High-Performance Materials from Bio-based Feedstocks. Группа авторов

Chapter 4 for electrochemical applications.

      Surface modification of porous carbons can be carried out to incorporate heteroatoms and functional groups through different methods including surface oxidation, halogenation, sulfonation, grafting, and impregnation [18]. Oxygen‐containing moieties such as carboxylic acids and phenolic hydroxyl groups have been successfully introduced onto the carbon surface via oxidative modification [18]. Apart from oxygen, also the incorporation of N‐, S‐, and P‐containing groups has been widely investigated. Sulfonation has been carried out to introduce –SO₃H group to the porous structure, offering enhanced catalytic activity (Chapters 2 and 3). The incorporation of nitrogen‐containing pyridine‐N and pyrrole‐N into carbon electrodes improves the pseudocapacitance as well as catalytic activity for the oxygen reduction reaction in fuel cells (Chapter 4). The presence of phosphorus groups in biowastes can improve the pseudocapacitance of the carbon electrodes (Chapter 4).

Examples of other carbon materials that have been applied in energy storage applications include hard carbon, carbon nanofibers (CNFs), carbon nanotubes (CNTs), graphene, and carbon aerogels. Hard carbon can be produced from pyrolysis of biowastes such as fruit waste, sucrose, or glucose, and possesses a highly irregular and disordered carbon structure that make it a promising anode material for Na‐ion batteries [19]. The preparation of these carbons from biomass feedstocks and electrochemical applications are presented in Chapters 4 and 5. Production of biomass‐derived CNT and graphene and their catalytic performance are discussed in Chapter 2.

      Starbon^® is a special type of porous carbon with high mesoporosity, produced from polysaccharide hydrogels as structural templates. The relatively large pores (compared to the more traditional activated carbons) can effectively adsorb and desorb bulky molecules, showing promising applications as catalysts, catalyst supports, adsorbents, and recently as battery materials. Surface modification through sulfonation of Starbon^® is very promising for catalysis applications. Chapter 3 highlights the synthesis and properties of (modified) Starbon^® and its applications in adsorption and catalysis.

      The versatility, environmental compatibility, and high availability are the driving forces for using bio‐ and agricultural wastes as starting materials of bio‐based carbon materials. For high‐performance applications, (modified) porous carbons have shown tremendous benefits and will continue developing to meet new application demands. Surface modification is necessary to fully exploit the potential of carbon materials. The challenges include the large‐scale yet well‐controlled and cost‐effective synthesis approaches. In addition, the inconsistency of the feedstocks and contamination may adversely affect the performance. Another concern is that biomass feedstock should not compete with food supply. Lignocellulosic biomass is particularly interesting for material development and plays an important role, both now and in the future.

       1.2.2.3 Inorganic Materials Derived from Biomass

      The elements C, O, H, and N generally present the major organic constituents of biomass in the form of polysaccharides, proteins, lipids, or other molecules. In addition to these, biomasses may also contain a significant fraction of inorganic material. The inorganic fraction can be separated from the organic matrix by combustion in the form of ash, of which the amount and elemental composition vary greatly between biomass sources and combustion conditions [20, 21]. Most commonly, inorganic elements consist of Si, Ca, K, P, Al, Mg, Fe, S, Na, and Ti with different proportions depending on the biomass source [20].

      Biomasses such as rice husk contain relatively high amounts of Si, which can be extracted and used in various applications from energy storage to construction materials [22]. The successful use of Si derived from biomass is shown as anode material for Li‐ion batteries. A major challenge for Si‐based anodes is the low capacity retention, large volume change during lithium insertion/deinsertion process, and poor electrical conductivity, which can be partly overcome by using nanostructured materials [23]. Chapter 4 provides some critical perspectives on the application of biomass‐derived Si in Li‐ion batteries.

      Another potential use of biomass ashes is demonstrated in the production of construction materials. Removal of the organic matrix by controlled combustion produces Si‐rich ash that can be used to produce geopolymer materials as an alternative to traditional Portland cement [24]. These biomass ashes can substitute aluminosilicate sources instead of traditional fly ash from coal burning and leads to lower greenhouse gas production. Although large‐scale application of bio‐based inorganic materials is not available at the present time, the utilization of inorganic materials from biomasses is expected to increase with increasing environmental awareness. Challenges include the reduction of transportation cost of bulky biomass, and the inhomogeneity of ashes needs to be overcome to promote their usage. Various treatment options and applications of biomass ashes for geopolymer applications are discussed and assessed in Chapter 13.

1.3 Structure of the Book

      This book covers a wide range of bio‐based materials for high‐performance applications, including their processing and comparison to state‐of‐the‐art materials. First, Chapters 2–5 focus on the synthesis and applications of biomass‐derived carbons. Chapter 2 starts with presenting the characteristics of biomasses and their thermochemical conversion into carbon‐based catalysts and catalyst supports, with examples of their application in various reactions. Chapter 3 focuses on Starbon^®, a mesoporous carbonaceous material derived from waste polysaccharides. The unique properties of pristine and modified Starbon^® are highlighted with selected applications in adsorption and catalysis. Chapter 4 presents the conversion of biowastes into carbon electrodes through carbonization and activation, emphasizing the importance of biowaste selection, structure control, and heteroatom doping for optimizing electrochemical performance. The chapter also presents selected applications of carbon electrodes in various energy devices. Chapter 5 continues with applications of bio‐derived materials in electrochemical energy storage and conversion devices such as fuel cells, capacitors, batteries, and as alternative binders therein.

      Chapters 6–11 put emphasis on the extraction, modification, and applications of polysaccharides and other biopolymers for various applications in the environment and health. Chapter 6 presents the recent developments in biocompatible DES used to modify the mechanical, morphological, and chemical properties of bio‐derived materials. In addition, the use of DES in the formation of biocomposites and gels is discussed. In Chapter 7, biopolymer composites prepared from cellulose, alginate, chitosan, and lignin for the recovery of precious and heavy metals are presented. The adsorption performance of biopolymer composites with magnetic materials, polymers, and other materials are