溶胶-凝胶流动相异型直接甲醇燃料电池性能研究

以掺杂石墨粉的中间相碳微球(MCMB/G)烧结管为阴极支撑体,采用浸涂工艺分别制备了扩散层和催化层并在其外表面包裹Nafion膜,制得管状异型阴极并组装成异型直接甲醇燃料电池;采用溶胶-凝胶法制备了适用于直接甲醇燃料电池的溶胶-凝胶流动相。研究了溶胶-凝胶流动相异型直接甲醇燃料电池的阻抗,考察了阴极支撑体壁厚、阴极扩散层载量、实验温度和溶胶黏度等对电池极化性能的影响。结果表明,异型电池阻抗比传统平板电池大,但活化后电池阻抗明显下降;较低的溶胶黏度和较高的工作温度有利于提高电池性能;支撑体壁厚为1.3 mm、扩散层载量为3.5 mg/cm2时的电极性能最优。     

磺化聚醚醚酮与壳聚糖共混制备直接甲醇燃料电池用质子交换膜

给出了不同磺化度下的磺化聚醚醚酮(SPEEK)用作质子交换膜的一系列性能,另外提出了一种新型的酸碱共混质子交换膜,其中,磺化聚醚醚酮和壳聚糖分别被选为酸性、碱性高分子电解质,并对所制备的质子交换膜的相关性能如质子传导性,甲醇渗透性,吸水率以及膜溶胀性、热稳定性等进行了表征,结果表明此种新型复合膜尽管在质子传导性能方面有所下降,阻醇性能改变不大,但是膜溶胀性和吸水率方面有了较大的改善.磺化度为71.4%的SPEEK与壳聚糖以5∶1摩尔比共混制备的质子交换膜,其性质可以与商品化的Nafion 117相媲美,有望在甲醇燃料电池中得到应用.     

Proton conductive polyimide ionomer membranes: Effect of NH,OH, and COOH groups

A new series of sulfonated polyimide (SPI) copolymers containing NH, OH, or COOH groups were synthesized by the polycondensation of 1,4,5,8‐naphthalnetetracarboxylic dianhydride, 3,3′‐bis(sulfopropoxy)‐4,4′‐diaminobiphenyl, and 3‐(4‐aminophenyl)‐5‐(3‐aminophenyl)‐1H‐1,2,4‐triazole (SPI‐8‐m), 3,5‐bis(4‐aminophenyl)‐1H‐1,2,4‐triazole (SPI‐8‐p), 3,6‐diaminocarbazole (SPI‐9), 3,5‐diamino‐1H‐1,2,4‐triazole (SPI‐10), bis(3‐aminopropyl)‐amine (SPI‐11), 2,6‐diaminopurine (SPI‐12), 2,4‐diamino‐6‐hydroxyprymidine (SPI‐13), or 3,5‐bis(4‐aminophenoxy)benzoic acid (SPI‐14). The obtained SPIs were soluble in polar organic solvents and gave tough and flexible membranes by solution casting. The SPI membranes having NH and COOH groups showed high thermal (decomposition temperature ≈200 °C) and mechanical (maximum stress >22 MPa) stability. Introducing NH groups, especially triazole and carbazole groups, was effective in improving proton conductive properties of SPI membranes at low humidity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2846–2854, 2010     

Expeditious preparation of triazole-linked glycolipids via microwave accelerated click chemistry and their electrochemical and biological assessments

A series of triazole-linked ester-type glycolipids were efficiently prepared via a two-step sequence involving microwave accelerated ‘click’ chemistry and debenzylation. All carbon chain length varied O-alkynyl fatty esters used to couple with 1-azido-tetra-O-benzyl-β-d-glucoside showed excellent tolerance to the microwave-assisted 1,3-dipolar cycloaddition (click reaction), forming the unique cycloadducts in almost quantitative yields of 92.9-99.0% within a quarter. The desired glycolipids were then readily afforded via the successive hydrogenolysis promoted by PdCl₂/H₂. Their adsorption competence on gold electrode were evaluated through EIS (electrochemical impedance spectroscopy) measurement and the resulting structure-activity relationship (SAR) was discussed. In addition, the cytotoxicity of this triazolyl glycolipid class on HeLa (cervix cancer) cell line was identified by MTT assay.     

Uncertainty of measurement for summed masses: application to controlled substances

Because sentences for drug possession depend on the mass of the seized drug, testing laboratories must often determine the summed mass of numerous items submitted under a single case. One common practice for this purpose is to continue analyzing and weighing samples until a legal threshold is passed, at which point it is important to inform the court whether the summed mass is significantly above the threshold, or only marginally so. This paper develops a means for estimating the uncertainty of the summed mass for the common situation where the readability, d, of the balance dominates the uncertainty. It is seen that for all sample sizes the uncertainty, UM, is given by the remarkable simple expression UM = (d/2) × [N + SQRT(3N)] + N × CCE, where N is the number of items and CCE is the absolute value of the calibration check error. In most instances, this can be further simplified to UM = N × d.     

