氨电氧化催化剂及其低温直接氨碱性膜燃料电池性能的研究进展

氨是一种无碳富氢的能源载体,体积能量密度高,易液化储存,是理想的储氢介质。以氨直接作为燃料,在低温碱性膜燃料电池中通过氨氧化反应实现化学能到电能的转化,是氨能源高效利用的理想路径之一。然而,低温氨氧化反应动力学缓慢、催化剂价格昂贵、易中毒等问题严重影响氨燃料电池性能,限制其大规模的商业化应用。因此,设计高效、廉价、稳定的催化剂是发展低温氨燃料电池技术的关键。本文首先综述了近些年研究者在氨氧化反应机理方面的探索,在深入理解反应体系的基础上,重点介绍了含贵金属和非贵金属催化剂设计制备及其在氨氧化反应中的进展,并总结了氨氧化催化剂在氨燃料电池中的性能。最后针对氨氧化催化剂目前存在的问题和未来的发展方向提出了建议,旨在为氨氧化催化剂的设计及低温氨燃料电池技术的发展提供研究思路。     

载阿霉素透明质酸纳米粒的制备及其抗肿瘤活性

目的以组氨酸(histidine,His)修饰的透明质酸(hyaluronic acid,HA)为载体,阿霉素(doxorubicin,DOX)为模型药物,制备纳米粒DOX/His-HA,并分析其理化性质和体内外抗肿瘤活性。方法通过化学交联法将组氨酸与HA进行结合,采用超声法制备纳米粒DOX/His-HA。用DAWN HELEOSⅡ动态激光光散射仪测定His-HA纳米粒的粒径和Zeta电位,透射电镜观察其形态;紫外-可见分光光度计测定DOX/His-HA纳米粒中DOX的吸光度值,计算其包封率、载药量和DOX的体外释放度。采用MTT法检测DOX/His-HA对Hep G2细胞的生长抑制作用;摄入试验观察Hep G2细胞对DOX/His-HA的摄入情况;抑瘤试验分析DOX/His-HA的体内抗肿瘤活性。结果 His-HA纳米粒呈球形,粒径为230~480 nm,分散度良好,Zeta电位为-19.3~-13.5 m V。DOX/His-HA的载药量和包封率分别达到(8.14±0.09)%和(91.37±0.69)%。在前4 h内,DOX/His-HA纳米粒均存在明显突释现象;4 h后,DOX/HisHA纳米粒逐渐表现出一定的缓释性。随着组氨酸取代度的增加,DOX/His-HA的Hep G2细胞毒性增强。组氨酸取代度越高,DOX/His-HA越易被细胞摄入。DOX/His-HA具有更强的抑瘤效果,且对正常组织无明显的毒副作用。结论制备的DOX/His-HA纳米粒是一种缓释性和肿瘤靶向性良好的给药系统。     

氨电氧化催化剂及其低温直接氨碱性膜燃料电池性能的研究进展

氨是一种无碳富氢的能源载体,体积能量密度高,易液化储存,是理想的储氢介质。以氨直接作为燃料,在低温碱性膜燃料电池中通过氨氧化反应实现化学能到电能的转化,是氨能源高效利用的理想路径之一。然而,低温氨氧化反应动力学缓慢、催化剂价格昂贵、易中毒等问题严重影响氨燃料电池性能,限制其大规模的商业化应用。因此,设计高效、廉价、稳定的催化剂是发展低温氨燃料电池技术的关键。本文首先综述了近些年研究者在氨氧化反应机理方面的探索,在深入理解反应体系的基础上,重点介绍了含贵金属和非贵金属催化剂设计制备及其在氨氧化反应中的进展,并总结了氨氧化催化剂在氨燃料电池中的性能。最后针对氨氧化催化剂目前存在的问题和未来的发展方向提出了建议,旨在为氨氧化催化剂的设计及低温氨燃料电池技术的发展提供研究思路。     

淀粉纳米粒的制备、改性及应用研究进展

介绍了淀粉纳米粒的制备以及改性的方法,综述了其在智能响应材料、复合材料、药物载体、生物吸附剂、乳液稳定剂等方面的研究现状,并对未来的发展趋势进行了展望。     

淀粉纳米粒的制备与应用研究进展

淀粉纳米粒因其可再生、环保可降解等诸多优点,成为当下纳米材料研究领域的热点,具有广阔的应用前景。对淀粉颗粒结构迚行了剖析,对淀粉纳米粒制备方法迚行了综述,介绍了酸处理法、酶处理法、物理法、纳米沉淀、乳液交联及一些复合方法制备淀粉纳米粒的优势及所存在的局限。阐述了淀粉纳米粒作为复合材料充填剂、乳液稳定剂、包装材料、药物载体、污水处理剂和造纸粘合剂的应用性能,对其研究方向和工业应用前景迚行了展望。     

