氧分压对固体氧化物电解池性能的影响

High-temperature (700–900 ℃) steam electrolysis based on solid oxide electrolysis cells (SOECs) is valuable as an efficient and clean path for large-scale hydrogen production with nearly zero carbon emissions, compared with the traditional paths of steam methane reforming or coal gasification. The operation parameters, in particular the feeding gas composition and pressure, significantly affect the performance of the electrolysis cell. In this study, a computational fluid dynamics model of an SOEC is built to predict the electrochemical performance of the cell with different sweep gases on the oxygen electrode. Sweep gases with different oxygen partial pressures between 1.01 × 10³ and 1.0 × 10⁵ Pa are fed to the oxygen electrode of the cell, and the influence of the oxygen partial pressure on the chemical equilibrium and kinetic reactions of the SOECs is analyzed. It is shown that the rate of increase of the reversible potential is inversely proportional to the oxygen partial pressure. Regarding the overpotentials caused by the ohmic, activation, and concentration polarization, the results vary with the reversible potential. The Ohmic overpotential is constant under different operating conditions. The activation and concentration overpotentials at the hydrogen electrode are also steady over the entire oxygen partial pressure range. The oxygen partial pressure has the largest effect on the activation and concentration overpotentials on the oxygen electrode side, both of which decrease sharply with increasing oxygen partial pressure. Owing to the combined effects of the reversible potential and polarization overpotentials, the total electrolysis voltage is nonlinear. At low current density, the electrolysis cell shows better performance at low oxygen partial pressure, whereas the performance improves with increasing oxygen partial pressure at high current density. Thus, at low current density, the best sweep gas should be an oxygen-deficient gas such as nitrogen, CO₂, or steam. Steam is the most promising because it is easy to separate the steam from the by-product oxygen in the tail gas, provided that the oxygen electrode is humidity-tolerant. However, at high current density, it is best to use pure oxygen as the sweep gas to reduce the electric energy consumption in the steam electrolysis process. The effects of the oxygen partial pressure on the power density and coefficient of performance of the SOEC are also discussed. At low current density, the electrical power demand is constant, and the efficiency decreases with growing oxygen partial pressure, whereas at high current density, the electrical power demand drops, and the efficiency increases.     

将密度泛函理论计算纳入高等化学教学初探——对乙酸乙酯碱性水解机理的理论研究

使用Gaussian 09软件对乙酸乙酯碱性水解反应的机理进行了研究。本研究融合了本科教学中有机化学、物理化学和结构化学的相关知识,以乙酸乙酯水解机理为问题导向,阐述了研究和解决问题的思路和方法,探索了将第一性原理计算引入高等教育的方式。     

"我"——"三草酸合铁(Ⅲ)酸钾晶体"的生长及影响因素

This article tries to personify potassium ferrioxalate crystal as "I" to describe the formation process and the factors affecting the growth of potassium ferrioxalate crystal. After growing into beautiful green crystals, I dreamed I was participating in the jewelry beauty contest. A serious of wonderful conversations between emerald and I revealed the properties and applications of potassium ferrioxalate crystal. It inspires and guides students to understand the growth of crystals and their properties, and it also stimulates students' interest in studying chemistry.     

气相色谱-串联质谱法测定食用油中两种非邻苯二甲酸酯类增塑剂

建立了气相色谱-串联质谱同时测定食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯两种非邻苯二甲酸酯类增塑剂的方法。样品采用乙腈提取,于-20℃冷冻除脂净化,用气相色谱-串联质谱选择反应监测模式测定。两种化合物的检出限为0.03 mg/kg,定量限为0.1 mg/kg,线性范围为0.1~10 mg/kg。3个添加水平（0.1、0.3和1.0 mg/kg）下的回收率为81.04%~108.31%,相对标准偏差为0.70%~9.91%。该方法简便、准确,适用于食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯的检测。     

CuCl_2/离子液体催化炔丙醇、仲胺与CO_2的三组分反应

以二氧化碳代替传统剧毒的光气等来合成氨基甲酸酯已成为研究的热点,然而现存的体系普遍需要高温高压等苛刻反应条件才能催化反应,并且很少有催化体系能够有效地回收和再利用.探索了将CuCl_2/离子液体(IL)用于炔丙醇、仲胺和CO_2的三组分反应合成β-羰基氨基甲酸酯.在常压、45℃的温和条件下,以较低催化当量(2%摩尔分数)的廉价易得的2价铜将多种类型的炔丙醇和仲胺通过简单的"一锅法"合成相应的目标化合物,并且循环利用3次后产率并未见明显下降.分步反应结合NMR监测的机理实验证明,炔丙醇与CO_2先生成的α-亚甲基环碳酸酯是反应的重要中间体,且醋酸型离子液体对炔丙醇和CO_2的活化具有重要作用.     

