Atmosphere-free activation methodology for holey graphene/cellulose nanofiber-based film electrode with highly efficient capacitance performance

An efficient chamber-induced activation method was applied for the preparation of holey graphene/cellulose nanofiber-based film with high specific surface area(SSA)and multiple channels through the graphene nanosheets.With the cellulose nanofiber(CNF)simultaneously serving as“dispersing agent,”“spacer,”and“activating agent,”the graphene oxide(GO)nanosheets are perforated by the pyrolysis gas from CNF in the confined space inside the hybrid films,uniformly dispersed,and sandwiched between CNF networks with less agglomeration and restacking.Additionally,we have proved that H2O and H2 are primarily responsible for the activation and etching of GO/CNF film.As the CNF content increases,the mesoporosity of the activated reduced GO/CNF(A-RGO/CNF)film increases,and the graphene nanosheets show more nanopore perforations.Benefitting from the high SSA,high density,moderate mesoporosity,and abundant channels for ion diffusion through the graphene nanosheets,the A-RGO/CNF film exhibits the highest specific capacitance of 323(236)F g^(−1)(F cm^(−3))at 1Ag^(−1).For the A-RGO5/CNF5 film containing half CNF and half GO,an excellent comprehensive electrochemical performance including superior rate performance(208(160)F g^(−1)(F cm^(−3))at 60Ag^(−1))is exhibited.Moreover,the A-RGO5/CNF5 electrode in an all-solid-state flexible symmetric supercapacitor delivers a high specific capacitance of 250(193)F g^(−1)(F cm^(−3))at 1Ag^(−1).This study provides a novel idea for the preparation of holey graphene-based film for supercapacitor electrodes.The strategy of simultaneously employing CNF as“dispersing agent,”“spacer,”and“activating agent”also offers a new vision for the assembly of homogeneous nanohybrid material and the utilization of pyrolysis gas.

Cellulose nanofiber-derived carbon aerogel for advanced room-temperature sodium–sulfur batteries

Room-temperature sodium–sulfur(RT/Na–S)batteries are regarded as promising large-scale stationary energy storage systems owing to their high energy density and low cost as well as the earth-abundant reserves of sodium and sulfur.However,the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application.Herein,we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three-dimensional cellulose nanofiber-derived carbon aerogel on a glass fiber separator(denoted NSCA@GF).The hierarchical porous structures,favorable electronic conductivity,and three-dimensional interconnected network of N,S-codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion,which can act as the barrier layer and an expanded current collector to increase sulfur utilization.Moreover,the hetero-doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion,which is confirmed from experimental and theoretical results.As a result,the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity(788.8 mAh g^(−1) at 0.1 C after 100 cycles)and superior cycling stability(only 0.059%capacity decay per cycle over 1000 cycles at 1 C),thereby demonstrating the significant potential for application in high-performance RT/Na–S batteries.

Bacterial Cellulose Nanofibers as Reinforcement for Preparation of Bamboo Pulp Based Composite Paper

Bamboo fibers(BFs),with features of renewability and biodegradability,have been widely used in paper-making products.In order to improve the mechanical properties and water absorption behaviors of the BF paper,bacterial cellulose nanofibers(BCNFs)as environmentally friendly nano-fibrillated cellulose(NFC)were combined with BFs.The structures and properties of the BF/BCNF composite paper were characterized by field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),Fourier transforms infrared(FTIR)spectroscopy,mechanical tests,pore size tests,and water absorption tests.The results indicated that the addition of BCNFs could significantly improve the water absorption capacity and mechanical properties.The water absorption ratio of the BF/BCNF composite paper with a BCNF mass fraction of 9%comes to 443%,about 1.33 times that of the pure BF paper.At the same BCNF content,the tensile strength of the BF/BCNF composite paper in dry and wet states was 12.37 MPa and 200.9 kPa,respectively,increasing by 98.24%and 136.91%as compared with that of the BF paper.

