Lignin-based Carbon Nanofibers Research Articles

Preparation, performance enhancement, and energy storage applications of lignin-based carbon nanofibers

Preparation, performance enhancement, and energy storage applications of lignin-based carbon nanofibers

Preparation of flexible and binder-free lignin-based carbon nanofiber electrode materials by electrospinning in aqueous system

Abstract Lignin, as a widely distributed, renewable and environmentally friendly source of carbon, could been utilized for carbon nanofibers to not only maximize the usage of resources, but also expand the energy-related opportunities. In this research, flexible lignin-based carbon nanofibers are prepared by electrospinning lignin nanofibers in a new green aqueous solution of lignin and polyvinyl alcohol (PVA), which is then characterized by physical and chemical characterizations. The results reveal that optimal carbonization temperature of 800 °C shows great improvements on the structural properties of lignin-based carbon nanofibers, which can be applied as binder-free electric double layer capacitor (EDLC) electrodes with good flexibility. The 2032 type button battery has a superior electrochemical performance with a large specific capacitance of 217.2 F g−1 at a 0.2 A g−1 current density, and remarkable cyclic stability of 94.9 % capacitance retention even after 10,000 charge and discharge cycles, due to the abundance of mesoporous volume and large microporous surface area of lignin-based carbon nanofiber electrodes carbonized in 800 °C.

Preparation and characterization of bifunctional wolfsbane-like magnetic Fe3O4 nanoparticles-decorated lignin-based carbon nanofibers composites for electromagnetic wave absorption and electrochemical energy storage

Recently, with the pursuit of high-efficiency electromagnetic wave absorption (EMWA) and electrochemical energy storage (EES) materials, multifunctional lignin-based composites have attracted significant interest due to their low cost, vast availability, and sustainability. In this work, lignin-based carbon nanofibers (LCNFs) was first prepared by electrospinning, pre-oxidation and carbonization processes. Then, different content of magnetic Fe3O4 nanoparticles were deposited on the surface of LCNFs via the facile hydrothermal way to produce a series of bifunctional wolfsbane-like LCNFs/Fe3O4 composites. Among them, the synthesized optimal sample (using 12 mmol of FeCl3·6H2O named as LCNFs/Fe3O4–2) displayed excellent EMWA ability. When the minimum reflection loss (RL) value achieved −44.98 dB at 6.01 GHz with an thickness of 1.5 mm, and the effective absorption bandwidth (EAB) was up to 4.19 GHz ranging from 5.10 to 7.21 GHz. For supercapacitor electrode, the highest specific capacitance of LCNFs/Fe3O4–2 reached 538.7 F/g at the current density of 1 A/g, and the capacitance retention remained at 80.3 %. Moreover, an electric double layer capacitor of LCNFs/Fe3O4–2//LCNFs/Fe3O4–2 also showed a remarkable power density of 7755.29 W/kg, outstanding energy density of 36.62 Wh/kg and high cycle stability (96.89 % after 5000 cycles). In short, the construction of this multifunctional lignin-based composites has potential applications in electromagnetic wave (EMW) absorbers and supercapacitor electrodes.

Automated trackspinning of aligned lignin fibers as precursors of green carbon nanofibers

At present, most carbon fibers are made from non-renewable polyacrylonitrile. Substantial efforts have been made to replace petroleum-based precursors for carbon fiber production. Interestingly, lignin is a carbon fiber precursor material that is cheap, highly available and sustainable. Submicron-scale lignin-based carbon nanofibers are used in numerous areas, such as electronic devices, batteries, supercapacitors and low-cost, high-performance structural composite materials. Trackspinning (TS) technology offers a way to scale up the versatile, but inefficient contact drawing technique to produce small-diameter lignin fibers from environmentally friendly aqueous solutions. In this study, the effects of TS based on probe drawing of low-concentration lignin nanofibers blended with poly(ethylene oxide) and glycerol in sodium hydroxide (NaOH) solution were investigated. The TS lignin fibers were well aligned and reached diameters as small as 500–1000 nm as the drawing length was increased. Lignin fiber macromolecular alignment was isotropic at low levels of draw, and the dichroic ratio increased from 1 to 2.25 with doubling of the drawing length. The most highly drawn trackspun lignin fibers had a mechanical strength of 3.92 MPa and a Young’s modulus of 2.15 GPa, which were similar to reported values for solvent-electrospun lignin nanofibers. These findings support the potential to utilize TS to produce small-diameter lignin fibers using a simple aqueous solvent approach.

