Photocatalytic Functional Materials for Environmental Remediation

DR. ALAGARSAMY PANDIKUMAR is Scientist at CSIR-Central Electrochemical Research Institute, Karaikudi, India. His current research involves development of novel materials with graphene, graphitic carbon nitrides, transition metal chalcogenides in combination with metals, metal oxides, polymers and carbon nanotubes for photocatalysis, photoelectrocatalysis, dye-sensitized solar cells, and electrochemical sensor applications. DR. KANDASAMY JOTHIVENKATACHALAM is Professor of Chemistry at Anna University, BIT campus, Tiruchirappalli, India. His research interests are photocatalysis, photoelectrochemistry, photoelectrocatalysis, and chemically modified electrodes.

List of Contributors xi

Preface xv

1 Titanium Dioxide and Carbon Nanomaterials for the Photocatalytic Degradation of Organic Dyes 1
Nagamalai Vasimalai

Abbreviations 1

1.1 Introduction 2

1.1.1 Impact of Dye Effluents on the Environment and Health 3

1.2 Principles and Mechanism of Photocatalysis 6

1.2.1 Direct Photocatalytic Pathways 7

1.2.1.1 The Langmuir–Hinshel Wood Process 8

1.2.1.2 The Eley–Rideal Process 8

1.2.2 Indirect Photocatalytic Mechanisms 8

1.3 Importance of Titanium Dioxide 9

1.3.1 Rutile 10

1.3.2 Anatase 10

1.3.3 Brookite 10

1.4 Titanium Dioxide for the Photocatalytic Degradation of Organic Dyes 11

1.4.1 Approaches Enhance the Photocatalytic Activity of TiO2 12

1.4.2 Metal and Multi‐Atom Doped TiO2 13

1.5 Carbon Nanomaterials for the Photocatalytic Degradation of Organic Dyes 15

1.5.1 Activated Carbon 16

1.5.2 Graphite 17

1.5.3 Graphene 19

1.5.4 Carbon Nanotubes and Fullerenes 20

1.5.5 Carbon Black 21

1.5.6 Carbon Nanofibers 22

1.5.7 Carbon Quantum Dots 22

1.5.8 Mesoporous Carbon 24

1.6 Conclusion and Trends 26

References 27

2 Visible Light Photocatalytic Degradation of Environmental Pollutants Using Metal Oxide Semiconductors 41

S. Thangaraj Nishanthi

2.1 Introduction 41

2.2 Photocatalysis 42

2.3 Mechanism and Fundamentals of Photocatalytic Reactions 42

2.4 Synthesis of Different Photocatalysts 44

2.4.1 Hydrothermal/Solvothermal Methods 45

2.4.2 Electrodeposition 46

2.4.3 Chemical Bath Deposition 46

2.4.4 Sol‐Gel Process 47

2.4.5 Chemical Precipitation 47

2.5 Factors Affecting Photocatalytic Degradation 47

2.5.1 Catalyst Loading 47

2.5.2 pH of the Solution 48

2.5.3 Size and Structure of the Photocatalyst 49

2.5.4 Reaction Temperature 49

2.5.5 Concentration and Nature of Pollutants 49

2.5.6 Inorganic Ions 50

2.6 Metal Oxide Semiconductors 50

2.7 Ternary/Quaternary Oxides 54

2.8 Composites Semiconductors 55

2.9 Sensitization 56

2.10 Conclusions 57

References 57

3 Contemporary Achievements of Visible Light‐Driven Nanocatalysts for the Environmental Applications 69

Panneerselvam Sathishkumar, Nalenthiran Pugazhenthiran, Ramalinga V. Mangalaraja, Kiros Guesh, David Contreras, and Sambandam Anandan

