Today's world is facing major challenges that directly affect our modern life. The de-mand for energy is expected to double by the year 2050. As a consequence of increased energy utilization the need is growing to protect our environment from the adverse ef-fects of pollution and the destruction of natural habitats. To ensure sufficient supply of clean water and air and to nourish the growing population without conflicts and poverty are additional global challenges. In this arena, the transformation of the fos-sil energy system into a sustainable operation and the technical increase of energy efficiency are key objectives of chemical sciences with their ability to create novel fu-els, materials and processes of molecular transformations. Using the energy of sun-light to split water into hydrogen as a clean energy source and storing energy in batter-ies and super capacitors are two popular examples of energy science. Both challenges critically involve the availability of novel carbon materials. Carbon is the most versa-tile chemical element for designing molecules and materials. It enables us to address a wide range of functional characteristics by varying the assembly of only one type of atoms interacting with each other in essentially only two binding modes, i. e. sp²/sp3 hybridization.
The unlimited number of combinations of the two basic bonding motives allows the realization of molecular and supra-molecular properties limited only by our imagi-nation. Hetero-atomic additions to the carbon backbone give additional chemical and structural diversity that needs exploitation in interface-controlled material science ap-plications. The interplay between combining building blocks of carbon and decorat-ing the products with hetero-elements forms the basis of a knowledge-based carbon material science. A critical strategy of material design is to combine carbon with other materials with diverging properties into spatial arrangements that create synergistic functions. Such materials, known as composites, were developed for carbon-based systems with the maturation of polymer science and are implemented today innu-merous products ranging from materials for packaging, dental and medical use, en-ergy production and storage, to structural materials for lightweight applications.
nanocarbon composites are multiphase materials, in which a nanostructured filler (i. e. particles, whiskers, fibers, nanotubes or lamellae) is dispersed in an organic (i. e. polymer) or inorganic (i. e. carbon, ceramic or metal) matrix. In the last few years, carbon in the form of nanotubes (CNTs) in addition to nanostructured fibers or as graphene has attracted wide interest as a filler for nanocomposites. Typical applica-tion profiles area high electrical conductivity in transparent conducting polymers or a remarkable fracture toughness reinforcing ceramics such as hydroxyapatite for bone replacement. Nanocomposites have a considerable impact on large-scale industrial applications of lightweight structural materials in aerospace and e-mobility, of elec-trically conducting plastics for electronic applications or as packaging materials with reduced gas permeability for foodstuff and air-sensitive goods.
nanocarbon hybrids area new class of composite materials in which the carbon nanostructures are compounded with thin layers of metals, semiconductors, inor-ganic glasses or ceramics. The carbon component gives ready access for gases and fluids to a large fraction of the inner surface area of the inorganic compound. In ad-dition, a large interface between two materials with different bulk properties allows for the design of materials with interface-dominated properties. Their special appeal arises from charge and energy transfer through this interface, giving rise to transport properties different from the linear combination of the respective bulk properties. Although still at a nearly stage of research, such hybrid materials have demonstrated potential in applications concerning energy conversion and environmental protec-tion. These include improved sensitivities in bio/chemical sensors, increased energy densities in batteries and larger capacities in super capacitors, higher current sinfield emission devices, more efficient charge separation and thus superior activities in photocatalysts and improved efficiencies in photovoltaics. AP\This book is dedicated exclusively to the family of nanocarbon hybrids covering a multidisciplinary research field that combines materials chemistry and physics with nanotechnology and applied energy sciences. It provides both introductory material on fundamental principles as well as reviews of the current research. Therefore, this book should be helpful for Master and PhD students wishing to become familiar with a modern field of knowledge-driven material science as well as for senior researchers and industrial staff scientists who explore the frontiers of knowledge.
