Synthesis and Electrochemical Performance of Biomass-Derived Carbons from Rice Husk and Seaweed for Energy Storage Applications = 쌀겨와 해조류로부터 얻은 바이오매스 유래 탄소의 합성 및 전기화학적 성능 연구: 에너지 저장 응용 분야

다국어 초록 (Multilingual Abstract)

The growing global demand for sustainable and high-performance energy storage systems has accelerated research into eco-friendly electrode materials. Traditional synthetic carbons, though widely used, often face limitations related to cost, complex synthesis, and environmental impact. Biomass-derived carbons have emerged as a promising alternative due to their abundance, renewability, low cost, and tunable structural and chemical properties. Agricultural residues and marine biomass, such as rice husk and seaweed, offer unique hierarchical structures and inherent heteroatoms, making them particularly suitable for a range of electrochemical energy storage applications. This thesis focuses on the synthesis, characterization, and application of biomass-derived carbons for advanced energy storage devices. Porous carbons were derived from rice husk and seaweed using tailored carbonization and activation methods, resulting in materials with high surface area, hierarchical porosity, and heteroatom doping. These features enhance charge storage, ion transport, and electronic conductivity, which are critical for improving device performance and longevity. The structural, morphological, and electrochemical properties of the synthesized carbons were systematically investigated. The study highlights the relationship between precursor type, synthesis conditions, and functional performance in energy storage systems. The results demonstrate that biomass-derived carbons can significantly enhance electrochemical behavior, providing high capacity, excellent rate capability, and long-term cycling stability. Overall, this work establishes biomass- derived carbons as versatile and sustainable electrode materials, offering a pathway toward eco-friendly, high-performance energy storage solutions. The findings contribute to the rational design of electrode materials from renewable resources, bridging the gap between sustainable material development and practical energy storage applications. In Chapter 1, the background and motivation for this study are presented, emphasizing the increasing demand for sustainable, high-performance energy storage systems and the limitations of conventional synthetic carbons in terms of cost, availability, and environmental impact. Biomass-derived carbons are introduced as a renewable and cost-effective alternative, offering tunable porosity, hierarchical structures, and intrinsic heteroatom functionalities. Lead–carbon batteries and zinc-ion capacitors are discussed as model devices to illustrate the potential of tailored biomass- derived carbons in enhancing electrochemical performance. The chapter also outlines the research objectives, including the development of scalable synthesis methods, optimization of carbon structure and composition, and evaluation of their influence on device performance, providing a comprehensive framework for the thesis. Chapter 2 reviews the existing literature on biomass-derived carbons and their applications in energy storage devices. Emphasis is placed on rice husk- and seaweed- based carbons, highlighting their natural abundance, hierarchical porosity, high surface area, and heteroatom content, which play a critical role in charge storage and ion transport. Recent advances in electrode design for lead–carbon batteries and zinc- ion capacitors are examined, focusing on strategies to suppress sulfation, enhance rate capability, and improve cycling stability. Research gaps are identified, particularly the need for environmentally friendly, scalable, and cost-effective approaches to produce high-performance biomass-derived carbons. In Chapter 3, the synthesis and characterization of rice husk-derived porous carbon nanosheets are described. The chapter discusses structural tuning through carbonization and activation to achieve high surface area, optimized pore distribution, and improved electronic conductivity. These carbons are applied as coating layers on negative electrodes of lead–carbon batteries, demonstrating significant improvements in charge acceptance, suppression of lead sulfate formation, and long-term cycling stability. Material characterization using SEM, TEM, XPS, Raman spectroscopy, and BET analysis is presented to correlate structural features with electrochemical performance, highlighting the potential of rice husk carbons as sustainable, high- performance electrode materials. Chapter 4 continues with the detailed study of rice husk-derived carbon batteries, analyzing the mechanisms behind sulfation suppression, enhanced electron transport, and improved cycle life. Comparative discussions with conventional carbon materials illustrate the advantages of biomass-derived carbons in practical battery applications. Chapter 5 focuses on seaweed-derived heteroatom-doped carbons as cathodes for aqueous zinc-ion capacitors. Seaweed was selected as a sustainable precursor with intrinsic heteroatoms and a naturally porous structure. Through controlled carbonization and activation, hierarchical porous carbons with enhanced surface area and redox-active sites were produced. Heteroatom functionalities (N, O, P) contribute to efficient Zn²⁺ ion adsorption, pseudocapacitive charge storage, and improved ion transport. Electrochemical testing demonstrates high specific capacitance, excellent rate performance, and long-term cycling stability, highlighting the effectiveness of seaweed-derived carbons for high-performance ZICs. Finally, Chapter 6 summarizes the key findings of the thesis, emphasizing the structure–property–performance relationships of rice husk and seaweed-derived carbons. The chapter outlines the contributions of this work to sustainable energy storage materials and proposes future research directions for scaling up biomass- derived carbons, exploring new biomass sources, and further enhancing electrochemical performance for next-generation energy storage devices.