Synthesis and characterization of lignin-based carbon nanofiber supported Platinum–Ruthenium nanoparticles obtained from wood sawdust and applications in alcohol fuel cells

Direct alcohol fuel cells (DAFC) are an interesting topic today and many studies are being carried out on their development. In this study, the PtRu catalyst was developed by carbon nanofibers (CNF), which are thought to be highly effective in increasing the active surface area for alcohol oxidation in fuel cells. The methanol and ethanol oxidation electrocatalytic activities of synthesized CNF-supported Platinum–Ruthenium (PtRu@CNF) nanoparticles were investigated. In alcohol oxidation measurements of CNF-supported Pt–Ru nanoparticles; The ratio of diffusion efficiency, oxidation potential, forward oxidation peak current density, and forward peak current density to reverse peak current density was found to be quite good. The forward peak current densities of ethanol and methanol oxidation for the synthesized PtRu@CNF catalyst were found to be 29.17 mA/cm2 and 48.14 mA/cm2, respectively. The prepared PtRu@CNF nanoparticles have high conductivity, low onset potential, and high electrochemical surface area (ECSA; 20.30 cm2) as a suitable catalyst for the DAFCs.

Construction of self-supporting ultra-micropores lignin-based carbon nanofibers with high areal desalination capacity

Lignin is a renewable biomacromolecule that can be used as precursors for carbon materials. In this work, highly flexible lignin-based carbon nanofibers with abundant ultra-micropores are constructed via electrospinning, oxidative stabilization and carbonization. The results indicate that replacing PAN with 80 % lignin is feasible in regulating ultra-micropores. The synthesized L4P1-CNFs possess many attractive properties (e.g., pore size distribution, electrochemical and deionization property) compared with that produced from other non-renewable precursors or more-complexed processes. It shows excellent electrochemical double-layer capacitance in 6 M KOH (233 to 162 F g−1 at 0.5 to 5 A g−1) and 1 M NaCl (158 to 82 F g−1 at 0.5 to 5 A g−1) electrolytes. Upon assembling into CDI cells, the average salt adsorption rate could reach 1.79 mg g−1 min−1 at 1.2 V and 3.32 mg g−1 min−1 at 2 V in 500 mg L−1. Benefiting from the excellent flexibility, we innovatively stack four layers of L4P1-CNFs to improve the areal electrosorption capacity to 0.0817 mg cm−2 at 500 mg L−1, significantly higher than that of traditional carbon-based electrodes. The good desalination property makes lignin-based carbon nanofibers ideal for practical, low-cost capacitive deionization applications.

Lignin-derived carbon nanofibers with the micro-cracking structure for high-performance capacitive deionization

The binder-free electrode materials have excellent practical application value, especially for carbon-based electrodes. As a naturally occurring carbon precursor, lignin can be developed for the electrode material of capacitive deionization with high energy storage and high adsorption performance. In this paper, nanofibers containing mesoporous fracture systems are prepared by depolymerized lignin. The microcracks are uniformly distributed on the carbon nanofiber tube bundles. It can provide a favorable place for ion storage, and the notches structure further improves the ion adsorption performance. This study provides a simple and efficient strategy for the converting lignin into carbon fibers with the micro-cracking structure. It is expected to promote the application of lignin-based carbon nanofibers in capacitive deionization.

