ISBN: 3-540-64386-9
TITLE: Electrochemical Engineering
AUTHOR: Wendt, Hartmut; Kreysa, Gerhard
TOC:

Chapter 1 
The Scope and History of Electrochemical Engineering 
1.1 Carl Wagner and the Beginning of Electrochemical 
Engineering Science 1 
1.2 Electrochemistry and Electrochemical Engineering Science 2 
1.3 Electrochemical Engineering Science and Technology 
Since the Mid-1960s 3 
1.4 What Means Electrochemical Engineering Science 
and Technology Today? 5 
References 7 
Further Reading 7 
Chapter 2 
Basic Principles and Laws in Electrochemistry 
2.1 Stoichiometry of Electrochemical Reactions 8 
2.2 Faraday's Law 10 
2.3 Production Rates and Current Densities 11 
2.4 Ohm's Law and Electrolyte Conductivities 12 
2.5 Parallel Circuits and Cells with Electrolytic Bypass 
and Kirchhoff's Rules 14 
Further Reading 16 
Chapter 3 
Electrochemical Thermodynamics 
3.1 Equilibrium Cell Potential and Gibbs Energy 17 
3.2 Electrode Potentials, Reference Electrodes,Voltage Series, 
Redox Schemes 21 
3.3 Reaction Enthalpy, Reaction Entropy, Thermoneutral Cell 
Voltage and Heat Balances of Electrochemical Reactions 28 
3.4 Heat Balances of Electrochemical Processes 29 
3.5 Retrieval of Thermodynamic Data and Activity Coefficients 31 
3.6 Thermodynamics of Electrosorption 35 
References 37 
Chapter 4 
Electrode Kinetics and Electrocatalysis 
4.1 The Electrochemical Double Layer 39 
4.2 Kinetics of Interfacial Charge Transfer 41 
4.3 Electrode Kinetics of Multielectron Charge Transfer Reactions 45 
4.4 Thermal Activation and Activation Energies of 
Electrochemical Reactions 49 
4.5 Electrochemical Reaction Orders 49 
4.6 Current Density/Potential Correlations for 
Different Limiting Conditions 51 
4.6.1 Micro- and Macrokinetics of Electrochemical 
Reactions 51 
4.6.2 Mass Transfer Controlled Current Potential Curves 52 
4.6.2.1 Reaction Controlled Current Voltage Curves 54 
4.6.3 Charge Transfer Controlled Current Voltage 
Correlation 55 
4.6.4 Combined Activation and Mass Transport Control 56 
4.7 Reaction Controlled Current Voltage Curves 57 
4.7.1 Introductory Remarks 57 
4.7.2 Fast Preceding Reaction of an Electroactive 
Minority Species 58 
4.7.3 Fast Consecutive Reactions 60 
4.8 Electrocatalysis 61 
4.8.1 Principles of Electrocatalysis 61 
4.8.2 Heterogeneous Electrocatalysis in Cathodic 
Evolution and Anodic Oxidation of Hydrogen 61 
4.8.2.1 The Volcano Curve 62 
4.8.3 Electrocatalysis in Anodic Oxygen Evolution 
and Cathodic Oxygen Reduction 64 
4.8.4 Redox Catalysis 66 
4.9 Catalyst Morphology and Utilisation 68 
4.9.1 Structural Features and Catalyst Morphology 
of Electrocatalysts for Gas Evolving and Gas 
Consuming Electrodes 68 
4.9.2 Utilisation of Porous Electrocatalyst Particles 69 
4.10 Electrocatalysis in Electroorganic Synthesis 71 
4.10.1 Introduction into the Field of Electroorganic 
Synthesis 71 
4.10.1.1 Mediated Electrochemical Conversions of 
Organic Substrates 71 
4.10.1.2 Direct Anodic and Cathodic Electrochemical 
