Controlling porosity in lignin-derived nanoporous carbon for supercapacitor applications

Assembly of Organosolv Lignin Residues into Submicron Spheres: The Effects of Granulating in Ethanol/Water Mixtures and Homogenization

The production of chemicals and various materials from black liquor lignin will greatly improve the economics of biomass refining. In the present work, organosolv lignin residues (OLRs) from the organosolv pulping process were used to fabricate submicron lignin spheres using ethanol/water mixtures as an antisolvent, in conjunction with homogenization. Both the ethanol content in the ethanol/water mixture and the applications of homogenization were investigated as key factors affecting the agglomeration of OLRs. The results show that the solubility of the amphiphilic OLRs in ethanol was approximately 28 and 32 times greater than those of alkali lignin and kraft lignin, respectively. Using the optimal percentage of ethanol together with homogenization enhanced the nucleation of lignin macromolecules, such that the colloidal spheres of OLR were spontaneously assembled via gradual hydrophilic-lipophilic aggregation. The resulting OLR colloidal spheres had a yolk-shell structure and a mean particle diameter of around 200 nm, when the ethanol content was 50% and the homogenization time was 15 min or more. This study demonstrates a simple means of utilizing OLRs to produce lignin-based spheres. The lignin spheres generated in this work are thought to have potential applications in many fields as porous carbon precursors for energy storage, sensitive functional materials, and controlled-release fertilizer carriers.

Lignin-derived carbon nanosheets for high-capacitance supercapacitors

We disclose a simple and eco-friendly method to prepare carbon nanosheets (CNSs) by freeze-casting of lignin aqueous dispersion followed by direct carbonization. These lignin-derived CNSs show high performances as electrodes in supercapacitors.

Recent Advancements in Functionalized Paper-Based Electronics

Building electronic devices on ubiquitous paper substrates has recently drawn extensive attention due to its light weight, low cost, environmental friendliness, and ease of fabrication. Recently, a myriad of advancements have been made to improve the performance of paper electronics for various applications, such as basic electronic components, energy storage devices, generators, antennas, and electronic circuits. This review aims to summarize this progress and discuss different perspectives of paper electronics as well as the remaining challenges yet to be overcome in this field. Other aspects included in this review are the fundamental characteristics of paper, modification of paper with functional materials, and various methods for device fabrication.

Popcorn-Derived Porous Carbon for Energy Storage and CO2 Capture

Porous carbon materials have drawn tremendous attention due to its applications in energy storage, gas/water purification, catalyst support, and other important fields. However, producing high-performance carbons via a facile and efficient route is still a big challenge. Here we report the synthesis of microporous carbon materials by employing a steam-explosion method with subsequent potassium activation and carbonization of the obtained popcorn. The obtained carbon features a large specific surface area, high porosity, and doped nitrogen atoms. Using as an electrode material in supercapacitor, it displays a high specific capacitance of 245 F g(-1) at 0.5 A g(-1) and a remarkable stability of 97.8% retention after 5000 cycles at 5 A g(-1). The product also exhibits a high CO2 adsorption capacity of 4.60 mmol g(-1) under 1066 mbar and 25 °C. Both areal specific capacitance and specific CO2 uptake are directly proportional to the surface nitrogen content. This approach could thus enlighten the batch production of porous nitrogen-doped carbons for a wide range of energy and environmental applications.

Fungal Enzymes for Bio-Products from Sustainable and Waste Biomass

Lignocellulose, the most abundant renewable carbon source on earth, is the logical candidate to replace fossil carbon as the major biofuel raw material. Nevertheless, the technologies needed to convert lignocellulose into soluble products that can then be utilized by the chemical or fuel industries face several challenges. Enzymatic hydrolysis is of major importance, and we review the progress made in fungal enzyme technology over the past few years with major emphasis on (i) the enzymes needed for the conversion of polysaccharides (cellulose and hemicellulose) into soluble products, (ii) the potential uses of lignin degradation products, and (iii) current progress and bottlenecks for the use of the soluble lignocellulose derivatives in emerging biorefineries.

Nitro Lignin-Derived Nitrogen-Doped Carbon as an Efficient and Sustainable Electrocatalyst for Oxygen Reduction

The use of lignin as a precursor for the synthesis of materials is nowadays considered very interesting from a sustainability standpoint. Here we illustrate the synthesis of a micro-, meso-, and macroporous nitrogen-doped carbon (NDC) using lignin extracted from beech wood via alkaline hydrothermal treatment and successively functionalized via aromatic nitration. The so obtained material is thus carbonized in the eutectic salt melt KCl/ZnCl2. The final NDC shows an excellent activity as electrocatalyst for the oxygen reduction reaction.

Synthesis and characterization of phenol–furfural resins using lignin modified by a low transition temperature mixture

An efficient and green method for the modification of lignin by a low transition temperature mixture was used in the synthesis of phenol–furfural resins.

3D hierarchical porous N-doped carbon aerogel from renewable cellulose: an attractive carbon for high-performance supercapacitor electrodes and CO2 adsorption

3D hierarchical porous N-doped carbon aerogel from renewable cellulose: an attractive carbon for high-performance supercapacitor electrode and CO₂ adsorption.

Nitrogen- and sulfur-doped carbon nanoplatelets via thermal annealing of alkaline lignin with urea as efficient electrocatalysts for oxygen reduction reaction

Novel N–S–C hybrids were synthesized by a facile one-step pyrolysis method, in which the obtained N–S–C 900 was a robust catalyst with enhanced ORR activity and excellent operational stability in alkaline media, superior to the Pt/C catalyst.

Facile synthesis of N/P co-doped carbons with tailored hierarchically porous structures for supercapacitor applications

A facile process was designed to synthesize nitrogen/phosphorous co-doped hierarchically porous carbons with excellent performance for supercapacitors.

