Full
ZHANG Rui (2000-), male, Master candidate. E-mail: 2476095292@qq.com
Outline
Carbon aerogels can be used as exceptional carrier materials in many applications like energy storage, wastewater treatment, and electronics due to their large specific surface area and high porosity. However, some challenges such as high production costs, complex manufacturing processes and the use of toxic precursors hinder their applications. Lignin as a naturally abundant, environmentally friendly, and cost-effective aromatic polymer presents a promising solution, which can be used as a precursor for carbon aerogels. Recent studies focus on harnessing the unique chemical structure and reactive groups of lignin to develop high-performance and lignin-based carbon aerogels.
However, the widespread adoption of carbon aerogels is hindered by several challenges. The high costs for conventional preparation methods restrict their large-scale production mainly due to expensive precursors and complex manufacturing processes. Also, controlling the pore structure and morphology during synthesis remains a significant hurdle, affecting the consistency of their performance. To address these issues, some researchers turn their attention to lignin as a natural and abundant polymer. Lignin is cost-effective and environmentally friendly and features a complex chemical structure with numerous reactive functional groups, making it an ideal precursor for carbon aerogels. Significant progress has been achieved in the preparation techniques for lignin-based carbon aerogels. In the gelation process, some research efforts focus on optimizing reaction conditions to improve the degree of cross-linking in lignin. Researchers can tailor gel structures that serve as a foundation for the subsequent formation of the aerogel network via adjusting the types and quantities of initiators and cross-linkers. In the drying phase, multiple methods are explored. Freeze-drying is widely used due to its ability to largely preserve the original pore structure of gel, yielding carbon aerogels with a high porosity and a uniform pore distribution. Supercritical drying also offers some benefits in maintaining nanostructure though it requires specialized equipment and expensive solvents. Meanwhile, ambient drying is simple and great cost-effective ratio, which still has some challenges like uneven drying and structural shrinkage that need to be addressed. For carbonization, the temperature, rate and duration of this process significantly affect the final properties of the carbon aerogel. High-temperature carbonization can enhance carbon content and specific surface area. However, it also leads to pore collapse. A judicious combination of these parameters can yield carbon aerogels with optimized pore structures and improved mechanical properties.
In applications, lignin-based carbon aerogels have superior performance. In energy storage, they can enhance the capacitance and cycling stability of supercapacitors. Their extensive specific surface area provides more active sites for charge storage, and the porous structure facilitates rapid ion diffusion. As catalysts or catalyst supports, the high surface area and porous nature of lignin-based carbon aerogels effectively disperse active components, thereby improving catalytic activity and selectivity. In gas storage and separation, their well-defined pore structures enable the selective adsorption of specific gas molecules. In wastewater treatment, they efficiently remove various pollutants, including heavy metals, dyes, and organic contaminants, based on the physical and chemical adsorption mechanisms.
This review represents the preparation and application of lignin-based carbon aerogels. The gelation, drying, and carbonization processes are critical steps that determine the final properties of the carbon aerogel. Freeze-drying is a preferred drying method, and some efforts in this method should direct towards further reducing its energy consumption and costs. Precise control of the carbonization process is essential for achieving carbon aerogels with the desired pore structures and properties.
The gelation of lignin often requires considerable time, which hampers production efficiency. Also, the carbonization process is complex and difficult to control with precision, leading to inconsistencies in product quality. A future research should focus on modifying lignin to enhance its reactivity, thereby reducing gelation time. The development of more advanced composite templates for carbonization should facilitate a better control for pore structure. In addition, investigating novel methods to introduce functional groups into lignin-based carbon aerogels can broaden their applications in emerging fields like flexible electronics and biosensors.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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