3.1 Introduction 69

3.1.1 Langmuir–Hinshelwood Approach 71

3.1.2 The Eley–Rideal Approach 71

3.1.3 Indirect Photocatalytic Approach 72

3.2 Types of Photocatalytic Reactor Models 73

3.3 Modification of Semiconductor Nanoparticles 90

3.3.1 Metal Nanoparticles 90

3.3.2 Non‐Metal Deposition 91

3.4 Emerging Photocatalysts 95

3.4.1 Perovskite Photocatalysts 95

3.4.2 C3N4‐Supported Photocatalysts 96

3.5 Mechanisms of Photocatalysis 99

3.6 Conclusion 116

References 121

4 Application of Nanocomposites for Photocatalytic Removal of Dye Contaminants 131

Sivaraman Somasundaram, Pitchaimani Veerakumar, King‐Chuen Lin, and Vignesh Kumaravel

4.1 Nanocomposites and Applications 131

4.2 Dyes: Introduction, Classification, and Impacts on the Environment 131

4.3 Strategies of Dye Contaminant Removal 133

4.4 Photodegradation and the Removal of Dyes Using Nanocomposites 134

4.4.1 Zeolite‐Based Nanocomposites 153

4.4.2 Clay‐Supported Nanocomposites 153

4.4.3 Polymer‐Based Nanocomposites 154

4.5 Photocatalytic Reactors for Dye Degradation 156

4.6 Summary 156

References 157

5 Photocatalytic Active Silver Phosphate for Photoremediation of Organic Pollutants 163

Sachin V. Otari and Hemraj M. Yadav

5.1 Introduction 163

5.2 Properties of Ag3PO4 165

5.2.1 Structural Features 165

5.2.2 Antimicrobial Properties 166

5.3 Photoremediation of Organic Pollutants 167

5.3.1 Effect of Morphology 168

5.3.1.1 Size and Structure of the Photocatalyst 168

5.3.1.2 Facet‐Dependent Photocatalysts 171

5.3.2 Effect of Composition 172

5.3.2.1 Carbon Materials 173

5.3.2.2 Semiconductor Materials 176

5.3.2.3 Magnetic Particles 179

5.3.2.4 Metal Particles 179

5.3.3 Doping Effect 182

5.4 Conclusions and Future Prospects 182

Acknowledgements 183

References 183

6 Plasmonic Ag‐ZnO: Charge Carrier Mechanisms and Photocatalytic Applications 191

Raghavachari Kavitha, Shivashankar Girish Kumar, and Channe Gowda Sushma

6.1 ZnO‐Based Photocatalysis 191

6.2 Why Deposit Silver on ZnO Surface? 192

6.3 Methods to Decorate Silver NPs on the Surface of ZnO 193

6.4 Mechanism of Charge Carrier Transfer Dynamics in Ag‐ZnO 197

6.4.1 Schottky Barrier and Charge Transfer Process 198

6.4.2 Surface Plasmon Resonance Effects 198

6.4.3 Defect Chemistry of Ag‐ZnO 199

6.5 Influence of Silver Content on Optimizing the Photocatalytic Activity 200

6.6 Structure–Morphology Relationship on Photocatalytic Activity 201

6.7 Co‐modification of Ag‐ZnO for Photocatalysis 204

6.8 Conclusion and Future Prospects 207

References 208

7 Multifunctional Hybrid Materials Based on Layered Double Hydroxide towards Photocatalysis 215

Lagnamayee Mohapatra and Dhananjaya Patra

7.1 Introduction 215

7.2 Hybrid LDHs from LDH Precursors 216

7.3 Photocatalytic Applications of Different LDH‐Based Hybrid Materials 217

7.3.1 LDH‐Based Mixed Metal Oxides (MMO) 221

7.3.2 Hybrid MMOs for Dye Degradation 225

7.3.3 LDH Nanocomposites 227

7.3.4 Intercalated LDH 231

7.4 Conclusions 233

References 234

8 Magnetically Separable Iron Oxide‐Based Nanocomposite Photocatalytic Materials for Environmental Remediation 243

