丙烯直接环氧化Cu基催化剂的研究进展与挑战

作为一种重要的化工原料,环氧丙烷年产量近千万吨,然而目前工业上制备环氧丙烷的方法仍然面临着成本高、副产物多以及污染严重等问题。直接氧气氧化法进行丙烯环氧化因为具有原子经济、环保等优点受到了越来越多的关注。但是,催化过程中丙烯的α-H和环氧丙烷都具有很高的活性,使得在高转化率的条件下提升环氧丙烷选择性成为一个巨大的挑战。研究者们发现相较于其他币族金属,Cu基催化剂表现出更优异的丙烯直接环氧化反应性能。本综述总结梳理了近年来关于Cu基催化剂催化丙烯直接环氧化反应的研究成果,聚焦于Cu基催化剂改性方法,并对Cu基催化剂依然存在的问题和挑战进行深入探讨。     

In-situ polymerized cross-linked binder for cathode in lithium-sulfur batteries

Volume expansion and polysulfide shuttle effect are the main barriers for the commercialization of lithium-sulfur(Li-S) battery.In this work,we in-situ polymerized a cross-linked binder in sulfur cathode to solve the aforementioned problems using a facile method under mild conditions.Polycarbonate diol(PCDL),triethanolamine(TEA) and hexamethylene diisocyanate(HDI) were chosen as precursors to prepare the cross-linked binder.The in-situ polymerized binder(PTH) builds a strong network in sulfur cathode,which could restrain the volume expansion of sulfu r.Moreover,by adopting functional groups of oxygen atoms and nitrogen atoms,the binder could effectively facilitate transportation of Li-ion and adsorb polysulfide chemically.The Li-S battery with bare sulfur and carbon/sulfur composite cathodes and cross-linked PTH binder displays much better electrochemical performance than that of the battery with PVDF.The PTH-bare S cathode with a mass loading of 5.97 mg/cm^2 could deliver a capacity of 733.3 mAh/g at 0.2 C,and remained 585.5 mAh/g after 100 cycles.This in-situ polymerized binder is proved to be quite effective on restraining the volume expansion and suppressing polysulfide shuttle effect,then improving the electrochemical performance of Li-S battery.     

Enhanced TE properties of Cu@Ag/Bi2Te3 nanocomposites by decoupling electrical and thermal properties

Cu@Ag/Bi2Te3 nanocomposites were prepared for the first time by ultrasonic dispersion-rapid freezedrying method combined with spark plasma sintering(SPS).By changing the content of Cu@Ag nanoparticle,we could modulate the temperature dependent thermoelectric properties.The highest ZT value can be obtained at 450 K for 1 vol%Cu@Ag/Bi2Te3,which is benefited from the decoupling of electrical and thermal properties.With the increase of electrical conductivity,the absolute value of Seebeck coefficient lifts while the thermal conductivity declines.Meanwhile,the average ZT value between 300 K and 475 K was 0.61 for 1 vol%Cu@Ag/Bi2Te3,which is much higher than that of pristine Bi2 Te3.Therefore,the decoupling effect of Cu@Ag nanoparticles incorporation could be a promising method to broaden the application of Bi2Te3 based thermoelectric materials.     

Novel advances in metal-based solar absorber for photothermal vapor generation

Access to safe drinking water has become an extremely urgent research topic worldwide. In recent years, the technology of solar vapor generation has been extensively explored as a potential and effective strategy of transforming elements content in seawater. In this review, the basic concepts and theories of metal-based photothermal vapor generation device (PVGD) with excellent optical and thermal regulatory are introduced. In the view of optical regulation, how to achieve high-efficiency localized evaporation in different evaporation system (i.e., volumetric solar heating and interface solar heating) is discussed; from the aspect of thermal regulation, the importance of selective absorption surface for interfacial PVGD is analyzed. Based on the above discussion and analysis, we summarize the challenges of metal-based desalination device.     

