Composites combining electrostatic charge accumulation and faradic reaction mechanisms are especially attractive high-performance supercapacitor electrodes for electrochemical energy storage. Up to now, it is difficult to prepare low-cost carbon composites from renewable resources. In this work, an outstanding and low-cost composite was fabricated by using sustainable N-self-doped carbon framework as a hierarchical porous carbon substrate from renewable resource. The N-self-doped carbon framework was fabricated from chitosan via a facile yet unique self-assembly and ice template method without any physical or chemical activation, and exhibited hierarchical porous structure. This texture not only allowed the efficient infiltration and uniform coating of polyaniline (PANI) in the inner network but also permitted a rapid penetration and desorption of electrolytes. Due to short diffusion pathway, uniformly coating of PANI, and high accessibility of PANI to electrolytes, the composite electrode had a very high supercapacitance of 373 F g–1 (1.0 A g–1) and excellent rate capability (275 F g–1, 10 A g–1) in a three-electrode system. The symmetric supercapacitor also showed a supercapacitance of high up to 285 F g–1 (0.5 A g–1), and a very high energy density of 22.2 Wh kg–1. Furthermore, the composite also presented a good cycling stability.Keywords: Carbon composite; Chitosan; Polyaniline; Supercapacitor;

•Hierarchical N-doped porous carbon was cost-efficiently synthesized from cellulose.•The doping N can be easily tunable, and has a remarkable impact on porous carbon.•The doping N can significantly improve the supercapacitance of porous carbon.Producing hierarchical porous N-doped carbon from renewable biomass is an essential and sustainable way for future electrochemical energy storage. Herein we cost-efficiently synthesized N-doped porous carbon from renewable cellulose by using urea as a low-cost N source, without any activation process. The as-prepared N-doped porous carbon (N-doped PC) had a hierarchical porous structure with abundant macropores, mesopores and micropores. The doping N resulted in more disordered structure, and the doping N content in N-doped PC could be easily tunable (0.68–7.64%). The doping N functionalities could significantly improve the supercapacitance of porous carbon, and even a little amount of doping N (e.g. 0.68%) could remarkably improve the supercapacitance. The as-prepared N-doped PC with a specific surface area of 471.7 m2 g−1 exhibited a high specific capacitance of 193 F g−1 and a better rate capability, as well as an outstanding cycling stability with a capacitance retention of 107% after 5000 cycles. Moreover, the N-doped porous carbon had a high energy density of 17.1 W h kg−1 at a power density of 400 W kg−1.

Flexible supercapacitors are extremely important for future various electronic devices. However, the development of cost-efficient and high-performance flexible supercapacitor electrodes remains a big challenge today. Herein, we present a novel flexible nanocomposite based on a cellulose-derived framework coated with polyaniline (PANI). In this nanocomposite, the cellulose nanofiber (CNF) provides mechanical strength due to its interconnected network, while the strapped cellulose-derived carbon sheet (CCS) with a unique morphology produces a porous structure and offers fast transfer pathways for the efficient diffusion of electrode ions. PANI imparts conductivity to the CNF and provides abundant active sites for charge storage. The porous structure and supercapacitive performance of this kind of nanocomposite can be easily tailored by changing the feeding mass ratio of the CNF, CCS, and PANI. A relatively low CCS loading can produce a flexible electrode with an ultrahigh specific areal capacitance of 1838.5 mF cm−2 (150 F g−1) (1 mA cm−2), while high CCS loading can produce a free-standing electrode with a higher specific areal capacitance of 3297.2 mF cm−2 (220 F g−1) (1 mA cm−2). Besides, the robust three-dimensional network guarantees good cycling stability of the nanocomposite electrode (more than 83% retention after 3000 cycles). The tunable structure and electrochemical performance make the nanocomposite an ideal electrode for various electronic devices.

