Graphene Chemistry Theoretical Perspectives

What are the chemical aspects of graphene as a novel 2D material and how do they relate to the molecular structure? This book addresses these important questions from a theoretical and computational standpoint. 

Graphene Chemistry: Theoretical Perspectives presents recent exciting developments to correlate graphene’s properties and functions to its structure through state-of-the-art computational studies. This book focuses on the chemistry aspect of the structure-property relationship for many fascinating derivatives of graphene; various properties such as electronic structure, magnetism, and chemical reactivity, as well as potential applications in energy storage, catalysis, and nanoelectronics are covered. The book also includes two chapters with significant experimental portions, demonstrating how deep insights can be obtained by joint experimental and theoretical efforts. 

Topics covered include:

• Graphene ribbons: Edges, magnetism, preparation from unzipping, and electronic transport
• Nanographenes: Properties, reactivity, and synthesis
• Clar sextet rule in nanographene and graphene nanoribbons
• Porous graphene, nanomeshes, and graphene-based architecture and assemblies
• Doped graphene: Theory, synthesis, characterization and applications
• Mechanisms of graphene growth in chemical vapor deposition
• Surface adsorption and functionalization of graphene
• Conversion between graphene and graphene oxide
• Applications in gas separation, hydrogen storage, and catalysis

Graphene Chemistry: Theoretical Perspectives provides a useful overview for computational and theoretical chemists who are active in this field and those who have not studied graphene before. It is also a valuable resource for experimentalist scientists working on graphene and related materials, who will benefit from many concepts and properties discussed here.

Dr De-en Jiang, Chemical Sciences Division, Oak Ridge National Laboratory, USA
Dr Jiang has been working on computational study of graphene since 2006. In the past five years, he has published 15 papers in this topic which have been cited over 340 times. He has also written two book chapters on graphene-related topics. Using computational methods, he demonstrated the chemical reactivity of graphene's zigzag edge and showed the critical size for the onset of magnetism in nanographenes. Together with his colleagues, he was also the first to show a proof of concept for the extraordinary gas-separating power of porous graphene.

Dr Zhongfang Chen, Department of Chemistry, University of Puerto Rico, San Juan
Dr Chen is a computational chemist and computational nanomaterials scientist. He has published over 140 papers or book chapters and his papers have been cited more than 3200 times, giving him an h-index of 31. Nine papers have been highlighted by news media (Chem. & Eng. News and/or Nachrichten aus der Chemie, Nature China) and one article was featured by Nature Chemistry. Dr Chen has been involved in research on carbon graphene and its non-carbon analogues since 2008, and has published around 20 papers in this field so far. He is investigating the intrinsic properties of pristine and functionalized carbon and non-carbon graphenes, and exploring their applications in nanoelectronics, nanocatalysis and nanosensors.

