金属氧化物阳极失效过程的电化学监测

采用循环伏安和电化学阻抗谱等电化学方法对金属氧化物阳极在硫酸中的寿命加速过程进行了监测.检测了阳极伏安电量,双电层电容,氧化物膜电阻和析氧反应的电荷传递电阻等电化学参数随电解时间的变化,并提出金属氧化物阳极电解失效的机理.     

柔性Pd@PANI/rGO纸阳极在甲醇燃料电池中的应用

利用脉冲电压法在自组装制得的柔性石墨烯纸表面聚合聚苯胺,以该复合材料作为甲醇燃料电池的阳极电极基体,采用循环伏安法在其表面电沉积纳米Pd制备出无需外加粘接和支撑的催化电极。通过扫描电子显微镜、X射线光电子能谱和红外光谱分析该材料的表面形貌和化学组成,并通过电化学测试该电极在甲醇氧化过程中的催化性能。结果表明,该阳极材料柔韧性好,原料利用率高,聚苯胺在石墨烯纸表面分散良好,形貌均一,聚苯胺的存在提高了催化剂的催化效率,使得甲醇的氧化峰电流密度从3 mA·mg~(-1)提高到67 mA·mg~(-1),且延长了催化剂的使用寿命,正向与反向扫描的阳极峰值电流密度的比值(jf/jb值)达到5.7。     

微生物燃料电池多孔阳极的制备及阳极改性研究

以石墨粉为阳极基体,使用相转换法,制备了一种孔隙梯度分布的多孔阳极材料。将这种阳极组装为双室型微生物燃料电池进行电化学性能测试。另外,在阳极中添加了10%石墨质量比的聚苯胺,对阳极进行改性。相转换的改性方式能够使聚苯胺与阳极颗粒均匀混合,保证了改性的效率。电化学测试结果表明,单纯石墨阳极的功率密度为26.3mW·m~(-2)。而添加了聚苯胺后,功率密度提高到了80.2mW·m~(-2)。阻抗谱测试也显示,添加聚苯胺后的阳极,其欧姆阻抗与界面阻抗均有一定程度的降低。     

电解-电化学混合电容器的制备与性能

为解决电化学电容器工作电压过低的问题, 本文以钽电解电容器的烧结型钽块为阳极, 聚苯胺(PANI)/TiO₂电化学电容器复合电极为阴极, 成功制备了高能量密度、高工作电压的电解-电化学混合电容器. PANI/TiO₂复合电极是通过在多孔阳极氧化钛纳米管阵列中电化学聚合PANI 制得. 该阴极具有优良的倍率特性, 当平均功率密度为0.55 mW·cm^-2时, 对应的比容量仍达到10.0 mF·cm^-2. 由于与电解电容器复合, 该混合电容器的单元工作电压可高达100 V. 而且电化学电容器阴极的比容量远大于阳极, 故阴极所需尺寸远小于阳极, 节省的空间可用于增大阳极尺寸, 从而使混合电容器的比容量极大提高. 所制备的混合电容器体积能量密度和质量能量密度分别是钽电解电容器的4 倍和3 倍. 将该混合电容器在100 V下进行短路充放电实验, 循环10000 次后发现容量未衰减, 等效串联电阻未增加, 显示出极好的循环稳定性和功率特性. 计算表明其最大功率密度高达847.5 W·g^-1. 电化学阻抗谱显示其具有优良的阻抗特性和频率特性.     

电极液酸度及稀土浓度对硫酸体系电解还原提纯镱的影响

研究了在硫酸体系中,采用钌铱钛合金网为阳极,金属汞为阴极,在无惰性气氛的保护下,尝试电解还原镱,在诸多电极条件实验中着重研究了阳极液酸度、阴极液酸度以及料液浓度变化时电流、目标离子的还原率等电解还原过程的变化。研究表明,当阳极液酸度为2.0 mol.L-1,阴极液pH=0.3,阴极液稀土料液浓度为0.5 mol.L-1时,镱的还原率可达95%以上,硫酸镱纯度达到99%以上,稀土总回收率高于99%。     

