High Hydroxyl Content Research Articles

Co-modification of corn straw lignin and its enhancement on glue-free fiberboard based on freezing activated wood fibers

Glue-free fiberboard, as a substitute for traditional fiberboard, does not contain a large amount of synthetic resins, which can avoid harm to human health and environment. However, glue-free fiberboard still has some disadvantages of insufficient mechanical strength and excessive thickness swelling of water absorption. Here, corn straw lignin was co-modified by demethylation/hydrothermal degradation to obtain high hydroxyl content increased by 210.85% compared with raw lignin. The co-modified lignin was then introduced into freezing activated wood fibers to prepare the environment-friendly medium density fiberboard (MDF). The effect of co-modified lignin content on the properties of MDF was investigated. MDF with 3 wt% co-modified lignin exhibited the best comprehensive performance with the modulus of elasticity (MOE) of 5809 MPa, modulus of rupture (MOR) as high as 70 MPa, internal bonding strength (IB) of 2.29 MPa and thickness swelling (TS) as low as 16.65%, completely matching the requirements of the Chinese national standard GB/T 11718-2009 and EU national standard BS EN 622–5–2009. The interaction mechanism of co-modified lignin on the wood fibers was further explored by Fourier infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) and scanning electron microscope (SEM) analysis. The phenolic structures of co-modified lignin could be chemically crosslinked with wood fibers during the hot-pressing process and the large amount of hydroxyl groups provided strong hydrogen bond interactions for the glue-free fiberboard. The glue-free fiberboard enhanced by co-modified lignin with excellent comprehensive performance exhibits a broad application prospect.11MDF: medium density fiberboard; MOR: modulus of rupture; MOE: modulus of elasticity; IB: internal bonding strength; TS: thickness expansion; DSC: differential scanning calorimetry

Isolation and Fractionation of the Tobacco Stalk Lignin for Customized Value-Added Utilization.

The value-added utilization of tobacco stalk lignin is the key to the development of tobacco stalk resources. However, the serious heterogeneity is the bottleneck for making full use of tobacco stalk lignin. Based on this, lignin was separated from tobacco stalk through hydrothermal assisted dilute alkali pretreatment. Subsequently, the tobacco stalk alkaline lignin was fractionated into five uniform lignin components by sequential solvent fractionation. Advanced spectral technologies (FT-IR, NMR, and GPC) were used to reveal the effects of hydrothermal assisted dilute alkali pretreatment and solvent fractionation on the structural features of tobacco stalk lignin. The lignin fractions extracted with n-butanol and ethanol had low molecular weight and high phenolic hydroxyl content, thus exhibiting superior chemical reactivity and antioxidant capacity. By contrast, the lignin fraction extracted with dioxane had high molecular weight and low reactivity, nevertheless, the high residual carbon rate made it suitable as a precursor for preparing carbon materials. In general, hydrothermal assisted dilute alkali pretreatment was proved to be an efficient method to separate lignin from tobacco stalk, and the application of sequential solvent fractionation to prepare lignin fractions with homogeneous structural features has specific application prospect.

Adsorption removal of organic phosphonate HEDP by magnetic composite doped with different rare earth elements

Rare-earth-based magnetic adsorbents were prepared by co-precipitation of europium (Eu), lanthanum (La) and cerium (Ce) with Fe2+/Fe3+ and powdered activated carbon (PAC), respectively. The obtained magnetic adsorbents Fe/Eu@PAC, Fe/La@PAC and Fe/Ce@PAC were used to remove organic phosphonate 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) from reverse osmosis (RO) concentrates. The maximum adsorption capacities of Fe/Eu@PAC, Fe/La@PAC and Fe/Ce@PAC composites were 27.45, 16.58 and 15.99 mg-P/g at 298 K and pH=8.0, respectively. Fe/Eu@PAC composite with the highest adsorption capacity could completely remove HEDP from the solution at 1 g/L dosage. In addition, its adsorption capacity reached 80% of the equilibrium adsorption capacity at 30 min and 298 K, indicating a fast adsorption rate. The difference in adsorption performance of the three adsorbents was mainly due to the difference in zero charge point (pHpzc) and hydroxyl content. Both the pHpzc value and the hydroxyl content increased in the order of Fe/Eu@PAC>Fe/La@PAC>Fe/Ce@PAC. A higher pHpzc value was beneficial to improve the electrostatic interaction. Furthermore, the higher hydroxyl content was also conducive to improving the role of ligand exchange and hydrogen bonding. XPS analysis showed that the ligand exchange capacity of Eu 3d3/2 and La 3d3/2 was stronger than that of Eu 3d5/2 and La 3d5/2. In addition, the size of the ionic radius was not the main factor that affects the ligand exchange capacity of the rare-earth-based adsorbent. The results of this study suggest that magnetic Fe/Eu@PAC composites can be used as a promising high-performance adsorbent for the removal of phosphonates from water.