The first part of this book introduces the concept of nanocarbons as building blocks. It establishes a scientific foundation for their subsequent use in hybrids and composites. Chapter 1 provides a concise introduction into the world of carbon nano-tubes (CNTs) , explaining their unique structural characteristics, synthesis routes and key characterization techniques. It summarizes the profile of exceptional properties of CNT. Chapter 2 concentrates on the synthesis and characterization of graphene-based materials, including single-layer and few-layer graphene as well as graphene oxide and its chemically/thermally reduced counterpart. The chapter further demonstrates that the dispersion of nanocarbons remains a key challenge for their implementa-tion into hybrids. Chapters 3 and 4 are dedicated to the post-synthesis processing of nanocarbons. In particular, Chapter 3 focuses on the chemical functionalization of CNTs, providing examples for a whole range of covalent and noncovalent functional-ization routes. Chapter 4 offers a comprehensive review on doping and filling of CNTs and the effect of defects on the hybridization of CNTs with polymers.
The second part of this book, comprising Chapter 5 to 10, is dedicated to the synthesis of nanocarbon hybrids and composites. Chapter 5 begins by identifying the general synthesis routes towards nanocarbon hybrids, which can be categorized into ex situ (i. e. "building block") and in situ approaches, and comparing their advantages and disadvantages on the basis of some of the most intriguing recent results. Ingen-eral, the ex situ route is a two-step process in which the inorganic compound is syn the-sized first, taking advantage of the existing wealth of knowledge in synthesizing nano-materials (i. e. structure-property relationship) . In a second step, the inorganic com-pound is linked to the nanocarbon surface via covalent, noncovalent or electrostatic interactions. In the in situ approach the inorganic or polymeric compound is grown on the (modified) nanocarbon surface from molecular precursors via (electro) chemical, vapor-based or physical deposition techniques, exploiting the stabilizing effects of nanocarbon as templates and as local heatsinks.
The examples discussed in Chapter 5 cover a wide range of synthetic aspects, yet concentrate on hybrids involving CNTs, while Chapter 6 summarizes recent de-velopments on the hybridization of graphene-based materials. Chapter 7on the other hand introduces sustainable carbon materials made from hydrothermal carbonization (HTC) as promising candidates for hybrid materials. Chapter 8 then combines nanocar-bons with polymers and documents that engineering the interfaces is a challenge that is equally important in the synthesis of nanocarbon hybrids and of carbon composites. The book section is concluded by Chapters 9 and 10, which are dedicated to specific examples of hybrids. Chapter 9 describes hybrids whose components are all carbon based, such as CNTs hybridized with graphene, while Chapter 10 discusses the incor-poration of graphene oxide into metal-organic framework structures (MOFs) .
The third part of the book highlights the potential of nanocarbon hybrids for various important applications, particularly concerning environmental and sustain-able energy applications. These include electrode materials in batteries and electro-chemical capacitors (Chapters 11 and 12) , sensors and emitters in field emission de-vices (Chapter 13) , electrocatalysts in fuel cells (Chapter 14) , supports for heteroge-neous catalysts (Chapter 15) , next-generation photocatalysts (Chapter 16) , as well as active compounds in electrochromic and photovoltaic applications (Chapters 17 and 18) . All these chapters discuss the benefits of nanocarbon hybrids in the respective ap-plication, identify major challenges and critically review the present state of research with the most intriguing recent developments. Finally, Chapter 19 elaborates on the importance of defects and edge atoms in graphene-based hybrid materials.
This book illustrates that nanocarbon hybrid materials are an exciting new class of multi-purpose composites with great potential to become the next-generation energy materials. The synergistic effects in nanocarbon hybrids are manifold and it is clear that a detailed fundamental understanding of their origins will be essential to exploit the options given by combining classes of materials with diverging properties.
We foremost express our deepest thanks to our colleagues who spent consider-able time and effort in writing the chapters in this book. We hope that this book will be useful to those interested in the subject of nanocarbon hybrids from many differ-ent perspectives and that it will establish a sound foundation for future research. We further would like to thank Julia Lauterbach and Karin Sora of De Gruyter Publishers for their tireless support and guidance. It is a particular pleasure to acknowledge the students of the Münster group for their invaluable help in proof-reading.
June 2014 Dominik Eder and Robert Schlögl