목차 (Table of Contents)

• List of figures ........................................................................................................ vi
• List of Tables ......................................................................................................... xiii
• Abstract ................................................................................................................. xv
• Chapter 1. General Introduction ...................................................................... 1
• 1.1 Background and Research Motivation ............................................................ 2
• 1.2 Carbon Materials ............................................................................................. 5
• 1.2.1 Conventional Carbon Materials ................................................................... 5
• 1.2.2 Activated Carbon ......................................................................................... 8
• 1.3 Energy Storage Devices: An Overview .......................................................... 14
• 1.3.1 Theoretical Background of Carbon-Based Energy Storage Systems .......... 17
• 1.3.2 Lead–Carbon Batteries ................................................................................ 22
• 1.3.3 Zinc–Ion Capacitors ..................................................................................... 25
• 1.4 Scope and Objectives of the Thesis ................................................................ 28
• 1.5 References ....................................................................................................... 32
• Chapter 2. Review Of Literature ....................................................................... 38
• 2.1 Biomass as a Sustainable Carbon source ........................................................ 39
• 2.2 Synthetic Strategies for Biomass-Derived Porous Carbon Materials ............. 44
• 2.2.1 Pretreatment of Biomass Precursors ............................................................ 44
• 2.2.2 Carbonization Process .................................................................................. 45
• 2.3 Rice Husk-Derived Carbon Materials ............................................................. 53
• 2.3.1 Structure and Composition .......................................................................... 53
• 2.3.2 Applications in Energy Storage Device ....................................................... 59
• 2.4 Seaweed-Derived Carbon Materials ............................................................... 62
• 2.4.1 Structure and Heteroatom Composition ...................................................... 62
• 2.4.2 Applications for Energy Storage Device...................................................... 67
• 2.5 Biomass-Derived Carbons in Lead–Carbon Batteries and its Mechanism ..... 70
• 2.6 Biomass-Derived Carbons in Zinc-Ion Capacitors and its Mechanism .......... 75
• 2.7 Research Gaps ................................................................................................. 81
• 2.8 References ....................................................................................................... 84
• Chapter 3. Rice husk porous carbon as coating layer for the anode of lead
• carbon battery ..................................................................................................... 93
• 3.1 Introduction ..................................................................................................... 94
• 3.2 Material and chemicals ................................................................................... 96
• 3.3 Synthesis of Rice Husk carbon ....................................................................... 96
• 3.4 Effect of Silica in rice husk carbon ................................................................. 98
• 3.5 Effect of Lignin During Activation ................................................................. 99
• 3.6 Surface modifications ..................................................................................... 101
• 3.7 Characterization Techniques ........................................................................... 103
• 3.7.1 Structural and Morphological Analysis ....................................................... 103
• 3.7.2 Electrochemical Setup Testing for Hydrogen Evolution ............................. 103
• 3.8 Preparation of Active Electrodes, Cell Setup, and Evaluation of Battery
• Behaviour ............................................................................................................. 104
• 3.9 Results, Mechanistic Insights, and Discussion ............................................... 107
• 3.9.1 Structural Framework and Morphological Analysis .................................... 107
• 3.9.2 Electrochemical Performance ...................................................................... 122
• 3.9.3 Electrochemical Performance and Reaction Mechanisms of Thermally and
• Aminated RHAC Electrodes in Lead–Carbon Batteries In Lead–Carbon
• Batteries ................................................................................................................ 127
• 3.10 Conclusion .................................................................................................... 133
• 3.11 References ..................................................................................................... 135
• Chapter 4. Seaweed-Derived Nitrogen Porous Carbon Cathodes for Zinc-Ion
• Hybrid Supercapacitors ..................................................................................... 139
• 4.1 Introduction ..................................................................................................... 140
• 4.2 Experimental Section ...................................................................................... 142
• 4.2.1. Materials ..................................................................................................... 142
• 4.2.2. Synthesis of Seaweed-Derived Nitrogen-Doped Porous Carbon Nanosheets
• (SNPCNs) ............................................................................................................. 142
• 4.2.3. Effect of lignin during activation ................................................................ 144
• 4.2.4. Electrode preparation and Electrochemical Measurements ........................ 146
• 4.2.5. Measurements and Characterization ........................................................... 147
• 4.3 Results and discussion .................................................................................... 148
• 4.3.1 Characterization of prepared seaweed carbon ............................................. 148
• 4.3.2 Electrochemical Performance of Zn//SNPCN Capacitors ........................... 159
• 4.4 Conclusion ...................................................................................................... 169
• 4.5 References ....................................................................................................... 170
• Chapter 5. General Conclusion ......................................................................... 173
• 5.1 Summary of Key Findings .............................................................................. 175
• 5.2 Contributions of the Thesis ............................................................................. 177
• Korean abstract ..................................................................................................... 179
• Acknowledgement ................................................................................................ 181