紫外分光光度法测定琼脂糖磁性纳米粒的四氧化三铁含量

目的:采用紫外分光光度法测定琼脂糖磁性纳米粒的四氧化三铁含量。方法:将琼脂糖磁性纳米粒用硝酸硝化后,游离出铁离子与邻菲罗啉形成橙红色配合物,用分光光度法测定吸光度。结果:铁离子与邻菲罗啉生成的配合物,在510 nm波长处有最大吸收;在0.0036~0.036μmol/m L浓度范围内,吸光度与浓度之间呈良好的线性关系,标准曲线为A=11.436C-0.0006,R2=0.9999;总平均回收率99.91%,RSD=0.81%(n=9)。结论:该方法操作简便,结果准确可靠,适用于测定琼脂糖磁性纳米粒的四氧化三铁含量。     

催化氨氧化法制备丁酮肟研究

对催化氨氧化法进行了小试实验并优化了工艺参数：以叔丁醇与水的混和液作溶剂，以TS-1作催化剂，双氧水采用滴加方式，酮、氨、双氧水的物质的量配比为1：1．3：I．2时，酮的转化率约为80％，丁酮肟选择性大于98％。     

产朊假丝酵母尿酸酶脂质纳米粒的制备及其药效学特性分析

目的制备产朊假丝酵母尿酸酶(uricase,URI)脂质纳米粒,并分析其药效学特性。方法采用旋转蒸发法制备3批URI脂质纳米粒(lipid nanoparticles containing uricase from Candida utilis,LNURI),检测其包封率、URI活性、酶的最适作用温度和最适作用pH值。采用次黄嘌呤和氧嗪酸钾建立高尿酸大鼠模型,分别于建模后1 h经尾静脉注射LNURI和游离URI,建模后3、5、7、8、12 h,测定大鼠血清中尿酸水平。结果制备的3批LNURI的平均包封率为(64.27±2.26)%;LNURI的最适作用温度为40℃,最适作用pH值为8.0,在同样的作用温度和pH值条件下,LNURI的活性明显高于游离URI;LNURI降低高尿酸模型大鼠血清中尿酸水平的效果较URI更显著。结论成功制备了产朊假丝酵母尿酸酶脂质纳米粒,其可降低高尿酸模型大鼠血清中尿酸水平。     

无机原料制备TS-1分子筛及其催化环己酮氨氧化

分别以硅溶胶和白炭黑为硅源、三氯化钛为钛源合成了TS-1分子筛。采用XRD、FT-IR、SEM、TEM和低温N2吸附-脱附等方法表征,表明两种无机硅源均可制备结晶度较好和晶体结构完整的TS-1分子筛。将制备的TS-1分子筛用于催化环己酮氨氧化,结果表明,在优化反应条件下,硅溶胶制备的TS-1分子筛具有比白炭黑制备的TS-1更好的催化性能。     

晚香玉香精壳聚糖纳米粒的制备及表征

以三聚磷酸钠(TPP)为交联剂,通过离子凝胶法制备晚香玉香精壳聚糖纳米粒。研究了壳聚糖质量浓度、香精质量浓度、乳化剂与香精的质量比及反应时间对晚香玉香精壳聚糖纳米粒粒径的影响,并采用动态激光光散射仪(DLS)、透射电镜(TEM)、红外光谱仪(IR)及热重分析仪(TGA)对其结构及性能进行了表征。结果表明,当壳聚糖质量浓度为1.71 g/L、香精质量浓度为1.72 g/L、m(乳化剂)∶m(香精)=1∶2、反应时间为1 h时,制备的晚香玉香精壳聚糖纳米粒平均粒径为138 nm,粒径分布系数为0.100,香精装载量达28.4%,能减缓高温下香精的释放速率。     

Copper nanoparticles/polyaniline-derived mesoporous carbon electrocatalysts for hydrazine oxidation

Copper nanoparticles-decorated polyaniline-derived mesoporous carbon that can serve as noble metal-free electrocatalyst for the hydrazine oxidation reaction (HzOR) is synthesized via a facile synthetic route. The material exhibits excellent electrocatalytic activity toward HzOR with low overpotential and high current density. The material also remains stable during the electrocatalytic reaction for long time. Its good electrocatalytic performance makes this material a promising alternative to conventional noble metal-based catalysts (e.g., Pt) that are commonly used in HzOR-based fuel cells.

