Carbon and Metal Oxides Based Nanomaterials for Flexible High Performance Asymmetric Supercapacitors (eBook)

Dr. Yating HU received both of her Bachelor and Doctoral degrees in Department of Materials Science and Engineering from the National University of Singapore (in the year of 2011 and 2017, respectively). From the year of 2011 to 2012, she worked as a process engineer in solar cell industry but her passion for research in materials science had driven her to come back to the university and pursue her Ph.D. degree. Her supervisor during Ph.D. studies is Prof. John Wang and her research focused on nanomaterials for energy storage application. She mainly used carbon, manganese oxides and iron oxides based materials to develop various electrodes for supercapacitors. After obtaining her Ph.D., she has been working as a research fellow in the same group. Currently, she is working on manganese compound based nanomaterials for energy storage and electrocatalysis applications.

Supervisor’s Foreword 6
Parts of this thesis have been published in the following journal articles:Y. Hu, H. Liu, Q. Ke and J. Wang, “Effects of nitrogen doping on supercapacitor performance of a mesoporous carbon electrode produced by a hydrothermal soft-templating process”. Journal of Materials Chemistry A, 2 (2014) 11753–11758.Y. Hu and J. Wang, “MnOx nanosheets for improved electrochemical performances through bilayer nano-architecting”. Journal of Power Sources, 286 (2015) 394–399.Y. Hu, C. Guan, G. Feng and J. Wang, “Flexible asymmetric supercapacitor based on structure-optimized Mn3O4/rGO nanohybrid paper with high energy and power density”. Advanced Functional Materials, 25(2015) 7291-7299.Y. Hu, C. Guan and J. Wang, “Hybrid Fe2O3 nano-cluster/rGO Paper as an Effective Negative Electrode for Flexible Supercapacitors”, Chemistry of Materials, 28 (2016) 7296–7303.Y. Hu, Y. Zhang, Y. Cai and J. Wang, “Controllable structure transitions of Mn3O4 nanomaterials and their effects on electrochemical properties”, Nanoscale Horizons, 2 (2017) 326–332. 8
Acknowledgements 9
Contents 10
List of Figures 13
List of Tables 19
Symbols 20
1 Introduction 22
1.1 Brief Overview of Supercapacitors 22
1.2 What Makes a Good Supercapacitor Electrode Material 23
1.3 Recent Advances and Challenges 25
1.3.1 Advantages of Supercapacitors 25
1.3.2 Challenges of Supercapacitors 26
1.3.3 Asymmetric Supercapacitors 27
1.3.4 Flexible Supercapacitors 28
1.4 Electrode Materials for Supercapacitors 30
1.4.1 Carbon Materials 30
1.4.1.1 Activated Carbons (ACs) 31
1.4.1.2 Graphene 31
1.4.1.3 Templated Mesoporous Carbon Materials (MCMs) 32
1.4.2 Conducting Polymers 32
1.4.2.1 Polyaniline 34
1.4.2.2 Polypyrrole 34
1.4.3 Transition Metal Oxides and Their Hybrids 35
1.4.3.1 Manganese Oxides 36
1.4.3.2 Manganese Oxides and Carbon-Based Hybrids 38
1.4.3.3 Ruthenium Oxides 41
1.4.3.4 Nickel Oxide/Hydroxide 42
1.4.3.5 Iron Oxides 43
1.5 Project Motivations and Designs 43
1.6 Research Objectives 45
References 46
2 Experimental Section 51
2.1 Materials 51
2.2 Materials Synthesis 51
2.3 Characterizations 52
2.3.1 Chemical and Composition Analysis 52
2.3.2 Morphological Studies 52
2.3.3 Electrochemical Measurements 53
3 Nitrogen Doping of Mesoporous Carbon Materials 54
3.1 Introduction 54
3.2 Synthesis Methods 55
3.3 Results and Discussion 56
3.3.1 Microstructure and Chemical Composition Characterizations 56
3.3.2 Electrochemical Characterizations 60
3.4 Remarks 65
References 65
4 Improving the Surface Area and Loading Mass of MnOx Based Electrode Materials 67
4.1 Introduction 67
4.2 Synthesis Methods and Electrochemical Characterizations 68
4.3 Results and Discussion 69
4.3.1 Characterizations of the First Layer of MnO2 Nanosheet 69
4.3.2 Bilayer Integration and Characterizations 71
4.4 Remarks 78
References 78
5 Mn3O4 Nanomaterials with Controllable Morphology and Particle Sizes 80
5.1 Introduction 80
5.2 Synthesis Methods 81
5.3 Results and Discussions 81
5.3.1 Temperature of Hydrothermal Growth 81
5.3.2 Tuning of Particle Sizes Through CTAB 84
5.3.3 Electrochemical Characterization of Mn3O4 Nanoparticles/rGO Hybrid 86
5.4 Remarks 88
References 89
6 Optimized Hybrid Mn3O4 Nanofiber/rGO Paper for High Performance Flexible ASCs 91
6.1 Introduction 91
6.2 Synthesis Methods 92
6.3 Results and Discussion 92
6.3.1 Electrochemical Reduction of Hybrid Mn3O4/GO Papers 92
6.3.2 Characterizations of the MG Papers 95
6.3.3 Electrochemical Performance of MG//rGO ASCs 97
6.3.3.1 Using Aqueous Electrolyte 98
6.3.3.2 Using Ionic Liquid Electrolyte 101
6.4 Remarks 102
References 105
7 Hybrid Fe2O3 Nanoparticle Clusters/rGO Paper for Flexible Supercapacitors 107
7.1 Introduction 107
7.2 Synthesis Methods 108
7.3 Results and Discussion 108
7.3.1 Fe2O3/rGO Characterizations 108
7.3.2 Electrochemical Characterizations of rGO and FG Papers 111
7.3.3 Asymmetric Supercapacitor and Electrochemical Tests 116
7.4 Remarks 119
References 119
8 Conclusions and Recommendations 121
8.1 Conclusions 121
8.2 Recommendations 123
References 124