Conversions of Organic Substrates 72 
4.10.2 Electrocatalytic Oxidations by Oxides 
of Multiply-Valent Metals 72 
4.10.2.1 The Heterogeneously Catalysed Benzene Oxidation 
at Pb/PbO_2 Electrodes in Sulfuric Acid 74 
4.10.3 Electrocatalytic Hydrogenation and Electrocatalyzed 
Mediated Reduction 74 
4.10.4 The Electrode Surface as Medium Catalysing 
Chemical Reactions of Electrogenerated 
Reactive Organic Intermediates 75 
4.10.4.1 Electrocatalytic Action of Electrosorbed Non-Reactant 
SpeciesElectrocatalysis of the Second Kind 78 
4.10.5 Kinetics and Selectivity of Homogeneous Chemical 
Consecutive Reactions Following Charge Transfer 79 
References 80 
Further Reading 80 
Chapter 5 
Mass Transfer by Fluid Flow, Convective Diffusion and Ionic Electricity 
Transport in Electrolytes and Cells 
5.1 Introduction 81 
5.2 Fluid Dynamics and Convective Diffusion 81 
5.3 Fluid Dynamics of Viscous, Incompressible Media 84 
5.3.1 Laminar vs Turbulent Flow 86 
5.3.2 Velocity Distributions for Laminar Flow 87 
5.3.2.1 Singular Electrode: Unidirectional Laminar 
Flow Along a Plate 87 
5.3.2.2 Pair of Planar Electrodes 88 
5.3.2.3 Circular Capillary Gap Cell 89 
5.4 Mass Transport by Convective Diffusion 90 
5.4.1 Fundamentals 90 
5.4.2 Dimensionless Numbers Defining Mass Transport 
Towards Electrodes by Convective Diffusion 92 
5.4.3 Hydrodynamic Boundary Layer and Nernst 
Diffusion Layer: Planar Electrodes 93 
5.4.4 Mass Transport Towards a Singular Planar 
Electrode Under Laminar Forced Flow 95 
5.4.5 Channel Flow and Mass Transfer to Electrodes 
of Parallel Plate Cells for Free and Forced Convection 97 
5.4.5.1 Free Convection at Isolated Planar Electrodes 
and between Two Vertical Electrodes 97 
5.4.5.2 Convective Mass Transfer for Parallel Plate Cells 
with Forced Convection: Planar Plate Cells 98 
5.4.5.3 Mass Transfer in Circular Capillary Gap Cells 101 
5.4.6 Convective Mass Transfer Toward Rotating 
Electrodes 102 
5.4.6.1 Rotating Cylinder 102 
5.4.6.2 Rotating Disc Electrode 102 
5.4.7 Mass Transfer at Gas Evolving Electrodes 103 
5.4.7.1 Calculating k_{m, bubble} According to the Penetration 
Model or Model of Periodic Boundary Layer Renewal 105 
5.4.7.2 Calculating Bubble-Enhanced Mass Transfer 
According to Flow Model 105 
5.4.8 Mass Transfer in Three-Dimensional Electrodes 106 
5.4.9 Summary 107 
5.5 Heat Transport 107 
5.5.1 ChiltonColburn Analogy of Mass and Heat 
Transfer 107 
5.5.2 General Description of Heat Generation and Heat 
Transfer in Electrolyzers and Fuel Cells 108 
5.5.2.1 Heat Balance and Steady State-Temperature of Cells 109 
5.6 Ionic Charge and Mass Transport in Electrolytes 110 
5.6.1 Strong Electrolytes 110 
5.7 Temperature Dependence of Electrolyte Conductivities 111 
5.8 Molten Salt Electrolytes 113 
5.9 Segregation in Stagnant Electrolytes of Binary Molten 
Carbonates in Fuel Cells 114 
5.10 Current Density Distribution in Cells and Electrochemical 
Devices 117 