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水合肼生产中氧化反应的研究和应用

分析了尿素法生产水合肼的氧化反应历程及影响因素，改进了反应器，并找到了最佳的工艺控制条件：①控制n(尿素)：n(次氯酸钠)=(1．05～1．10)：1，各原料的消耗较低，总经济效益佳；②采用-5℃冷冻盐水移走尿素、次氯酸钠混合段内氯化反应放出的热量，控制物料混合终点温度在15～30℃；③采用列管式加热器，将氯化反应与水解反应在不同的设备中进行，水合肼的收率提高到83％～85％；④采用列管式加热器代替双夹套反应器，提高了加热强度，生产能力大，1套合成反应器可生产1万t／a80％的水合肼。     

埃洛石负载的纳米金可控制备及对环己烷选择性氧化的催化性能

埃洛石纳米管（HNTs）是一类具有独特物理结构和化学性质的天然黏土化合物,本文以经过提纯和聚二烯丙基二甲基氯化铵溶液（PDDA）改性的埃洛石为载体,将预先制备的粒径可控的金溶胶负载到改性埃洛石（PHNTs）表面得到负载型的纳米金颗粒,通过调节氯金酸前体的浓度和用量,实现了对负载型纳米金尺寸的有效调控,透射电镜表征结果显示,埃洛石负载的纳米金分散性良好,平均粒径分别处于2nm以下、2～5nm和5nm以上。以环己烷的液相选择性氧化为模型反应,评价了所制备的不同尺度负载型纳米金粒子的活性和对环己醇和环己酮的选择性。结果表明：纳米金颗粒的平均粒径处于2～5nm时,表现出最好的催化活性和选择性,在170℃和2.0MPa下反应2h,环己烷的转化率可达10.29%,环己醇和环己酮的选择性达85.75%,优于该反应体系使用的工业催化剂对活性和选择性的指标要求。此外,X射线光电子能谱仪表征结果显示,当埃洛石负载的纳米金平均粒径处于2～5nm时,金元素主要以Au⁰ 的形式存在。     

Polyaniline nanofibers supported on titanium as templates for immobilization of Pd nanoparticles: A new electro‐catalyst for hydrazine oxidation

Palladium nanoparticles (Pd‐NPs)/polyaniline (PAni)/titanium (Ti) catalysts were prepared using electroless deposition of Pd‐NPs on PAni matrixes coated on Ti substrate. PAni/Ti electrodes were synthesized by electro‐polymerization of aniline on Ti. The morphology of Pd‐NPs on PAni/Ti electrodes were characterized by scanning electron microscopy technique and results indicated that Pd‐NPs were uniformly dispersed on the surface of PAni film. The electro‐catalytic properties of Pd‐NPs/PAni/Ti catalysts toward oxidation of hydrazine were investigated by different electrochemical methods and results showed that Pd‐NPs/PAni/Ti catalysts have high electrochemical activity. In addition, the mechanism of hydrazine electrochemical oxidation catalyzed by Pd‐NPs/PAni/Ti was investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Catechol-functionalized microporous organic polymer as supported media for Pd nanoparticles and its high catalytic activity

We report a new hydroxyl functionalized microporous organic polymer (MOPOH) based on the polymerization of catechol with terephthalaldehyde using phenolic resin-inspired chemistry. This catechol-decorated material, with surface area of 874 m² g⁻¹ and micro, mesopores, facilitates the immobilization and dispersion of Pd nanoparticles (NPs) on the polymer matrix. The surface area of the created composite (Pd@MOPOH) decreases to 419 m² g⁻¹ and the pore size distribution is narrowly distributed at 1.54 nm due to the filling of mesopores. The CO₂ capture capacities for MOPOH and Pd@MOPOH at 273 K and 1 bar are 13.4 and 9.2 wt%, respectively. The resultant Pd NPs are crystalline and uniform with a mean diameter of 4.8 nm. The well-dispersed Pd@MOPOH exhibits excellent catalytic activity toward the model reduction of 4-nitrophenol into 4-aminophenol. Significantly, nearly no Pd leaching is detected during the catalytic cycles, showing active and durable nature of the heterogeneous nanocatalyst.     

