Gd0.2Ce0.8O1.9纳米颗粒对固体氧化物电解池La0.6Sr0.4Co0.2Fe0.8O3-δ阳极 析氧反应的影响

化石燃料的使用排放了大量CO2,对气候和环境造成了日益严重的危害.固体氧化物电解池(SOEC)能够利用可再生能源产生的电能将CO2高效转化成CO,降低CO2排放的同时,又能减少化石燃料的使用,近年来受到研究者的广泛关注.相比于低温液相CO2电还原,SOEC高的运行温度保证了其较高的反应速率,即较高的电流密度.典型的SOEC单电池由多孔阴极、致密电解质和多孔阳极以三明治的方式组装而成.CO2分子在阴极得到两个电子解离成CO和一个O2–;生成的O2–通过致密电解质传导至阳极,在阳极失去四个电子发生析氧反应(OER)生成一个O2.相比于两电子的阴极反应,阳极四电子的析氧反应更难进行,可能是整个电极过程的速控步,因此开发高性能的阳极材料有望显著提高SOEC的CO2电还原性能.La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)因具有较高的混合离子-电子导电性而被用作SOEC阳极材料,但受LSCF-气体两相界面的限制,其OER性能较低.研究表明,LSCF-掺杂的CeO2-气体所构成的三相界面相比于LSCF-气体两相界面具有更高的电化学反应活性,即OER反应更易在三相界面进行.因此,本文将Gd0.2Ce0.8O1.9(GDC)纳米颗粒浸渍到SOEC LSCF阳极来提高其OER活性,考察了纳米颗粒浸渍量(3,5,10和20 wt%)对SOEC电化学性能的影响.结果表明,SOEC的电化学性能随浸渍量的增加而逐渐升高,当GDC纳米颗粒浸渍量为10 wt%时(10GDC/LSCF),SOEC的电化学性能达到最高,在800 oC和1.6 V的电流密度为0.555 A cm–2,是LSCF阳极SOEC性能的1.32倍.继续增加浸渍量到20 wt%,电化学性能反而开始下降.电化学阻抗谱测试结果表明,GDC纳米颗粒的加入减小了SOEC的极化电阻.对应的弛豫时间分布函数解析结果表明10GDC/LSCF阳极上的OER由四个基元反应构成.电镜和O2-程序升温脱附结果表明,GDC纳米颗粒的加入显著增加了10GDC/LSCF阳极三相界面和表面氧空位的数量以及体相氧的流动性,从而促进了OER四个基元反应的反应速率,降低了这几个过程的极化电阻,因而降低了OER反应的极化电阻,提高了SOEC电还原CO2的电化学性能.     

Studies on the Anode/Electrolyte Interfacein Lithium Ion Batteries

Summary.  Rechargeable lithium ion cells operate at voltages of 3.5–4.5 V, which is far beyond the thermodynamic stability window of the battery electrolyte. Strong electrolyte reduction and anode corrosion has to be anticipated, leading to irreversible loss of electroactive material and electrolyte and thus strongly deteriorating cell performance. To minimize these reactions, anode and electrolyte components have to be combined that induce the electrolyte reduction products to form an effectively protecting film at the anode/electrolyte interface, which hinders further electrolyte decomposition reactions, but acts as membrane for the lithium cations, i.e. behaving as a solid electrolyte interphase (SEI). This paper focuses on important aspects of the SEI. By using key examples, the effects of film forming electrolyte additives and the change of the active anode material from carbons to lithium storage alloys are highlighted. Received May 30, 2000. Accepted June 14, 2000     

Preconcentration and Separation of Trace Amounts of Strontium Ions from Alkali and Alkaline Earth Metal Ions Using Octadecyl Silica Membrane Disks Modified with Decyl-18-Crown-6 and Its Determination by Flame Atomic Absorption Spectrometry

 A simple and reliable method for rapid and selective separation of trace amounts of Sr²⁺ ions from alkali and alkaline earth metal ions by using octadecyl silica membrane disks modified with decyl- 18-crown-6 in the presence of 1.0 × 10⁻³ M picric acid is presented. The influence of picric acid concentration, flow rates and nature and amount of the stripping acid have been investigated. Maximum capacity of the membrane disks modified with 10 mg of the macrocycle was found to be 484 μg of Sr²⁺ ions. The proposed method permitted enrichment factors of about 80 and higher. The limit of detection of the proposed method is 1.5 μg per 1000 ml. The method was successfully applied to the recovery of Sr²⁺ ions from different synthetic and water samples. Received August 10, 2000. Revision April 17, 2001.     