Mesoporous carbon soft-templated from lignin nanofiber networks: microphase separation boosts supercapacitance in conductive electrodes

Lignin was used to fabricate electrospun fibers with mesopores from a PVA precursor (soft templating). The resultant carbon mat was flexible, conductive and displayed supercapacitance, a remarkable property in a biomass-derived electrode.

Processed Lignin as a Byproduct of the Generation of 5-(Chloromethyl)furfural from Biomass: A Promising New Mesoporous Material

The lignin by-product of the conversion of lignocellulosic biomass to 5-(chloromethyl)furfural (CMF) has been characterised by thermogravimetric analysis, N2 physisorption porosimetry, attenuated internal reflectance IR spectroscopy, elemental analysis and solid-state NMR spectroscopy. The lignin (LCMF) has a moderate level of mesoporosity before thermal treatment and a surface area of 63 m(2)  g(-1) , which increases dramatically on pyrolysis at temperatures above 400 °C. An assessment of the functionality and textural properties of the material was achieved by analysing LCMF treated thermally over a range of pyrolysis temperatures. Samples were sulfonated to test their potential as heterogeneous acid catalysts in the esterification of levulinic acid. It was shown that unpyrolysed catalysts gave the highest ester yields of up to 93 %. To the best of our knowledge, this is the first example of mesoporous lignin with an appreciable surface area that is produced directly from a bio-refinery process and with further textural modification of the material demonstrated.

Lignin-Derived Advanced Carbon Materials

Lignin is a highly abundant source of renewable carbon that can be considered as a valuable sustainable source of biobased materials. By applying specific pretreatments and manufacturing methods, lignin can be converted into a variety of value-added carbon materials. However, the physical and chemical heterogeneities of lignin complicate its use as a feedstock. Herein lignin manufacturing process, the effects of pretreatments and manufacturing methods on the properties of product lignin, and structure-property relationships in various applications of lignin-derived carbon materials, such as carbon fibers, carbon mats, activated carbons, carbon films, and templated carbon, are discussed.

Enzymatic conversion of lignin into renewable chemicals

The aromatic heteropolymer lignin is a major component of plant cell walls, and is produced industrially from paper/pulp manufacture and cellulosic bioethanol production. Conversion of lignin into renewable chemicals is a major unsolved problem in the development of a biomass-based biorefinery. The review describes recent developments in the understanding of bacterial enzymes for lignin breakdown, such as DyP peroxidases, bacterial laccases, and beta-etherase enzymes. The use of pathway engineering methods to construct genetically modified microbes to convert lignin to renewable chemicals (e.g. vanillin, adipic acid) via fermentation is discussed, and the search for novel applications for lignin (e.g. carbon fibre).

Characterization of lignin derived from water-only and dilute acid flowthrough pretreatment of poplar wood at elevated temperatures

BACKGROUND

Flowthrough pretreatment of biomass is a critical step in lignin valorization via conversion of lignin derivatives to high-value products, a function vital to the economic efficiency of biorefinery plants. Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization.

RESULTS

In this study, the effects of flowthrough pretreatment conditions on lignin separation from poplar wood were reported as well as the characteristics of three sub-sets of lignin produced from the pretreatment, including residual lignin in pretreated solid residues (ReL), recovered insoluble lignin in pretreated liquid (RISL), and recovered soluble lignin in pretreatment liquid (RSL). Both the water-only and 0.05 % (w/w) sulfuric acid pretreatments were performed at temperatures from 160 to 270 °C on poplar wood in a flowthrough reactor system for 2-10 min. Results showed that water-only flowthrough pretreatment primarily removed syringyl (S units). Increased temperature and/or the addition of sulfuric acid enhanced the removal of guaiacyl (G units) compared to water-only pretreatments at lower temperatures, resulting in nearly complete removal of lignin from the biomass. Results also suggested that more RISL was recovered than ReL and RSL in both dilute acid and water-only flowthrough pretreatments at elevated temperatures. NMR spectra of the RISL revealed significant β-O-4 cleavage, α-β deoxygenation to form cinnamyl-like end groups, and slight β-5 repolymerization in both water-only and dilute acid flowthrough pretreatments.

CONCLUSIONS

Elevated temperature and/or dilute acid greatly enhanced lignin removal to almost 100 % by improving G unit removal besides S unit removal in flowthrough system. Only mild lignin structural modification was caused by flowthrough pretreatment. A lignin transformation pathway was proposed to explain the complexity of the lignin structural changes during hot water and dilute acid flowthrough pretreatment.Graphical abstractLignin transformations in water-only and dilute acid flowthrough pretreatment at elevated temperatures.

Electrochemical performance of hierarchical porous carbon materials obtained from the infiltration of lignin into zeolite templates

Hierarchical porous carbon materials prepared by the direct carbonization of lignin/zeolite mixtures and the subsequent basic etching of the inorganic template have been electrochemically characterized in acidic media. These lignin-based templated carbons have interesting surface chemistry features, such as a variety of surface oxygen groups and also pyridone and pyridinic groups, which results in a high capacitance enhancement compared to petroleum-pitch-based carbons obtained by the same procedure. Furthermore, they are easily electro-oxidized in a sulfuric acid electrolyte under positive polarization to produce a large amount of surface oxygen groups that boosts the pseudocapacitance. The lignin-based templated carbons showed a specific capacitance as high as 250 F g(-1) at 50 mA g(-1) , with a capacitance retention of 50 % and volumetric capacitance of 75 F cm(-3) at current densities higher than 20 A g(-1) thanks to their suitable porous texture. These results indicate the potential use of inexpensive biomass byproducts, such as lignin, as carbon precursors in the production of hierarchical carbon materials for electrodes in electrochemical capacitors.