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Graphical abstract Highlights • Enzyme and cold alkali assisted mechanical production of CNF was studied. • Thermal stability of CNF will be affected by cellulose crystalline structure. • Presence of hemicellulose in CNF improves their thermal stability. • Presents new avenues for research on CNF-based electronic devices. Abstract Lignocellulosic biomass is the most abundant renewable resource on the earth. With the development of related fields, the high value utilization of lignocellulosic biomass has gradually become a new avenue for research. In this study, unbleached bagasse pulp was pretreated with xylanase and cold alkali to partially remove hemicellulose and convert to some cellulose I into cellulose II. Cellulose nanofibrils (CNF) were then obtained through ultra-micro grinding and high-pressure homogenization. The prepared CNF were characterized by TEM, Zeta potential, ATR-FTIR and XRD, and a thermogravimetric analyzer was used to analyze the thermal stability of CNF. The results show that xylanase pretreatment can improve the dispersion of fibers during mechanical treatment and can enhance the crystallinity of CNF. With an increase in alkali concentrations, the proportion of cellulose II structures increased, while cellulose crystallinity levels decreased due to the folding of cellulose chains. Under the common influence of crystallinity and crystal structures, the thermal stability of the CNF prepared after cold alkali pretreatment underwent an increasing trend. This shows that the influence of crystal structures on the thermal stability of CNF gradually plays a dominant role as alkali concentrations increase. [ABSTRACT FROM AUTHOR]

In the present study, cellulose nanofibrils (CNF) were produced from unbleached eucalyptus pulp, and the effect of enzymatic treatment on the properties of CNF was studied. Moreover, the mechanism of enzymatic treatment on the dispersion and film properties of CNF was speculated. The xylanase pretreatment facilitated the deconstruction of pulp into CNF via mechanical shearing and high-pressure homogenization, while the hemicellulose composition was preserved. Compared to the control, the CNF suspensions made from the xylanase pretreated pulp were more crystalline with higher dispersion, optical and rheological properties. CNF films were produced with a vacuum filtration process. The optical and mechanical strength properties of the CNF films were improved by the removal of hemicellulose. It was found that the carboxyl and hydroxyl groups played key roles in affecting the dispersion and film properties of the CNF. The carboxyl group content increased after the enzymatic pretreatment, which benefits the even distribution of CNF in water. The mechanical strength of the CNF films was further improved by exposing the hydroxyl group when lignin-carbohydrate complexes were de-structured by the enzymes. This study expanded the application of CNF produced from unbleached pulp. The theoretical foundation for stabilizing the CNF suspension and the high-speed dehydration of CNF films were explored for the continuous roll to roll production of CNF film. [ABSTRACT FROM AUTHOR]

• PFOTES was used to enhanced the tribo-polarity and hydrophobicity of CNF-based TENG. • PFOTES-CNF-based TENG exhibit enhanced triboelectric performance. • The Isc reached 9.3 μA, which is about twice that of a pure CNF-based TENG. • The PFOTES-CNF-based TENG retains 70% of the initial output at 70% ambient humidity. Cellulose is the most abundant natural polymer on earth. Because it is renewable, biodegradable, and biocompatible, it offers distinct advantages as a starting material for bio-based triboelectric nanogenerator (bio-TENG). However, weak polarity, poor hydrophobicity, and insufficient functionalization on the natural cellulose surface severely limit the development of high-performance cellulose-based TENGs. In this work, chemical functionalization is employed to control the surface polarizability and hydrophobicity of cellulose nanofibrils (CNFs). Functional groups on the CNF surface are modified with triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane (PFOTES) in a straightforward and facile process. Fluorine-bearing silane chains are grafted to the surface of CNFs, which increases their triboelectric charge density and improves their hydrophobicity. Experimental results demonstrate that the surface polarity of CNFs is greatly improved after PFOTES modification. The PFOTES-CNF-based TENG exhibits good resistance to humidity and long-term cycle stability, and it retains 70% of the initial output performance at 70% ambient humidity. The short-circuit current of the PFOTES-CNF-based TENG reached 9.3 μA, which is about twice that of CNF-based TENG prior to modification. These results clearly indicate that PFOTES can be used to control CNF surface polarizability and hydrophobicity, advancing the search for durable, high-performance, degradable bio-TENGs. [ABSTRACT FROM AUTHOR]

