TiO2-Coated Silicon Nanoparticle Core-Shell Structure for High-Capacity Lithium-Ion Battery Anode Materials.

Silicon-based anode materials are considered one of the highly promising anode materials due to their high theoretical energy density; however, problems such as volume effects and solid electrolyte interface film (SEI) instability limit the practical applications. Herein, silicon nanoparticles (SiNPs) are used as the nucleus and anatase titanium dioxide (TiO2) is used as the buffer layer to form a core-shell structure to adapt to the volume change of the silicon-based material and improve the overall interfacial stability of the electrode. In addition, silver nanowires (AgNWs) doping makes it possible to form a conductive network structure to improve the conductivity of the material. We used the core-shell structure SiNPs@TiO2/AgNWs composite as an anode material for high-efficiency Li-ion batteries. Compared with the pure SiNPs electrode, the SiNPs@TiO2/AgNWs electrode exhibits excellent electrochemical performance with a first discharge specific capacity of 3524.2 mAh·g-1 at a current density of 400 mA·g-1, which provides a new idea for the preparation of silicon-based anode materials for high-performance lithium-ion batteries.

Robust and adhesive lignin hybrid hydrogel as an ultrasensitive sensor.

The fabrication of hydrogel for sensing purposes remains to be a challenge since the hydrogel needs to have both good mechanical strength and adhesiveness. This work reports a robust and adhesive hydrogel mainly constructed with AgNPs@lignin, polyacrylamide (PAM) and sodium alginate (SA). The silver nanoparticles (AgNPs) were in-situ generated via the reaction between lignin and silver ammonia ([Ag(NH3)2]+). The resultant lignin hybrid hydrogel exhibited a stress, strain and tearing energy up to 0.055 MPa, 1000% and 250 J·m-2, respectively. Furthermore, the hydrogel adhered to different materials with an adhesion energy of higher than 230 J·m-2. This hydrogel was demonstrated to be an ideal sensing material since it could detect both large-scale motions and tiny physiological signals including breathing and pulse. The hydrogel also exhibited good antibacterial performance and biocompatibility. This work provides a good example to design a lignin-based high-performance hydrogel material for sensing purposes.

Wheat straw components fractionation, with efficient delignification, by hydrothermal treatment followed by facilitated ethanol extraction.

Lignocellulosic biomass fractionaion into its three major components is critically important for efficient feedstock utilization. The hydrothermal-ethanol method has broad application as its first step, hydrothermal treatment, provides high hemicellulose separation efficiency. However, it severely inhibits the delignification on the subsequent ethanol extraction. In this study, the second step, ethanol extraction, was facilitated by the addition of 3% NaOH and 3% H2O2, resulting in a significant improvement of lignin separation (by 48.2%). SEM, AFM, XPS, and XRD were used to characterize the surface composition of the remaining solids (crude cellulose) while the structure of isolated lignin was characterized by FT-IR, CP/MAS 13C NMR, GPC and TGA. The lignin samples isolated with both facilitated and non-facilitated ethanol extraction were compared to elucidate the lignin removal mechanism. The results showed that lignin degradation and crosslinking/polymerization occur in parallel during both the hydrothermal treatment and ethanol extraction.

Morphological changes of lignin during separation of wheat straw components by the hydrothermal-ethanol method.

The separation efficiencies of wheat straw components by hydrothermal treatment and ethanol extraction have been compared. The results showed that the lignin removal rate by two-step hydrothermal-ethanol method was significantly lower than that of single-step ethanol extraction. Microscopic and adsorption studies (using SEM/AFM, XPS and pore structure analysis) showed that during the hydrothermal treatment a large lignin fraction migrated from the intercellular layer and cell wall and deposited on the fiber surface. Furthermore, the deposited lignin then spread on the fiber surface to form a lignin coating layer, which prevented its dissolution in ethanol. Without prior heating, i.e., upon a single step ethanol extraction, the massive lignin deposition was avoided, presumably due to its efficient dissolution hindering its tight binding with carbohydrate polymers on the fiber surface. Therefore, the lignin removal efficiency was drastically reduced as a result of hydrothermal treatment compared to ethanol extraction.

Pore structure and pertinent physical properties of nanofibrillated cellulose (NFC)-based foam materials.

Nanofibrillated cellulose (NFC)-based foam materials have broad prospects in replacing traditional foams, due to its facile natural biodegradation. This study addressed the relationship between the foam preparation process parameters and resulting pore structure. An aqueous NFC suspension was freeze-dried while adding an organic solvent, ethanol, to adjust the curing process. The effects of the solid content and freeze-drying temperature on the microstructure and mechanical stability as well as heat transfer performance of the produced NFC-based foam were investigated. The foam obtained at a 3%-5% solid content featured a well-defined lamellar and interlayer pillar support structure. With an increase in the solid content, the average wall thickness increased whereas the average pore area decreased. Yet the pore density increased with the pore distribution becoming non-uniform. With a decrease in freezing temperature, the wall thickness decreased (with no wall structure at -196 °C) but the pore density increased, with the pores being distributed more uniformly. The foam mechanical strength and thermal conductivity were found to be linked to porosity. The foam material had the most suitable mechanical and thermal insulation properties when prepared with a 5% solid content at a freeze-drying temperature of -55 °C.

Joint action of ultrasonic and Fe³âº to improve selectivity of acid hydrolysis for microcrystalline cellulose.

In this study, the combination of Fe(3+)/HCl and ultrasonic treatment was applied to selectively hydrolyze cellulose for the preparation of microcrystalline cellulose (MCC). It was found that the crystallinity and specific surface area of hydrocellulose samples were higher (78.92% and 2.23581 m(2)g(-1), respectively), compared with the method that only used Fe(3+)/HCl catalyst without ultrasonic treatment. Meanwhile, the hydrolysate can be extracted and reused for cellulose hydrolysis for three runs, which was effective in saving the dosage of chemicals and reducing the pollution of the environment without affecting the properties of hydrocellulose. Moreover, the increased concentration of total reducing sugar (TRS) after three runs may be used as a valuable source in biofuels production. The technology of cellulose hydrolysis, by retaining the crystalline region for MCC products while promoting hydrolysis of amorphous region for further utilization is of great novelty, which may prove valuable in converting biomass into chemicals and biofuels, environmentally and economically.

Ultrasonic enhance acid hydrolysis selectivity of cellulose with HCl-FeCl3 as catalyst.

The effect of ultrasonic pretreatment coupled with HCl-FeCl3 catalyst was evaluated to hydrolyze cellulose amorphous regions. The ultrasonic pretreatment leads to cavitation that affects the morphology and microstructure of fibers, enhancing the accessibility of chemical reagent to the loosened amorphous regions of cellulose. In this work, Fourier transform infrared spectroscopy (FTIR) was used to identify characteristic absorption bands of the constituents and the crystallinity was evaluated by the X-ray diffraction (XRD) technique. The results indicated that appropriate ultrasonic pretreatment assisted with FeCl3 can enhance the acid hydrolysis of amorphous regions of cellulose, thus improving the crystallinity of the remaining hydrocellulose. It was observed that sonication samples that were pretreated for 300 W and 20 min followed by acid hydrolysis had maximum of 78.9% crystallinity. The crystallinity was 9.2% higher than samples that were not subjected to ultrasound. In addition, the average fines length decreased from 49 µm to 37 µm.