Structural Changes of Wheat Straw Lignin during Formic Acid Treatment

The aromatic nature of lignin makes it a potential renewable source of chemicals and other valuable products.Isolation of lignin from lignocellulosic biomass using organic solvents enables the production of high-purity lignin.The use of formic acid in the organosolv pulping and fractionation process has been widely studied.Characterization of lignin is necessary to achieve valueadded applications of lignin.To simplify the isolation of formic acid-treated lignin,herein,milled wheat straw lignin(MWSL) was employed as an archetype for characterization of the structural changes of lignin during formic acid treatment.The results showed that the MWSL was GSH-type(comprising p-hydroxyphenyl(H),guaiacyl(G),and syringyl(S) monolignols) and underwent structural changes during formic acid treatment.Lignin was esterified during the formic acid treatment.The content of alkyl hydroxyl groups in lignin decreased upon formic acid treatment,corresponding to an increase of the number of double bond equivalents(DBE).Lignin units with active reaction sites were liable to slight condensation,which resulted in a moderate increase of the molecular weight.The molecular weight distribution of formic acid-treated MWSL(FMWSL) was wider than that of the MWSL,although the molecular weight of both species did not differ significantly.The β-O-4 linkage in lignin was partially cleaved during formic acid treatment,resulting in the production of new phenolic structures.This improved the solubility of lignin in the cooking liquor and its reactivity for downstream applications.

Simultaneous Optimization of Efficiency,Stretchability,and Stability in All-Polymer Solar Cells via Aggregation Control

With the emergence of Y-series small molecule acceptors,polymerizing the small molecule acceptors with aromatic linker units has attracted significant research attention,which has greatly advanced the photovoltaic performance of all-polymer solar cells.Despite the rapid increase in efficiency,the unique characteristics(e.g.,mechanical stretchability and flexibility)of all-polymer systems were still not thoroughly explored.In this work,we demonstrate an effective approach to simultaneously improve device performance,stability,and mechanical robustness of all-polymer solar cells by properly suppressing the aggregation and crystallization behaviors of polymerized Y-series acceptors.Strikingly,when introducing 50 wt%PYF-IT(a fluorinated version of PY-IT)into the well-known PM6:PY-IT system,the all-polymer devices delivered an impressive photovoltaic efficiency of 16.6%,significantly higher than that of the control binary cell(15.0%).Compared with the two binary systems,the optimal ternary blend exhibits more efficient charge separation and balanced charge transport accompanying with less recombination.Moreover,a high-performance 1.0 cm^(2)large-area device of 15%efficiency was demonstrated for the optimized ternary all-polymer blend,which offered a desirable PCE of 14.5%on flexible substrates and improved mechanical flexibility after bending 1000 cycles.Notably,these are among the best results for 1.0 cm^(2)all-polymer OPVs thus far.This work also heralds a bright future of all-polymer systems for flexible wearable energy-harvesting applications.

Refining acceptor aggregation in nonfullerene organic solar cells to achieve high efficiency and superior thermal stability

With the rapid increase in photoelectric conversion efficiency of organic photovoltaics(OPVs),prolonging the operational lifetime of devices becomes one of the critical prerequisites for commercial applications.Guided by the theoretical calculations of molecular stacking and miscibility,we proposed an effective approach to simultaneously improve device performance and thermal stability of high-efficiency OPVs by refining the aggregation of Y-series acceptors.The key to this approach is deliberately designing an asymmetric Y-series acceptor,named Y6-CNO,which acts as a third component regulator to finely tune the degree of acceptor aggregation and crystallization in the benchmark PM6:Y6-BO system.Strikingly,a champion photovoltaic efficiency of 18.0%was achieved by introducing 15 wt%Y6-CNO into the PM6:Y6-BO system,significantly higher than the control binary cell(16.7%).Moreover,annealing at 100°C for over 1,200 h does not markedly affect the photovoltaic performance of the optimal ternary devices,maintaining above 95%of the initial performance and exhibiting an exceptionally high T_(80)lifetime of 9,000 h under continuous thermal annealing.By contrast,binary devices suffer from excessive crystallization of acceptors with long-term annealing.Additionally,mixing thermodynamics combined with morphological characterizations were employed to elucidate the microstructure-thermal stability relationships.The ternary OPVs consisting of symmetric and asymmetric homologous acceptors form better charge transport channels and can effectively suppress excessive aggregation of acceptors under long-term annealing.This work demonstrates the effectiveness of refining acceptor aggregation via molecular design for highly efficient and stable nonfullerene-based OPVs.

Aerosol-assisted submicronγ-Fe2O3/C spheres as a promising heterogeneous Fenton-like catalyst for soil and groundwater remediation:Transport,adsorption and catalytic ability

This research reports a novel heterogeneous Fenton-like catalyst which could freely move through the model sediments and easily seize the pollutants in addition to efficiently catalyze H2O2,well suitable for soil and groundwater remediation.Herein,submicron y-Fe2O3/C spheres were synthesized through a facile one-step aerosol-based process.In a series of column tests,these spheres exhibit better transport ability due to their optimal size,conforming to the prediction by the Tufenkji-Elimelech filtration theo ry.Meanwhile,y-Fe2O3/C spheres could act as a strong adsorbent for organic pollutants owing to the presence of carbon,thereby providing a driving force to gather contaminants into their vicinity and facilitating the reaction.In addition,immobilization of y-Fe2O3 nanoparticles into carbon spheres protects iron oxides from aggregation,and thus retains the number of active sites for catalytic decomposition of H2O2.Hence,the system containing the as-prepared y-Fe2O3/C spheres and H2O2 shows the high removal efficiency and degradation efficiency in the remediation of recalcitrant organic contaminants such as methylene blue and sulfamethoxazole.

回转窑内煤粉燃烧影响因素数值模拟

为提高回转窑内煤粉燃烧效率,实现回转窑的节能运行,建立了回转窑内煤粉燃烧数学模型。通过控制单一变量和设计多指标正交试验工况,研究了空气过剩系数、煤粉粒径、旋流角度、内外风量比4个因素对回转窑内煤粉燃烧的影响,得到了最优操作参数组合。结果表明,随着空气过剩系数和煤粉粒径增大,火焰长度增大、火焰直径减小,火焰变得细长。随着旋流角度增大,火焰形状变短变粗。随着内外风量比增大,火焰长度先增大后减少、火焰直径先减少后增大。四个因素按影响程度从高到低排序依次为煤粉粒径、内外风量比、空气过剩系数、旋流角度。回转窑内煤粉燃烧的最优操作参数组合为空气过剩系数1.1、煤粉粒径40μm、旋流角度25°、内外风量比0.9。相较原始工况,优化工况的火焰长度和火焰直径分别增大了8.9%和13.9%。