This book systematically explores carbon nitride-based semiconductors for photocatalytic hydrogen production through water splitting. Beginning with fundamental concepts of hydrogen generation, it details modifications to pure g-C3N4 and interfacial engineering designs before examining various composite materials: CeO2/g-C3N4 nanocomposites demonstrate enhanced charge separation, while CoO nanoparticle integration improves visible-light absorption. The text analyzes N-doped ZnO/g-C3N4 heterojunctions, MnO2-loaded architectures for oxidative stability, and oxygen-deficient LaVO4/g-C3N4 systems. Advanced configurations include Co-C3N4/BiPO4 dual-cocatalysts, atomically dispersed Co-N4 sites in 2D frameworks, and B/P-doped variants for bandgap modulation, concluding with molten-salt synthesized Fe@C3N4 nanosheets. Each systems synthesis, characterization, mechanistic pathways, and hydrogen evolution performance are rigorously evaluated, culminating in forward-looking perspectives for next-generation photocatalyst development.
Chapter 1 Introduction 1
1.1 Hydrogen evolution 1
1.2 Modification of pure g-C3N4 2
Reference 5
Chapter 2 CeO2/g-C3N4 nanocomposite 7
2.1 Background 7
2.2 Preparation of CeO2/g-C3N4 composite 8
2.3 Characterization of CeO2/g-C3N4 composite 9
2.3.1 XRD of CeO2/g-C3N4 composite 9
2.3.2 TEM of CeO2/g-C3N4 composite 10
2.3.3 XPS of CeO2/g-C3N4 composite 12
2.3.4 UV-vis absorption and PL spectra of CeO2/g-C3N4 composite 15
2.4 Photocatalytic H2 generation testing of CeO2/g-C3N4 composite 16
2.4.1 Hydrogen production efficiency 16
2.4.2 Charge separation and transfer performance 19
2.4.3 Photocatalytic H2 evolution mechanism 20
2.5 Conclusion 21
Reference 22
Chapter 3 In-situ growing of CoO nanoparticles on g-C3N4 composite 27
3.1 Background 27
3.2 Preparation of CoO/g-C3N4 composite 28
3.3 Characterization of CoO/g-C3N4 composite 29
3.3.1 XRD of CoO/g-C3N4 composite 29
3.3.2 TEM of CoO/g-C3N4 composite 30
3.3.3 XPS of CoO/g-C3N4 composite 31
3.3.4 UV-vis absorption and PL spectra of CoO/g-C3N4 composite 33
3.4 Photocatalytic H2 generation testing of CoO/g-C3N4 composite 35
3.4.1 Hydrogen production efficiency 35
3.4.2 Charge separation and transfer performance 37
3.4.3 Mechanism of hydrogen production 39
3.5 Conclusion 40
Reference 40
Chapter 4 ZnO/g-C3N4 with N dopant 44
4.1 Background 44
4.2 Preparation of ZnO/g-C3N4 with N dopant 45
4.3 Characterization of ZnO/g-C3N4 with N dopant 46
4.3.1 TEM of ZnO/g-C3N4 with N dopant 46
4.3.2 XRD of ZnO/g-C3N4 with N dopant 47
4.3.3 XPS of ZnO/g-C3N4 with N dopant 48
4.3.4 UV-vis absorption and PL spectra of ZnO/g-C3N4 with N dopant 53
4.4 Photocatalytic activity testing of ZnO/g-C3N4 with N dopant 54
4.4.1 Hydrogen production and NO removal efficiency 54
4.4.2 Charge separation and transfer performance 57
4.4.3 Mechanism of enhanced photocatalytic activity 59
4.5 Conclusion 60
Reference 61
Chapter 5 Manganese dioxides with different exposed crystal plane supported on g-C3N4 65
5.1 Background 65
5.2 Preparation of MnO2/g-C3N4 composite 66
5.3 Characterization of MnO2/g-C3N4 composite 67
5.3.1 XRD of MnO2/g-C3N4 composite 67
5.3.2 TEM of MnO2/g-C3N4 composite 68
5.3.3 UV-vis absorption and PL spectra of MnO2/g-C3N4 composite 69
5.3.4 XPS and EPR of MnO2/g-C3N4 composite 71
5.4 Photocatalytic H2 generation testing MnO2/g-C3N4 composite 75
5.4.1 Hydrogen production efficiency 75
5.4.2 Charge separation and transfer performance 76
5.4.3 Mechanism of hydrogen production 78
5.5 Conclusion 79
Reference 80
Chapter 6 LaVO4/g-C3N4 composite with oxygen defect 82
6.1 Background 82
6.2 Preparation of LaVO4/g-C3N4 composite 83
6.3 Characterization of LaVO4/g-C3N4 composite 84
6.3.1 XRD of LaVO4/g-C3N4 composite 84
6.3.2 TEM of LaVO4/g-C3N4 composite 85
6.3.3 XPS of LaVO4/g-C3N4 composite 87
6.3.4 UV-vis absorption and PL spectra of LaVO4/g-C3N4 composite 91
6.4 Photocatalytic water splitting testing 93
6.4.1 Water splitting efficiency 93
6.4.2 Charge separation and transfer performance 95
6.4.3 Mechanism of water splitting 96
6.5 Conclusion 98
Reference 99
Chapter 7 Co-C3N4/BiPO4 composite 101
7.1 Background 101
7.2 Preparation of Co-C3N4/BiPO4 composite 102
7.3 Characterization of Co-C3N4/BiPO4 composite 103
7.3.1 XRD of Co-C3N4/BiPO4 composite 103
7.3.2 TEM of Co-C3N4/BiPO4 composite 104
