Non–Noble Metal Fuel Cell Catalysts

Written and edited by a group of top scientists and engineers in the field of fuel cell catalysts from both industry and academia, this book provides a complete overview of this hot topic. It covers the synthesis, characterization, activity validation and modeling of different non–noble metal and metalfree electrocatalysts for the reduction of oxygen, as well as their integration into acid or alkaline polymer exchange membrane (PEM) fuel cells and their performance validation, while also discussing those factors that will drive fuel cell commercialization. With its well–structured approach, this is a must–have for researchers working on the topic, and an equally valuable companion for newcomers to the field.

Preface XIII List of Contributors XV 1 Electrocatalysts for Acid Proton Exchange Membrane (PEM) Fuel Cells – an Overview 1 Michael Bron 1.1 Introduction 1 1.2 Acid PEM Fuel Cell Background and Fundamentals 2 1.2.1 Acid PEM Fuel Cell Overview – History, Status, and Advantages 2 1.2.2 Acid PEM Fuel Cell Reactions – Thermodynamics and Kinetics 4 1.3 Acid PEM Fuel Cell Catalysis for Cathode O2 Reduction Reaction 9 1.3.1 Electrochemical Thermodynamics of O2 Reduction Reaction 10 1.3.2 Pt–Based Catalysts for the Oxygen Reduction Reaction 10 1.3.3 Electrochemical Kinetics and Mechanism of the O2 Reduction Reaction Catalyzed by Pt Catalysts 16 1.4 Catalyst Challenges and Perspective in Acid PEM Fuel Cells 18 1.4.1 Pt Catalyst Cost Analysis and Major Challenges 18 1.4.2 Sustainability 19 1.4.3 Major Technical Challenges for Non–noble Metal Catalysts and Mitigation Strategies 19 1.4.4 Non–noble Metal Catalyst Overview 20 1.5 Conclusion 22 References 22 2 Heat–Treated Transition Metal–NxCy Electrocatalysts for the O2 Reduction Reaction in Acid PEM Fuel Cells 29 Fr´ed´eric Jaouen 2.1 Introduction 29 2.1.1 Why the Search for Non–precious Metal Catalysts for O2 Reduction? 29 2.1.2 Activity, Power Performance, and Durability Constraints on Me/N/C Catalysts 33 2.1.3 Milestones Achieved by Me/N/C Catalysts over the Last 50 Years 37 2.1.3.1 Milestone 1 37 2.1.3.2 Milestone 2 38 2.1.3.3 Milestone 3 39 2.1.3.4 Milestone 4 39 2.1.3.5 Milestone 5 39 2.2 Synthesis Approaches for Heat–Treated Me/N/C Catalysts 40 2.2.1 The Supported–Macrocycle Approach 41 2.2.2 The Templating Method 42 2.2.3 The Foaming Agent Approach 43 2.2.4 The N Molecule or Metal–Ligand Approach 45 2.2.5 The N–Polymer Approach 48 2.2.6 Gaseous N–Precursor Approach (NH3 and CH3CN) 50 2.2.7 Thermally Decomposable Metal–Organic Frameworks (MOF) 52 2.3 Important Parameters for Highly Active Me/N/C Catalysts 54 2.3.1 Pyrolysis Temperature 54 2.3.1.1 Metal Macrocycles Supported on Carbon and Pyrolyzed in Inert Atmosphere 54 2.3.1.2 Separate Metal and Nitrogen Precursors or Metal–Ligand Complexes Impregnated on a Carbon Support and Pyrolyzed in Inert or Reactive Atmosphere 56 2.3.2 The Transition Metal 57 2.3.2.1 Binary Metal Catalysts 58 2.3.2.2 Metal Concentration 59 2.3.3 The Nitrogen Content and Speciation by X–ray Photoelectron Spectroscopy (XPS) 61 2.3.4 The Carbon Support/Host 64 2.4 Nature of the Active Sites 73 2.4.1 Time–of–Flight Secondary Ion Mass Spectroscopy 73 2.4.2 X–ray Absorption Spectroscopy and Extended X–ray Absorption Fine Structure 75 2.4.2.1 Studies on Pyrolyzed Macrocycles 76 2.4.2.2 Studies on Catalysts Synthesized from Separate Metal, N and C Precursors 77 2.4.3 M¨ossbauer Spectroscopy 79 2.4.3.1 Studies on FePc and Fe– Porphyrin, Unpyrolyzed or Pyrolyzed at T < 500 ◦C 80 2.4.3.2 Studies on Fe Macrocycles Pyrolyzed at T ≥ 700 ◦C 81 2.4.3.3 Studies on Fe–N–C Catalysts Obtained by