5.11 Primary Current Density Distribution 119 
5.12 Secondary Current Density Distribution 121 
5.13 Secondary Current Density Distribution and "Throwing Power" 
in Electrodeposition and Electrocoating 122 
5.14 The Wagner Number 124 
5.15 Tertiary Current Distribution 125 
References 127 
Further Reading 127 
Chapter 6 
Electrochemical Reaction Engineering 
6.1 Introductory Remarks 128 
6.2 Microkinetic Models 128 
6.3 Mode of Operation 129 
6.4 Electrical Control of Cells 131 
6.5 Macrokinetic Models 131 
6.5.1 Stirred-Batch Tank Reactor 131 
6.5.2 Continuously Stirred Tank Reactor 132 
6.5.3 Plug-Flow Reactor (PFR) 133 
6.5.3.1 Plug Flow Electrolyzer with Uniform Current Density 135 
6.5.3.2 PFR Operated at Mass Transfer Limited and 
Higher Current Density 135 
6.5.4 Cell Cascades 136 
6.5.5 Extended Modelling of Electrolyzers 138 
6.5.6 Residence-Time Distribution 139 
6.5.7 The Selectivity Problem of Consecutive Reactions 
in Batch Reactors 142 
6.6 Coupling of Electrochemical and Chemical Reactors 146 
6.7 Electrolyzer Design and Chemical Yield Losses Due To 
Parasitic Chemical Reactions 148 
6.8 Performance Criteria of Electrochemical Reactors 149 
6.8.1 Fractional Conversion, X 150 
6.8.2 Relative Amount of Charge-Q_r 150 
6.8.3 Overall Conversion Related Yield Theta_p 150 
6.8.4 Current Efficiency Phi^e 151 
6.8.5 Parameters for Energy Considerations 152 
References 152 
Further Reading 152 
Chapter 7 
Electrochemical Engineering of Porous Electrodes and Disperse 
Multiphase Electrolyte Systems 
7.1 Introduction 153 
7.2 Three-Dimensional Electrodes 154 
7.2.1 General Considerations 154 
7.2.2 Fundamental Equations 155 
7.2.2.1 Nanoporous Electrode Particles 156 
7.2.2.2 Microporous Electrodes 156 
7.2.2.3 Packed and Fluidized Bed Electrodes 157 
7.2.3 Gas Consuming Nanoporous Electrodes for 
Fuel Cells and Nanoporous Catalyst Particles 
and Layers for Gas Evolving Electrodes 157 
7.2.3.1 Physical Structure of Particulate, Gas Consuming 
Nanoporous Gas Diffusion Electrodes 157 
7.2.3.2 Physical Structure of Raney Nickel Coatings 
for Hydrogen Evolving Cathodes 159 
7.2.3.3 Modelling Hydrogen Concentration Profiles 
and Catalyst Efficiencies for Hydrogen Consuming 
Fuel Cell Anodes or Other Gas Diffusion Electrodes 160 
7.2.3.4 Modelling of Hydrogen Concentration Profiles 
and Catalyst Efficiencies for Hydrogen Evolving 
Nanoporous Raney-Nickel Catalyst Coatings 165 
7.2.4 Porous Battery Electrodes 171 
7.2.5 Packed Bed and Fluidized Bed Electrodes 
Composed of Coarse Particles173 
7.2.5.1 Fluidized Bed Electrodes 178 
7.3 Ionic Conductivity of Electrolytes Containing Dispersed 
Gas Bubbles in Gas Evolving Electrolyzers 179 
7.4 Electrolyzers with Gaseous Reactants 183 
7.5 Electrochemical Liquid/Liquid Systems 186 
References 186 
Further Reading 186 
Chapter 8 
Electrochemical Cell and Plant Engineering 
8.1 Materials Choice and Corrosion Problems 187 
8.1.1 Metals 188 
8.1.2 Carbon 192 
8.2 Electrode Materials 193 