Electrostatic Self-Assembly of Ti_(3)C_(2)T_(x) MXene/Cellulose Nanofiber Composite Films for Wearable Supercapacitor and Joule Heater

The titanium carbide nanosheets(MXene)hold great potential for fabricating high-performance electronics due to their two-dimensional layered structure,high electrical conductivity,and versatile surface chemistry.However,assembling the small MXene nanosheets into flexible macroscopic films for wearable electronics still remains a challenge.Herein,we report the hierarchical assembling of MXene nanosheets and cellulose nanofibers into high-performance composite films via an electrostatic self-assembly strategy induced by polyethyleneimine.Benefited from the nacre-like microstructure of MXene"bricks"and cellulose nanofibers"mortars"interlocked by polyethyleneimine via hydrogen bonding and electrostatic interaction,composite films possess integrated superior flexibility,high tensile strength,and stable electrical conductivity,which are advantageous for wearable electronic applications.To provide a proof-of-concept design,a symmetric quasi-solid-state supercapacitor with the as-prepared composite film as electrode is fabricated,which exhibits a specific capacitance of 93.9 mF cm^(-2)at a current density of 0.1 mA cm^(-2)and almost constant capacitive behavior under different bending states.In addition,the composite film possesses capacities of electrothermal conversion and complete degradation in a hydrogen peroxide solution.These results demonstrate that the electrostatically self-assembled composite films hold great promise in the development of highly flexible,mechanically robust,and environmentally friendly energy storage and conversion devices.

ZIF-67@Cellulose nanofiber hybrid membrane with controlled porosity for use as Li-ion battery separator

Zeolitic imidazolate framework-67(ZIF-67) was synthesized on the surface of cellulose nanofibers(CNFs)in methonal to address the problems of unhomogeneous pore size and pore distribution of pure CNF membrane.A combination of Energy Dispersive X-Ray Spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS) and X-ray powder diffraction(XRD) patterns were used to determine the successful synthesis of ZIF-67@CNFs.The size of the ZIF-67 particles and pore size of the ZIF-67@CNF membrane were50-200 nm and 150-350 nm, respectively.The prepared ZIF-67@CNF membrane exhibited excellent thermal stability,lower thermal shrinkage and high surface wettability.The discharge capacity retention of the Li-ion batteries(LIBs) made with ZIF-67@CNF,glass fiber(GF),CNF and commercial polymer membranes after 100 th cycle at 0.5 C rate were 88.41%,86.22%,83.27%,and 81.03%,respectively.LIBs with ZIF-67@CNF membrane exhibited a better rate capability than these with other membranes.No damage of porous structure or peel-off of ZIF-67 was observed in the SEM images of ZIF-67@CNF membrane after100 th cycle.The improved cycling performance,rate capability,and good electrochemical stability implied that ZIF-67@CNFs membrane can be considered as a good alternative LIB separator.

Tensile Properties of Mechanically-Defibrated Cellulose Nanofiber-Reinforced Polylactic Acid Matrix Composites Fabricated by Fused Deposition Modeling

Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these polymers,polylactic acid(PLA)is particularly promising due to its good mechanical properties,biocompatibility and thermoplasticity.In this work,we aim to enhance the mechanical properties of PLA using mechanically-defibrated cellulose nanofibers(CNFs)that exhibit remarkable mechanical properties and biodegradability.We also employ fused deposition modeling(FDM),one of the three-dimensional printing methods for thermoplastic polymers,for the low-cost fabrication of the products.Mechanically-defibrated CNF-reinforced PLA matrix composites are fabricated by FDM.Their tensile properties are investigated in two printing directions(0°/90°and+45°/-45°).The discussion about the relationship between printing direction and tensile behavoir of mechanically-defibrated CNF-reinforced PLA matrix composite is the unique point of this study.We further discuss the microstructure and fracture surface of mechanically-defibrated CNF-reinforced PLA matrix composite by scanning electron microscope.