Zirconia nano-powders with controllable polymorphs synthesized by a wet chemical method and their phosphate adsorption characteristics & mechanism

Adsorption is a simple and efficient phosphorus removal method used to control the eutrophication of water bodies. A simple and gentle atmospheric pressure hydrothermal method by adjusting the dosage of ammonium chloride and sodium hydroxide was used to synthesize amorphous, monoclinic, and tetragonal zirconia nano-powders with high specific surface areas (383.91 m2/g, 330.01 m2/g, and 234.36 m2/g) and particle size of about 40 nm for phosphate adsorption. When pH = 6.3, the phosphate adsorption capacity of the amorphous monoclinic phase and the tetragonal phase respectively reached 102.58 mg P/g, 68.11 mg P/g, and 37.25 mg P/g and the adsorption process of the three crystal forms of zirconia powders conformed to the Langmuir adsorption model. In the first 2 min of rapid adsorption, amorphous zirconia completed 76.23% of the adsorption process and the monoclinic phase also completed more than 60%. The adsorption process of the three crystal forms of zirconia was completed within 240 min and conformed to the pseudo-second-order kinetic model. Their adsorption characteristics of the three crystal forms of zirconia decreased with the increase in pH. While the pH was above than the isoelectric point of the solution, the adsorption capacity was significantly reduced. The large specific surface area and high hydroxyl content of the zirconia nano-powder made a great contribution to the adsorption process.

Heterogeneous activation of peroxymonosulfate by Co3O4 loaded biochar for efficient degradation of 2,4-dichlorophenoxyacetic acid

Carbon-based catalysts have the advantage of biological cleaning and cost-effectiveness in water treatment. This work used a two-step calcination method to prepare a novel nanometer composite material (CBC-1), where flake-like Cobalt oxide (Co 3 O 4 ) loaded on rice husk biochar. CBC-1 was used to activate PMS and degrade 2,4-dichlorophenoxyacetic acid (2,4-D) in the water phase. SEM, XRD, FT-IR, BET, XPS, EPR and other characterization methods showed that both sulfate radical and hydroxyl radical were involved in 2,4-D degradation. Both the high hydroxyl (-OH) content and Co (II) of the catalyst are beneficial to the activation of PMS. The pseudo-first order reaction rate constant of CBC-1 was 5.3 and 16 times that of pure Co 3 O 4 and biochar. This research provides new ideas for the application of carbon-based materials in the water treatment process and achieves the goals of treating waste water polluted by pesticides effectively and resource utilization of agricultural waste. • Provided a new view for the waste utilization of rice husk. • Enhanced the catalytic activity of Co 3 O 4 with rice husk biochar added. • CBC-1/PMS system exhibited satisfactory degradation efficiency of 2,4-D within 10 min. • The higher hydroxyl content of CBC-1 is helpful for enhancing the catalytic ability.

Preparation of FeOOH nanoparticles using an impinging stream-rotating packed bed and their catalytic activity for ozonation of nitrobenzene

BackgroundFeOOH has the advantages of low price, high stability and high surface hydroxyl content that make it an excellent catalyst for wastewater treatment. However, it also has the problems of wide particle size distribution, non-uniform dispersion and long preparation time in traditional reactors. MethodsFeOOH nanoparticles were prepared from FeSO4 and NaOH in an impinging stream-rotating packed bed (IS-RPB-FeOOH), and their properties and catalytic activities were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Significant findingsThe prepared FeOOH nanoparticles are shown to be α-FeOOH with a specific surface area of 246.717 m2/g, a surface hydroxyl density of 8.166 mmol/g, a length of 30 nm, and a narrow particle size distribution. Compared with the stirred tank reactor, the reaction time is reduced from 30 min to 4 min and the specific surface area is increased by 2.1 times in IS-RPB. The removal rate of nitrobenzene by IS-RPB-FeOOH can reach 94.3% after 40 min, which is 8.8% and 19.5% higher than that of FeOOH nanoparticles prepared using a stirred tank reactor (STR-FeOOH) and ozonation alone, respectively.