• A novel CNF/rGO aerogel with supporting column and 2D layered structure was prepared. • CNF/rGO aerogel film with low loading has efficient thermal management performance. • Thermal conductivity of CNF/rGO aerogel with 1 wt.% rGO can reach upto 16.304 W/m K. • The CNF/rGO aerogel film shows potential for emergent energy storage devices. Cellulosic materials are especially suitable for use in flexible electronic products because of their light weight, good tolerance, flexibility, and biodegradability. In this work, cellulose nanofibril/reduced graphene oxide (CNF/rGO) nanocomposites are prepared and the thermal properties of the nanocomposites are analyzed. A supporting column and 2D layered structure porous paper is obtained with CNF/rGO as the heat conduction skeleton, which shows excellent thermal conductivity. The results show that this novel CNF/rGO porous paper has an ultrahigh in-plane thermal conductivity of up to 16.30 W/m K when only 1 wt.% rGO is added in, demonstrating efficient thermal management performance of the CNF-based nanocomposites with low rGO loading. We believe that the development of thermal management techniques using CNFs and rGO for emergent energy storage devices will lead to efficient technologies, further easing our daily lives. [ABSTRACT FROM AUTHOR]

Nanocomposites consisting of cellulose nanofibrils (CNFs) and nano-aluminum nitride (AlN) were prepared using a simple vacuum-assisted filtration process. Bleached sugarcane bagasse pulp was treated with potassium hydroxide and sodium chlorite, and was subsequently ultra-finely ground and homogenized to obtain CNFs. Film nanocomposites were prepared by mixing CNFs with various AlN amounts (0–20 wt.%). X-ray diffraction revealed that the crystal form of CNF-AlN nanocomposites was different to those of pure CNFs and AlN. The mechanical performance and thermal stability of the CNF-AlN nanocomposites were evaluated through mechanical tests and thermogravimetric analysis, respectively. The results showed that the CNF-AlN nanocomposites exhibited excellent mechanical and thermal stability, and represented a green renewable substrate material. This type of nanocomposite could present great potential for replacing traditional polymer substrates, and could provide creative opportunities for designing and fabricating high-performance portable electronics in the near future. [ABSTRACT FROM AUTHOR]

Highlights • Enzyme and cold alkali assisted mechanical production of CNF were studied. • Cold alkali pretreatment could change cellulose structure from type I to type II. • Environment-friendly method for preparing high thermal stable CNF was obtained. Abstract In this work, cellulase, low-concentration cold alkali and cellulase combined with cold alkali were used to pretreat unbleached bagasse pulp from which cellulose nanofibrils (CNFs), about 30 nm in diameter, were successfully prepared through ultrafine grinding and high-pressure homogenization. X-ray diffraction analysis showed that cellulase pretreatment increased the crystallinity of CNFs. After low-concentration cold alkali pretreatment, the crystallinity of CNFs significantly reduced and the crystal structure of the cellulose changed from type I to type II. Thermogravimetric analysis showed that CNFs prepared by cellulase combined with cold alkali treatment produced more regenerated cellulose and had lower thermal stability. The use of cellulase and low-concentration cold alkali pretreatments combined with ultrafine grinding and high-pressure homogenization is an environment-friendly method for preparing CNFs. The use of low-concentration cold alkali reduces the consumption of alkali and clean water. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermal conductivity CNF/AlN films were obtained by a simple vacuum filtration method. • Addition of AlN increased the thermal impedance of the CNF/AlN hybrid films. • High thermal conductivity (4.20 W/mK for 25 wt.% of AlN) achieved along film surface. • This CNF/AlN film effectively facilitates thermal management of energy storage device. Abstract As energy storage devices are becoming more highly integrated, it is inevitable that heat accumulation will occur under high power working conditions. Finding efficient thermal management materials for cooling down electronic components is an urgent problem for energy storage devices. In this work, a thermally conductive film with tailorable macroproperties is fabricated by using a simple vacuum filtration method, using cellulose nanofibrils as the polymer substrate and assembly with aluminum nitride nanosheets. The interaction between the cellulose nanofibrils and aluminum nitride nanosheets is studied, and the electronic components made using the composite exhibit excellent thermal conductivity, thermal stability and mechanical flexibility. A high thermal conductivity is achieved along the film surface (up to 4.20 W/mK for 25 wt.% of aluminum nitride). This green material can effectively promote potential applications as lateral heat spreaders in flexible energy storage devices and the thermal conductivity may facilitate the applications in thermal management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developing a superhydrophobic triboelectric material. • Designing a triboelectric nanogenerator with an internal grid structure. • It can collect distributed energy and exhibit excellent output performance. The development of triboelectric nanogenerators (TENGs) has made it possible to collect large-scale distributed energy, and their applications in the field of energy harvesting are promising. However, the erosion of water molecules in humid environments is a major challenge limiting the application of triboelectric materials. In this study, superhydrophobic methylated cellulosic triboelectric materials were prepared and rectangular TENG with an internal grid structure was designed for distributed energy harvesting. Interfacial modification of the cellulose nanofibrils (CNF) surface by silica nanoparticles to form a nanoscale microstructured surface further enhances the hydrophobicity of the triboelectric material. It was found that the modified CNF triboelectric material has excellent super-hydrophobicity (WCA: 154.7°), surface roughness (RMS: 72.61), and low surface energy. In addition, the RT-TENG internal grid structure is designed to allow external impact forces to be applied more uniformly to the surface of the f triboelectric material, demonstrating excellent electrical output performance (120 V) and cycling stability (10,000 cycles) when applied to distributed energy harvesting. This study provides a novel strategy for the design and preparation of superhydrophobic triboelectric materials and guides the study of distributed energy harvesting. [ABSTRACT FROM AUTHOR]

