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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]

• 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]

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]

• 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]