Sakthivel Thangavel, Nivea Raghavan, and Gunasekaran Venugopal

8.1 Introduction 243

8.2 Synthesis Techniques for Magnetic Nanophotocatalyst Composites 246

8.3 Three Types of Semiconductor Magnetic‐Based Nanocomposites 249

8.4 Graphene‐Based Magnetically Separable Composites 251

8.4.1 Metal Di‐Chalcogenides‐Magnetic Nanocomposite Photocatalysts 252

8.4.2 Graphitic Carbon Nitride‐Based Magnetic Photocatalysts 254

8.5 The Effect of Iron Oxide‐Based Photocatalysts on Pollutants 255

8.5.1 Organic Dye Pollutant Degradation 255

8.5.2 Non‐Dye or Colorless Compounds 256

8.5.3 Heavy Metals 258

8.5.4 Pharmaceutical Waste 259

8.6 Summary 260

References 260

9 Photo Functional Materials for Environmental Remediation 267

Pazhanivel Devendran and Meenakshisundaram Swaminathan

9.1 Introduction 267

9.2 Photoelectric Effect 267

9.3 Photo Functional Materials (Photocatalysts) 268

9.4 Photodegradation of Textile Dyes 271

9.5 Semiconductor‐Based Photocatalysts 272

9.6 Carbon Nanotubes (CNTs) 274

9.7 Photo Functional Semiconductors on CNT Hybrid Materials for Tunable Optoelectronic Devices 275

9.8 Fabrication of CdS Quantum Dot Sensitized Solar Cells Using Nitrogen‐Functionalized CNTs/TiO2 Nanocomposites 276

9.9 Graphene Sheet 280

9.10 CdS/G Nanocomposites for Efficient Visible Light Driven Photocatalysis 281

9.11 Graphitic Carbon Nitride (g‐C3N4) 283

9.12 Conclusions 284

References 285

10 Graphitic Carbon Nitride‐Based Nanostructured Materials for Photocatalytic Applications 291

Jayaraman Theerthagiri, Kumaraguru Duraimurugan, Hyun‐Seok Kim, and Jagannathan Madhavan

10.1 Introduction 291

10.2 General Mechanism: Reaction Pathway 292

10.3 g‐C3N4 and Composites in Photocatalytic Degradation 294

10.4 Conclusions and Future Directions 304

Acknowledgements 305

References 305

11 Metal–Organic Frameworks for Photocatalytic Environmental Remediation 309

Mohan Sakar and Trong‐On Do

11.1 Introduction 309

11.2 Structural Features of MOFs 310

11.3 Synthesis of MOFs 312

11.3.1 Evaporation Method 313

11.3.2 Vapor Diffusion Method 313

11.3.3 Gel Crystallization Process 313

11.3.4 Solvothermal Synthesis 313

11.3.5 Microwave‐Assisted Synthesis 314

11.3.6 Sonochemical Methods 314

11.3.7 Electrochemical Synthesis 314

11.3.8 Mechanochemical Synthesis 315

11.4 Photocatalytic MOFs by Design 315

11.5 Photocatalytic Applications of MOFs 317

11.5.1 Degradation of Organic Pollutants 317

11.5.2 CO2 Reduction 320

11.5.3 Heavy Metal Reduction 323

11.5.4 Others 326

11.6 Conclusions and Future Prospects 327

Acknowledgements 329

References 329

12 Active Materials for Photocatalytic Reduction of Carbon Dioxide 343

Balasubramanian Viswanathan

12.1 Introduction 343

12.2 CO2 Photoreduction – Essentials 345

12.3 Heterogeneous Photocatalytic Reduction of Carbon Dioxide with Water 348

12.4 Nanomaterials and New Combinations of Materials for Carbon Dioxide Reduction 350

12.5 Selection of Materials 355

12.6 Material Modifications for Improving Efficiency 359

12.7 Perspectives in the Photocatalytic Reduction of Carbon Dioxide 363

Acknowledgements 367

References 367

Index 373