PEDOT-PSSA as an alternative support for Pt electrodes in PEFCs

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT-PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H+-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT-PSSA composite also helps reducing Nation content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT-PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT-PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT-PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm(-2) at a load current-density of 1800 mA cm(-2) with Nation content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes.

PEDOT-PSSA as an alternative support for Pt electrodes in PEFCs

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT-PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H+-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT-PSSA composite also helps reducing Nation content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT-PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT-PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT-PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm(-2) at a load current-density of 1800 mA cm(-2) with Nation content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes

Growth of alkali metal periodates from silica gel and their characterization

Single crystals (up to 1 cm size) of K, Rb and Cs periodates have been grown in silica gel. In general, good quality crystals were obtained in gel of specific gravity 1.04 and pH 4. The metal/iodine ratios were determined and compared with calculated values. Morphological studies were carried out using a bicircle optical goniometer. Other characterization methods include X-ray diffraction, optical absorption, differential scanning calorimetry and optical microscopy. Microscopic examination of CsIO4 crystals in particular has revealed the existence of ferroelastic domains in the crystal. The structural basis for the occurence of ferroelasticity in this crystal is discussed and the high temperature space group is predicted.

High pressure electrical measurements on Ge-Te-Se glasses

Electrical resistivity measurements have been carried out on bulk Ge-Te-Se glasses in a Bridgman anvil System. The resistivity of the Ge-Te-Se samples is found to decrease continuously with increasing pressure, with the metallization occurring around 8 GPa. Ge20TexSe80-x glasses (10 less than or equal to x less than or equal to 50) with the mean co-ordination number Z(av) = 2.4 exhibit a plateau in resistivity up to about 4 GPa pressure, followed by a continuous decrease to metallic values. On the other hand, Ge10TexSe90-x glasses (10 less than or equal to x less than or equal to 40) having Z(av) = 2.2, exhibit a smaller plateau (only up to 1 GPa), followed by a decrease in resistivity with pressure. This subtle difference in the high pressure resistivity of Ge-Te-Se glasses with Z(av) < 2.4 and Z(av) greater than or equal to 2.4 can be associated with the changes in the local structure of the chalcogenide glasses with composition.

郭永怀先生的精神永存

2009年4月4日是著名力学家、应用数学家、"两弹一星"功勋奖章获得者、中国科学院院士、中国科学院力学研究所副所长郭永怀先生诞辰100周年.为学习郭永怀先生的崇高品德,弘扬郭永怀先生的科学思想,中国科学院力学研究所于4月3日举行"纪念郭永怀先生诞辰100周年大会暨学术报告会",并出版纪念文集.本期从中选登了郑哲敏院士的"郭永怀先生的精神永存"、俞鸿儒院士的"郭永怀先生引导我做实验",以示缅怀和敬意.

许氏平鲉幼鱼的赖氨酸需求量

通过8周的生长实验确定了许氏平(Sebastes schlegeli)幼鱼的赖氨酸需求量。饲料必需氨基酸组成(除赖氨酸外)参照鱼体肌肉蛋白的氨基酸模式,配制赖氨酸含量为1.542、.04、2.54、3.04、3.54和4.04%的等氮等能的六种半精制饲料。研究结果表明,随着饲料中赖氨酸含量的增加,增重率逐渐提高,当饲料中赖氨酸含量为3.54%时,达到最大值(P<0.05)。基础饲料组的蛋白质贮积率最低,且显著低于3.54%组(P<0.05),和其他组之间差异不显著(P>0.05)。随着饲料中赖氨酸含量的增

激波管壁AlO自由基B~2∑~+-X~2∑~+和C~2∏_r-X~2∑~+带系辐射光谱的研究

爆轰驱动过程中产生的高温高压气流对铝质膜片、激波管壁产生烧蚀和冲刷作用,以致激波管壁、端盖上附有氧化铝等杂质,而高温下AlO自由基在气体分子的高速碰撞下被激发并产生强烈的辐射,从而干扰了高温气体辐射光谱的分析。用爆轰驱动加热技术将空气加热到4 000~7 000 K,利用多通道光学分析仪对AlO自由基辐射光谱进行分析,实验发现在460~530 nm波长范围内有多支辐射非常强烈的AlO自由基B2Σ+-X2Σ+(T00=20 689 cm-1)带系辐射谱带,且每支谱带都由多个带头组成,带头间隔约为2 nm,带头处于高频位置并向低频方向伸延。通过实验与理论计算相结合,重点分析了AlO自由基B2Σ+-X2Σ+带系辐射光谱的结构特征。AlO自由基C2Πr-X2Σ+(T00=33 047 cm-1)带系辐射光谱处于270~335 nm波长范围内,其辐射强度相对于B2Σ+-X2Σ+带系较弱,并且与OH基A2Σ+-X2Π(T00=32 682 cm-1)带系辐射光谱互相干扰而难以分辨,对该波段高温空气的辐射光谱分析产生不利的影响。