• CNFs reinforced pure cellulose paper (CCP) was prepared by facile filtration process. • The ionic conductivity of CCP with 20 wt.% CNFs was 25 % higher compared to polypropylene (PP) separator. • The tensile of CCP with 20 wt.% CNFs was 227 % higher compared to cellulose paper (CP) separator. • CCP with 20 wt.% CNFs has better working stability than control. • The LIB assembled with CCP separator displays better cycle performance than control. Separator is a vital component of lithium-ion batteries (LIBs) due to its important roles in the safety and electrochemical performance of the batteries. Herein, we reported a cellulose nanofibrils (CNFs) reinforced pure cellulose paper (CCP) as a LIBs separator fabricated by a facile filtration process. The nanosized CNFs played crucial roles as a tuner to optimize the pore size of the as-prepared CCP, and also as a reinforcer to improve the mechanical strength of the resultant CCP. Results showed that the tensile strength of the CCP with 20 wt.% CNFs was 227 % higher compared to the commercial cellulose separator. In addition, the lithium cobalt oxide/lithium metal battery assembled with CCP separator displayed better cycle performance and working stability (capacity retention ratio of 91 % after 100 cycles) compared to the batteries with cellulose separator (52 %) and polypropylene separator (84 %) owing to the multiple synergies between CCP separator and electrolytes. [ABSTRACT FROM AUTHOR]

• Hemicelluloses content in the range of 9.7–21.7 wt.% led to CNFs with average diameter. • CNFs shows good thermal stability when hemicelluloses content is low. • A decrease in hemicelluloses will improve the thermal stability of the CNFs. In this work, cellulose nanofibrils (CNFs) are produced from bagasse pulps with differing hemicelluloses contents by ultrafine grinding and high-pressure homogenization. The results showed that hemicelluloses content in the range of 9.7–21.7 wt.% led to nanofibrils with average diameter. A decrease in hemicelluloses content can enhance the crystallinity and improve the thermal stability of the CNFs. The activation energy of the CNF samples with hemicelluloses contents of 9.7 wt.%, 12.72 wt.%, 15.7 wt.%, 18.76 wt.%, and 21.7 wt.% are 713.03, 518.93, 462.62, 421.78, and 211.11 kJ/mol, respectively, when the conversion rate is increased from 30%–90%. These results demonstrate that hemicelluloses content has a considerable influence on the properties of CNFs. This work provides a theoretical basis for high-value utilization of CNFs, and enriches useful information on the application of CNF materials. [ABSTRACT FROM AUTHOR]

• Potential of cellulose nanofibrils for electronic was highlighted. • Application of cellulose nanofibril-based materials for SCs, LIBs, and solar cells is reviewed. • Challenges of cellulose nanofibril-based energy storage devices were reviewed. In recent years, extensive efforts have been devoted to electronic miniaturization and integration. Accordingly, heating up of electronics has become a critical problem that needs to be urgently solved by efficient and reliable thermal management. Electronic device substrates made of cellulose nanofibrils (CNFs) exhibit outstanding flexibility, mechanical properties, and optical properties. Combining CNFs with high-thermal-conductivly fillers is an effective thermal management technique. This paper focuses on the thermal management of electronic devices and highlights the potential of CNF-based materials for efficient thermal management of energy storage electronic such as supercapacitors, lithium-ion batteries and solar cells. A high-thermal-conductivity composite material for electronic devices can be obtained by combining CNFs as the framework material with carbon nanotubes, graphene, and inorganic nitrides. Moreover, The research progress in the application of CNFs-based materials for supercapacitors, lithium-ion batteries and solar cells is highlighted, and the emerging challenges of different CNFs-based energy storage devices are discussed. [ABSTRACT FROM AUTHOR]