Alkali synergetic two-step mechanical refining pretreatment of pondcypress for the fiber with intact 3D structure and ultrahigh cellulose accessibility fabrication

Although lignocellulosic biomass has promising applications in biodegradable cellulose-based composite materials due to its high specific surface area and high rigid intensity, lignocellulosic fiber with multiple surface reactive sites and intact spatial structure is still a great challenge as a versatile carrier for composite materials. Herein, a feasible strategy that combined alkaline hydrogen peroxide (AHP) impregnation and two-step mechanical refining was presented to treat the pondcypress (taxodium ascendens) for enhancing cellulose accessibility and specific surface area. Additionally, the prepared pondcypress fiber kept the intact spatial structure. First, the destruction of molecular structure barrier was synergistically realized by the NaOH and H2O2, that improved the efficiency of 2nd mechanical refining. Subsequently, the fibers exhibited an excellent dissociated result under the effect of shear stress and friction at low energy consumption (1637 kW h/t). As a result, the fibers achieved ultrahigh cellulose accessibility of 77.07 % and high surface active hydroxyl content of 2.164 × 10−3 mol/g due to the exposure of S2 cell wall at the 16 % H2O2 and 17.5 % NaOH. Moreover, despite the fibers were fibrillated after treatments, the intact spatial structure of fiber was observed by SEM. These results confirm that AHP impregnation and two-step mechanical refining are an effective method to dissociate the fiber, and this work opens up more avenues to use the lignocellulosic fiber in cellulose-based composite materials.

Effect of different catalysts on recovery and reuse of waste polyurethane rigid foam

The sharp increase of waste polyurethane rigid foam has caused great harm to the natural environment. Ethylene glycol (EG) and propylene glycol (PG) was the alcoholysis agents, and KOH and Zn3[Co(CN)6]2(DMC) were used as catalysts for alcoholysis of waste polyurethane rigid foam. Regenerated polyols were prepared. The effects of different catalysts on the infrared, viscosity and hydroxyl content of alcoholysis products were discussed. Regenerated polyurethane rigid foam was prepared from alcoholysis products and analyzed by compression strength, thermal conductivity, water absorption, scanning and thermogravimetry. The effects of different catalysts on the recycling of waste polyurethane rigid foam were studied. The experimental results show that DMC catalyst is more effective than KOH catalyst under the same conditions.The alcoholysis product of DMC system has lower viscosity and higher hydroxyl content, which is more suitable for the preparation of regenerated polyurethane rigid foam., The compressive strength of the prepared regenerated polyurethane rigid foam is 254 Kpa, and the thermal conductivity is 0.0213 W m−1·K−1 when the amount of DMC added is 0.04%. Meanwhile, the regenerated polyurethane rigid foam has good hydrophobicity, excellent heat preservation performance, complete cell morphology and good thermal stability. It can replace the traditional polyols to prepare the regenerated polyurethane material which meets the national standard ‘rigid polyurethane foam for building insulation’ (GB/ T21558-2005).

Thermal Properties of Ethanol Organosolv Lignin Depending on Its Structure

In general, lignin exhibits unpredictable and nonuniform thermal properties due to the structural variations caused by the extraction processes. Therefore, a systematic understanding of the correlation between the extraction conditions, structural characteristics, and properties is indispensable for the commercial utilization of lignin. In this study, the effect of extraction conditions on the structural characteristics of ethanol organosolv lignin (EOL) was investigated by response surface methodology. The structural characteristics of EOL (molecular weight, hydroxyl content, and intramolecular coupling structure) were significantly affected by the extraction conditions (temperature, sulfuric acid concentration, and ethanol concentration). In addition, the correlation between the structural characteristics and thermal properties of the extracted EOLs was estimated. The relevant correlations between the structural characteristics and thermal properties were determined. In particular, EOLs that had a low molecular weight, high phenolic hydroxyl content, and low aryl–ether linkage content exhibited prominent thermal properties in terms of their initial decomposition rate and a high glass transition temperature, Tg. Correspondingly, EOL-PLA blends prepared using three EOL types exhibited improved thermal properties (starting point of thermal decomposition and maximum decomposition temperature) compared to neat PLA and had thermal decomposition behaviors coincident with the thermal properties of the constituent EOLs.