Acknowledgements xxi

1 Introduction 1

De-en Jiang and Zhongfang Chen

2 Intrinsic Magnetism in Edge-Reconstructed Zigzag

Graphene Nanoribbons 9

Zexing Qu and Chungen Liu

2.1 Methodology 10

2.1.1 Effective Valence Bond Model 10

2.1.2 Density Matrix Renormalization Group Method 11

2.1.3 Density Functional Theory Calculations 12

2.2 Polyacene 12

2.3 Polyazulene 14

2.4 Edge-Reconstructed Graphene 17

2.4.1 Energy Gap 17

2.4.2 Frontier Molecular Orbitals 18

2.4.3 Projected Density of States 19

2.4.4 Spin Density in the Triplet State 20

2.5 Conclusion 22

Acknowledgments 23

References 23

3 Understanding Aromaticity of Graphene and Graphene Nanoribbons by the Clar Sextet Rule 29

Dihua Wu, Xingfa Gao, Zhen Zhou, and Zhongfang Chen

3.1 Introduction 29

3.1.1 Aromaticity and Clar Theory 30

3.1.2 Previous Studies of Carbon Nanotubes 33

3.2 Armchair Graphene Nanoribbons 34

3.2.1 The Clar Structure of Armchair Graphene Nanoribbons 34

3.2.2 Aromaticity of Armchair Graphene Nanoribbons and Band Gap Periodicity 37

3.3 Zigzag Graphene Nanoribbons 40

3.3.1 Clar Formulas of Zigzag Graphene Nanoribbons 40

3.3.2 Reactivity of Zigzag Graphene Nanoribbons 40

3.4 Aromaticity of Graphene 42

3.5 Perspectives 44

Acknowledgements 45

References 45

4 Physical Properties of Graphene Nanoribbons: Insights from First-Principles Studies 51

Dana Krepel and Oded Hod

4.1 Introduction 51

4.2 Electronic Properties of Graphene Nanoribbons 53

4.2.1 Zigzag Graphene Nanoribbons 53

4.2.2 Armchair Graphene Nanoribbons 56

4.2.3 Graphene Nanoribbons with Finite Length 58

4.2.4 Surface Chemical Adsorption 60

4.3 Mechanical and Electromechanical Properties of GNRs 63

4.4 Summary 66

Acknowledgements 66

References 66

5 Cutting Graphitic Materials: A Promising Way to Prepare Graphene Nanoribbons 79

Wenhua Zhang and Zhenyu Li

5.1 Introduction 79

5.2 Oxidative Cutting of Graphene Sheets 80

5.2.1 Cutting Mechanisms 80

5.2.2 Controllable Cutting 83

5.3 Unzipping Carbon Nanotubes 85

5.3.1 Unzipping Mechanisms Based on Atomic Oxygen 86

5.3.2 Unzipping Mechanisms Based on Oxygen Pairs 88

5.4 Beyond Oxidative Cutting 91

5.4.1 Metal Nanoparticle Catalyzed Cutting 92

5.4.2 Cutting by Fluorination 95

5.5 Summary 96

References 96

6 Properties of Nanographenes 101

Michael R. Philpott

6.1 Introduction 101

6.2 Synthesis 103

6.3 Computation 103

6.4 Geometry of Zigzag-Edged Hexangulenes 104

6.5 Geometry of Armchair-Edged Hexangulenes 107

6.6 Geometry of Zigzag-Edged Triangulenes 110

6.7 Magnetism of Zigzag-Edged Hexangulenes 112

6.8 Magnetism of Zigzag-Edged Triangulenes 114

6.9 Chimeric Magnetism 115

6.10 Magnetism of Oligocenes, Bisanthene-Homologs, Squares and Rectangles 117

6.10.1 Oligocene Series: C4m+2H2m+4 (na = 1; m = 2, 3, 4 . . .) 117

6.10.2 Bisanthene Series: C8m+4H2m+8 (na = 3; m = 2, 3, 4 . . .) 119

6.10.3 Square and Rectangular Nano-Graphenes: C8m+4H2m+8

(m = 2, 3, 4 . . .) 122

6.11 Concluding Remarks 122

Acknowledgment 123

References 124

7 Porous Graphene and Nanomeshes 129

Yan Jiao, Marlies Hankel, Aijun Du, and Sean C. Smith

7.1 Introduction 129

7.1.1 Graphene-Based Nanomeshes 130

7.1.2 Graphene-Like Polymers 130

7.1.3 Other Relevant Subjects 131

7.1.3.1 Isotope Separation 131

7.1.3.2 Van der Waals Correction for Density Functional Theory 132

7.1.3.3 Potential Energy Surfaces for Hindered Molecular Motions Within the Narrow Pores 133

7.2 Transition State Theory 134

7.2.1 A Brief Introduction of the Idea 134

7.2.2 Evaluating the Partition Functions: The Well-Separated “Reactant” State 136

7.2.3 Evaluating Partition Functions: The Fully Coupled 4D TS Calculation 137

7.2.4 Evaluating Partition Functions: Harmonic Approximation for the TS Derived Directly from Density Functional Theory Calculations 138