Efficient centrifugal spinning of soda lignin for the production of activated carbon nanofibers with highly porous structure

In this study, centrifugally spun soda lignin (SL) nanofibers were prepared as precursors to produce lignin-based carbon nanofibers (LCNF) and activated carbon nanofibers (LACNF). The impact of concentration of spinning solution and rational speed on the spinnability and fiber diameters were systematically examined by scanning electron microscopy (SEM). The result showed that the produced fibers diameter was in the range of 0.47–2.36 μm. The effect of SL nanofiber diameter on its morphology and thermal properties during carbonization was obtained by SEM, thermogravimetric (TGA) and differential calorimetric scanning (DSC) analyses. Subsequently, the SL nanofibers were ease to transform into LCNF and further LACNF with highest specific surface area of approximately 1900 m2/g, which is superior to those of LACNF in previously prepared by electrospinning. It can be concluded that centrifugal spinning method is a facile and efficient technique to develop large scale production of lignin-based nanofibers and in particular LACNF with high specific surface area.

Constructing porous lignin-based carbon nanofiber anodes with flexibility for high-performance lithium/sodium-ion batteries

Lithium (Li)/sodium (Na)-ion batteries have been widely studied as energy storage power sources because of their long cycle life and high energy density. Lignin, which is environmentally friendly, inexpensive, and has a high carbon content, is considered one of the most promising raw materials for anodes. Hence, in this study, a porous lignin-based carbon nanofiber anode was obtained using gas–electric blending. The prepared anode is flexible, self-supporting, and can be directly used without any binders in Li/Na-ion batteries. It showed an excellent first reversible specific capacity of 1783.8 mAh/g at 0.2 C current density and maintained a specific capacity of 1429.7 mAh/g after 50 cycles in the Li-ion battery. Even at a high current density of 2 C, it exhibited a high reversible specific capacity of 1135.4 mA/h/g in the first cycle and retained 1064.7 mAh/g after 100 cycles. Furthermore, it also exhibited an excellent specific discharge capacity, stable cycle performance, and high rate performance in Na-ion batteries. This study demonstrates that lignin has broad application prospects as a high-performance energy storage material.

Multifunction lignin-based carbon nanofibers with enhanced electromagnetic wave absorption and surpercapacitive energy storage capabilities

It is difficult for green sustainable lignin-based materials to simultaneously obtain efficient electromagnetic wave absorption (EMWA) and supercapacitive energy storage (SCES), which has not yet been reported. Herein, the light-weight lignin-based carbon nanofibers (LCNFs) with proper pore size, well graphitization degree, and heteroatom doping were tailored through electrospinning and carbonization processes. Interestingly, the graphitization degree and porous structure of LCNFs could be easily adjusted by changing the activating temperature, and the higher conductivity was achieved for preparing LCNFs at higher activating temperature due to the differences in the crystal size and activating degree of LCNFs. As a result, in the field of EMWA, the LCNFs-950 exhibited the minimum reflection loss (RL) value was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness, which meant this absorbent could absorb and/or dissipate more than 99.9% of incident electromagnetic wave (EMW). Furthermore, the LCNFs-950 also exhibited excellent SCES ability. In two-electrode system, the optimal LCNFs-950 symmetric supercapacitor specific capacitance reached 139.4 F/g at a current density of 0.5 A/g, meanwhile, the energy density was 41.4 Wh/kg at a power density of 3500 W/Kg. These multifunctional features of LCNFs will be highly promising for the next-generation environmental remediating materials.