高效液相色谱法同时测定化工废水中乙醇酸、乙醛酸和草酸的含量

水样经0.22μm亲水针筒式过滤器过滤,根据需要进行稀释后,在Acclaim MixedMode WAX-1色谱柱(4.6mm×150mm,5μm)上进行分离,以90mmol·L~(-1)磷酸盐缓冲溶液[pH 6.0,溶剂为10%(体积分数)乙腈溶液]为流动相进行等度洗脱,在波长210nm处进行紫外检测。结果表明:乙醇酸、乙醛酸和草酸的质量浓度分别在3.51～2 500,4.20～8 000,18.0～800mg·L~(-1)内与对应的峰面积呈现线性关系,检出限(3S/N)分别为1.00,1.24,4.82mg·L~(-1),测定下限(10S/N)分别为3.32,4.15,16.1mg·L~(-1)。对实际样品进行加标回收试验,乙醇酸、乙醛酸和草酸的回收率分别在98.2%～101%,99.6%～103%,99.2%～101%之间,测定值的相对标准偏差(n=6)分别为0.77%,0.65%,1.1%。     

控温超声提取-高效液相色谱法测定空气PM2.5中16种多环芳烃

剪碎的滤膜经乙腈于35℃超声提取60 min,提取液以12 000r·min~(-1)转速离心10min,采用高效液相色谱法测定上清液中16种多环芳烃的含量。以Agilent Eclipse PAH-C18色谱柱为分离柱,用乙腈和水以不同比例混合的溶液为流动相进行梯度洗脱,用二极管阵列检测器和荧光检测器测定。16种多环芳烃的质量浓度均在0.02～1.00mg·L~(-1)内与其对应的峰面积呈线性关系,检出限(3S/N)为0.05～0.25ng·m~(-3)。以空白滤膜为基体进行加标回收试验,所得回收率为87.8%～103%,回收量的相对标准偏差(n=6)小于5.0%。     

冷冻研磨超声浸提分离-气相色谱-质谱法测定充油丁苯橡胶中8种多环芳烃的含量

为从充油丁苯橡胶样品中分离提取其中所含8种多环芳烃化合物(PAHs,包括苯并[a]蒽、艹屈、苯并[b]荧蒽、苯并[j]荧蒽、苯并[k]荧蒽、苯并[e]芘、苯并[a]芘及二苯并[a,h]蒽),采用了冷冻研磨、超声浸提法。试验选择了5件样品分别将其粉碎至约2mm~3的颗粒,并取一定量的颗粒样品置于研磨仪中进行冷冻研磨至粉末状态。称取加工成粉末状的样品1.00g,加入正己烷-丙酮(1+1)混合溶液10mL,在40℃超声提取35min。将所得提取液氮吹浓缩至近干,用正己烷1mL溶解残渣,所得溶液经滤膜过滤,滤液供气相色谱-质谱分析。采用VB-17MS毛细管色谱柱,在90～300℃温度区间按程序升温模式进行分离。在质谱分析中,用电子轰击离子源和选择离子监测模式。测得8种PAHs的线性范围均在0.05～5.0mg·L~(-1)之间,检出限(3S/N)在0.01～0.02mg·L~(-1)之间。在样品溶液中加入混合标准溶液进行回收试验,测得回收率在84.5%～106%之间,并从测定值计算其相对标准偏差(n=6)在1.6%～4.9%之间。     

原位制备的铁配合物催化烯烃选择性环氧化

制备了配体2-(2-吡啶基)-噁唑啉。该含氮配体能够在乙腈溶液中与三氟甲磺酸亚铁和其它辅助配体原位形成具有催化活性的六配位金属亚铁配合物。量子化学计算表明配体上的氮原子而非氧原子与铁配位。研究表明,以H_2O_2为氧化剂,该金属配合物能够在乙腈溶液中高活性地催化末端芳香烯烃和脂肪烯烃的环氧化反应;该反应条件温和、迅速、选择性好并且适用底物范围宽泛。辅助配体、溶剂和氧化剂等因素对反应的活性和选择性影响很敏感,文中对这些影响进行了较详细的研究。