Ce1-xGdxO2-x/2的溶胶-凝胶法合成及其性质

利用溶胶-凝胶法合成了Ce₁-xGdxO_2-x/2(x=0.1～0.6)系列固体电解质,系统地研究了其结构、热膨胀系数和导电性.XRD结果表明,160℃即完全形成立方萤石结构.由于溶胶-凝胶法合成的物质粒度均匀,颗粒小,故在较低温度(1300℃)时即可形成高致密样品,此温度明显低于传统的高温固相法烧结温度(1600～1650℃).高温X射线衍射测得Ce_0.8Gd_0.2O_1.9的热膨胀系数为8.125×10^-6K₁.阻抗谱表明,溶胶-凝胶法合成可减少或消除固体电解质的晶界电阻,600℃时Ce_0.8Gd_0.2O_1.9的电导率为5.26×10^-3S/cm,活化能E_a=0.82eV.     

离子交换净化辐照三烷基氧化膦中脂肪酸

本文研究了用大孔阴离子交换树脂D301R从乏萃取剂30%TRPO-煤油溶液中净化去除脂肪酸的方法,探讨了该法用于乏萃取剂净化的可行性。     

单相Ce0.5Zr0.5O2立方固溶体的高压高温合成

以化学沉淀法制备的 Ce O2 和 Zr O2 纳米微粒为前驱体 ,首次在高压高温 (3 .1 GPa,1 0 73 K)下合成了单相 Ce0 .5Zr0 .5O2 面心立方固溶体 .使用 X射线衍射、TG-DTA、XPS、Raman、电子自旋共振谱和交流阻抗谱等对样品的结构、Ce离子的价态和导电性进行了表征 .实验结果表明 ,纳米 Ce O2 -50 % Zr O2 混合物在高压 (0 .9GPa以上 )高温 (1 0 73 K以上 )条件下可以发生固态反应 ,高压下固溶温度明显降低 .Ce0 .5Zr0 .5O2 面心立方固溶体在 773 K以下是热稳定的 ,不发生结构转变 ,固溶体中 Ce离子完全以 Ce4 + 形式存在 ,773 K退火也不引起 Ce4 + 向 Ce3 + 转变 ,晶格中氧缺位非常少 .Ce0 .5Zr0 .5O2 面心立方固溶体是离子导电 ,82 3 K时电导率 σ=1 .2× 1 0 -5S/cm,与纯 Ce O2 在同温度下的电导率同数量级 ;1 1 2 3 K时 σ=2 .1× 1 0 -3 S/cm,小于掺入稀土或碱土氧化物的氧化锆和氧化铈基电解质的电导率 .在高温区和低温区 ln(σT)与 1 /T的关系满足斜率不同的二条直线 ,低温活化能小于高温活化能 .固溶体的显微硬度 (50 g载荷 )为 572 HV.     

Determination of selected persistent organochlorine pollutants in human milk using solid phase disk extraction and narrow bore capillary GC-MS

Summary A simple and rapid procedure based on solid phase disk extraction (SPDE), adsorption chromatography on acidified silica gel and GC-MS analysis was developed for the determination of 8 organochlorine pesticides and 19 PCB congeners in human milk. By using the SPDE procedure, a high throughput and parallel sample processing could be achieved. Method variables were optimized on whole cow's milk (3.5% fat) fortified at levels close to concentrations found in human milk. Recoveries of target analytes were acceptable and ranged from 69 to 102% and 86 to 120% for whole and skimmed milk, respectively. By the use of two stage clean-up and narrow bore capillary columns, detection limits as low as 20 pg mL⁻¹ could be obtained. The method was used for the determination of organochlorine pollutants in human milk from 19 individuals from Romania. The concentrations of PCBs were low, whereas those of organochlorine pesticides were higher than the values reported from other European countries.     

固相微萃取-高效液相色谱联用技术的进展

固相微萃取（SPME）技术是近年来发展起来的一种无溶剂,集采样、萃取、浓缩、进样于一体的样品预处理新技术,它与同效液相色谱技术的联用已受到人们的瞩目;该文评述了SPME-HPLC联用技术的进展,并展望这一技术的应用前景。     

固相分光光度法测定枸杞中的痕量锗

建立了以苯基荧光酮为显色剂固相分光光度法测定痕量锗的新方法。在0 .1 5 mol/L HCl介质中 ,锗吸附于树脂上 ,再与苯基荧光酮显色 ,直接在最大吸收波长 5 35 nm处对树脂相进行测量。锗含量在 0～ 2 5 0 μg/L范围内符合比尔定律 ,表观摩尔吸光系数为 2 .6× 1 0 6L· mol-1· cm-1。该法已应用于枸杞中痕量锗的测定     

毛细管区带电泳分离测定邻、对、间氯代苯酚

通过改变电泳条件,用毛细管区带电泳成功地分离了邻、对、间氯代苯酚,并检测到废水中样品的含量。研究了缓冲溶液种类、浓度、pH值、电泳电压以及内标物的选择,并得出了三种样品的标准曲线、线性范围以及加样回收率,为环境样品的监测提供了依据。