Electrochemical activation of catalysis : promotion, electrochemical promotion, and metal-support interactions / Costas G. Vayenas ...[and others].

Format:

Book

Contributor:

Vayenas, C. G. (Costas G.)

Language:

English

Subjects (All):

Catalysis.

Electrocatalysis.

Physical Description:

xxxii, 574 pages : illustrations ; 26 cm

Place of Publication:

New York : Kluwer Academic/Plenum Publishers, [2001]

Summary:

This book describes the phenomenology, theory and potential applications of the phenomenon of electrochemical promotion, where electrochemically induced ion spillover activates and controls heterogeneous catalysis. The origin of electrochemical promotion is discussed in light of a plethora of surface spectroscopic and electrochemical techniques. Electrochemical and classical promotion are compared, their common rules are identified and promotional kinetics are rigorously modeled and compared with experiment.

Contents:

Chapter 1 Introduction, Brief History and Basic Concepts

1.1 The Phenomenon of Electrochemical Promotion 1

1.2 Basic Concepts and Terminology 8

1.3 Structure of This Book 10

Chapter 2 Promotion in Heterogeneous Catalysis

2.1.1 Catalysis, Chemical and Electrochemical Promotion: An Example 17

2.2 Chemisorption and Catalytic Kinetics 20

2.3 Catalytic Kinetics and Promoters 22

2.4 Interactions of Adsorbates Acting as Promoters or Poisons with Catalyst Surfaces 23

2.4.2 Electropositive (Electron Donor) and Electronegative (Electron Acceptor) Promoters 24

2.4.3 Electropositive Promoters: Alkali Metals 24

2.4.4 Electronegative Promoters 30

2.5 Adsorption on Surfaces Modified by Electropositive or Electronegative Promoters 35

2.5.1 Adsorption of Gases on Surfaces Modified by Alkali Promoters 35

2.5.2 Adsorption of Gases on Surfaces Modified by Electronegative Adatoms 56

2.6 Catalytic Activity on Surfaces Modified by Promoters or Poisons 72

2.6.1 CO Oxidation on Li-doped Pt(111) Surfaces 73

2.6.2 Ethylene Epoxidation 74

2.6.3 Synthesis Gas Conversion Reactions 77

2.7 Summarizing Comments and Rules 82

Chapter 3 Solid Electrolytes, Catalysis and Spillover

3.1 Solid Electrolytes 91

3.2 Solid Electrolyte Potentiometry (SEP) 94

3.3 Electrocatalytic Operation of Solid Electrolyte Cells 96

3.4 Spillover-backspillover Phenomena 101

3.4.1 Phenomenology 101

3.4.2 Mechanisms: Donor and Acceptor Phases 101

3.4.3 Thermodynamics and Kinetics of Spillover-Backspillover Between a Solid Electrolyte and a Metal Catalyst-Electrode 104

Chapter 4 Electrochemical Promotion of Catalytic Reactions

4.1 Experimental Setup 111

4.1.1 The Reactor and the Gas Analysis System 111

4.1.2 The Catalyst Film 113

4.1.3 Counter and Reference Electrodes 117

4.1.4 Quasireference Electrodes 118

4.2 Catalyst-Electrode Film Characterization 118

4.2.1 Catalytic Characterization: Measurement of the Metal/Gas Interface Area A[subscript G] 119

4.2.2 Electrochemical Characterization: Measurement of the Catalyst-Solid Electrolyte Exchange Current I[subscript 0] 121

4.3 A NEMCA Experiment: Galvanostatic and Potentiostatic Transients 128

4.3.1 Electrochemical Promotion Using O[superscript 2-] Conductors 128

4.3.2 Electrochemical Promotion Using Na[superscript +] Conductors 131

4.3.3 General Features and Comparisons 137

4.4 Catalyst Work Function Variation with Potential in Solid Electrolyte Cells 138

4.5 Definitions, Phenomenology and Key Aspects of Electrochemical Promotion 140

4.5.1 NEMCA Time Constant [tau] 140

4.5.2 Enhancement Factor or Faradaic Efficiency 141

4.5.3 Rate Enhancement Ratio [rho] 146

4.5.4 Promotion Index PI[subscript i] 148

4.5.5 Electrophobic and Electrophilic Reactions 151

4.5.6 Dependence of Catalytic Rates and Activation Energies on Catalyst Potential U[subscript WR] and Work Function [Phi] 152