8.2.1 Stainless Steel 194 
8.2.2 Nickel 194 
8.2.3 Lead 195 
8.2.4 Titanium 195 
8.2.5 Noble Metals 195 
8.2.6 Massive Carbon 196 
8.3 Electrode Design 196 
8.3.1 Gas Evolving Electrodes 196 
8.3.2 Gas Consuming Electrodes, Gas Diffusion Electrodes 197 
8.4 Separators: Membranes and Diaphragms 199 
8.4.1 Membranes 201 
8.4.2 Diaphragms 203 
8.5 Polymeric Materials for Cell Bodies and Electrolyte Loops 203 
8.6 Gaskets 205 
8.7 Electrodes 206 
8.7.1 Horizontal Electrodes 206 
8.7.2 Membrane Electrolyzer 207 
8.8 Cell and Electrode Design 208 
8.8.1 Zero Gap Electrolysis Cells  208 
8.8.2 Vertical/Horizontal Electrodes 209 
8.8.3 Divided/Undivided Monopolar/Bipolar Cells 
and Modes of Electrolyte Flow 209 
8.8.4 Special Cell Designs 210 
8.8.5 Capillary Gap Cells 216 
8.8.6 Swiss Roll Cell 216 
8.8.7 Cells with Three-Dimensional Electrodes 217 
8.9 Power Supply for Electrochemical Plants 218 
8.9.1 Rectifiers 218 
8.9.2 Transformer Wiring 218 
8.9.3 Further Equipment 219 
Further Reading 220 
Chapter 9 
Process Development 
9.1 Scope and Purpose of Laboratory and Pilot Plant 
Measurements 221 
9.2 Laboratory Methods 222 
9.2.1 Steady-State Measurements of Current Density 
Potential Correlations 222 
9.2.1.1 General Remarks 222 
9.2.1.2 Measuring Devices 223 
9.2.1.3 Evaluation of Rotating Disc Measurements 223 
9.2.1.4 Current-Voltage Correlation for Competing 
Reactions by Non-Electrochemical Methods 225 
9.2.1.5 The Ring Disc Electrode 226 
9.2.2 Non-Steady State Methods 230 
9.2.2.1 General Remarks 230 
9.2.2.2 Potentiodynamic Polarisation Curves 230 
9.2.2.2.1 Cyclic Voltammetry and Linear Potential 
Sweep Method 231 
9.2.2.2.2 Initial Polarisation Curves 233 
9.2.2.3 Square-Wave Pulses 233 
9.2.2.4 Eliminating the IR Drop 235 
9.2.2.4.1 Galvanostatic Methods 236 
9.2.2.4.2 Potentiostatic Procedures 236 
9.3 Pilot Plant Methods 236 
9.3.1 General Considerations 236 
9.3.2 Mass-Transfer Measurements 237 
9.3.3 Determination of Residence-Time Distributions 238 
9.4 Mathematical Modelling and Optimisation by Factorial 
Design of Experiments 239 
9.4.1 Introduction 239 
9.4.2 General Procedure for Optimum Finding 
by Experiment 239 
9.4.3 Factorial Design of Experiments 240 
9.5 Cost Analysis 243 
9.5.1 Composition of Productions Costs 243 
9.5.2 Total and Specific Investment Costs 244 
9.5.3 Cost Optimisation with Respect to Current Density 245 
9.5.4 Optimisation of Non-Selective Electrolysis Processes 248 
9.5.4.1 Current Density Against Current Efficiency 249 
9.5.4.2 Temperature vs Current Efficiency 250 
9.5.5 Examples Including Influences of Process Parameters 
on the Equipment for Non-Electrochemical 
Unit Operations and Corresponding Costs 250 
Further Reading 251 
Chapter 10 
Industrial Electrodes 
10.1 Catalytically Activated Electrodes 252 
10.2 Functioning, Longevity and Application of 
Electrocatalyst Coatings 253 
10.3 Design of Industrial Electrodes 255 
10.3.1 Monopolar Electrodes and Current Density 