7.3 Gas and Isotope Separation 139

7.3.1 Gas Separation and Storage by Porous Graphene 139

7.3.1.1 Porous Graphene for Hydrogen Purification and Storage 139

7.3.1.2 Porous Graphene for Isotope Separation 140

7.3.2 Nitrogen Functionalized Porous Graphene for Hydrogen Purification/Storage and Isotope Separation 140

7.3.2.1 Introduction 140

7.3.2.2 NPG and its Asymmetrically Doped Version for D2/H2

Separation – A Case Study 141

7.3.3 Graphdiyne for Hydrogen Purification 144

7.4 Conclusion and Perspectives 147

Acknowledgement 147

References 147

8 Graphene-Based Architecture and Assemblies 153

Hongyan Guo, Rui Liu, Xiao Cheng Zeng, and Xiaojun Wu

8.1 Introduction 153

8.2 Fullerene Polymers 154

8.3 Carbon Nanotube Superarchitecture 156

8.4 Graphene Superarchitectures 160

8.5 C60/Carbon Nanotube/Graphene Hybrid Superarchitectures 163

8.5.1 Nanopeapods 163

8.5.2 Carbon Nanobuds 165

8.5.3 Graphene Nanobuds 168

8.5.4 Nanosieves and Nanofunnels 169

8.6 Boron-Nitride Nanotubes and Monolayer Superarchitectures 171

8.7 Conclusion 173

Acknowledgments 173

References 174

9 Doped Graphene: Theory, Synthesis, Characterization, and Applications 183

Florentino L´opez-Ur´?as, Ruitao Lv, Humberto Terrones, and Mauricio Terrones

9.1 Introduction 183

9.2 Substitutional Doping of Graphene Sheets 184

9.3 Substitutional Doping of Graphene Nanoribbons 194

9.4 Synthesis and Characterization Techniques of Doped Graphene 196

9.5 Applications of Doped Graphene Sheets and Nanoribbons 200

9.6 Future Work 201

Acknowledgments 202

References 202

10 Adsorption of Molecules on Graphene 209

O. Leenaerts B. and Partoens F. M. Peeters

10.1 Introduction 209

10.2 Physisorption versus Chemisorption 210

10.3 General Aspects of Adsorption of Molecules on Graphene 212

10.4 Various Ways of Doping Graphene with Molecules 215

10.4.1 Open-Shell Adsorbates 215

10.4.2 Inert Adsorbates 217

10.4.3 Electrochemical Surface Transfer Doping 220

10.5 Enhancing the Graphene-Molecule Interaction 221

10.5.1 Substitutional Doping 221

10.5.2 Adatoms and Adlayers 222

10.5.3 Edges and Defects 224

10.5.4 External Electric Fields 224

10.5.5 Surface Bending 225

10.6 Conclusion 226

References 226

11 Surface Functionalization of Graphene 233

Maria Peressi

11.1 Introduction 233

11.2 Functionalized Graphene: Properties and Challenges 236

11.3 Theoretical Approach 237

11.4 Interaction of Graphene with Specific Atoms and Functional Groups 238

11.4.1 Interaction with Hydrogen 238

11.4.2 Interaction with Oxygen 240

11.4.3 Interaction with Hydroxyl Groups 241

11.4.4 Interaction with Other Atoms, Molecules, and Functional Groups 245