新型电聚合交联聚苯胺电化学传感器的研制及其在抗坏血酸测定中的应用

以苯胺、对苯二胺、1,3,5-三苯胺基苯为单体,采用循环伏安法在金电极上电化学聚合制备了一种新型的交联聚苯胺(CPAN)电化学传感器。采用交流阻抗谱和电化学方法对该传感器进行了表征。结果表明:交联剂1,3,5-三苯胺基苯结构单元被成功地引入到聚苯胺链中,所得的CPAN与线性聚苯胺(LPAN)相比,导电性增强,电子传输速率加快。CPAN/Au电极对抗坏血酸具有良好的电催化氧化作用,在优化的条件下,测得抗坏血酸浓度在1.0×10-4～1.0×10-2 mol.L-1范围内与传感器峰电流呈线性关系,检出限(3S/N)为3.3×10-5 mol.L-1。该传感器的响应时间为5s,测定结果的相对标准偏差(n=6)为2.0%～2.5%,回收率在98.0%～102%之间。     

Ti基IrO2＋Ta2O5阳极在H2SO4溶液中的电解时效行为

研究了450 ℃制备所得Ti/70％IrO2 30％Ta2O5（摩尔分数）高寿命阳极在H2SO4溶液电解过程中电极的物理、化学及电化学性能的时效行为.结果发现，整个电解过程可分为“活化”、“稳定”及“失效”三个阶段.在“活化”及“稳定”区内主要发生电极表面活性氧化物的溶解，涂层中IrO2金红石相的（110）、（101）晶面择优取向随电解时间延长而减弱，而（002）晶面择优增强.但是在“失效区”内，各晶面的择优程度却不随电解时间的变化而变化，这表明在“失效区”内氧化物的损失机制发生了变化.电化学阻抗谱测试表明，电极的析氧电化学反应电阻随电解时间的延长发生缓慢而连续的上升，而整个电极的物理阻抗在“失效区”内却发生突升现象.X射线衍射分析（XRD）表明，随电解时间的延长TiO2金红石相的衍射强度增大，达“失效区”时衍射强度发生突升.根据实验现象特别是“失效区”内阳极的时效行为提出高寿命Ti基氧化物涂层阳极的失效机制.     

丁二酸在Ti/TiO2膜电极上的电化学合成

在包含原料马来酸的硫酸溶液中, 通过原位阳极氧化法制备了Ti/TiO2膜电极, 然后采用极性转换技术在原溶液中电化学合成丁二酸. 采用XPS, XRD和SEM分析了膜电极上的元素组成、价态分布和氧化膜的晶相结构及表面形貌. 结果表明, 阳极氧化膜层内只含有Ti和O两种元素, 且Ti均为Ti4+; TiO2氧化膜是金红石相, 表观呈现带孔的条纹形貌. 通过循环伏安、恒电位阶跃和恒电流电解技术研究了Ti/TiO2原位氧化膜电极的电化学性质, 结果表明, 该膜电极对马来酸电还原合成丁二酸具有较好的电催化活性. 以钛基氧化钌电极(DSA)为阳极, Ti/TiO2原位氧化膜电极为阴极进行恒电流电解了实验. 结果表明, 丁二酸的还原产率为95.94%, 电流效率为95.57%, 产物纯度为99.28%, 熔点为185~187 ℃.     

V（Ⅲ）-V（Ⅳ）电解液的电解合成

以硫酸氧钒(VOSO4)为原料,电解合成了用于制备钒电池的混合价态钒离子[V(Ⅲ)-V(Ⅳ)]电解液.较适宜的电化学反应条件为:以Ir-Ta/Ti为阳极,导电石墨板为阴极;4 mol·L-1 H2SO4为阳极电解液,2 mol·L-1 VOSO4-2 mol·L-1H2SO4混合溶液为阴极电解液,于1A电解6 h.在此条件下进行电化学反应,电解液的电化学活性高,电导率稳定;电解过程实现了较高的电流效率(接近100%)和较低的电能损耗(345 Wh·kg-1).     

NanoTiO2-聚苯胺复合膜电极电化学降解2,4,6-三硝基苯酚

利用溶胶-凝胶法和电化学聚合制得Ti/nanoTiO2-聚苯胺(PAn)复合膜电极,用X射线衍射仪、扫描电子显微镜及循环伏安法对电极的结构、表面形貌和电催化性能进行了表征。SEM测试表明,Ti/nanoTiO2-PAn电极上聚合的苯胺呈短纤维形貌,短纤维的直径较为均匀,为150 nm左右。以此电极进行电化学降解2,4,6-三硝基苯酚,在25℃,电解时间为180 min,电极间距离为2 cm,废水pH值在7～8之间,浓度为50 mg/L的2,4,6-三硝基苯酚模拟废水中COD,降解效率可达到41.2%。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.