Preface v

Contributing authors xvii

Part I: Nanocarbon building blocks

Paul Gebhardt and Dominik Eder

1 A short introduction on carbon nanotubes 3

1.1 Introduction 3

1.2 Structural aspects 4

      1.2.1 Chirality 4

      1.2.2 Defects 5

      1.2.3 Doping 6

1.3 Properties of CNTs 7

      1.3.1 Mechanical properties 7

      1.3.2 Electronic properties 8

      1.3.3 Thermal properties 9

1.4 Characterization 10

1.5 Synthesis 11

      1.5.1 Laser ablation 12

      1.5.2 Arc discharge 12

      1.5.3 Molten salt route / electrolytic process 13

      1.5.4 Chemical vapor deposition (CVD) 13

1.6 Post-synthesis treatments 14

      1.6.1 Purification 14

      1.6.2 Separation of metallic and semiconducting CNTs 15

      1.6.3 Functionalization 16

      1.6.4 Assembly 18

1.7 Summary 18

Keith Paton

2 Synthesis, characterisation and properties of graphene 25

2.1 Introduction 25

2.2 Properties 25

2.3 Synthesis 26

      2.3.1 Micromechanical cleavage 26

      2.3.2 Liquid phase exfoliation 27

      2.3.3 Precipitation from metals/CVD 30

      2.3.4 Epitaxial growth from SiC 31

2.4 Characterization 32

Michele Melchionna and Maurizio Prato

3 Functionalization of carbon nanotubes 43

3.1 Introduction 43

3.2 Functionalization. Why? 44

3.3 Types of functionalization 46

      3.3.1 Covalent functionalization 46

      3.3.2 Noncovalent functionalization 54

3.4 Functionalization with metals 61

3.5 Summary 65

S.M. Vega-Diaz, F. Tristán López, A. Morelos-Gómez,R. Cruz-Silva, and M. Terrones