4.5.7 Activation Energy and Preexponential Factor Dependence on Work Function 164

4.5.8 Selectivity Modification 168

4.5.9 Promotional Effects on Chemisorption 170

4.5.10 "Permanent NEMCA" 176

4.6 Prediction of the Magnitude of the Faradaic Efficiency 179

4.7 Synopsis of the Phenomenology: Reactions Studied so Far 181

Chapter 5 Origin of NEMCA

5.1 Problems and Methods 189

5.2 A Galvanostatic NEMCA Transient Revisited 191

5.3 Analysis of Rate Time Constants During Galvanostatic Transients 198

5.3.2 Time constants During Galvanostatic Transients and Faradaic Efficiency 200

5.3.3 Transient Analysis and Promotion Index 200

5.4 Work Function and Electrochemical Promotion 203

5.4.1 Work Function, Fermi Level, Vacuum Level, Galvani and Volta Potentials, Dipole Moments 203

5.4.2 The Work Function of Catalyst Films Deposited on Solid Electrolytes 205

5.4.3 The Work Function of Catalyst Films Deposited on Solid Electrolytes: Rationalization of the Potential-Work Function Equivalence 218

5.4.4 Spatial Variations 222

5.4.5 Transients and Measurement of Dipole Moments 223

5.4.6 Deviations from the Equality in the Changes of Extraction Potential and Electrode Potential 224

5.5 Temperature Programmed Desorption (TPD) 228

5.6 Solid Electrolyte Cyclic Voltammetry 233

5.6.1 Detection of Adsorbed Species 233

5.6.2 Potential Programmed Reduction 237

5.7 AC Impedance Spectroscopy 237

5.7.1 General Features 237

5.7.2 Measurement of the tpb Length 243

5.8 XPS Investigations 244

5.8.1 XPS in Catalysis and Solid State Electrochemistry 244

5.8.2 XPS Studies of Metals Supported on Na[superscript +] Conductors 254

5.9 UPS Investigations 255

5.10 SERS Investigations 256

5.11 PEEM Investigations 257

5.12 Scanning Tunelling Microscopy 259

5.12.1 Direct Atomic Scale Observation of Electrochemically Controlled Spillover/Backspillover 259

5.12.2 Ordered Promoter Adlattices and Electrochemical Promotion 264

5.13 Quantum Mechanical Calculations 267

5.14 The Effective Double Layer 271

Chapter 6 Rules and Modeling of Promotion

6.1 Electron Acceptor and Electron Donor Adsorbates 279

6.2 Electrophobic, Electrophilic, Volcano and Inverted Volcano Reactions: Rationalization, Rules, and Predictions 281

6.2.1 Similarities and Differences Between Electrochemical and Classical Promotion 283

6.2.2 Promotional Rules 285

6.2.3 Connection Between [Phi]and Adsorbate Coverage 295

6.2.4 Local Promotional Rules 296

6.2.5 Practical Considerations 298

6.3 Rationalization of the Promotional Rules 299

6.3.1 Derivation of the Experimental Local Rules L1 and L2 from the Fundamental Rules F1 and F2 299

6.3.2 Experimental Confirmation and First Principle Rationalization of Rules F1 and F2 300

6.3.3 Summary of Promotion Rules 302

6.4 Mathematical Modelling of Electrochemical Promotion and Classical Promotion 305

6.4.2 Adsorption in Presence of a Double Layer 306

6.4.3 Adsorption in Absence of Coadsorbing Species 312

6.4.4 Adsorption Isotherms, Nernst Equation and Potential-Work Function Equivalence 313

6.4.5 Catalytic Kinetics in Presence of a Double Layer 315

Chapter 7 The Absolute Potential

7.2 Absolute Potential Scales in Aqueous Electrochemistry 334

7.3 Absolute Potential Scale and Zero Energy Level of Electrons in Solid State Electrochemistry 336

7.3.1 The Nature of the Effective Double Layer 338

7.3.2 Experimental Establishment of the Absolute Potential Scale 340

7.4 The Work Function of Catalyst Films Deposited on Solid Electrolytes: Rationalization of the Potential-Work Function Equivalence 345

