Rongfeng Hu,Zhao Zeng,Shihao Jin,Kaixu Yang,Fei Liu,Yun Yi,Jianxin Cao
LiFe1–xMnxPO4 (0 < x < 1) has a high operating voltage range and theoretical energy density, but its actual capacity decreased due to its low electronic conductivity. To overcome this problem, we successfully prepared LiFe0.4Mn0.6PO4/C (LFMP/C) with a uniform carbon coating by a one-step solvothermal method using bamboo shavings as the carbon source. The results showed that heating at a reaction temperature of 180 °C for 18 h was the optimal synthesis condition to obtain LFMP/C. The addition of bamboo shaving-based carbon was effective in inhibiting excessive grain growth and reducing particle size. The disordered carbon layer enhanced the surface conductivity by connecting the surfaces of the particles. The synergistic effect of the nanoparticle size and the pores distributed around the particles increased the specific surface area and thus improved the contact area between the active substance and the electrolyte. Furthermore, there were improvements in electronic conductivity and ionic mobility. LFMP/C-16 showed initial discharge capacities of 150.1 and 143.5 mAh·g–1 at rates of 0.1 and 0.2C, respectively, with a capacity retention rate of 97.73% after 100 cycles, indicating excellent cyclic performance.
Bamboo shavings, the outer or intermediate layer of bamboo stems, are the bulk of by-products produced in bamboo processing. In this study we investigated the isolation, chemical characterization, and immunostimulatory activity in vitro of the hemicelluloses from bamboo shavings. Shavings were first pretreated by steam explosion. The optimal pretreatment was found to be steam explosion at 2.2 MPa for 1 min. Following this pretreatment, the yield of hemicelluloses reached (2.05±0.22)% (based on the dry dewaxed raw materials), which was 5.7-fold higher than that of untreated samples. Bamboo-shavings hemicellulose (BSH) was then prepared by hot water extraction and ethanol precipitation from the steam-exploded shavings. Purification of BSH by anion-exchange chromatography of diethylaminoethanol (DEAE)-sepharose Fast Flow resulted in a neutral fraction (BSH-1, purity of 95.3%, yield of 1.06%) and an acidic fraction (BSH-2, purity of 92.5%, yield of 0.79%). The weight-average molecular weights ( M w ) of BSH-1 and BSH-2 were 12 800 and 11 300 g/mol, respectively. Chemical and structural analyses by Fourier transform infrared spectroscopy (FT-IR), 1D ( 1 H and 13 C) and 2D (heteronuclear single quantum correlation (HSQC)) nuclear magnetic resonance (NMR) spectra revealed that BSH-1 was O -acetylated-arabinoxylan and BSH-2 was O -acetylated-(4- O -methylglucurono)-arabinoxylan. BSH-1 had a higher content of acetyl groups than BSH-2. For the immunomodulatory activity in vitro, BSH and BSH-2 significantly stimulated mouse splenocyte proliferation while BSH-1 had no effect; BSH, BSH-1, and BSH-2 markedly enhanced the phagocytosis activity and nitric oxide production of the murine macrophage RAW264.7 in a dose-dependent manner. Our results suggest that the water-extractable hemicelluloses from steam-exploded bamboo shavings are naturally acetylated and have immunostimulatory activity.
Bamboo shavings hierarchical porous carbon (BPC) possesses excellent prospects for applications in supercapacitors . Herein, the formation mechanism of the hierarchical porous structure of BPC is systematically investigated in an attempt to clarify the role of three components (cellulose, hemicellulose , and lignin) in bamboo shavings on the pore structure and electrochemical properties of BPC. An efficient three-component separation method of bamboo shavings is proposed. We adopt a green activation strategy of CO 2 -catalyzed induction of small doses of K 2 CO 3 to prepare bamboo shavings and their different components into honeycomb-like hierarchical porous carbons with excellent supercapacitor performance . The findings demonstrate that cellulose and hemicellulose mainly provide the microporous structure for BPC. Lignin provides not only a large number of mesopores but also abundant micropores. Compared with porous carbon derived from other components, lignin-derived porous carbon exhibits the optimal specific capacitance (273 Fg −1 at 0.5 Ag −1 ) and rate performance (capacity retention of 82.6% at 20 Ag −1 ) attributed to the largest specific surface area (1985 m 2 g −1 ) and micro-mesopore volume, indicating that lignin provides an important guarantee for the excellent specific capacitance and rate performance of BPC. The cellulose-derived porous carbon demonstrates superior cycling stability (98.2% capacitance retention over 15,000 cycles) due to its extraordinary electrical conductivity and stable carbon backbone, which means that cellulose is essential to the outstanding cycling stability of the BPC. Furthermore, the existence of hemicellulose also promotes the electrochemical performance of BPC to some extent. With the combined action of lignin, cellulose and hemicellulose, the BPC demonstrates excellent electrochemical properties. This work provides a promising ideas for the subsequent adjustment of pore structure and optimization of electrochemical properties of biomass-derived carbon by adjusting the content of each component in biomass.
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