Procuring the nano-scale lignin in prehydrolyzate as ingredient to prepare cellulose nanofibril composite film with multiple functions

Cellulose is lack of UV-blocking and antibacterial properties, which have limited its application. In this work, the nanoscale lignin with high content of hydroxyl groups and small particle size in prehydrolysate was isolated and used as a green reinforcement ingredient for fabrication of cellulose nanofibril (CNF) films with excellent mechanical properties, as well as UV protection and antibacterial capabilities. Cryogenic transmission electron microscopy (Cryo-TEM) and nuclear magnetic resonance analyses showed that the resulting lignin was in the form of nanoparticles (6–12 nm) with high phenolic hydroxyl contents (4.9 mmol/g). The optimum lignin inclusion rate of 5% allowed it to reinforce CNF composite film, increasing its tensile strength from 108.5 to 143.3 MPa. In addition, the film exhibited excellent UV protection capabilities. It blocked 91.5% of UV-A and 99.9% of UV-B light. Finally, the resulting lignin-based CNF films exhibited antibacterial activities against both Escherichia coli and Streptococcus hemolyticus. This work demonstrates the utility of nanoscale lignin from prehydrolysate can be used to produce cellulose-based composite films with valuable properties.

Using a recyclable acid hydrotrope and subsequent short-term ultrasonic pretreatment to facilitate high-value lignin extraction and high-titer ethanol production

Pretreatment to enhance the enzymatic digestibility of cellulose usually alters the structure of lignin, resulting in subsequent inferior depolymerization and utilization. Herein, a physicochemical pretreatment strategy, specifically, using a recyclable acid hydrotrope (p-toluenesulfonic acid, p-TsOH) followed by 10 s of ultrasonic treatment, was developed to facilitate high-value lignin extraction from lignocellulosic biomass and improve enzymatic hydrolysis for high-titer ethanol production. The wood material (poplar) was first treated with the recyclable p-TsOH aqueous solution under mild conditions (C80T80t15) to extract the lignin. The obtained lignin exhibited excellent properties, including a high hydroxyl (OH) content (4.19 and 4.07 mmol/g of aliphatic and phenolic OH, respectively), abundant β-O-4 aryl ether linkages (60%), a low Mw (3357 ± 121 g/mol), and a narrow polydispersity (2.28, Mw/Mn), according to the results from FTIR spectroscopy, TGA, 31P NMR spectroscopy, 2D-HSQC NMR spectroscopy, and GPC. The pretreated substrates were then subjected to 10 s of ultrasonication to improve the enzymatic saccharification and finally afford ethanol by quasi-simultaneous enzymatic saccharification and fermentation (Q-SSF). The highest ethanol concentration (40.08 ± 3 g/L) was obtained after 60 h of fermentation, and the residual glucose concentration was only 4.22 ± 1 g/L; this experimental ethanol yield was equivalent to the theoretical ethanol yield of 81.87 ± 4% based on the glucan content. In short, this pretreatment method simultaneously enhanced the accessibility of cellulose to enzymatic hydrolysis and provided high-value lignin.

Understanding the effect of hydroxyl/epoxy group on water desalination through lamellar graphene oxide membranes via molecular dynamics simulation

The lamellar graphene oxide (GO) membranes could offer well-defined 2D nanochannels for fast water permeation and excellent ions rejection. In this work, lamellar GO membranes were constructed by stacking GO nanosheets layer-by-layer via molecular simulation. The effect of hydroxyl and epoxy groups as well as their content on the desalination performance in lamellar GO membranes were investigated by molecular dynamics simulation. The transport and separation mechanisms of water molecules and ions passing through the lamellar GO membranes with different functional group were also revealed from thermodynamic and hydrogen bond network. It is found that water flux in GO membranes would be influenced by the order of water molecules and the hydrogen network formed between functional groups and water molecules. GOOH membranes showed a higher Na+ rejection rate than Cl− at high hydroxyl contents.