Converting cellulose to renewable energies and chemicals is the most promising and sustainable route to solving the crisis of fossil fuel resources. Up to now, however, it is still a big challenge to effectively transform recalcitrant cellulose into targeted compounds. For the first time, this study proposes a new and highly effective catalysis system with a synergy effect to convert cellulose into formic acid and levulinic acid simultaneously by using in situ carbonic acid from CO2 as a green acid in the presence of CrCl3. The synergy effect of in situ carbonic acid and CrCl3 could highly effectively hydrolyze cellulose to glucose, isomerize glucose to fructose, dehydrate fructose to HMF, and rehydrate HMF to formic acid and levulinic acid in a one-pot way. Here, 49% formic acid and 32% levulinic acid could be obtained from cellulose at a moderate condition. Our results demonstrated that this new catalysis system is comparable to other catalysis systems, and in situ carbonic acid can be used as a low-cost acid to replace mineral acids such as H2SO4, HCl, and H3PO4 and organic acids such as C6H6O3S, H2C2O4, and Cl3CCOOH to constitute novel, highly effective, low-cost, and less environmental impact catalysis systems for producing formic acid and levulinic acid from cellulose.Keywords: Carbon dioxide; Cellulose; Formic acid; In situ carbonic acid; Levulinic acid; Lewis acid

Hierarchical porous N-doped carbons have attracted great interest in energy storage and CO2 capture applications due to their unique porous structure and physicochemical properties. Fabrication of cost-effective and eco-friendly hierarchical porous N-doped carbons from renewable biomass resources is a sustainable route for future energy storage. However, it is still a big challenge to produce N-doped carbons with hierarchical porous structure from cellulose, which is the most abundant and widely available renewable resource on earth. Here, we designed a facile and effective strategy to produce hierarchical porous N-doped carbons from cellulose for high-performance supercapacitor and CO2 capture applications. In this method, hierarchical porous cellulose aerogels were first obtained via a dissolving–gelling process and then carbonized in NH3 atmosphere to give hierarchical porous N-doped carbon aerogels with more interconnected macropores and micropores. Due to the unique porous structure and physicochemical properties, the as-prepared N-doped carbon aerogels had a high specific capacitance of 225 F g−1 (0.5 A g−1) and an outstanding cycling stability. For the first time, we also demonstrated that this N-doped carbon aerogel exhibited a exceptional CO2 adsorption capacity of 4.99 mmol g−1, which is much higher than those of other porous carbons. This novel hierarchical porous N-doped carbon has great potential applications in CO2 capture, energy storage, porous supports, and electrochemical catalysis.

Hierarchical porous N-doped carbons show great potential applications in energy storage and CO2 capture. Renewable biomass chitosan, which is abundant and simultaneously contains large amounts of N and C, is an ideal alternative to fossil resources for sustainable and scale-up production of cost-effective N-self-doped carbons. In this work, we employed a new and effective strategy to obtain 3D hierarchical porous N-self-doped carbons from chitosan. The hierarchical porous structure of the N-self-doped carbons could be easily tailored to obtain nanorod interconnected and fiber-wall interconnected architectures without using any porogen, catalyst or activator. The nanorod interconnected porous carbon displayed a high specific surface area of 1408 m2 g−1 while the fiber-wall interconnected porous carbon exhibited an excellent specific capacitance of 261 F g−1 (0.5 A g−1) due to the desirable hierarchical framework. In addition, these hierarchical porous carbons had a good CO2 capture performance (3.07–3.44 mmol g−1 at 25 °C). This unique method is supposed to be a new strategy to create novel 3D hierarchical porous carbons for promising applications in supercapacitors, lithium ion batteries, fuel cells and sorbents.

Catalytic process is the key process for many chemical industries. In this study, a novel heterogeneous Pd (CMH–Pd(0)) has been prepared by the deposition of palladium nanoparticles (Pd NPs) onto the surface of carboxymethyl functionalized hemicelluloses using ethanol as solvent and in situ reducing agent. The as prepared catalyst was characterized by TEM, HR-TEM, XRD, FT-IR, TGA and XPS. The loading level of Pd in the CMH–Pd(0) catalyst was 0.38 mmol g−1. The catalyst showed high catalytic activity and versatility towards Heck coupling reactions under aerobic conditions and could be readily recovered and reused in at least five successive cycles without obvious loss in activity. The catalyst is promising for its renewability, environmental benefits, efficient catalytic activity, mild reaction conditions, simple product work-up and easy catalyst recovery.