Octadecylamine Graft-modified Cellulose Nanofiber and Its Reinforcement to Poly(butylene adipate-co-terephthalate) Composites

Biodegradable polymers such as poly(butylene adipate-coterephthalate)(PBAT)have attracted great interest as alternatives to traditional petroleum-based polymers.Nonetheless,it is necessary to improve some properties of PBAT,such as mechanical strength.Cellulose nanofiber(CNF)can improve PBAT mechanical strength,but its dispersion and compatibility in the PBAT matrix require further improvement.In this study,octadecylamine(ODA)was utilized to graft-modify CNF to change the fiberto-fiber interaction and improve its compatibility with the PBAT matrix.PBAT composites with 1 wt%CNF were prepared using a masterbatch premixing method to avoid CNF aggregation during extrusion.The effects of ODA graft modification on CNF properties were studied;varying degrees of CNF modification were investigated for their effect on PBAT properties.ODA-modified CNF(OCNF)/PBAT melt-extruded composites possessing 17.2%higher tensile strength than pure PBAT polymer were obtained without affecting the thermal stability of PBAT.As a result,surface modification of CNF with ODA is an effective strategy for improving CNF-PBAT compatibility.

Structural Properties and Potential Applications of Cellulose Nanofiber from Bamboo Shoot Shell

Bamboo shoot shell（BSS）,a by-product from bamboo shoot processing industries,is a natural resource of cellulose. In this study,high-pressure homogenization assisted with acidolysis treatment was employed to produce BSS cellulose nanofiber（CNF）,and the structure was characterized by powder X-ray diffraction（XRD）,Fourier-transform infrared（FT-IR） spectroscopy,atomic force microscopy（AFM）,high resolution transmission electron microscopy（HTTEM）,thermogravimetric analysis（TGA）,and ^13 C nuclear magnetic resonance（NMR）. Moreover,the structure and properties of CNF were compared with those of BSS insoluble dietary fiber（IDF）. The results showed that CNF was in the form of a grid-like micro fiber,and its particle size was obviously reduced,while the crystallinity,thermal stability and solubility were increased. The results indicated that high-pressure homogenization assisted with acidolysis treatment was an effective method to prepare the BSS CNF,which could be a promising biopolymer reinforced material.

Preparation and Characterization of Co_(3)O_(4)/Graphene/Cellulose Nanofiber Composite Films

Nanocellulose has served as an eye-catching nanomaterial for constructing advanced functional devices with renewability,light weight,flexibility,and environmental friendliness.In this study,Co_(3)O_(4)/graphene/cellulose nanofiber(CNF)flexible composite films,in which the CNF acted as a spacer for the graphene,were prepared via a facile and scalable vacuum filtration method.The effects of the CNF on the microstructure,hydrophilicity,thermal stability,tensile strength,surface resistance,and electrochemical performance of the Co_(3)O_(4)/graphene/CNF composite films were systematically investigated.The results showed that the synergistic interaction of the CNF and graphene substantially improved the overall properties of the Co_(3)O_(4)/graphene/CNF composite films,particularly their hydrophilicity and tensile strength.Meanwhile,Co_(3)O_(4)/graphene/CNF composite films with a CNF content of 4%appeared to have the optimal electrochemical performance,with an area specific capacitance of 56 mF/cm^(2) and prominent capacitance retention of 95.6%at a current density of 1 A/g after 1000 cycles.This work demonstrated that the prepared Co_(3)O_(4)/graphene/CNF flexible composite films have great application potential in the field of flexible energy storage devices.

Emulsion Graft Polymerization of Methyl Methacrylate onto Cellulose Nanofibers

Methyl methacrylate (MMA) was successfully grafted onto cellulose nanofibers (CNFs) at room temperature in an emulsion system using a diethyl(1,10-phenanthroline N1,N10)zinc(II) complex (Phen-DEZ) with oxygen as the radical initiator. The effects of reaction temperature, initiator concentration, and monomer content on the grafting reaction were investigated. The molecular weight of the non-grafted PMMA, which was produced during graft polymerization, was more than 1 million, as determined by size exclusion chromatography. The PMMA-grafted CNFs were analyzed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, which confirmed the grafting of PMMA on the nanofiber surface. The study presents a strategy for the grafting of high-molecular weight PMMA onto CNFs in an emulsion system using Phen-DEZ and O2.