Distribution on Their Surface 255 
10.3.2 Electrodes for Bipolar Electrode Stacks 257 
10.3.3 Gas Evolving Electrodes 258 
10.4 Structural Features of Electrocatalysts for Gas Evolving and 
Gas Consuming Electrodes 260 
10.5 Electrocatalytically Activated Dimensionally Stable 
Chlorine-Evolving Electrodes 260 
10.5.1 Technological History 260 
10.5.2 Electrocatalysis and Selectivity of Anodic 
Chlorine Evolution at RuO_2-Anodes 261 
10.5.3 Preparation and Formulation of the Coatings 261 
10.5.4 Improvement of Adhesion and Strength 
of the Coatings 261 
10.5.5 Design of Cells Using DSAs 262 
10.5.6 Lifetime of Dimensionally Stable Chlorine 
Evolving Anodes 263 
10.5.7 DSAs for Chlorate and Hypochlorite Production 264 
10.6 Oxygen Evolving Anodes 265 
10.6.1 Technical Processes 265 
10.6.2 Electrocatalysis of Oxygen Evolution in Advanced 
Alkaline Water Electrolysis 265 
10.6.2.1 Coatings Containing Cobalt and Iron Oxides 265 
10.6.3 Electrocatalysis of the Anodic Oxygen Evolution 
by Raney-Nickel Coatings 266 
10.6.4 Catalyst-Coated Titanium Electrodes for Oxygen 
Evolution From Acid Solutions 266 
10.7 Hydrogen Evolving Cathodes 268 
10.7.1 Technoeconomical Significance of Cathodic 
Hydrogen Evolution 268 
10.7.2 Electrocatalyst Coatings for Hydrogen Evolution 
from Alkaline Solution 268 
10.7.2.1 Technically Applied Coatings 268 
10.7.2.2 Nickel Sulfide Coatings 269 
10.7.2.3 Raney-Nickel Coatings 269 
10.7.2.3.1 Precursor Alloys and Fabrication 
of Coated Cathodes 269 
10.7.2.3.2 Utilisation of the Catalyst in 
Raney-Nickel Coatings 271 
10.7.2.3.3 Performance and Ageing of Raney-Nickel Coatings 272 
10.7.3 Coatings of Platinum Metal Oxides 273 
10.7.4 Active Coatings of Flame Sprayed, Doped Nickel Oxide 273 
10.7.5 Platinum and Platinum Metal Cathodes in Membrane 
Water Electrolyzers 273 
10.8 Fuel-Cell Electrodes 274 
10.8.1 Low- and High-Temperature Fuel Cells 274 
10.8.2 Structural Design of Gas-Diffusion Electrodes 
in Low-Temperature Fuel Cells 275 
10.8.3 Oxygen Reduction Catalysts in 
Low-Temperature Cells 276 
10.8.4 Catalysts for Anodic Hydrogen Oxidation 276 
10.8.5 Properties, Preparation and Improvement 
of Electrocatalysts in Gas Diffusion Electrodes 
for Low Temperature Cells 277 
10.8.5.1 Pt-Activated Active Carbon 277 
10.8.5.2 Particle Size of Pt Nanocrystals on Active Carbon 
and Their Effective Catalytic Activity 278 
10.8.5.3 Pt-Alloy Catalysts 278 
10.8.6 Morphology and Structure of Complete 
PTFE-Bonded Active-Carbon Electrodes 279 
10.8.7 Ageing of Pt-Catalysts 280 
10.8.8 Electrocatalysis of Anodic Methanol Oxidation 281 
10.8.8.1 Technoeconomic Significance of the Process 281 
10.8.8.2 Self-Poisoning of Methanol Oxidising Pt-Catalyst 
by Oxidation Products of Methanol 281 
10.8.8.3 Anodic Methanol Oxidation at Alloy Catalysts 281 
10.8.9 Gas-Diffusion Electrodes in Membrane (PEM) 
Fuel Cells 282 
10.8.9.1 Rationale of Developing a Method of Internal 
Wetting for Membrane Fuel Cell Electrodes 282 