Pyrolysis of Separate Fe, N, and C Precursors 85 2.4.4 Turnover Frequency and Site Density 91 2.5 Electrochemical Investigation by RDE/RRDE Methods 94 2.5.1 RDE and the Thin Film Problem: Model and Experiment 94 2.5.2 Activity for H2O2 Reduction or Oxidation: a Major Difference from Pt–Based Catalysts 99 2.5.3 The pH Effect: Another Look at the Turnover Frequency of Different Active Sites 103 2.6 Conclusions 105 Acronyms 106 Acknowledgments 106 References 107 3 Modified Carbon Materials for O2 Reduction Reaction Electrocatalysts in Acid PEM Fuel Cells 119 Deepika Singh, Jesaiah King, and Umit S. Ozkan 3.1 Introduction 119 3.2 Doped Carbon Materials 119 3.2.1 Nitrogen–Doped Carbons 121 3.2.1.1 N–Doped CNTs and CNFs 122 3.2.1.2 N–Doped Fullerene 124 3.2.1.3 Carbon Nitrides 124 3.2.1.4 Graphitic Carbon Nitride 125 3.2.1.5 N–Doped Graphene 125 3.2.2 Doping with Other Heteroatoms 127 3.3 Doped Carbons as ORR Catalysts 130 3.3.1 Nitrogen–Doped Carbon Materials Prepared without a Metal 139 3.4 Conclusions 140 Acknowledgment 141 References 141 4 Transition Metal Chalcogenides for Oxygen Reduction Electrocatalysts in PEM Fuel Cells 157 Kunchan Lee, Nicolas Alonso–Vante, and Jiujun Zhang 4.1 Introduction 157 4.2 Non–noble Metal Chalcogenide Electrocatalysts for Oxygen Reduction Reaction 160 4.3 Synthesis Methods for Non–noble Metal Chalcogenides 163 4.3.1 Nonorganic Solvent Methods 164 4.3.2 Organic Solvent Methods at Low Temperature 165 4.4 Oxygen Reduction Reaction on Non–noble Metal Chalcogenides 168 4.4.1 Mechanism of Oxygen Reduction Reaction 168 4.4.2 Theoretical Approach for ORR Mechanism 172 4.5 Methanol Tolerance 175 4.6 Fuel Cell Measurements 177 4.7 Conclusions 178 References 179 5 Transition Metal Oxides, Carbides, Nitrides, Oxynitrides, and Carbonitrides for O2 Reduction Reaction Electrocatalysts for Acid PEM Fuel Cells 183 Akimitsu Ishihara, Hideto Imai, and Ken–ichiro Ota 5.1 Introduction 183 5.2 Transition Metal Nitrides and Carbonitrides as Cathode Catalysts 185 5.3 Stability of Oxides in Acid Electrolyte 186 5.4 Non–noble Metal Oxide–Based Cathode Catalysts 187 5.4.1 Stability of Group 4 and 5 Metal Oxide–Based Catalysts 187 5.4.2 Formation of Complex Oxide Layer Containing Active Sites 188 5.4.3 Substitutional Doping of Nitrogen 189 5.4.4 Creation of Oxygen Defects without Using Carbon and Nitrogen 191 5.4.5 Oxidation of Compounds Including Carbon and Nitrogen 193 5.4.6 Performance of Single Cell with Oxide–Based Cathodes 197 5.5 Conclusions 198 Acknowledgments 198 References 199 6 Theoretical Modeling of Non–noble Metal Electrocatalysts for Acid and Alkaline PEM Fuel Cells 205 Eben Dy and Zheng Shi 6.1 Introduction 205 6.2 Mechanisms of ORR 205 6.2.1 Role of the Catalyst 206 6.2.2 Effect of pH 208 6.3 Simple Metal–N4 Macrocycles 212 6.4 Heat–Treated Transition Metal Nitrogen–Carbon Precursors (M–Nx/C) 216 6.5 Functionalized Graphitic Materials 221 6.5.1 Doped Graphene Materials 222 6.5.2 Doped Carbon Nanotube Materials 227 6.5.3 Metal–Functionalized Graphene Materials 229 6.6 Conducting Polymers 232 6.7 Outlook 235 References 236 7 Membranes for Alkaline Polyelectrolyte Fuel Cells 243 Jing Pan, Chen Chen, and Lin Zhuang 7.1 Introduction 243 7.2 Two Main Challenges of APEs 244 7.2.1 Pursuing High Conductivity as well as Low Swelling Degree 244 7.2.2 High Chemical Stabilities of Cation Groups 244 7.3 APEs Reported in the Literature 245 7.3.1 Heterogeneous APE Membranes 246 7.3.1.1 Ion–Solvating Polymers 246 7.3.1.2 Organic–Inorganic Hybrid APE Membranes 247 7.3.1.3 Composite APE Membrane 248 7.3.2 Homogeneous APE Membranes 249 7.3.2.1 Film–Modified APEs 249 7.3.2.2 Polymer–Modified APEs 