7.3.3 XPS of Co-C3N4/BiPO4 composite 106
7.3.4 UV-vis absorption and PL spectra of Co-C3N4/BiPO4 composite 109
7.4 Photocatalytic water splitting testing Co-C3N4/BiPO4 composite 111
7.4.1 Water splitting efficiency 111
7.4.2 Charge separation and transfer performance 113
7.4.3 Mechanism of hydrogen production 115
7.5 Conclusion 116
Reference 116
Chapter 8 Atomic Co-N4 sites in 2D polymeric carbon nitride 119
8.1 Background 119
8.2 Preparation of Atomic Co-N4 sites in 2D polymeric carbon nitride 120
8.3 Characterization of Co1@2DPCN 121
8.3.1 XRD of Co1@2DPCN 121
8.3.2 FT-IR, BET, SEM and TEM of Co1@2DPCN 123
8.3.3 HAADF-STEM, EXAFS, XPS of Co1@2DPCN 126
8.3.4 Optical and electrochemical properties assessment 131
8.4 Photocatalytic performance 132
8.4.1 Photocatalytic H2 generation testing 132
8.4.2 Density functional theory calculations 135
8.5 Conclusion 138
Reference 138
Chapter 9 B and P doped g-C3N4 142
9.1 Background 142
9.2 Facile synthesis of B and P doped g-C3N4 143
9.3 Characterization of B and P doped g-C3N4 143
9.3.1 XRD, SEM and TEM of B and P doped g-C3N4 143
9.3.2 UV-vis absorption 146
9.3.3 PL spectra of B and P doped g-C3N4 148
9.3.4 XPS of B and P doped g-C3N4 149
9.4 Photocatalytic activity testing 152
9.4.1 Hydrogen production efficiency 152
9.4.2 Charge separation and transfer performance 155
9.4.3 Enhanced photocatalytic mechanism 158
9.5 Conclusion 159
Reference 159
Chapter 10 Molten salt preparation of Fe@C3N4 nanosheets 161
10.1 Background 161
10.2 Preparation of Fe@C3N4 162
10.3 Characterization of Fe@C3N4 163
10.3.1 XRD, SEM and TEM of Fe@C3N4 163
10.3.2 UV-vis spectroscopy of Fe@C3N4 165
10.3.3 PL spectroscopy of Fe@C3N4 166
10.3.4 XPS of Fe@C3N4 167
10.4 Photocatalytic activity testing of Fe@C3N4 170
10.4.1 Hydrogen production efficiency 170
10.4.2 EPR, DFT and charge separation and transfer performance 172
10.4.3 Mechanism of hydrogen production 175
10.5 Conclusion 176
Reference 176
Preface
Nowadays, global environmental issues and energy crises are attracting significant attention worldwide. As fundamental non-renewable energy sources, coal and oil face depleting reserves due to accelerated extraction rates driven by rapid societal development. In this context, China faces growing challenges in energy transition. Hydrogen energy emerges as a promising solution, possessing high renewability potential, exceptional combustibility, abundant availability, and large-scale storage capacity. Particularly, photocatalytic water splitting technology enables solar-to-hydrogen energy conversion through semiconductor catalysts without generating secondary pollution.
Among non-metallic semiconductor materials, graphitic carbon nitride (g-C3N4) demonstrates significant potential for photocatalytic hydrogen production. However, pure carbon nitride exhibits inherent limitations including limited specific surface area, inefficient photoinduced charge carrier migration, narrow spectral absorption range, and rapid electron-hole recombination, resulting in suboptimal photocatalytic hydrogen production efficiency. This monograph focuses on enhancing light absorption/utilization efficiency and suppressing charge recombination in carbon nitride through strategic doping modification and heterojunction construction, while systematically analyzing the photocatalytic mechanisms of carbon nitride-based materials.
This publication aims to provide researchers in photocatalytic water splitting with comprehensive preparation methodologies and application guidelines for carbon nitride-based materials, offering scientific foundation and technical references for advancing this field. The content synthesizes extensive research literature, with substantive contributions from multiple authors: Liu Xuecheng (Chapters 1-3, 100,000 words), Yao Bin (Chapters 4-6, 100,000 words), Qi Ning (Chapters 7-8, 50,000 words), and Xu Hanyu (Chapters 9-10, 50,000 words).
We gratefully acknowledge the academic publication fund support from Chongqing Technology and Business University. The monograph was revised and compiled by Liu Xuecheng. Due to the limited level of the editor, there may be inappropriate content selection and wording in the book. We kindly ask readers and peers to criticize and correct us.
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