The fabrication of superabsorbents for oil spillage cleanup is a hot topic today. However, the development of a low cost and highly efficient superabsorbent is still a big challenge. In this paper, we demonstrate a simple method to produce a low-cost, ultralight, elastic, and highly recyclable superabsorbent from renewable cellulose fibers via simple and environmentally friendly microfibrillation treatment and freeze-drying. Since microfibrillation of cellulose fibers resulted in hierarchical fibers that possess both fiber bulk and considerable microfibrils on the fiber surface, hierarchically porous sponges with ultralow density (0.0024 g cm−3) and high porosity (up to 99.84%) were obtained after freeze drying. The porous sponges after hydrophobic modification were elastic and exhibited rapid and outstanding absorption performances for various oils and organic solvents. The hydrophobic superabsorbent could selectively absorb oil from an oil–water mixture and showed an ultra-high absorption capacity of 88–228 g g−1, which is comparable to those of other novel carbon-based superabsorbents. More importantly, the superabsorbent showed excellent flexibility and elasticity, and could be repeatedly squeezed without structure failure (more than 30 times). The absorbed oil could be readily and rapidly recovered by means of simple mechanical squeezing, while the superabsorbent could be reused at once without any other treatment. The superabsorbent showed excellent recyclability and could be reused for at least 30 cycles while still maintaining high oil absorption capacity (137 g g−1 for pump oil). These advantages make the superabsorbent an ideal alternative for oil spillage cleaning.

•A novel plasticizer ChCl/urea was found to effectively plasticize cellulose films.•ChCl/urea showed good compatibility with cellulose.•No chemical reaction and crystallization occurred to ChCl/urea plasticized cellulose film.•ChCl/urea was comparable to glycerol and sorbitol, and could be used as a potential plasticizer for cellulose film.Recently, choline chloride/urea (ChCl/urea), a typical deep eutectic solvent (DES), has been found to possess various applications in organic synthesis, electrochemistry, and nanomaterial preparation. Herein we reported the first attempt to plasticize regenerated cellulose film (RCF) using ChCl/urea as an effective plasticizer. Meanwhile, RCFs plasticized with glycerol and sorbitol were also prepared for comparison. The plasticized RCFs were investigated by Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffraction (XRD), atomic force microscopy (AFM), and mechanical testing. Transparent and soft RCFs could be successfully prepared in the presence of ChCl/urea, and high elongation at break (34.88%) suggested a significant plasticizing efficiency. No new crystal and phase separation occurred to ChCl/urea plasticized RCFs. The thermal stability of ChCl/urea plasticized RCF was lowered. These results indicated that ChCl/urea was an effective plasticizer for producing cellulose films.

•Zn2+ and Ni2+ showed obvious effect on converting biomass into lactic acid.•Cu2+ and Fe3+ could accelerate the formations of levulinic acid and formic acid.•Positive correlations among xylose, glucose, and cellulose degradation were observed.•HTC of monosaccharide can be used to screen catalysts for biomass upgradation.Hydrothermal conversion (HTC) is an important thermochemical process to upgrade low-cost biomass into valuable chemicals or fuels. As compared with non-catalytic HTC, catalytic HTC shows high energy efficiency on biomass upgradation. In this work, the catalytic performances of various transition metal sulfates (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+) in the HTCs of xylose, glucose, and cellulose under different conditions were explored. Among these catalysts, Zn2+ and Ni2+ showed obvious effects on the conversions of xylose, glucose, and cellulose into lactic acid, while Cu2+ and Fe3+, which could significantly accelerate the hydrolysis of cellulose into glucose at 200 °C, displayed high efficiency on converting glucose and cellulose into levulinic acid and formic acid at high temperature. Additionally, significant positive correlative relationships among xylose, glucose, and cellulose degradations were observed. This study is helpful for screening appropriate catalysts for biomass upgradation through catalytic HTC of monosaccharide.