11.5 Surface Functionalization of Graphene Nanoribbons 247

11.6 Conclusions 248

References 249

12 Mechanisms of Graphene Chemical Vapor Deposition (CVD) Growth 255

Xiuyun Zhang, Qinghong Yuan, Haibo Shu, Feng Ding

12.1 Background 255

12.1.1 Graphene and Defects in Graphene 255

12.1.2 Comparison of Methods of Graphene Synthesis 257

12.1.3 Graphene Chemical Vapor Deposition (CVD) Growth 257

12.1.3.1 The Status of Graphene CVD Growth 257

12.1.3.2 Phenomenological Mechanism 260

12.1.3.3 Challenges in Graphene CVD Growth 260

12.2 The Initial Nucleation Stage of Graphene CVD Growth 261

12.2.1 C Precursors on Catalyst Surfaces 262

12.2.2 The sp C Chain on Catalyst Surfaces 262

12.2.3 The sp2 Graphene Islands 263

12.2.4 The Magic Sized sp2 Carbon Clusters 264

12.2.5 Nucleation of Graphene on Terrace versus Near Step 266

12.3 Continuous Growth of Graphene 271

12.3.1 The Upright Standing Graphene Formation on Catalyst Surfaces 271

12.3.2 Edge Reconstructions on Metal Surfaces 273

12.3.3 Growth Rate of Graphene and Shape Determination 275

12.3.4 Nonlinear Growth of Graphene on Ru and Ir Surfaces 276

12.4 Graphene Orientation Determination in CVD Growth 278

12.5 Summary and Perspectives 280

References 282

13 From Graphene to Graphene Oxide and Back 291

Xingfa Gao, Yuliang Zhao, Zhongfang Chen

13.1 Introduction 291

13.2 From Graphene to Graphene Oxide 292

13.2.1 Modeling Using Cluster Models 292

13.2.1.1 Oxidative Etching of Armchair Edges 292

13.2.1.2 Oxidative Etching of Zigzag Edges 293

13.2.1.3 Linear Oxidative Unzipping 294

13.2.1.4 Spins upon Linear Oxidative Unzipping 296

13.3 Modeling Using PBC Models 297

13.3.1 Oxidative Creation of Vacancy Defects 297

13.3.2 Oxidative Etching of Vacancy Defects 298

13.3.3 Linear Oxidative Unzipping 299

13.3.4 Linear Oxidative Cutting 300

13.4 From Graphene Oxide back to Graphene 302

13.4.1 Modeling Using Cluster Models 302

13.4.1.1 Cluster Models for Graphene Oxide 302

13.4.1.2 Hydrazine De-Epoxidation 302

13.4.1.3 Thermal De-Hydroxylation 307

13.4.1.4 Thermal De-Carbonylation and De-Carboxylation 308

13.4.1.5 Temperature Effect on De-Epoxidation and De-Hydroxylation 309

13.4.1.6 Residual Groups of Graphene Oxide Reduced by Hydrazine and Heat 311

13.4.2 Modeling Using Periodic Boundary Conditions 312

13.4.2.1 Hydrazine De-Epoxidation 312

13.4.2.2 Thermal De-Epoxidation 313

13.5 Concluding Remarks 314

Acknowledgement 314

References 314

14 Electronic Transport in Graphitic Carbon Nanoribbons 319

Eduardo Costa Gir˜ao, Liangbo Liang, Jonathan Owens, Eduardo Cruz-Silva, Bobby G. Sumpter, Vincent Meunier