Programmable and reconfigurable humidity-driven actuators made with MXene(Ti_(3)C_(2)T_(x))-cellulose nanofiber composites for biomimetic applications

Smart actuators have a wide range of applications in bionics and energy conversion.The ability to reconfigure shape is essential for soft actuators to achieve various shapes and deformations,which is a crucial feature for next-generation actuators.Nonetheless,it is still an enormous challenge to establish a straightforward approach to creating programmable and reconfigurable actuators.MXene-cellulose nanofiber composite film(MCCF)with a brick-and-mortar hierarchical structure was produced through a vacuum filtration process.MCCF demonstrates impressive mechanical properties such as a tensile stress of 68 MPa and a Young’s modulus of 4.65 GPa.Besides,the MCCF highlights its potential for water-assisted shaping/welding due to the abundance of hydrogen bonds between MXene and cellulose nanofibers.MCCF also showcases capabilities as a humiditydriven actuator with a rapid response rate of 550°·s^(−1).Using the methods of water-assisted shaping/welding,several bionic actuators(such as flower,butterfly,and muscle)based on MCCF were designed,highlighting their versatility in applications of smart actuators.The research showcases the impressive capabilities of MXene-based actuators and offers beneficial insights for the advancement of future intelligent materials.

High-performance flexible all-solid-state asymmetric supercapacitors based on binder-free MXene/cellulose nanofiber anode and carbon cloth/polyaniline cathode

The search for wearable electronics has been attracted great efforts,there is an ever-growing demand for all-solid-state flexible energy storage devices.However,it is a challenge to obtain both positive and negative electrodes with excellent mechanical strength and match positive and negative charges to achieve high energy densities and operate voltages to satisfy practical application requirements.Here,flexible MXene(Ti_(3)C_(2)Tx)/cellulose nanofiber(CNF)composite film negative electrodes(MCNF)were fabricated with a vacuum filtration method,as well as positive electrodes(CP)by combining polyaniline(PANI)with carbon cloth(CC)using an in-situ polymerization method.Both positive and negative free-standing electrodes exhibited excellent electrochemical behavior and bendable/foldable flexibility.As a result,the all-pseudocapacitance asymmetric device of MCNF//CP assembled with charge-matched between anode and cathode achieves an extended voltage window of 1.5 V,high energy density of 30.6 Wh·kg^(−1)(1211 W·kg^(−1)),86%capacitance retention after 5000 cycles,the device maintains excellent bendability,simultaneously.This work will pave the way for the development of all-pseudocapacitive asymmetric supercapacitors(ASC)with simultaneously preeminent mechanical properties,high energy density,wide operating voltage window.

Flexible and ultrathin dopamine modified MXene and cellulose nanofiber composite films with alternating multilayer structure for superior electromagnetic interference shielding performance

With the development of modern electronics,especially the next generation of wearable electromagnetic interference(EMI)shielding materials requires flexibility,ultrathin,lightweight and robustness to protect electronic devices from radiation pollution.In this work,the flexible and ultrathin dopamine modified MXene@cellulose nanofiber(DM@CNF)composite films with alternate multilayer structure have been developed by a facile vacuum filtration induced self-assembly approach.The multilayered DM@CNF composite films exhibit improved mechanical properties compared with the homogeneous DM/CNF film.By adjusting the layer number,the multilayered DM3@CNF2 composite film exhibits a tensile strength of 48.14 MPa and a toughness of 5.28 MJ·m^(–3) with a thickness about 19μm.Interestingly that,the DM@CNF film with annealing treatment achieves significant improvement in conductivity(up to 17264 S·m^(–1))and EMI properties(SE of 41.90 dB and SSE/t of 10169 dB·cm^(2)·g–1),which still maintains relatively high mechanical properties.It is highlighted that the ultrathin multilayered DM@CNF film exhibits superior EMI shielding performance compared with most of the metal-based,carbon-based and MXene-based shielding materials reported in the literature.These results will offer an appealing strategy to develop the ultrathin and flexible MXene-based materials with excellent EMI shielding performance for the next generation intelligent protection devices.

