Electrospining: Research progress in preparing lignin-based carbon nanofibers for supercapacitors using electrospinning technology

Background

The efficient utilization of biomass materials has become a research hotspot in the pursuit of green energy and environmentally friendly materials. Lignin is a complex amorphous polyphenolic biopolymer, a key structural material for most plant support tissues, and an important component of biomass materials. It is the second largest biomass resource in the plant kingdom after cellulose and an abundant renewable natural resource. It has a hydrophobic backbone composed of phenylpropane monomers. The high carbon content and extensively bridged polymer structure of lignin can be used to produce high-value products. In addition, lignin also has functional groups such as carbonyl, carboxyl, phenolic, and fatty hydroxyl groups. These groups give lignin hydrophilicity, antioxidant activity, antifungal activity, and free radical scavenging properties. These properties give lignin broad application prospects in the fields of food, cosmetics, electrochemistry, and medicine. However, only 2% of the lignin produced globally is used for commercial purposes, and the rest is burned as fuel. Therefore, increasing the added value of lignin to expand its application range is a challenge that currently requires rapid attention.

The main point of this paper

Value-added methods for lignin:

There are various methods for value-added of lignin, among which electrospinning technology is undoubtedly one of the leading methods. Electrospinning is a widely used and feasible technology for producing ultrafine fibers. It has become the focus of attention of the industry and researchers due to its simple manufacturing and setup

Advantages of electrospinning for preparing lignin fibers:

Electrospinning can effectively prepare micron and nanometer lignin fibers. Due to their relatively fast processing speed and the availability of green solvents, they have unparalleled advantages in terms of production cost and environmental protection of lignin fibers

Physicochemical properties of lignin fibers:

The lignin fibers prepared by electrospinning have small diameters and high specific surface areas. At the same time, due to the better orientation of lignin molecular chains, the lignin-based carbon fibers prepared on this basis have better mechanical properties

Potential of lignin as a precursor for carbon nanofibers:

Due to the high carbon content, low cost and renewability of lignin, lignin fibers are recommended as an attractive alternative to petroleum precursors to make carbon nanofibers (CNFs), which show great potential in the preparation of carbon-based functional materials

Application of lignin-based carbon nanofibers in supercapacitors:

The focus is on the preparation of lignin-based carbon nanofibers in supercapacitors using lignin fibers formed by electrospinning as precursors. Lignin-based carbon nanofibers have unique chemical stability, abundance and environmental friendliness, making them ideal for preparing high-performance supercapacitor electrode materials

Other methods for preparing lignin fibers:

Lignin nanofibers can also be prepared by melt spinning, solution spinning or other methods such as melt blowing, centrifugal spinning, drum spinning and reverse extrusion. The diameter, morphology and mechanical properties of lignin nanofibers obtained by these methods are different

Environmentally friendly supercapacitor electrode materials: preparation and application of lignin-based carbon nanofibers

High-value utilization of lignin and supercapacitors:

As an underutilized but promising environmentally friendly supercapacitor electrode material, lignin has unique chemical stability, abundance and environmental friendliness, and is an ideal choice for preparing high-performance supercapacitor electrode materials

Advantages of electrospinning technology:

Electrospinning technology is a technology for mass production of uniform lignin-based nanofibers, and is the simplest method for large-scale production of lignin-based nanofibers of a specific diameter. It has unparalleled advantages in production cost and environmental protection of lignin fibers

Preparation of lignin-based carbon nanofibers:

Lignin-based carbon nanofibers can be prepared by electrospinning technology and carbonized at different temperatures. Studies have shown that regardless of the carbonization temperature, all carbon nanofibers have a continuous and uniform structure, are dense and no phase separation is observed

Structure and properties of lignin-based carbon nanofibers:

Nanofibers carbonized at 800℃ or 1000℃ mainly contain amorphous carbon and some non-carbon elements. When the carbonization temperature is high (1200℃ or 1400℃), non-carbon elements are effectively removed to form nanocrystalline graphite, indicating that high-temperature carbonization is conducive to the formation of an ordered carbon structure

Application of lignin in supercapacitors:

Lignin-based carbon fibers are used in supercapacitors due to their excellent properties such as fast charging and discharging speed, high energy density and long cycle life.

Summarize

Electrospinning technology plays an important role in the development of various advanced lignin-based nanofibrous materials, on which basis, lignin nanocarbon fibers prepared by pre-oxidation and carbonization have broad application prospects. The application of supercapacitors is very interesting.

This paper starts with the description of lignin, introducing the definition, structure and properties of lignin. In the context of the increasing depletion of fossil fuel resources and the rapid development of biorenewable materials, lignin, as the second largest wood fibrous natural polymer after cellulose in reserves, has attracted more and more attention from the chemical, material and structural industries. A brief introduction is given to the history and background of the principle of electrospinning. Researchers around the world have contributed to the development of electrospinning by revealing the capabilities of the electrospinning process and discovering techniques and methods to overcome the limitations of this technology. Finally, the preparation of lignin-based nanofibers by electrospinning and the preparation of lignin-based carbon nanofibers by carbonization are reviewed for their applications in supercapacitors.

In general, lignin is a renewable resource, and its natural content is second only to cellulose, providing an inexhaustible raw material for the preparation of lignin-based carbon fibers. Lignin has strong physical and chemical properties and contains a large number of aromatic hydrocarbon benzene ring structures, which enables it to be prepared into carbon fibers to better maintain the original filament structure and obtain greater tensile strength. Lignin-based nanocarbon fibers prepared by electrospinning have high surface area, high porosity, high conductivity and excellent graphite content. The development of the preparation and properties of lignin-based nanocarbon fibers has greatly increased its application in technological applications, especially in energy storage.