250 7.3.2.3 Monomer–Polymerized APE 250 7.4 Strategies for Improving the Ionic Conductivity of APE 254 7.5 Efforts of Improving the Chemical Stability of the Cationic Functional Group 258 7.5.1 Cationic Groups with Conjugated Structure 258 7.5.2 Cationic Groups with Strong Electron Donor 260 7.6 Research on the Chemical Stability of APE Backbone 261 7.7 Conclusions and Perspective 261 References 264 8 Electrocatalysts for Alkaline Polymer Exchange Membrane (PEM) Fuel Cells – Overview 271 Rongzhong Jiang and Deryn Chu 8.1 Introduction 271 8.2 Alkaline Fuel Cell Overview – History, Status, and Advantages 272 8.3 Alkaline Fuel Cell and Alkaline PEM Fuel Cell – Thermodynamics and Kinetics 274 8.3.1 Thermodynamics of H2/O2 Fuel Cell Reactions in Alkaline Electrolyte 274 8.3.2 Kinetics of O2 Reduction in Alkaline Fuel Cells 276 8.3.3 Mechanisms of Oxygen Reduction at Noble Metal Surface 279 8.3.4 Mechanisms of Oxygen Reduction at Non–noble Metal Surface 282 8.3.5 Kinetics and Mechanisms of H2 Oxidation 284 8.4 Silver–Based Materials for Cathode Electrocatalysts in Alkaline PEM Fuel Cells 286 8.4.1 Starting Materials and Synthesis Strategies for Silver–Based Electrocatalysts 287 8.4.1.1 Chemical Synthesis of Powder Ag Catalysts 288 8.4.1.2 Some Synthetic Methods for Porous Ag Membranes and Porous Electrodes 291 8.4.2 Physical and Electrochemical Characterizations 291 8.4.2.1 X–ray Powder Diffraction (XRD) 291 8.4.2.2 X–ray Photoelectron Spectroscopy (XPS) 293 8.4.2.3 Transmission Electron Microscopy (TEM) 293 8.4.2.4 Electrochemical Method 295 8.4.3 Silver–Based Catalysts for Alkaline PEM Fuel Cells 297 8.5 Catalysts for Oxidation of a Broad Range of Fuels for Alkaline PEM Fuel Cells 298 8.5.1 Non–carbon Fuels and Specific Catalysts for Their Oxidation 298 8.5.1.1 Hydrogen 298 8.5.1.2 Borohydride 298 8.5.1.3 Hydrazine 299 8.5.1.4 Ammonia 299 8.5.1.5 Sulfide 300 8.5.2 Single–Carbon Organic Fuels and Specific Catalysts for Their Oxidation 300 8.5.2.1 Methanol 300 8.5.2.2 Formaldehyde 301 8.5.2.3 Formic Acid 301 8.5.3 Organic Fuels Containing Carbon–Carbon (C–C) Bond in the Molecules and Specific Catalysts for Their Oxidation 302 8.5.3.1 Ethanol 302 8.5.3.2 Ethylene Glycol and Dimethyl Ether 303 8.5.3.3 Other Organic Fuels Containing Two or More C–C Bonds in Their Molecules 305 8.5.4 Electrochemical Kinetics and Mechanisms of Fuel Electrooxidation in Alkaline Media 305 8.6 Major Challenges of Alkaline Fuel Cells and Alkaline PEM Fuel Cells 307 Acknowledgments 309 References 309 9 Carbon Composite Cathode Catalysts for Alkaline PEM Fuel Cells 319 Qing Li and Gang Wu 9.1 Introduction 319 9.2 Metal–Free Carbon Catalysts 321 9.2.1 Nitrogen Doping into Carbon 322 9.2.2 Nitrogen–Doped Carbon Nanotube Catalysts 324 9.2.3 Nitrogen–Doped Graphene Catalysts 325 9.2.4 Other Heteroatom–Doped Carbon Catalysts 328 9.3 Heat–Treated M–N–C (M: Fe, Co) Carbon Composite Catalysts 330 9.3.1 Heating Temperatures 330 9.3.2 Type of Transition Metals 332 9.3.3 Nitrogen Precursors 333 9.4 Nanocarbon/Transition Metal Compound Hybrid Catalysts 336 9.4.1 Nanocarbon/Metal Oxides Hybrid Catalysts 337 9.4.2 Carbon/Metal Chalcogenide Hybrid Catalysts 341 9.4.3 Nanocarbon/Macrocycle Compound Catalysts 342 9.5 ORR Mechanism on NPMCs in Alkaline Media 344 9.6 NPMC Cathode Performance in Anion Exchange Membrane Fuel Cell 346 9.7 Summary and Perspective 348 References 349 10 Non–precious Metal Oxides and Metal Carbides for ORR in Alkaline–Based Fuel Cells 357 Wenling Chu, Drew Higgins, Zhongwei Chen, and Rui Cai 10.1 Introduction 357 10.2 Metal Oxides 359 10.2.1 Manganese Oxides 360 10.2.2 Other Metal Oxides 362 10.3 Perovskite–Type