Layer-by-Layer Assembly of Graphene Oxide and Polyethylenimine on Carbon Nanofiber Films for Supercapacitor Applications

Although lignin-based carbon nanofibers (CNFs) have been successfully applied in the environmental, energy, and aerospace fields, obtaining fibers with excellent electrochemical performance is an urgent problem to be solved. In this work, lignin-based precursor fibers with nanofiber structures are prepared as the basal layer for the layer-by-layer (LbL) assembly of the electroactive substance polyethylenimine (PEI) and graphene oxide (GO) to obtain structured lignin-based CNFs with excellent electrochemical properties. The uniformly distributed multilayered nano-architecture and interconnected network structure provide a high specific surface area and effective contact area, thus promoting ion diffusion and transport and improving the electrical interaction and chemical reactions of the lignin-based CNFs. The specific capacitances and energy densities reach 339.3 F/g and 30.16 Wh/kg, respectively. Furthermore, the lignin-based CNFs exhibit an excellent durability and quick response to temperature (the current changes rapidly in 2 s of temperature rise). This work puts forward a simple and efficient strategy to fabricate nanocomposite fibers with orderly and controllable structures by LbL assembly using lignin-based raw materials. These nanocomposite fibers exhibit great potential for application in supercapacitor, fire alarm, and environment-friendly energy products.

Fabricating lignin-based carbon nanofibers as versatile supercapacitors from food wastes

Recently, the high-value utilization of food wastes has attracted great interest in sustainable development. Focusing on the major application of electrochemical energy storage (ECES), light-weight lignin-based carbon nanofibers (LCNFs) were controllably fabricated as supercapacitors from melon seed shells (MSS) and peanut shells (PS) through electrospinning and carbonizing processes. As a result, the optimal specific capacitance of 533.7 F/g in three-electrode system, energy density of 69.7 Wh/kg and power density of 780 W/Kg in two-electrode system were achieved. Surprisingly, the LCNFs also presented a satisfied electromagnetic absorption property: The minimum reflection loss (RL) value reached −37.2 dB at an absorbing frequency of 7.98 GHz with an effective frequency (RL < 10 dB) of 2.24 GHz (6.88 to 9.12 GHz) at a thickness of 3.0 mm. These features make the multifunctional LCNFs highly attractive for light-weight supercapacitor electrodes and electromagnetic wave absorbers applications.

Lignin-based carbon nanofibe rs: Morphologies, properties, and features as substrates for pseudocapacitor electrodes

In this work, lignin-based carbon nanofibers (LCNFs) were for the first time served as substrate for in-situ electrodeposition of polyaniline (PANI) and tested as pseudocapacitor. Two LCNFs with different lignin ratios were designed to distinguish their morphology and structural properties. Next, PANI deposition mechanisms on both LCNFs were investigated and the electrochemical performance of the resulting LCNF/PANIs were evaluated. It was found although LCNF2 was composed of less uniform nanofibers due to more presence of lignin in precursor dope, it had higher tensile strength/modulus than LCNF1 (strength: 34.3MPa to 24.2 MPa; Modulus: 2.40 GPa to 1.45GPa) and was more cost-effective. Particularly, the beaded fibers on LCNF2 contributes to the deposition of PANI with higher specific mass capacitance (612.8 F g−1 to 547.0 F g−1). Upon assembling into solid-state supercapacitors, the Cm of LCNF2/PANI device was determined to be 229 F g−1 and the maximum energy density was 11.13Wh kg−1 at a power density of 0.08 kW kg−1. This work showed LCNF produced from renewable and low-cost lignin could be directly used as substrate for PANI deposition. Moreover, the composition in spinning dope played an important role in determining the performances of resulting pseudocapacitors.