4 The importance of defects and dopants within carbon nanomaterials during the fabrication of polymer composites 71

4.1 Introduction 71

      4.1.1 Carbon nanostructures and their properties 72

      4.1.2 Doped carbon nanostructures 74

      4.1.3 Defects in carbon nanostructures 76

      4.1.4 Functionalization of carbon nanostructures for nanocomposites 79

4.2 Incorporation of nanocarbons into polymer composites and hybrids 83

      4.2.1 Types of polymer composites 83

      4.2.2 Synthesis approaches 86

4.3 Properties 89

      4.3.1 Mechanical properties 89

      4.3.2 Thermal properties 93

      4.3.3 Electrical properties 95

      4.3.4 Optical properties 97

      4.3.5 Biocompatibility 98

      4.3.6 Biodegradation 99

      4.3.7 Permeability 102

4.4 Summary 104

Part II: Synthesis and characterisation of hybrids

Cameron J. Shearer and Dominik Eder

5 Synthesis strategies of nanocarbon hybrids 125

5.1 Introduction 125

5.2 Ex situ approaches 127

      5.2.1 Covalent interactions 127

      5.2.2 Noncovalent interactions 129

5.3 In situ approaches 134

      5.3.1 In situ polymerization 135

      5.3.2 Inorganic hybridization from metal salts 137

      5.3.3 Electrochemical processes 142

      5.3.4 Sol-gel processes 146

      5.3.5 Gas phase deposition 148

5.4 Other nanocarbons 152

5.5 Comparison of synthesis techniques 153

5.6 Summary 154

C.N.R. Rao, H.S.S. Ramakrishna Matte, and Urmimala Maitra

6 Graphene and its hybrids with inorganic nanoparticles, polymers and other materials 171

6.1 Introduction 171

6.2 Synthesis 172

6.3 Nanocarbon (graphene/C60/SWNT) hybrids 175

6.4 Graphene-polymer composites 178

6.5 Functionalization of graphene and related aspects 182

6.6 Graphene-inorganic nanoparticle hybrids 185

6.7 Graphene hybrids with Sn02, MoS2 and WS2 as anodes in batteries 189

6.8 Graphene-MOF hybrids 192

6.9 Summary 195

Markus Antonietti, Li Zhao, and Maria-Magdalena Titirici

7 Sustainable carbon hybrid materials made by hydrothermal carbonization and their use in energy applications 201

7.1 Introduction 201

7.2 Hydrothermal synthesis of carbonaceous materials 202

      7.2.1 From pure carbohydrates 202

      7.2.2 From complex biomass 209

      7.2.3 Energy applications of hydrothermal carbons and their hybrids 210

7.3 Summary 221

Juan J. Vilatela

8 Nanocarbon-based composites 227

8.1 Introduction 227

8.2 Integration routes: From filler to other more complex structures 228

      8.2.1 Filler route 229

      8.2.2 Evaluation of reinforcement 230

      8.2.3 Other properties 232

8.3 Hierarchical route 235

      8.3.1 Structure and improvement in properties 236

      8.3.2 Other properties 238

8.4 Fiber route 240

      8.4.1 Different assembly routes 241

      8.4.2 Assembly properties and structure 243

      8.4.3 Assembly composites 245

      8.4.4 Other properties of nanocarbon assemblies 248

8.5 Summary 248

Robert Schlögl

9 Carbon-Carbon Composites 255

9.1 Introduction 255

9.2 Typology of C3 materials 256

9.3 Synthesis 259

9.4 Identification of the structural features of C3 material 264

9.5 Surface chemistry 266

9.6 Summary 268

Teresa J. Bandosz

10 Graphite oxide-MOF hybrid materials 273

10.1 Introduction 273

10.2 Building blocks 274

      10.2.1 Graphite oxide 274

      10.2.2 Metal Organic Frameworks: MOF-5, HKUST-1 and MIL-lOO(Fe) 275

10.3 Building the hybrid materials: Surface texture and chemistry 276

10.4 MOF-Graphite oxides composites as adsorbents of toxic gases 281

      10.4.1 Ammonia 282

      10.4.2 Nitrogen dioxide 284

      10.4.3 Hydrogen sulfide 286

10.5 Beyond the MOF-Graphite oxides composites 288

10.6 Summary 289

Part III: Applications of nanocarbon hybrids

Dang Sheng Su

11 Batteries/Supercapacitors: Hybrids with CNTs 297

11.1 Introduction 297

11.2 Application of hybrids with CNTs for batteries 298

      11.2.1 Lithium ion battery 298

      11.2.2 Lithium sulfur battery 307

      11.2.3 Lithium air battery 308

11.3 Application of hybrids with CNTs in supercapacitor 310

      11.3.1 CNT-based carbon hybrid for supercapacitors 311

      11.3.2 CNT-based inorganic hybrid for supercapacitors 313

11.4 Summary 314

Zhong-Shuai Wu, Xinliang Feng, and Klaus Müllen

12 Graphene-metal oxide hybrids for lithium ion batteries and electrochemical capacitors 319

12.1 Introduction 319

12.2 Graphene for LIBs and ECs 320

12.3 Graphene-metal oxide hybrids in LIBs and ECs 321

      12.3.1 Typical structural models of graphene-metal oxide hybrids 321

      12.3.2 Anchored model 323

      12.3.3 Encapsulated model 327

      12.3.4 Sandwich-like model 330