Cellulose nanocrystals (CNCs) pre-grafted with polymerizable groups have been used as nano crosslinking joints and nano reinforcements to synthesize highly-elastic hydrogels. However, the polymerizable CNCs usually have dispersion problems during hydrogel fabrication because of the hydrophobicity of the grafted polymerizable groups. In this study, TEMPO oxidation was successfully utilized to overcome this problem by introducing more hydrophilic groups on the CNCs surface, facilitating their homogeneous distribution in aqueous solution and hydrogels. Furthermore, AC and UC gels crosslinked by CNCs that were pre-grafted with acryloyl chloride (AC) and 10-undecylenoyl chloride (UC) on their surfaces were fabricated for finding out a more effective way to synthesize stronger nanocomposite hydrogels. The results showed that UC gels showed both higher tensile strength and higher elongation than the corresponding AC gels. It was shown that UC gels, which had longer grafted carbon chain lengths on CNC surfaces, possessed a better energy dissipation capacity under stretching than AC gels. The water swelling ratios of UC gels (13.0–36.7 g g−1) were also much higher than those of the corresponding AC gels (11.2–21.0 g g−1) as a result of larger spaces to hold water in the hydrogel network. This work gives an insight into the influence of carbon chain length on the properties of CNC crosslinked nanocomposite hydrogels, and provides an effective way to fabricate nanocomposite hydrogels with higher mechanical strength.

•Completely biomass-derived ESO–EC film was prepared in this work.•The mechanical performances of ESO–EC films were better than traditional plasticized EC films.•ESO–EC films showed good thermal stability and non-flammability.•Oxygen and water vapor permeabilities of EC films were decreased by ESO plasticizer.Epoxidized soybean oil (ESO), which is a biomass-derived resource, was first used as a novel plasticizer for ethyl cellulose (EC) film preparation. Surface morphologies, mechanical performances, thermal properties, oxygen and water vapor permeabilities of plasticized EC films were detected in detail to evaluate the plasticizing effect of ESO and explore the plastication mechanisms. Results showed that ESO was an effective plasticizer that outstripped conventional plasticizers, i.e. dibutyl phthalate (DBP) and triethyl citrate (TEC) in producing high-quality films. Especially, at plasticizer concentrations of 15–25%, ESO–EC films had preferable mechanical properties and better thermal stability, as well as non-flammability. In addition, the water vapor permeability of ESO–EC films was lower than that of traditional plasticized films. Their oxygen permeability was also remained in a low level. These outstanding performances were related to the relatively high molecular weight, hydrophobicity, chemical structure of ESO, and the intermolecular interactions between ESO and EC chains.

•Regenerating cellulose in acetone could prepare almost amorphous cellulose.•Acetone can impede the recrystallization of cellulose and improve its digestibility.•For DRC-a and WRC-w, over 90% of conversion ratio was achieved within 4 h.The present study investigated the impact of regeneration process on the crystalline structure and enzymatic hydrolysis behaviors of microcrystalline cellulose (MCC) regenerated from ionic liquid 1-butyl-3-methylimidazolium chloride. The crystalline structures of these regenerated samples were analyzed by X-ray diffraction. Results suggested that almost amorphous cellulose was obtained by regenerating MCC in acetone (DRC-a), while partial cellulose II structure could be found in these regenerated samples from water and ethanol. Additionally, the enzymatic hydrolysis behaviors of MCC and its regenerated samples were comparatively studied. Results showed that above 90% of cellulose could be converted into glucose within 4 h for DRC-a and regenerated cellulose without drying (WRC-w) as compared to that of MCC (9.7%). Therefore, the regeneration process could significantly influence the crystallinity and digestibility of cellulose.

Hydrothermal conversion is an important thermochemical process to upgrade low-cost lignocellulose into valuable chemicals or fuels. Studies on hydrothermal products compositions and their distributions are of great significance in lignocellulose upgradation. In this work, the major products of bamboo hydrothermally treated at 180–240 °C for 3–60 min and their distributions were comparatively studied. According to the hydrothermal conditions, the hydrothermal products were composed of 37.11–89.98% of solid residues, 4.51–20.41% of water-soluble fractions (WS), and 4.23–16.17% of acetone-soluble fractions (AS). The products in WS fractions mainly consisted of furfural (FF), 5-hydroxymethylfurfural (HMF), and phenolic compounds, while the products in AS fractions were mainly 4-hydroxy-4-methyl-2-pentanone and complex aromatic compounds with multibenzene rings. Additionally, the highest yields of FF (33.4%) and HMF (15.6%) were observed at 200 °C for 60 min and 240 °C for 60 min, respectively.