Fungal Treatment Modifies Kraft Lignin for Lignin- and Cellulose-Based Carbon Fiber Precursors.

The kraft lignin’s low molecular weight and too high hydroxyl content hinder its application in bio-based carbon fibers. In this study, we were able to polymerize kraft lignin and reduce the amount of hydroxyl groups by incubating it with the white-rot fungus Obba rivulosa. Enzymatic radical oxidation reactions were hypothesized to induce condensation of lignin, which increased the amount of aromatic rings connected by carbon–carbon bonds. This modification is assumed to be beneficial when aiming for graphite materials such as carbon fibers. Furthermore, the ratio of remaining aliphatic hydroxyls to phenolic hydroxyls was increased, making the structure more favorable for carbon fiber production. When the modified lignin was mixed together with cellulose, the mixture could be spun into intact precursor fibers by using dry-jet wet spinning. The modified lignin leaked less to the spin bath compared with the unmodified lignin starting material, making the recycling of spin-bath solvents easier. The stronger incorporation of modified lignin in the precursor fibers was confirmed by composition analysis, thermogravimetry, and mechanical testing. This work shows how white-rot fungal treatment can be used to modify the structure of lignin to be more favorable for the production of bio-based fiber materials.

Fibrillating wood chips to facilitate high-valued lignin extraction and high titer ethanol production

In this study, a physical-chemical pretreatment strategy, using a twin-screw extrusion process for wood chips micro-fibrillation and subsequent chemical pretreatment with a recyclable acid hydrotrope, was developed to facilitate the extraction of high-valued lignin and the enzymatical hydrolysis of cellulose. At an optimum pretreatment severity of T70C70, the fibrillated wood chips were dissolved for approximately 89 % with a negligible loss of cellulose and considerable removals of lignin and hemicellulose (45 % and 65 %, respectively). The obtained lignin exhibited excellent structural profiles, such as high hydroxyl content (aliphatic OH of 2.31 mmol/g), more β-O-4 aryl ether linkages (59.05 %), low Mw (3736 g/mol), and narrow polydispersity (Mw/Mn, 2.03), according the characterization results from FTIR, TGA, GPC, 31P NMR, and 2D HSQC NMR measurements. The residual glucan-rich solid was enzymatically hydrolyzed for high titer ethanol production via a Q-SSF process, resulting in a high ethanol concentration of 47.62 g/L.

Fractionation by Sequential Antisolvent Precipitation of Grass, Softwood, and Hardwood Lignins Isolated Using Low-Cost Ionic Liquids and Water

In this study, fractionation by sequential anti-solvent precipitation was applied to ionoSolv lignins for the first time. Pretreatment with the aqueous low-cost protic ionic liquid N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4], 80 wt% in water) was applied to Miscanthus (herbaceous), willow (hardwood) and pine (softwood) to extract lignin. Then, lignin was sequentially precipitated by addition of water as anti-solvent. Fractionation appeared to be controlled by molecular weight of lignin polymers. Fractions isolated with minimal water volumes were shown to have high molecular weight, polydispersity, thermal stability and Tg (178 °C). Later precipitates were more monodisperse, had high phenolic and total hydroxyl content, lower thermal stability and Tg (136 °C). Addition of 1 g of water per g of dry IL was able to precipitate up to 90 wt% of lignin. Fractional precipitation represents a novel lignin isolation technique that can be performed as part of the lignin recovery procedure enabling a hig...

Ionic liquid assisted hydrothermal preparation of TiO2 with largely enhanced photocatalytic performance originated from effective separation of photoinduced carriers

In this paper, TiO2 with enhanced photocatalytic activity was prepared with the aid of ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF6) through a conventional hydrothermal method. The effects of different amounts of [BMIm]PF6 on the preparation and corresponding photocatalytic activity of TiO2 were investigated. Preparation of TiO2 was optimized by controlling the mass ratio of [BMIm]PF6 and TiO2. Photocatalytic property of TiO2 prepared was investigated using RhB as a simulated pollutant. The results show that TiO2 prepared with the aid of [BMIm]PF6 exhibits superior photocatalytic activity to the reference TiO2, when the mass ratio of [BMIm]PF6/TiO2 is 8%, TiO2 prepared has the highest separation rate of photogenerated charge pairs, leading to the highest photocatalytic activity. The enhanced photocatalytic performance of TiO2 prepared with the aid of [BMIm]PF6 is attributable to high surface hydroxyl content and enhanced separation of photoinduced charge pairs.