自旋极化的对称核物质和中子物质的性质

利用Skyrme有效相互作用对自旋极化的同位旋对称核物质和中子物质的特性进行了研究 .用 4种核子 -核子相互作用参数SⅢ ,SKM ,SLy2 30a和SLy2 30b ,分别描绘了核物质状态方程曲线 .可以发现不论使用哪一种参数 ,在自旋极化的同位旋对称核物质和中子物质中都存在着磁化相变转换点 .另外还对磁化系数进行了计算 ,给出了磁化系数比率随密度的变化关系 ,由于无限不连续点的存在 ,进一步肯定了在Skyrme Hartree Fock理论框架内两种物质会出现磁化相变转换点

北方稻田生态系统养分渗漏规律研究

1994～ 1 996年开展了 5种不同模式水稻田生态系统主要养分 N、P、K在整个生育期间随渗漏水淋失规律的研究。结果表明 :不同模式的水稻田生态系统中 ,淋失的 N素养分主要以 NO- 3- N为主 ,NH+ 4 - N淋失仅占很少部分 ,并且随着深度的增加 ,NO- 3- N的淋失逐渐增大 ,而NH+ 4 - N的淋失则逐渐减小。淋失的 P、K养分量很小 ,且随深度的变化其变化量亦不大

大气CH_4中碳稳定同位素组成的PreCon-GC/C-IRMS系统测定

利用预浓缩装置-气相色谱/燃烧-同位素比值质谱仪(PreCon-GC/C-IRMS)联用系统,建立了就采样、浓缩和在线质谱分析大气CH4中稳定碳同位素组成的测定方法。通过多组试验对比,分析并讨论了利用PreCon-GC/C-IRMS联用技术测定大气CH4中碳稳定同位素比值的试验条件、系统线性、稳定性及准确度和精密度等。结果表明,在本研究方法条件下,当离子流强度在1.0~20 V时,系统线性良好(斜率S=0.04‰/V),在4.0~15 V内其线性(斜率S=0.03‰/V)优于总体线性;系统测量稳定性可靠,δ13C值的测定结果的S.D<0.3‰,最大偏差<0.5‰,回收率达99.99%,准确度和精度均符合分析与研究要求。利用该系统对室内和室外草坪地空气中CH4的碳稳定同位素组成做初步测试,其碳同位素的平均值分别为-31.358‰和-33.085‰,且相同地点区域空气中CH4的1δ3C值,在1 d内和不同日期间的变化均在0.5‰以内,重现性良好。

混菌状态对新菌系产生VC前体KGA的影响

通过测定氧化葡萄糖酸杆菌产酸变化 ,研究了新菌系混菌状态对产酸的影响。结果显示 :新混菌体系中 ,种液KGA为4 1- 5 5mg ml,混合菌菌群氧化葡萄糖酸杆菌 掷孢酵母为 2 6 - 35 :1,混菌生物量达 0 4 6 - 0 6 0 (OD值 ) ,有利于二菌在发酵中相互协调 ,促进产酸 ,调节接种生物量可增加产酸速度 ,缩短产酸周期 ,但不影响最终产酸量

日光温室渗灌效果研究

对日光温室渗灌和沟灌的土壤环境、室内空气环境、作物生育及病害状况、水分利用效率等进行了研究.结果表明,与沟灌相比,渗灌可增加土壤水稳性团粒81.4%,降低土壤容重21.2%,增加土壤孔隙度29.0%,提高土壤温度1.1~1.7℃,降低空气湿度13.4%,节约灌溉用水36.7%,而且能促使作物早熟,提高作物产量,减少作物病害,降低生产成本,是目前日光温室理想的灌溉技术.

维生素C二步发酵的新组合菌系

以掷孢酵母作为伴生菌与氧化葡萄糖酸杆菌组成新混菌体系 ,对其产酸性能和特点进行了研究。实验室摇瓶结果显示 :新菌系混菌状态不同 ,产酸不同 ,以KGA含量为 4 8,小菌 /掷孢酵母为 31∶1种液接种时 ,最有利于产酸 ,增加接种生物量可提高产酸速度 ,缩短发酵周期 ,但不影响最终产酸量。相同条件下 ,新菌系产酸能力高于现有菌系 ,酸量增加 5mg/ml～ 7mg/ml,发酵周期缩短 6h～ 8h ,酸转化率提高 3%～ 4 % ,最高产酸点pH值下降约 0 5,表现出较大的产酸潜力和可修饰性

下辽河平原稻田非生长季碳排放观测研究

应用静态箱 /气相色谱法对下辽河平原稻田非生长季碳排放动态变化规律进行了测定。结果表明 ,非生长季 (10月至翌年 4月 )稻田CH4、CO2 和N2 O排放总体上随气温变化而发生变化。在冻融期 (3月中下旬 )CO2 和N2 O有明显的排放。非生长季节的稻田是大气CO2 和N2 O的源 ,作为大气CH4的源或汇的作用不明显。