10.8.9.2 Improving Catalyst Utilisation by Ionomer 
Impregnation of Gas-Diffusion Electrodes 282 
10.8.9.3 The Preparation of Membrane Electrode 
Assemblies (MEAs) for Membrane Fuel Cells 283 
10.8.10 Electrodes for High-Temperature Fuel Cells 284 
10.8.10.1 Stability of Electrode Structures 
at High Temperatures 284 
10.8.11 Electrode Kinetics and Electrocatalysis in 
Molten-Carbonate Fuel Cells 285 
10.8.11.1 Anodic Hydrogen Oxidation 285 
10.8.11.2 Cathodic Oxygen Reduction 285 
10.8.12 Electrodes in Solid-Oxide Fuel Cells (SOFC) 287 
10.8.12.1 Electrodes and Electrode Structure 287 
10.8.12.2 The SOFC-Anode 287 
10.8.12.3 The SOFC-Cathode 288 
References 289 
Further Reading 289 
Chapter 11 
Industrial Processes 
11.1 Introductory Remarks 290 
11.2 Inorganic Electrolysis and Electrosynthesis 291 
11.3 Chloralkali-Electrolysis 291 
11.3.1 The Electrochemical Reaction 292 
11.3.2 Thermodynamics and Energy Demands 292 
11.3.3 Anodic Chlorine Evolution 293 
11.3.4 The Cathodic Reaction 294 
11.3.4.1 Cathodic Sodium Deposition in the Mercury Process 294 
11.3.4.2 Cathodic Hydrogen Evolution in the 
Diaphragm and Membrane Process 295 
11.4 Process Technologies 295 
11.4.1 The Amalgam Process 295 
11.4.2 The Diaphragm Process 297 
11.4.3 The Membrane Process 298 
11.4.3.1 Process-Flow Sheets 300 
11.4.3.2 Brine Recycling 302 
11.4.4 Gas Purification and Conditioning 303 
11.4.4.1 Chlorine 303 
11.4.4.2 Hydrogen 304 
11.4.5 Comparison of the Three Processes 304 
11.5 Hypochlorite, Chlorate and Chlorine Dioxide 306 
11.5.1 Production of Sodium Hypochlorite 306 
11.5.1.1 Electrolytic Generation of Hypochlorite 306 
11.5.1.2 Current Efficiency Losses 307 
11.5.2 Production of Sodium Chlorate 307 
11.5.2.1 Balance of Plant of Chlorate Electrosynthesis 310 
11.5.2.2 Construction Materials 311 
11.5.3 Chlorine Dioxide from Sodium Chlorate 311 
11.6 Perchloric Acid, Perchlorates, Peroxidsulfates 312 
11.6.1 Perchloric Acid 312 
11.6.2 Sodium Perchlorate 312 
11.6.3 Peroxidisulfates 313 
11.7 Fluorine 315 
11.8 Hydrogen by Water Electrolysis 316 
11.8.1 Technoeconomic Environment 316 
11.8.2 Thermodynamics and Technological Principles 
of Electrolytic Water Splitting 317 
11.8.3 Process Technologies 318 
11.8.4 Conventional Alkaline Water Electrolysis 320 
11.8.4.1 Monopolar Technology 320 
11.8.4.2 Bipolar Technology 320 
11.8.4.3 Improved Alkaline Technologies 323 
11.8.5 New Technologies 324 
11.8.5.1 Membrane Water Electrolysis 324 
11.8.5.2 Steam Electrolysis 324 
11.8.6 Economic Implications of Technical 
Innovations for Alkaline Water Electrolysis 325 
11.9 Electrowinning and Electrorefining of Metals 326 
11.9.1 Metal Electrowinning and Refining from 
Aqueous Electrolytes 326 
11.9.2 Copper Electrowinning and Electrorefining 330 
11.9.3 Nickel Electrowinning 331 
11.9.4 Nickel from the Chloride Leach Process 333 
11.9.5 Nickel Refining 334 
11.9.6 Zinc Electrowinning 334 
11.9.7 Lead Electrorefining 335 