7.5 Definition and Properties of the Absolute Potential Scale in Solid Electrochemistry 351

7.6 Potential Distribution in a Solid Electrolyte Cell 356

7.7 Absolute Potential of Supported Catalysts 358

Chapter 8 Electrochemical Promotion with O[superscript 2-] Conductors

8.1 The Use of O[superscript 2-] Conductors 363

8.1.1 Complete Oxidation Reactions 363

8.1.2 Partial Oxidation Reactions 393

8.1.3 Dehydrogenation and Hydrogenation Reactions 403

8.1.4 NO Reduction Reactions 411

8.2 The Use of F[superscript -] Conductors 420

8.2.1 CO Oxidation on Pt/CaF[subscript 2] 420

8.3 The Use of Mixed Conductors 420

8.3.1 C[subscript 2]H[subscript 4] Oxidation on Pt/TiO[subscript 2] 420

8.3.2 C[subscript 2]H[subscript 4] Oxidation on Pt/CeO[subscript 2] 428

Chapter 9 Electrochemical Promotion with Cationic Conductors

9.1 The Use of Alkali Ion Conductors 435

9.1.1 Ethylene Oxidation on Pt/[beta]"-Al[subscript 2]O[subscript 3] 435

9.1.2 Ethylene Oxidation on Pt/NASICON 440

9.1.3 CO Oxidation on Pt/[beta]"-Al[subscript 2]O[subscript 3] 442

9.1.4 Ethylene Epoxidation on Ag/[beta]"-Al[subscript 2]O[subscript 3] 445

9.1.5 NO Reduction Studies on Pt/[beta]"-Al[subscript 2]O[subscript 3] 446

9.1.6 Benzene Hydrogenation on Pt/[beta]"-Al[subscript 2]O[subscript 3] 452

9.1.7 CO[subscript 2] Hydrogenation on Pd 453

9.1.8 Selective C[subscript 2]H[subscript 2] Hydrogenation on

Pt/[beta]"-Al[subscript 2]O[subscript 3] and Pd/[beta]"-Al[subscript 2]O[subscript 3] 453

9.1.9 NH[subscript 3] Decomposition on Fe/K[subscript 2]YZr(PO[subscript 4])[subscript 3] and on CaZr[subscript 0.9]In[subscript 0.1]O[subscript 3-[alpha] 456

9.1.10 Hydrogen Oxidation on Pt/glass 456

9.2 The Use of H[superscript +] Conductors 456

9.2.1 Hydrogen Oxidation on Pt/Nafion 456

9.2.2 Isomerization of 1-Butene on Pd-Black Cathodes/Nafion 117 466

9.2.3 Ethylene Cathodes Hydrogenation on Ni/CsHSO[subscript 4] 467

9.2.4 Ammonia Synthesis on Fe Supported on a Proton (CaZr[subscript 0.9]In[subscript 0.1]O[subscript 3-[alpha]) Conductor 468

9.2.5 Methane Dimerization Using Proton Conductors 470

9.2.6 C[subscript 2]H[subscript 4] Oxidation on Pt/CaZr[subscript 0.9]In[subscript 0.1]O[subscript 3-[alpha] 470

Chapter 10 NEMCA with Aqueous Electrolytes and Inorganic Melts

10.1 H[subscript 2] Evolution and Aldehyde Oxidation at Ib Metals in Alkaline Solutions 475

10.2 Hydrogen Oxidation on Pt in Aqeous Alkaline Solutions 476

10.3 Maleic Acid Hydrogenation on Pt in Aqueous Acidic Solutions 481

10.4 Production of Ammonium Polysulfide 482

10.5 SO[subscript 2] Oxidation in V[subscript 2]O[subscript 5]-K[subscript 2]S[subscript 2]O[subscript 7] Melts 482

Chapter 11 Electrochemical Promotion and Metal-Support Interactions

11.1 Metal-Support Interactions 487

11.2 Experimental Confirmation of the Mechanistic Equivalence of NEMCA and Metal-Support Interactions 490

11.3 Mathematical Modeling: Dimensionless Numbers Governing Electrochemical Promotion and Metal-Support Interactions 500

11.3.1 Modeling 501

11.3.2 Numerical Examples 507

11.3.3 Summary of Modelling Results 509

11.4 Interrelation of Promotion, Electrochemical Promotion and Metal-Support Interactions: The Double-Layer Model of Catalysis 509

Chapter 12 Practical Applications, Summary and Perspectives

12.1 Classical Promoter Selection 516

12.2 Material Cost Minimization: Dispersed and Commercial Catalysts 516

12.2.1 Electrochemical Promotion with Highly Dispersed Catalysts 518

12.2.2 Electrochemical Promotion of Commercial Catalysts 520

12.3 Bipolar Electrochemical Promotion 521

12.3.1 Electrochemical Promotion of C[subscript 2]H[subscript 4] Oxidation on Pt Using a Bipolar Design 521

12.3.2 Electrochemical Promotion of C[subscript 2]H[subscript 4] Oxidation on Pt Using Multi-Stripe and Multi-Dot Bipolar Catalysts 523

12.3.3 Electrochemical Promotion Using a Bipolar Monolithic Reactor 524

12.3.4 Electrochemical Promotion of Particulate Matter (Soot) Combustion Using a Ceria-Gadolinia Solid Electrolyte and a Dispersed Perovskite Catalyst 525

12.4 Summary and Perspectives 528

Appendix A Common Questions about Electrochemical Promotion

Appendix B Materials and Instrumentation for Starting Electrochemical Promotion Experiments

B.1 Catalyst-Electrodes, Solid Electrolytes 543

B.2 Instrumentation 547

B.3 Apparatus 550

B.4 Procedures 553.

Notes:

Includes bibliographical references and index.

ISBN:

0306467194

OCLC:

48140512