Effective fractionation strategy of sugarcane bagasse lignin to fabricate quality lignin-based carbon nanofibers supercapacitors

Lignin is recommended to a tempting alternative precursor of petroleum for fabricating carbon nanofibers (CNFs) due to its high carbon content, low-cost and renewable resources. However, the property of lignin-based carbon nanofibers (LCNFs) is inferior owing to the heterogeneity and 3D-network structure of lignin, which hinders its application in supercapacitors. The latest developments in fractionation technology have shown great potential for overcoming the aforementioned shortcomings. However, most of fractionation methods mainly rely on expensive chemicals and complex reaction process, such as enzymes, multiple solvents, membranes, and dialysis tubes. Herein, we proposed a controllable and effective strategy to fractionate lignin by only changing the ratio of ethanol/water (V/V) as mixture solvent. This gradient extraction method effectively removed the part of lignin with small molecular and branching structure, thus selectively getting the fractionated lignin with high molecular weight, narrow polydispersity index, and good linear structure. Fortunately, when the ratio of ethanol/water was 6:4, the corresponding LCNFs (LCNFs-L60) was obtained with large specific surface area, independent filamentous morphology networks and excellent electrochemical property. Its specific capacitance was up to 405.8 F/g. This way features controllable and sustainable for preparing high-quality LCNFs supercapacitors.

Effect of lignin structure in different biomass resources on the performance of lignin-based carbon nanofibers as supercapacitor electrode

Lignin is proposed to an attractive stuff for fabricating functional composite nano-carbon materials owing to its high carbon yield and low-cost. In this work, in order to unlocking the mechanism of the plant species of lignin on electrochemical energy storage capacity of lignin-based carbon nanofibers (LCNFs), three typical lignin from representative hardwood (poplar, PR), softwood (pine, PE) and grass (corn stalk, CS) materials, and containing different structural units (syringyl units (S), guaiacyl units (G), and/or p-hydroxyphenyl unit (H)) were chosen to prepare LCNFs with polyacrylonitrile (PAN) as blending agent. As compared with other LCNFs, poplar lignin (PRL) based LCNFs-PRL (5:5) with independent filamentous morphology networks exhibited higher tensile strength of 35.32 MPa, greater specific surface area of 1062.5 m2/g and larger specific capacitance of 349.2 F/g. Moreover, in a two electrode system, the assembled LCNFs-PRL (5:5)//LCNFs-PRL (5:5) symmetric supercapacitor also displayed an excellent energy density of 39.6 Wh/kg at the power density of 5000 W/kg and outstanding cycling stability of 90.52 % after 5000 cycles in Na2SO4 aqueous electrolyte. The results proved that hardwood lignin was a good green raw material for LCNFs. The mechanism of lignin chemical structure on the properties was demonstrated in detail by various characterization analysis, such as electrochemical test, nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC), which indicated that the structural units, molecular weight, homogeneity, hydrophilic and hydrophobic groups of lignin were more important for fabricating high quality LCNFs.

Facile synthesis of N-doped lignin-based carbon nanofibers decorated with iron oxides for flexible supercapacitor electrodes

Flexible films of N-doped porous iron oxides/lignin-based carbon nanofibers (CNF@Fe-N) were fabricated and employed for high-performance supercapacitor electrode materials. The CNF@Fe-N films were synthesized through a simple and effective method, which was carried out by an electrospinning technique from lignin/Hemin mixed solution and followed by carbonization. In situ growth of iron oxides on the surface and interior of carbon nanofibers contribute to enhancing the capacitive performance through inducing pseudocapacitance. In the unique structure, the fibrous network structure with rich micropores provides plenty of channels for transportation and penetration of electrolyte ions. The obtained CNF@Fe-N binder-free electrode exhibits a high gravimetric capacitance of 148. 1 F g−1 and high energy density of 12.28 W h L-1 at 0.5 A g−1, as well as an excellent cycling stability with 92.8% capacitance retention after 5000 charge/discharge cycles. The material also presents an outstanding flexibility and folding resistance. The low-cost and renewable sources, easy preparation and remarkable supercapacitive property render CNF@Fe-N a promising candidate in energy storage applications.