14.1 Introduction 319

14.2 Theoretical Background 320

14.2.1 Electronic Structure 320

14.2.1.1 Density Functional Theory 320

14.2.1.2 Semi-Empirical Methods 320

14.2.2 Electronic Transport at the Nanoscale 322

14.3 From Graphene to Ribbons 324

14.3.1 Graphene 324

14.3.2 Graphene Nanoribbons 325

14.4 Graphene Nanoribbon Synthesis and Processing 329

14.5 Tailoring GNR’s Electronic Properties 330

14.5.1 Defect-Based Modifications of the Electronic Properties 331

14.5.1.1 Non-Hexagonal Rings 331

14.5.1.2 Edge and Bulk Disorder 332

14.5.2 Electronic Properties of Chemically Doped Graphene Nanoribbons 332

14.5.2.1 Substitutional Doping of Graphene Nanoribbons 332

14.5.2.2 Chemical Functionalization of Graphene Nanoribbons 333

14.5.3 GNR Assemblies 334

14.5.3.1 Nanowiggles 334

14.5.3.2 Antidots and Junctions 335

14.5.3.3 GNR Rings 335

14.5.3.4 GNR Stacking 336

14.6 Thermoelectric Properties of Graphene-Based Materials 336

14.6.1 Thermoelectricity 336

14.6.2 Thermoelectricity in Carbon 336

14.7 Conclusions 338

Acknowledgements 339

References 339

15 Graphene-Based Materials as Nanocatalysts 347

Fengyu Li and Zhongfang Chen

15.1 Introduction 347

15.2 Electrocatalysts 347

15.2.1 N-Graphene 348

15.2.2 N-Graphene-NP Nanocomposites 350

15.2.3 Non-Pt Metal on the Porphyrin-Like Subunits in Graphene 351

15.2.4 Graphyne 352

15.3 Photocatalysts 353

15.3.1 TiO2-Graphene Nanocomposite 353

15.3.2 Graphitic Carbon Nitrides (g-C3N4) 355

15.4 CO Oxidation 356

15.4.1 Metal-Embedded Graphene 357

15.4.2 Metal-Graphene Oxide 358

15.4.3 Metal-Graphene under Mechanical Strain 359

15.4.4 Metal-Embedded Graphene under an External Electric Field 360

15.4.5 Porphyrin-Like Fe/N/C Nanomaterials 361

15.4.6 Si-Embedded Graphene 361

15.4.7 Experimental Aspects 361

15.5 Others 362

15.5.1 Propene Epoxidation 362

15.5.2 Nitromethane Combustion 362

15.6 Conclusion 363

Acknowledgements 364

References 364

16 Hydrogen Storage in Graphene 371

Yafei Li and Zhongfang Chen

16.1 Introduction 371

16.2 Hydrogen Storage in Molecule Form 373

16.2.1 Hydrogen Storage in Graphene Sheets 373

16.2.2 Hydrogen Storage in Metal Decorated Graphene 374

16.2.2.1 Lithium Decorated Graphene 375

16.2.2.2 Calcium Decorated Graphene 376

16.2.2.3 Transition Metal Decorated Graphene 377

16.2.3 Hydrogen Storage in Graphene Networks 377

16.2.3.1 Covalently Bonded Graphene 378

16.2.4 Notes to Computational Methods 381

16.3 Hydrogen Storage in Atomic Form 382

16.3.1 Graphane 382

16.3.2 Chemical Storage of Hydrogen by Spillover 383

16.4 Conclusion 386

Acknowledgements 386

References 386

17 Linking Theory to Reactivity and Properties of Nanographenes 393

Qun Ye, Zhe Sun, Chunyan Chi, and Jishan Wu

17.1 Introduction 393

17.2 Nanographenes with Only Armchair Edges 394

17.3 Nanographenes with Both Armchair and Zigzag Edges 397

17.3.1 Structure of Rylenes 398

17.3.2 Chemistry at the Armchair Edges of Rylenes 398

17.3.3 Anthenes and Periacenes 402

17.4 Nanographene with Only Zigzag Edges 405

17.4.1 Phenalenyl-Based Open-Shell Systems 406

17.5 Quinoidal Nanographenes 411

17.5.1 Bis(Phenalenyls) 412

17.5.2 Zethrenes 414

17.5.3 Indenofluorenes 417

17.6 Conclusion 417

References 418

18 Graphene Moir´e Supported Metal Clusters for Model Catalysis Studies 425

Bradley F. Habenicht, Ye Xu, and Li Liu

18.1 Introduction 425

18.2 Graphene Moir´e on Ru(0001) 426

18.3 Metal Cluster Formation on g/Ru(0001) 430

18.4 Two-dimensional Au Islands on g/Ru(0001) and its Catalytic Activity 434

18.5 Summary 440

Acknowledgments 441

References 441

Index

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