Oxides 364 10.3.1 Effect of A– and B–Site Cations 365 10.3.2 Effect of Preparation Methods 368 10.3.3 Durability of Perovskite–Type Oxides 370 10.3.4 Design Principles for ORR Activity on Perovskite–Type Oxides 371 10.4 Spinel–Type Oxides 372 10.5 Metal Carbides 377 10.6 Conclusion and Outlook 379 References 380 11 Automotive Applications of Alkaline Membrane Fuel Cells 389 Hirohisa Tanaka, Koichiro Asazawa, and Tomokazu Sakamoto 11.1 Introduction 389 11.2 History of Alkaline Fuel Cells in Automotive Applications 392 11.3 Fuel Used in Modern Alkaline PEM Fuel Cells in Automotive Applications 395 11.4 Components of an Alkaline PEM Fuel Cell Membrane Electrode Assembly for Automotive Applications 398 11.4.1 Anode Catalysts for the Direct Hydrazine Fuel Cell Vehicle 398 11.4.2 Cathode Catalysts 404 11.4.3 MEA Performance Using Non–noble Metal Catalysts 407 11.5 Major Challenges to Overcome in Alkaline PEM Fuel Cells 414 11.6 Conclusion 416 Acknowledgments 417 References 418 Index 423

Zhongwei Chen is an Associate Professor in the Department of Chemical Engineering at University of Waterloo. His current research interests are in the development of advanced electrode materials for metal–air batteries, lithium–ion batteries and fuel cells. He received his Ph.D. in Chemical and Environmental Engineering from the University of California–Riverside. Prior to joining the faculty at Waterloo in 2008, he was focusing on the advanced catalysts research in the Los Alamos National Laboratory (LANL) at New Mexico, USA. He has published 4 book chapters and more than 70 peer reviewed journal articles. These publications have earned him to date more than 3000 citations with H–index 28. He is also listed as inventor on 3 US patents and 8 provisional US patents. Jean–Pol Dodelet is Professor of Physical Chemistry at L′Institut National de la Recherche Scientifique (INRS, Canada). After receiving his Ph.D. in Physical Chemistry in 1969 from L′Université Catholique de Louvain (Belgium) he became a Postdoctoral Fellow and then Research Associate in Radiation Chemistry at the University of Alberta (Canada). In 1976, he became Professor of Physical Chemistry at L′Université du Québec à Trois Rivières (Canada), where he worked until 1981 on the photoconducting properties of molecular photoconductors, before he took his current position. At INRS, he first continued his work on molecular photoconductors before becoming interested, in 1990, in non–noble metal electrocatalysts, the research area where he is still active today. In the last several years, Dr. Dodelet collaborated with General Motors in the frame of an Industrial Research Chair in electrocatalysis, sponsored by General Motors of Canada and the Natural Sciences and Engineering Research Council of Canada. Jiujun Zhang is Principal Research Officer and Catalysis Core Competency Leader at the National Research Council of Canada′s Energy, Mining & Environment Portfolio (NRC–EME). After having received B.Sc and M.Sc in physical chemistry at Peking University he received his Ph.D. in Electrochemistry from Wuhan University in 1988. He then took a position as an associate professor at the Huazhong Normal University for two years, followed by postdoctoral research at the California Institute of Technology, York University, and the University of British Columbia. Dr. Zhang has over twenty–eight years of R&D experience in theoretical and applied electrochemistry and three years of electrochemical sensor experience. He holds several adjunct professorships, including one at the University of Waterloo, one at the University of British Columbia, and one at Peking University.