CO_2熔盐电化学转化碳材料的电化学特性

基于对熔融碳酸盐体系中电化学还原CO_2所得碳材料(electrolytic-carbon,EC)的形貌、结构、组成的认识,以粉末微电极循环伏安法测试为基础,在稀溶液中对EC的本征电化学行为进行了考察,以揭示这类碳材料的界面电化学特性。实验发现,在典型条件(450°C、4.5 V槽压)下制备的电解碳(450°C-4.5 V-EC)的伏安行为有别于多壁碳纳米管、石墨烯、石墨、乙炔黑等常见碳材料,在负电位区表现出显著的"双电层充放电响应迟滞"现象。通过考察溶液pH值、电位扫描速率、阴阳离子种类对这一现象的影响,发现pH和电解液组成都不影响这一现象的出现;电解液浓度提高和低扫描速率时滞后现象减弱,表明迟滞充放电是这类碳材料的本征特性,与其表面含氧官能团及其对阳离子的特性吸附密切相关。实验进一步研究了不同电解条件下制备的EC所展现的电化学特性吸附及电容性质,发现随着熔盐温度的升高,EC对电解液中阳离子的特性吸附能力降低,而相同温度不同槽压下制备的EC特性吸附能力相近,表现出相似的电容特性,这与EC的含氧量和比表面积有关。电解碳所展现的独特电容特性对其潜在的应用或可提供有价值的线索和指导。     

Clip[5]arenes: A new family of molecular clips

Here we report the design and syntheses of two new triptycene-based rigid acyclic C-shaped hosts, clip[5]arenes C[5]OH and C[5]ME, and the strong host–guest complexation between C[5]OH and an electron-poor bipyridinium salt, paraquat G. The K_a value for the host–guest complex C[5]OH???G was calculated to be (1.09?±?0.36)??×??10⁵?M^?1 in acetone by using a non-linear curve-fitting method based on the UV–vis absorption titration experiments. Furthermore, based on this new host–guest recognition motif, a novel pseudopolyrotaxane-like supramolecular structure was constructed with C[5]OH threaded on polyviologen polymer VP-10.     

Direct Electrochemistry of Hemoglobin and Its Electrocatalysis Based on Hyaluronic Acid and Room Temperature Ionic Liquid

A biocomposite material of hyaluronic acid (HA) and room temperature ionic liquid, 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate (BMIMBF₄) was fabricated and characterized by voltammetry and electrochemical impedance spectroscopy. Hemoglobin (Hb), as a model protein, was immobilized in this biocomposite on glassy carbon electrode to investigate its direct electrochemistry. A pair of well‐defined, quasireversible cyclic voltammetric peaks appeared with the formal potentials (E°′) at ?0.360 V (vs. SCE). The Hb modified electrode exhibited an excellent electrocatalytic activity to the reduction of H₂O₂ with a wide linear range, good selectivity, sensitivity and reproducibility, which had potential application to fabrication the third‐generation biosensor.     

High photocatalytic activity and stability for decomposition of gaseous acetaldehyde on TiO2/Al2O3 composite films coated on foam nickel substrates by sol-gel processes

A set of anatase titanium dioxide (TiO₂) films coated on foam nickel that modified by Al₂O₃ films as transition layer (indicated as TiO₂/Al₂O₃ films) were synthesized via sol-gel route. The bulk and surface properties of the TiO₂/Al₂O₃ films were characterized by thermal gravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and BET. The photocatalytic activities of TiO₂/Al₂O₃ films were investigated based on the degradation of gaseous acetaldehyde under ultraviolet (UV) irradiation. The foam nickel is a promising substrate material in practical applications because of its excellent hydrodynamic properties for gas passing. The TiO₂/Al₂O₃ composite films showed much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than the onefold TiO₂ films. The significant enhancement in photocatalytic activity and stability can be ascribed to the coating of Al₂O₃ transition layer, which concentrates the target substances around TiO₂ particles and increases the specific surface area (SSA) of the substrate (the SSAs of bare foam nickel and Al₂O₃ modified foam nickel are 0.12 and 113.7 m²/g, respectively) to provide more sites for TiO₂ loading.     