•Porous cellulose carbon aerogels were obtained via carbonized and activated simultaneously.•Cellulose carbon aerogel had a high specific surface area of 1364 m2/g and a high specific capacitance of 328 F g−1.•For the first time, we showed that the cellulose carbon aerogel had a good CO2 adsorption capacity.Fabrication of cost-effective and eco-friendly hierarchical porous carbons from the most abundant and widely available biomass cellulose represents a critical and sustainable way to solve the crisis of fossil resources. In this work, a hierarchical porous carbon aerogel with desirable macropores, mesopores, and micropores was obtained via dissolving-gelling and subsequent carbonizing-activating process. The CO2 activated carbon aerogel had a high specific surface area of 1364 m2/g and a high specific capacitance of 328 F g−1 (0.5 A g−1, 1.0 M H2SO4) as well as an outstanding cycling stability with 96% of the capacitance retention after 5000 charge/discharge cycles. More importantly, for the first time, we demonstrated that the cellulose-derived hierarchical porous carbon aerogel showed a good CO2 adsorption capacity of 3.42 mmol/g (at 1 atm and 298 K), which indicates the possibility of using this carbon aerogel for CO2 capture.Download full-size image

Flexible supercapacitors are extremely important for future various electronic devices. However, the development of cost-efficient and high-performance flexible supercapacitor electrodes remains a big challenge today. Herein, we present a novel flexible nanocomposite based on a cellulose-derived framework coated with polyaniline (PANI). In this nanocomposite, the cellulose nanofiber (CNF) provides mechanical strength due to its interconnected network, while the strapped cellulose-derived carbon sheet (CCS) with a unique morphology produces a porous structure and offers fast transfer pathways for the efficient diffusion of electrode ions. PANI imparts conductivity to the CNF and provides abundant active sites for charge storage. The porous structure and supercapacitive performance of this kind of nanocomposite can be easily tailored by changing the feeding mass ratio of the CNF, CCS, and PANI. A relatively low CCS loading can produce a flexible electrode with an ultrahigh specific areal capacitance of 1838.5 mF cm−2 (150 F g−1) (1 mA cm−2), while high CCS loading can produce a free-standing electrode with a higher specific areal capacitance of 3297.2 mF cm−2 (220 F g−1) (1 mA cm−2). Besides, the robust three-dimensional network guarantees good cycling stability of the nanocomposite electrode (more than 83% retention after 3000 cycles). The tunable structure and electrochemical performance make the nanocomposite an ideal electrode for various electronic devices.

The fabrication of superabsorbents for oil spillage cleanup is a hot topic today. However, the development of a low cost and highly efficient superabsorbent is still a big challenge. In this paper, we demonstrate a simple method to produce a low-cost, ultralight, elastic, and highly recyclable superabsorbent from renewable cellulose fibers via simple and environmentally friendly microfibrillation treatment and freeze-drying. Since microfibrillation of cellulose fibers resulted in hierarchical fibers that possess both fiber bulk and considerable microfibrils on the fiber surface, hierarchically porous sponges with ultralow density (0.0024 g cm−3) and high porosity (up to 99.84%) were obtained after freeze drying. The porous sponges after hydrophobic modification were elastic and exhibited rapid and outstanding absorption performances for various oils and organic solvents. The hydrophobic superabsorbent could selectively absorb oil from an oil–water mixture and showed an ultra-high absorption capacity of 88–228 g g−1, which is comparable to those of other novel carbon-based superabsorbents. More importantly, the superabsorbent showed excellent flexibility and elasticity, and could be repeatedly squeezed without structure failure (more than 30 times). The absorbed oil could be readily and rapidly recovered by means of simple mechanical squeezing, while the superabsorbent could be reused at once without any other treatment. The superabsorbent showed excellent recyclability and could be reused for at least 30 cycles while still maintaining high oil absorption capacity (137 g g−1 for pump oil). These advantages make the superabsorbent an ideal alternative for oil spillage cleaning.