Intrinsic conductive cellulose nanofiber induce room-temperature reversible and robust polyvinyl alcohol hydrogel for multifunctional self-healable biosensors

Polyvinyl alcohol(PVA)hydrogels are widely used for flexible sensors by adding various conductive substances due to their excellent mechanical properties and self-healing properties.However,most of the conductive substances added to PVA hydrogel sensors are currently complicated to prepare,costly,and environmentally unfriendly.Herein,to overcome this challenge,we successfully prepared intrinsic conductive cellulose nanofiber(G-CNF)by simply applying sulfuric acid and a low-energy water bath with heat treatment,and obtained a powerful multifunctional self-healing PGC hydrogel biosensor using dynamic chemical cross-linking of PVA and borax with glycerol and G-CNF.The obtained PGC hydrogels have excellent mechanical properties(strain:950%),good adhesion ability,robust self-healing properties,and room-temperature reversibility,due to the presence of conductive networks and hydrogen bonds within PGC hydrogel.Especially,PGC hydrogels with the graphene structured G-CNF have a fast response to various signals and good stability with gauge factor(GF)values up to 1.83,as well as a sensitive response to temperature(temperature coefficient of resistance(TCR)up to 1.9),which can be designed as a variety of biosensors,such as human motion monitoring,information encryption/transmission,and real-time temperature monitoring biosensors.Thus,PGC hydrogels as multifunctional self-healing hydrogel biosensors pave the way for the development of flexible biosensors in wearable devices,human–computer interaction,and artificial-related applications.

Flexible, ultrathin, and multifunctional polypyrrole/cellulose nanofiber composite films with outstanding photothermal effect, excellent mechanical and electrochemical properties

Electrodes that combine energy storage with mechanical and photothermal performance are necessary for efficient development and use of flexible energy storage and conversion devices.In this study,the flexible,ultrathin,and multifunctional polypyrrole/cellulose nanofiber composite films were fabricated via a one-step“soak and polymerization”method.The dense sandwich structure and strong interfacial interaction endowed polypyrrole/cellulose nanofiber composite films with excellent flexibility,outstanding mechanical strength,and desired toughness.Interestingly,the polypyrrole/cellulose nanofiber composite film electrodes with quaternary amine functionalized cellulose nanofiber had the highest specific mass capacitance(392.90 F∙g^(–1))and specific areal capacitance(3.32 F∙cm^(–2))than the electrodes with unmodified and carboxyl functionalized cellulose nanofibers.Further,the polypyrrole/cellulose nanofiber composite films with sandwich structure had excellent photothermal conversion properties.This study demonstrated a feasible and versatile method for preparing of multifunctional composite films,having promising applications in various energy storage fields.

High-performance polyamide nanofiltration membrane with arch-bridge structure on a highly hydrated cellulose nanofiber support

Nanofiltration(NF)membranes with outstanding performance are highly demanded for more efficient desalination and wastewater treatment.However,improving water permeance while maintaining high solute rejection by using the current membrane fabrication techniques remains a challenge.Herein,polyamide(PA)NF membrane with archbridge structure is successfully prepared via interfacial polymerization(IP)on a composite support membrane of saltreinforced hydrophilic bacterial cellulose nanofibers(BCNs)nanofilm/polytetrafluoroethylene(BCNs/PTFE).The strong hydration of BCNs promotes Marangoni convection along water/organic solvent interface during the IP process,which creates extra area for interfacial reaction and produces a thin PA active layer with arch-bridge structures.These arch-bridge structures endow the resulting PA active layer with substantial larger active area for water permeation.Consequently,the PA NF membrane exhibits exceptional desalination performance with a permeance up to 42.5 L m^-2h^-1bar^-1 and a rejection of Na2SO4as high as 99.1%,yielding an overall desalination performance better than almost all of the state-of-the-art NF membranes reported so far in terms of perm-selectivity.