Efficient Thickness of Solid Oxide Fuel Cell Composite Electrode

The efficient thickness of a composite electrode for solid oxide fuel cells was directly calcu-lated by developing a physical model taking into account of the charge transfer process, the oxygen ion and electron transportation, and the microstructure characteristics of the elec-trode. The efficient thickness, which is defined as the electrode thickness corresponding to the minimum electrode polarization resistance, is formulated as a function of charge trans-fer resistivity, effective resistivity to ion and electron transport, and three-phase boundary length per unit volume. The model prediction is compared with the experimental reports to check the validity. Simulation is performed to show the effect of microstructure, intrinsic material properties, and electrode reaction mechanism on the efficient thickness. The results suggest that when an electrode is fabricated, its thickness should be controlled regarding its composition, particle size of its components, the intrinsic ionic and electronic conductivities,and its reaction mechanisms as well as the expected operation temperatures. The sensitivity of electrode polarization resistance to its thickness is also discussed.     

Methanol Tolerant Non-noble Metal Co-C-N Catalyst for Oxygen Reduction Reaction Using Urea as Nitrogen Source

A non-noble metal oxygen reduction reaction (ORR) catalyst labeled as Co-C-N(800) was synthesized by heat-treating a mixture of urea, cobalt chloride and acetylene black for 2 h at 800 oC in an inert nitrogen atmosphere. X-ray diffraction pattern indicates that a metallic β-Co is generated after the heat-treating process. The results from cyclic voltammograms show that the obtained Co-C-N(800) catalyst has good ORR catalytic activity in 0.5 mol/L H₂SO₄ solution. The catalyst is also good at methanol tolerance and stability in the acidic solution.     

Sulfonated poly(ether ether ketone)-based silica nanocomposite membranes for direct ethanol fuel cells

This paper reports on the preparation and characterization of sulfonated poly(ether ether ketone) (sPEEK)-based mixed matrix membranes. The inorganic matrix consisted of silica: Aerosil^®380, tetraethoxysilane (TEOS) or a combination of both to obtain an interconnected silica network. The behavior of these membranes in ethanol–water systems was studied for application in a direct ethanol fuel cell (DEFC). Uptake measurements showed that the converted TEOS content had a strong influence on the hydrophilicity of the membranes. Proton conductivity was strongly related to the water content in the membrane, but the proton diffusion coefficients of membranes with various Aerosil^®380–TEOS combinations were similar. Dynamic measurements in liquid–liquid (L–L) and liquid–gas (L–G) systems were performed to study the ethanol transport through the membrane. No reduction in ethanol permeability was obtained in the L–L system, but a remarkable reduction was obtained in the L–G system when 2 M ethanol was applied. The reinforcing characteristic of the combined Aerosil^®380–TEOS-system were best observed at 40 °C with 4 M ethanol. The fuel cell performance prediction based on the selectivity of proton diffusion coefficient to ethanol permeability coefficient showed for nearly all composite membranes an improvement with respect to the polymeric reference. The presence of an inorganic phase led to relatively constant proton diffusion coefficients and lower ethanol permeability coefficients in comparison with the polymeric reference.     

新型磺化聚酰亚胺膜的合成与表征

合成了4,4’-二(间氨基苯氧基)联苯-3,3’-二磺酸(mBAPBDS)单体, 采用红外光谱和核磁共振等方法对其结构进行了表征. 使用mBAPBDS, 2-(对胺基苯基)苯并噁唑-5-胺(APBA)和1,4,5,8-萘四甲酸二酐(NTDA)共聚合成了含有噁唑结构的新型磺化聚酰亚胺(NTDA-mBAPBDS/APBA), 通过控制磺化二胺与非磺化二胺的比例来控制磺化程度. NTDA-mBAPBDS/APBA共聚物表现出较好的溶解性、成膜性能和良好的热稳定性, 其磺酸基团分解温度高于300 ℃. 采用溶液浇铸法制备了磺化聚酰亚胺(SPIs)膜, 对膜的吸水率、溶胀度和质子电导率等性能进行了初步的研究. 结果表明, SPIs膜具有适当的吸水率和良好的尺寸稳定性, 其室温电导率在4.72×10－3和9.60×10－3 S/cm之间, 接近于相同条件下Nafion®117的电导率(9.80×10－3 S/cm).     

Cu~(2+)对质子交换膜燃料电池氧电极性能的影响

以旋转圆盘电极模拟PEMFC阴极,计时库仑、循环伏安、线性扫描等电化学方法研究Cu2+电解液对碳载铂催化剂电化学活性和氧还原性能的影响.结果表明,在恒电位0.49 V下,Pt/C催化剂活性比表面(ECA)明显减小,此际基底可能发生Cu欠电位沉积,从而掩盖催化剂的活性比表面;数据拟合指明Cu欠电位沉积占据催化剂表面部分氧原子吸附点位,使该点位桥式吸附的氧原子转变为顶式吸附氧原子.