      12.3.5 Layered model 332

      12.3.6 Mixed models 335

12.4 Summary 336

John Robertson

13 Nanocarbons for field emission devices 341

13.1 Introduction 341

13.2 Carbon nanotubes- general considerations 343

      13.2.1 Field emission from nanocarbons 346

      13.2.2 Emission from nanowalls and CNTs walls 346

13.3 Applications 347

      13.3.1 Field emission electron guns for electron microscopes 347

      13.3.2 Displays 348

      13.3.3 Microtriodes and E-beam lithography 349

      13.3.4 Microwave power amplifiers 351

      13.3.5 Ionization gauges 352

      13.3.6 Pulsed X-ray sources and tomography 352

13.4 Summary 353

Panagiotis Trogadas and Peter Strasser

14 Carbon, carbon hybrids and composites for polymer electrolyte fuel cells 357

14.1 Introduction 357

14.2 Carbon as electrode and electrocatalyst 357

      14.2.1 Structure and properties 357

      14.2.2 Electrochemical properties 360

      14.2.3 Applications 362

14.3 Carbon, carbon hybrids and carbon composites in PEFCs 368

      14.3.1 Carbon as structural component in PEFCs 368

      14.3.2 Carbon as PEFC catalyst support 369

      14.3.3 Carbon hybrids and composites as ORR electrocatalysts 379

      14.4 Summary 385

Benjamin Frank

15 Nanocarbon materials for heterogeneous catalysis 393

15.1 Introduction 393

15.2 Relevant properties of nanocarbons 394

      15.2.1 Textural properties and macroscopic shaping 394

      15.2.2 Surface chemistry and functionalization 397

      15.2.3 Confinement effect 400

15.3 Nanocarbon-based catalysts 401

      15.3.1 Dehydrogenation of Hydrocarbons 402

      15.3.2 Dehydrogenations of alcohols 407

      15.3.3 Other reactions 410

15.4 Nanocarbon as catalyst support 412

      15.4.1 Catalyst preparation strategies 412

      15.4.2 Applications in heterogeneous catalysis 416

15.5 Summary 422

Gabriele Centi and Siglinda Perathoner

16 Advanced photocatalytic materials by nanocarbon hybrid materials 429

16.1 Introduction 429

      16.1.1 Hybrid vs. composite nanomaterials 430

      16.1.2 Use of nanocarbon hybrid materials in photoreactions 432

16.2 Nanocarbon characteristics 433

      16.2.1 The role of defects 435

      16.2.2 Modification of nanocarbons 437

      16.2.3 New aspects 437

      16.2.4 Nanocarbon quantum dots 438

16.3 Mechanisms of nanocarbon promotion in photoactivated processes 440

16.4 Advantages of nanocarbon-semiconductor hybrid materials 443

16.5 Nanocarbon-semiconductor hybrid materials for sustainable energy 447

16.6 Summary 448

Jiangtao Di, Zhigang Zhao, and Qingwen Li

17 Electrochromic and photovoltaic applications of nanocarbon hybrids 455

17.1 Introduction 455

17.2 Nanocarbon Hybrids for electrochromic materials and devices 456

      17.2.1 Intrinsic electrochromism of nanocarbons 456

      17.2.2 Synthesis and electrochromic properties of nanocarbon-metal oxide hybrids 457

      17.2.3 Electrochromic properties of nanocarbon-polymer hybrids 459

17.3 Nanocarbon hybrids for photovoltaic applications 461

      17.3.1 Working mechanisms of PECs and OPVs 461

      17.3.2 Nanocarbon hybrids for PECs 462

      17.3.3 Nanocarbon hybrids for OPVs 468

17.4 Summary 469

Rubén D. Costa and Dirk M. Guldi

18 Carbon nanomaterials as integrative components in dye-sensitized solar cells 475

18.1 Today's dye-sensitized solar cells. Definition and potential 475

18.2 Major challenges in improving the performance of DSSCs 477

18.3 Carbon nanomaterials as integrative materials in semiconducting electrodes 479

      18.3.1 Interlayers made out of carbon nanomaterials 479

      18.3.2 Implementation of carbon nanomaterials into electrode networks 480

18.4 Carbon nanomaterials for solid-state electrolytes 484

      18.4.1 Fullerene-based solid-state electrolytes 484

      18.4.2 CNTs-based solid-state electrolytes 485

      18.4.3 Graphene-based solid-state electrolytes 487

18.5 Versatility of carbon nanomaterials-based hybrids as novel type of dyes 488

      18.5.1 Fullerene-based dyes 488

      18.5.2 Graphene-based dyes 490

18.6 Photoelectrodes prepared by nanographene hybrids 492

      18.6.1 Preparation of photoelectrodes by using noncovalently functionalized graphene 492

      18.6.2 Preparation of photoelectrodes by preparing nanographene-based building blocks via electrostatic interactions 494

18.7 Summary 496

Ljubisa R. Radovic

19 Importance of edge atoms 503

19.1 Introduction 503

19.2 External edges 505

19.3 Internal edges 515

19.4 Edge reconstruction 519

19.5 Summary 522

Index 527

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