Water molecule-induced hydrogen bonding between cellulose nanofibers toward highly strong and tough materials from wood aerogel

Lightweight,highly strong and bio-based structural materials remain a long-lasting challenge.Here,inspired by nacre,a lightweight and high mechanical performance cellulosic material was fabricated via a facile and effective top-down approach and the resulting material has a high tensile strength of149.21 MPa and toughness of 1.91 MJ/m^(3).More specifically,the natural balsawood(NW) was subjected to a simple chemical treatment,removing most lignin and partial hemicellulose,follow by freeze-drying,forming wood aerogel(WA).The delignification process produced many pores and exposed numerous aligned cellulose nanofibers.Afterwards,the WA absorbed a quantity of moisture and was directly densified to form above high-performance cellulosic material.Such treatment imitates highly ordered"brick-and-mortar" arrangement of nacre,in which water molecules plays the role of mortar and cellulose nanofibrils make the brick part.The lightweight and good mechanical properties make this material promising for new energy car,aerospace,etc.This paper also explains the strengthening mechanism for making biomimetic materials by water molecules-induced hydrogen bonding and will open a new path for designing high-performance bio-based structural materials.

Reactive Dyeing of Electrospun Cellulose Nanofibers by Pad-steam Method

Based on the functional properties of electrospun cellulose nanofibers(CNF),scientists are showing substantial interest to enhance the aesthetic properties.However,the lower color yield has remained a big challenge due to the higher surface area of nanofibers.In this study,we attempted to improve the color yield properties of CNF by the pad-steam dyeing method.Neat CNF was obtained by deacetylation of electrospun cellulose acetate(CA)nanofibers.Three different kinds of reactive dyes were used and pad-steam dyeing parameters were optimized.SEM images revealed smooth morphology with an increase in the average diameter of nanofibers.FTIR results showed no change in the chemical structure after dyeing of CNF.Color fastness results demonstrated excellent ratings for reactive dyes,which indicate good dye fixation properties and no color loss during the washing process.The results confirm that the pad-steam dyeing method can be potentially considered to improve the aesthetic properties of CNF,which can be utilized for functional garments,such as breathable raincoats and disposable face masks.

Quaternized chitosan-assisted in situ synthesized CuS/cellulose nanofibers conductive paper for flexible electrode

Cellulose nanofibers(CNF)are considered to be a potential substrate of energy material for energy storage devices due to the foldable,lightweight,recyclable and environmentally friendly feature.However,the energy materials tend to distribute unevenly or fall off from CNF easily,resulting in the decrease of the devices’overall performance.Here,for the first time,we used quaternized chitosan(QCS)as stabilizer and adhesive to in situ synthesize and deposite copper sulfide nanocrystals(CuS-NCs)on CNF and further obtained the conductive paper for flexible supercapacitors.In the presence of QCS,CuS-NCs deposited in situ on CNF can be capped and stabilized by the QCS molecular chains for uniform distribution,which is conducive to the capacitive behavior and electrochemical stability of composite paper.The result shows that the specific capacitance of the composite paper was as high as 314.3 F/g at a current density of 1 A/g,a high rate capacitance of 252.6 F/g was achieved even at a high current density of 10 A/g.It reveals that the composite paper exhibited better electrochemical performance than many other CuS-based electrode materials for supercapacitor.More importantly,the composite paper performed well in various folding state without changing much electrochemical performance.Therefore,this work provides a novel strategy to in situ fabricate paper-based electrode for nextgeneration flexible energy-storage system.

Effect of oxygen plasma treatment on the nanofiltration performance of reduced graphene oxide/cellulose nanofiber composite membranes

Graphene based nanosheets have been widely used as building blocks for fabrication of superior separation membrane for water processing.In particular,membranes made of reduced graphene oxide(rGO)show better stability compared with graphene oxide(GO).However,densely stacked of rGO often results in low water flux.In this study,cellulose nanofibers(CNFs)were incorporated into the rGO laminates by vacuum filtration of dilute GO/CNF solution and thermal reduction at 150C for 1.5 h.The resulting rGO/CNF membrane was treated with oxygen plasma for 1–4 min to create nanopores on the membrane surface for the purpose of enhancing nano-filtration performance.The results showed that the optimum membrane performance was obtained by using the equal amount of GO(31.83 mg m^(-2))and CNFs accompanied by 3 min of plasma treatment,exhibiting a pure water permeance of 37.23.9 L m^(-2)h^(-1)bar^(-1)maintaining a rejection above 90%for Acid Fuchsin(1.2×1.1 nm),Rose Bengal(1.5×1.2 nm)and Brilliant Blue(2.2×1.7 nm).