanicsBased Simulation of Ion Conduction in Oxide Electrolytes (Optional) / 161 4.9 Chapter Summary / 163 Chapter Exercises / 164 5 Fuel Cell Mass Transport 167 5.1 Transport in Electrode versus Flow Structure / 168 5.2 Transport in Electrode: Diffusive Transport / 170 5.3 Transport in Flow Structures: Convective Transport / 183 5.4 Chapter Summary / 199 Chapter Exercises / 200 6 Fuel Cell Modeling 203 6.1 Putting It All Together: A Basic Fuel Cell Model / 203 6.2 A 1D Fuel Cell Model / 206 6.3 Fuel Cell Models Based on Computational Fluid Dynamics (Optional) / 227 6.4 Chapter Summary / 230 Chapter Exercises / 231 7 Fuel Cell Characterization 237 7.1 What Do We Want to Characterize? / 238 7.2 Overview of Characterization Techniques / 239 7.3 In Situ Electrochemical Characterization Techniques / 240 7.4 Ex Situ Characterization Techniques / 265 7.5 Chapter Summary / 268 Chapter Exercises / 269 II FUEL CELL TECHNOLOGY 8 Overview of Fuel Cell Types 273 8.1 Introduction / 273 8.2 Phosphoric Acid Fuel Cell / 274 8.3 Polymer Electrolyte Membrane Fuel Cell / 275 8.4 Alkaline Fuel Cell / 278 8.5 Molten Carbonate Fuel Cell / 280 8.6 Solid-Oxide Fuel Cell / 282 8.7 Other Fuel Cells / 284 8.8 Summary Comparison / 298 8.9 Chapter Summary / 299 Chapter Exercises / 301 9 PEMFC and SOFC Materials 303 9.1 PEMFC Electrolyte Materials / 304 9.2 PEMFC Electrode/Catalyst Materials / 308 9.3 SOFC Electrolyte Materials / 317 9.4 SOFC Electrode/Catalyst Materials / 326 9.5 Material Stability, Durability, and Lifetime / 336 9.6 Chapter Summa