几种值得注意的有机原料清洁工艺技术

本文综述了基本有机原料生产中的几种清洁生产工艺。这些工艺, 或是显著提高目的产物的选择性, 从而不排放或少排放有害污染物; 或在生产过程中不用有害的或有污染的原料、催化剂和溶剂。文章也介绍了中国石油化工总公司在该领域的研究开发工作。     

二氧化碳氧化丙烷制丙烯催化反应的研究铬镁铝复合氧化物催化剂的制备、表面微量吸附量热及催化性能

以共沉淀法合成的铬镁铝类水滑石为前体,制备了一系列不同原子比的铬镁铝复合氧化物,研究了其对二氧化碳氧化丙烷制丙烯反应的催化性能.采用微量吸附量热技术,以CO2和NH3为探针分子定量地表征了样品表面酸碱中心的强度和数量,并与其催化性能进行了关联.结果表明,Cr:Mg:Al原子比为1:1:1的催化剂具有较大的比表面积(94.5m2/g),样品中Mg(Al1.5Cr05)O4物相的含量最多.样品表面存在数量较多强度较强的酸性中心和数量最少强度较弱的碱性中心,对NH3吸附,它的吸附热为145 kJ/mol,吸附覆盖度为3.55μmol/m2;对CO2吸附,它的吸附热为115kJ/mol,吸附覆盖度为0.063μmol/m2.该样品的催化活性最高,在温度为650℃,CO2/C3H8摩尔比为3.6,GHSV(C3H8)为3000 h-1时,C3H8的转化率为22.8%,C3H6的选择性为83.5%,收率为19.1%.     

A modified finite element method for determining equilibrium capillary surfaces of liquids with specified volumes

This paper describes a modified finite element method (MFEM) for determining the static equilibrium shape of the capillary surface of a liquid with a prescribed volume constrained by rigid boundaries with arbitrary shapes. It is assumed that the liquid is in static equilibrium under the influence of surface tension, adhesion, and gravity forces. This problem can be solved by employing the conventional FEM; however, a major difficulty arises due to the presence of the volume (integral) constraint and usually requires the use of the Lagrange multiplier method, the sequential unconstrained minimization technique, or the augmented Lagrange multiplier method. With the MFEM, the space variables defining the equilibrium surfaces (or curves) are expanded in terms of parametric interpolation functions, which are designed such that the boundary conditions and the integral constraint equation are automatically satisfied during each iteration of a direct numerical search process. Hence, there is no need to include Lagrange multipliers and/or penalty factors and the problem can be treated more simply as one involving unconstrained optimization. This investigation indicates that the MFEM is more efficient and reliable than the other methods. Results are presented for several case study problems involving liquid solder drops. Copyright © 2000 John Wiley & Sons, Ltd.     

A new lattice hydrodynamic model with the consideration of flux change rate effect

A new lattice hydrodynamic traffic flow model is proposed by considering the preceding lattice site’s flux change rate effect. Using linear stability theory, stability condition of the presented model is obtained. It is shown that the stability region significantly enlarges as the flux change rate effect increases. To describe the propagation behavior of a density wave near the critical point, nonlinear analysis is conducted and mKdV equation representing kink-antikink soliton is derived. To verify the theoretical findings, numerical simulation is conducted which confirms that preceding lattice site’s flux change rate can improve the stability of traffic flow effectively.     

三粒子纠缠W态隐形传态的正交完备基展开与算符变换

先是对利用单个两粒子及单个三粒子纠缠态作为量子信道实现三粒子纠缠W态的隐形传态方案进行讨论.然后由波函数的叠加原理与算符变换出发,将体系的总量子量按照Bell基展开实现量子隐形传态,给出了变换算符与实际操作算符之间的联系.进一步验证出变换算符可逆是成功实现三粒子纠缠W态隐形传态的必要条件的结论. 关键词： 三粒子纠缠W态 Bell基展开 变换算符 隐形传态