Tuning structure of spent coffee ground lignin by temperature fractionation to improve lignin-based carbon nanofibers mechanical performance

Fabricating lignin-based carbon nanofibers (LCNFs) with the lignin in spent coffee grounds (SCG) as raw material which are disposed as waste amounting to millions tons annual is benefit to promote economy and environmental protection. However, due to the heterogeneity and complex three-dimensional structure, the mechanic property is very poor. In this study, we propose a fractionating pretreatment method to overcome the above problems by regulating the structure of SCG lignin in which high-performance LCNFs were fabricated. On one hand, the linear structure of SCG lignin was optimized to fit the raw material of LCNFs by tuning the content of β-O-4 and C5-substituted condensed phenolic compounds. On the other hand, the carboxyl as the hydrophilic groups was removed so as to promote the mixing of lignin and polyacrylonitrile (PAN, blending agent) in organic solvents. Additionally, the heterogeneity was reduced by screening large molecular weight SCG lignin with low polydispersity index (PDI). Fortunately, with 1:1 mass ratio of the above fractionated lignin and PAN as substrate, the LCNFs could reach to comparable mechanic properties with those of pure PAN CNFs. This work can provide a new way to not only promote the utilization of SCG lignin but also accelerate the development of LCNFs.

Unlocking the response of lignin structure by depolymerization process improved lignin-based carbon nanofibers preparation and mechanical strength

We reported a new approach for development of lignin-based carbon nanofibers (LCNFs) from two lignin-derived bio-oil (LB) obtained from catalytic depolymerization reaction combined with the organic solvent gradient separation process (including ethanol-soluble LB (EL) and tetrahydrofuran-soluble LB (TL)). This approach was particularly unique and translatable as it uses small molecule TL with high reactivity and low heterogeneity obtained via stalk lignin depolymerization to produce good morphologies and mechanical performances of LCNFs mixed with polyacrylonitrile under 85% high replacement rates. We first detailed characterization studies such as 2D-HSQC NMR, 31P NMR, FT-IR, GPC, TGA and DSC were conducted to understand the properties of EL and TL. Then, the goal of the influence of EL and TL on the LCNFs morphologies and mechanical properties were accomplished by using SEM, XRD, Raman and material testing machine. As compared with EL, the TL had excellent linear structure with relatively less total phenolic–OH groups and heterogeneity, which could improve lignin structure with better alignment along PAN, and thus increased the lignin replacement rates and mechanical performances of LCNFs.

Lignin-based multi-channels carbon nanofibers @ SnO2 nanocomposites for high-performance supercapacitors

The lignin-based multi-channels carbon nanofibers (MCNFs) @ SnO2 nanocomposites with various microstructures are synthesized via co-electrospinning by regarding Poly (vinyl pyrrolidone) (PVP)–SnCl2·2H2O as shell materials and lignin-Poly (methyl methacrylate) (PMMA) at different mass ratios as core materials, followed by heat treatment and acid treatment. The experimental results show that when the mass ration of lignin to PMMA in the core region is 5:5, the obtained nanocomposites possess hierarchical internal channels, porous surface, and high specific surface area. This optimized nanocomposite as supercapacitor electrode shows high specific capacitance of 406 F g−1 at current density of 0.5 A g−1. In addition, the electrode exhibits unexceptionable cycling stability with only 5% capacitance decay over 10 000 cycles at 10 A g−1. Furthermore, the symmetric supercapacitor using the optimized nanocomposites as electrodes possesses remarkable power and energy densities. The superior electrochemical performance of nanocomposites is benefited from the hierarchical structures of MCNFs, faradaic pseudocapacitance of SnO2, and pore-forming effect of SnCl2·2H2O. The unique hierarchical nanocomposites show great potential in future development of lignin-based low-cost, non-toxic and eco-friendly carbon materials for high-performance energy storage devices.

Amine-Terminated Highly Cross-Linked Polyphosphazene-Functionalized Carbon Nanotube-Reinforced Lignin-Based Electrospun Carbon Nanofibers

To improve the mechanical properties of lignin-based carbon nanofibers, the amine-terminated highly cross-linked polyphosphazene-functionalized carbon nanotubes (PZAA@CNTs) were successfully synthe...