Phosphorene: a Potential 2D Material for Highly Efficient Polysulfide Trapping and Conversion

Effectively trapping lithium polysulfide species and accelerating the reaction conversion kinetics are the main strategies to improve the performance of lithium-sulfur(Li-S) batteries. Since the researchers found in 2014 that two-dimensional(2D) phosphorene nanosheets could be exfoliated from the bulk black phosphorus, numerous researches have been devoted to exploring the phosphorene with unique properties for the application in Li-S batteries. In this review, we summarize the recent theoretical and experimental progress of phosphorene for Li-S batteries. Besides, we also introduce the relationship between the interfacial interaction on phosphorene and the performance enhancement of Li-S batteries. Furthermore, future challenges and remaining opportunities for phosphorene in Li-S batteries are finally discussed.     

Synthesis of N-TiO2@NH2-MIL-88(Fe) Core-shell Structure for Efficient Fenton Effect Assisted Methylene Blue Degradation Under Visible Light

Core-shell TiO₂-based photocatalysts with specific composition, morphology, and functionality have attracted considerable attention for their excellent degradation properties on organic pollutants via a photocatalytic oxidation process. Herein, a N-TiO₂@NH₂-MIL-88(Fe) core-shell structure was prepared by coating NH₂-MIL-88(Fe) on nitrogen-doped TiO₂(N-TiO₂) nanoparticles. Introduction of heteroatom nitrogen to pure TiO₂ expands the spectral response range, leading to enhanced quantum efficiency of photocatalyst. Furthermore, loading NH₂-MIL-88(Fe) on N-TiO₂ improved the adsorption ability of the nanocomposites due to the porous tunnels of NH₂-MIL-88(Fe). The resulted core-shell N-TiO₂@NH₂-MIL-88(Fe) nanocomposites realized the transfer of photo excited electrons from N-TiO₂ to NH₂-MIL-88(Fe) rapidly, partially reduced Fe³⁺ to Fe²⁺ in NH₂-MIL-88(Fe), and further enhanced the Fenton effect on efficiently degrading methylene blue dye(MB) under visible light(λ ≥ 420 nm) with the assistance of H₂O₂.     

Environmentally Benign Solution-Based Procedure for the Fabrication of Metal Oxide Coatings on Metallic Pigments

Aluminum pigments were coated with Fe₂O₃ and CuO by solution-based thermal decomposition of the urea nitrate compounds hexakisureairon(III)nitrate and tetrakisureacopper(II)nitrate. The deposition process was optimized to obtain homogeneously coated aluminum pigments. The growth of the surface coatings was controlled by investigation with scanning electron microscopy, energy dispersive X-ray spectroscopy and static light scattering as well as infrared, X-ray diffraction and thermogravimetric analysis. The iron precursor showed an incomplete decomposition in solution, incorporating traces of urea molecules inside the coatings while the copper precursor showed complete dissociation accompanied by in situ formation of amine complexes. The amount of organic residues resulting from ligand fragments in the final oxide coatings could be reduced to 22 % for the iron oxide and 12 % for the copper oxide by further temperature treatment in solution (259 °C). Colorimetric investigations of the obtained pigments revealed an excellent hiding power, outperforming the pigments used in current state-of-the-art formulations.     

Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules

The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.     

Effect of methoxy position on dynamic mechanical and shape memory properties of methoxyphenol-based polybenzoxazines

Abstract

Two series of benzoxazines were synthesized from o-, m-, and p-methoxyphenols, two polyetheramines with different molecular weights, and formaldehyde. The glass transition temperatures (T _gs) of m-methoxyphenol-based polybenzoxazines are respectively higher than those of o- and p-methoxyphenol-based counterparts. The polybenzoxazines exhibit thermally induced one-way dual-shape memory behavior based on T _g, and the o- and p-methoxyphenol-based polybenzoxazines exhibit higher shape memory performance than m-methoxyphenol-based counterparts under motion constraints.     

Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties

In this study, a series of cyclotriphosphazene derivatives containing a Schiff base (3a–3d) were synthesized by the reactions of hexachlorocyclotriphosphazene (1) with bis-aryl Schiff bases ( 2a – 2d ) having different terminal groups (H, F, Cl, and Br). The products ( 3a – 3d ) were characterized by elemental and mass analyses, FT-IR, and ¹ H, ¹³ C, and ³¹ P NMR spectroscopies. Furthermore, the structure of compound 3a was also determined by X-ray crystallography. The thermal behaviors and the spectral properties of the new cyclotriphosphazene compounds ( 3a – 3d ) were investigated and the results were compared in the series.