Electrocatalytic oxidation and detection of hydrazine at carbon nanotube-supported palladium nanoparticles in strong acidic solution conditions

Pd nanoparticle catalysts supported by multiwall carbon nanotubes (Pd/MWNTs) prepared using a complexation–reduction method are used in this study for the electrochemical determination of hydrazine. The physico-chemical properties of the Pd/MWNT catalyst were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and scanning electron microscopy physico-chemical (SEM). These structural analyses reveal that the Pd/MWNTs-modified glassy carbon electrode possesses a three-dimensional network structure in which the Pd nanoparticles, with an average size of 5 nm, are uniformly distributed on the surface of the MWNTs. After Nafion solution was coated on the surface of the Pd/MWNT layer, the resulting Pd/MWNT–Nafion modified electrode retained the three-dimensional network structure. Electrochemical measurements show that the oxidation peak current of hydrazine decreases with increasing pH. Under optimum conditions, the Pd/MWNT–Nafion-based hydrazine sensor exhibits a broad linear calibration range (2.5–700 μM) and a low detection limit of 1.0 μM for hydrazine.     

水合肼制氢纳米催化剂改性制备及机理研究进展

安全高效、响应迅速的在线氢源能够有效地加速质子交换膜燃料电池(PEMFCs)的商业化应用,而设计和制备安全高效、成本低廉的催化剂是实现水合肼(N₂H₄·H₂O)催化制氢作为在线氢源的关键技术。总结了催化剂的合金化改性、形貌结构的调控、载体的负载和强碱性助剂的添加等因素和催化性能之间的构效关系,从活性位点的增多和本征活性的提高等方面讨论催化性能提升原因。结合理论计算总结N₂H₄在不同金属催化剂表面上的吸附性能和分解路径等机理研究,分析了N₂H₄在不同的活性位点结构上催化活性、H₂选择性和稳定性出现差异的原因。以期实现高效催化剂特定表界面结构和活性位点的几何结构和电子结构多尺度精准调控,为实现机理指导下催化剂的结构精准设计奠定基础。     

水合肼制氢纳米催化剂改性制备及机理研究进展

安全高效、响应迅速的在线氢源能够有效地加速质子交换膜燃料电池(PEMFCs)的商业化应用,而设计和制备安全高效、成本低廉的催化剂是实现水合肼(N₂H₄·H₂O)催化制氢作为在线氢源的关键技术。总结了催化剂的合金化改性、形貌结构的调控、载体的负载和强碱性助剂的添加等因素和催化性能之间的构效关系,从活性位点的增多和本征活性的提高等方面讨论催化性能提升原因。结合理论计算总结N₂H₄在不同金属催化剂表面上的吸附性能和分解路径等机理研究,分析了N₂H₄在不同的活性位点结构上催化活性、H₂选择性和稳定性出现差异的原因。以期实现高效催化剂特定表界面结构和活性位点的几何结构和电子结构多尺度精准调控,为实现机理指导下催化剂的结构精准设计奠定基础。     

The formation and catalytic activity of silver nanoparticles in aqueous polyacrylate solutions

Silver nanoparticles (AgNPs) have been synthesized in the presence of polyacrylate through the reduction of silver nitrate by sodium borohydride in aqueous solution. The AgNO3 and polyacrylate carboxylate group concentrations were kept constant at 2.0 × 10^–4 and 1.0 × 10^–2 mol·L^–1, respectively, while the ratio of [NaBH₄]/[AgNO₃] was varied from 1 to 100. The ultraviolet-visible plasmon resonance spectra of these solutions were found to vary with time prior to stabilizing after 27 d, consistent with changes of AgNP size and distribution within the polyacrylate ensemble occurring. These observations, together with transmission electron microscopic results, show this rearrangement to be greatest among the samples at the lower ratios of [NaBH₄]/[AgNO₃] used in the preparation, whereas those at the higher ratios showed a more even distribution of smaller AgNP. All ten of the AgNP samples, upon a one thousand-fold dilution, catalyze the reduction of 4-nitrophenol to 4-aminophenol in the temperature range 283.2–303.2 K with a substantial induction time being observed at the lower temperatures.

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The preparation and characterization of Au@TiO2 nanoparticles and their catalytic activity for CO oxidation

Au@TiO₂ core/shell nanoparticles were synthesized by a simple and efficient one-step method using tetrabutyl titanate as TiO₂ precursor. The samples were characterized by TEM, XRD, UV–vis and XPS. The experiments demonstrated that the average particles size of Au was 10–15 nm, and the thickness of TiO₂ shell was 1–3 nm. TiO₂ shell induced a red-shift of the absorption peak of Au. This material exhibited catalytic activity for CO oxidation. This study offered an approach for CO oxidation by using Au@TiO₂ model catalysts.