11.10 Metal Electrowinning from Molten Salt Electrolytes 335 
11.10.1 General Considerations 335 
11.10.2 Aluminium Production  the HallHeroult Process 336 
11.10.2.1 The Melt 336 
11.10.2.2 Electrode Reactions 338 
11.10.3 The Cell 339 
11.10.4 Alkali Metals from Chloride Melts 341 
11.10.5 Magnesium Electrolysis 342 
11.10.5.1 Production of the Feed Salt 343 
11.10.5.2 Magnesium Electrolysis Cells 344 
11.11 Organic Electrosynthesis Processes 345 
11.11.1 General Overview 345 
11.11.2 Cell Types Used in Commercial Electroorganic 
Synthesis 347 
11.11.3 Process and Reaction Techniques of Some 
Examples of Industrial Organic Electrosyntheses 349 
11.11.3.1 Adipodinitrile Production by the Monsanto/Baizer 
Process 349 
11.11.3.2 Electrosynthesis of Sebacic Diesters by 
Kolbe Synthesis 352 
11.11.3.3 Benzaldehydes by Direct Anodic Oxidation 
of Toluenes 353 
11.11.3.4 The Selective Anodic Oxidation of L-Sorbose 
in Commercial Vitamin C Synthesis 353 
11.11.3.5 Anodic Formation of Perfluoro-Propylene Oxide 355 
11.12 Selected Electrochemical Procedures Outside the Chemical and 
Metallurgical Industries 357 
11.12.1 Electrochemical Wastewater Treatment by 
Electrodeposition and by Electroosmosis 357 
11.12.1.1 General Considerations 357 
11.12.1.2 Particular Cells for Removal of Metal Ions 
from Effluents 358 
11.12.1.3 Electrodialysis 361 
11.12.2 Electrochemical Surface Treatment and 
Shaping of Metals 362 
11.12.2.1 Electrochemical Shaping 362 
11.12.2.2 Electropolishing 363 
11.12.2.3 Electrochemical Machining (ECM) 365 
11.12.2.4 Electrochemical Grinding 366 
11.12.3 Electroreforming of Microdies and Microtools 
by the LIGA-Process 368 
References 369 
Further Reading 369 
Chapter 12 
Fuel Cells 
12.1 Fuel Cells as Gas Supplied Batteries 370 
12.2 Theoretical Efficiency of Hydrogen/Oxygen Fuel Cells 371 
12.3 Fuel Cell Types 373 
12.3.1 Low-Temperature Fuel Cells  Their Technological State 375 
12.3.1.1 Phosphoric-Acid Cells 375 
12.3.1.2 Membrane Cells 376 
12.3.1.3 Direct and Indirect Methanol-Combusting 
Membrane Cells 377 
12.3.1.4 Process Principles of the PAFCs and PEMFCs 
with Proton Conducting Electrolyte 378 
12.3.2 High-Temperature Fuel Cells 379 
12.3.2.1 Molten-Carbonate and Solid Oxide Fuel Cells 379 
12.3.2.2 Process Schemes of MCFCs and SOFCs 379 
12.3.2.3 Internal Reforming in High-Temperature Fuel Cells 380 
12.3.3 Cell Technologies of MCFCs and SOFCs 381 
12.3.3.1 Molten-Carbonate Fuel Cells 381 
12.3.3.2 Solid Oxide Fuel Cells 382 
12.3.3.3 The Westinghouse Technology 382 
12.3.4 Flat-Plate Solid Oxide Cells 384 
12.4 Current Voltage Curves of Different Fuel Cells 385 
12.5 Fuel-Cell Systems 387 
12.5.1 Phosphoric-Acid Fuel Cell / PC25 387 
12.5.2 Molten Carbonate Cells 390 
12.5.2.1 ERC-2 MW Plant 390 
12.5.2.2 Hot Module of MTU 390 
12.5.3 Proton Exchange Membrane Cells 391 
12.5.3.1 The Ballard Cell 392 
12.5.3.2 De Nora's Cell 394 
Further Reading 394 
Subject Index 395 
END