Effect of extraction methods on the molecular structure and thermal stability of kenaf (Hibiscus cannabinus core) biomass as an alternative bio-filler for rubber composites

Lignin from kenaf (Hibiscus cannabinus) core was investigated as an alternative filler for rubber. Three types of extraction methods were used to isolate lignin from kenaf, namely kraft, soda and organosolv process. The particle size, surface area, functionalities changes, molecular weight and thermal properties of the lignin were characterized. The results showed that Kraft lignin (KL) has the smallest particle size (40.41 μm) compared to soda lignin (SL) (63.85 μm) and organosolv lignin (OL) (66.85 μm). This is in good agreement with the BET surface area of 9.52 m2/g, 1.25 m2/g and 2.40 m2/g respectively. However, the smaller surface area of SL compared to OL is due to the smaller pore size and pore volume of SL. KL also showed high hydroxyl content with corresponding high thermal stability as confirmed by NMR and TGA. The thermal stability of the lignin correlates well with the molecular weight (MW). From the overall characteristics, it can be concluded that KL, SL and OL can be used as an alternative filler in rubber compounds to substitute common fillers like silica and carbon.

Photocatalytic activity of TiO2 prepared by different solvents through a solvothermal approach

In this work, TiO2 was prepared by different solvents through a solvothermal approach using tetrabutyl titanate as raw material, afterward the samples were calcined at 723 K. The samples were investigated by Brunauer -Emmett-Teller (BET) method, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis diffuse reflectance (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS), and surface photovoltage spectroscopy (SPS). The photocatalytic activity of the samples was investigated using rhodamine B (RhB) as a model contaminant. TiO2 prepared using ethanol as solvent has the best photocatalytic performance under irradiation of 500 W Xe lamp. Compared with the samples without calcination, all samples after calcination display significantly improved photocatalytic performance, which can be tightly attributed to the enhanced separation of photoinduced carriers and relative high surface hydroxyl content.

Preparation of high hydroxyl self‐emulsifying polyester and compounding with acrylate

ABSTRACTWaterborne saturated polyester (WSP) with high hydroxyl content was prepared through solution polymerization by using stepwise feeding and stage heating methods. The stability of polyester dispersion was enhanced in terms of molecular structure and polymerization process. The conditions of polymerization process, monomer types, and catalyst type were determined. The effects of the ratio of alcohol‐to‐acid, trimethylolpropane (TMP) content and the feeding method, the content of terminal monomer and branched monomer on the dispersion were investigated. The stability of the self‐emulsifying polyester and the water resistance of the film were proved to be excellent. Through transesterification, waterborne unsaturated polyester (WUP) was synthesized by WSP. Polyester‐acrylate composite emulsion can be obtained by physical blending or chemical copolymerization of synthetic waterborne polyester. The viscosity of the composite emulsion was improved, and the hardness and water resistance were improved. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48278.

Phenolic hydroxyl functionalized partially reduced graphene oxides for symmetric supercapacitors with significantly enhanced electrochemical performance

In this paper, three-dimensional phenolic hydroxyl functionalized partially reduced graphene oxides with high hydroxyl content and significantly enhanced electrochemical performance have been successfully prepared by a one-pot hydrothermal method from graphene oxide dispersions. A very small amount of 4-aminophenol is employed as reducing and N-doping agent, structure modifier and the phenolic hydroxyl source, at the same time. The electrochemical test results show that as binder-free electrode, the as-synthesized sample with high hydroxyl content (6.15 at%) exhibits an ultrahigh specific capacitance of 284.1 F g−1 at current density of 0.3 A g−1 in 6 M KOH electrolyte, and retains for 80.4% even at a current density of 10 A g−1. Above all, the as-assembled symmetric supercapacitor shows superior energy density of 9.9 Wh kg−1 at a power density of 75.0 W kg−1. The significantly enhanced electrochemical performance can be ascribed to the high hydroxyl content and other oxygen functional groups, N-doping, modified porous framework and the high specific surface area of the graphene. Those special characteristics suggest that the as-synthesized graphene materials may have potential applications in high performance supercapacitors.