纳米TiO2膜电极的电化学阻抗谱

纳米TiO2膜电极的电化学阻抗谱;纳米TiO2膜;电化学阻抗谱;催化电极;异相氧化还原电对     

ZnFe2O4/TiO2纳米管阵列电极的制备及光电催化降解苯酚的研究

采用阳极氧化法和电沉积法制备出具有可见光响应的ZnFe2O4/TiO2纳米管阵列电极.用环境扫描电子显微镜(ESEM)、X-射线衍射(XRD)和透射电子显微镜(TEM)对制备的ZnFe2O4/TiO2纳米管阵列电极的表面形貌和结构进行了表征.结果表明,该方法成功地将ZnFe2O4纳米颗粒均匀分散在TiO2纳米管中,分布在管口处的较少.同时,详细讨论了反应物浓度、沉积时间、循环次数、沉积电压对ZnFe2O4/TiO2纳米管阵列电极性能的影响.通过在可见光下降解苯酚评价了复合电极的光催化活性,实验结果表明:由于ZnFe2O4和TiO2之间的协同效应,复合电极的光响应范围扩展到了可见光区域,光电催化活性提高1.5～2倍.     

Zn(Ⅱ)和La(Ⅲ)共掺杂TiO2纳米晶多孔膜电极光电化学行为研究

采用溶胶-凝胶法合成了Zn（Ⅱ）、La（Ⅲ）共掺杂TiO2纳米粒子（掺杂0．5％Zn（Ⅱ）及0．5％La（Ⅱ））,并制成了TiO2、掺杂0．5％Zn（Ⅱ）及共掺杂0．5％Zn（Ⅱ）和0．5％La（Ⅱ）的TiO2纳米晶多孔膜电极,对该3种电极进行了电化学及光电化学研究,实验发现,用Zn（Ⅱ）单独掺杂TiO2纳米多孔膜电极的光电流大于未掺杂的TiO2纳米多孔膜电极,而Zn（Ⅱ）和La（Ⅲ）共掺杂TiO2纳米多孔膜电极的光电流又大于Zn（Ⅱ）单独掺杂TiO2纳米多孔膜电极,对该掺杂电极的光电转换机理进行了探讨。     

不对称菁染料敏化纳米TiO2的光生电流过程

用光电化学方法研究了不对称菁类染料敏化TiO2纳米结构电极的光电转换过程.结果表明,该染料的电子激发态能级位置与TiO2纳米粒子导带边位置匹配较好,光激发染料后,其激发态电子可以注入到TiO2纳米多孔膜的导带,从而使TiO2纳米结构电极的吸收光谱和光电流谱红移至可见光区,其 IPCE(Incident photon-to-electron conversion efficiency)值最高可达84.3%.并进一步结合现场紫外-可见吸收光谱研究了外加电势对激发态染料往TiO2纳米多孔膜注入电子过程的影响.     

TiO2纳米晶多孔膜的电荷传输特性

用光电流作用谱、瞬态光电流、循环伏安及线性电位扫描法研究了TiO2纳米晶／纳米多孔膜电荷传输特性．结果表明TiO2纳米多孔膜的电荷传输与块体半导体不同．TiO2纳米晶电极的能带不弯曲，电子在导带中可向两个方向流动，电子既可以流向电极内部经由外电路输出．也可以流向电解质溶液被溶液中的受主捕获．在TiO2纳米多孔膜电极中，不仅在负电位区能带边随电位变化，而且在正电位区能带边随电位变化而移动，即带边不钉扎。加入合适的施主可提高光电转换效率．加入受主则在电极溶液界面引起电子的严重损失，降低光电转换效率．     

纳米TiO_2膜修饰电极异相电催化还原马来酸

通过电化学合成前驱体和溶胶 -凝胶法在Ti表面修饰一层纳米TiO2 膜 ,SEM ,XRD测试表明晶型为锐钛矿型 ,晶粒平均尺寸为 2 5nm .采用循环伏安法、循环方波伏安法和电解合成法研究了纳米TiO2 膜电极在硫酸介质中的氧化还原行为以及对马来酸 (maleicacid)还原的电催化活性 .结果表明 ,纳米TiO2 膜电极在阴极扫描时有两对可逆氧化还原峰 ,可逆半波电位Er1/ 2 分别为 -0 .5 3V和 -0 .92V (vs .SCE ,扫描速度 0 .0 5V·s-1) ,对应于TiO2 /Ti2 O3 和TiO2 /Ti(OH) 3 两个氧化还原电对的可逆电极过程 .其中TiO2 /Ti2 O3 电对对马来酸具有异相电催化还原活性 ,纳米TiO2 膜中的TiⅣ/TiⅢ 氧化还原电对作为媒质间接电还原马来酸为丁二酸 (butanediacid) ,反应机理为电化学偶联随后化学催化反应 (EC′)机理 .     

纳米SnO2/TiO2电极的制备及其电催化降解间-硝基苯酚

用电化学方法在乙二醇溶液中制备锡、钛醇盐配合物Sn0.75Ti(OCH2CH2OH)(7-x),将电解液水解、干燥后在400℃煅烧2 h,得到纳米级SnO2/TiO2粉体。通过红外光谱(FT-IR)和拉曼光谱(Raman)对电解产物进行测试,纳米SnO2/TiO2粉体通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)进行表征。实验表明,在有机体系电解得到的纳米SnO2/TiO2粉体颗粒分散较理想,粒径在100～200 nm。再通过溶胶-凝胶法在钛丝表面得到纳米SnO2/TiO2电极,采用循环伏安法研究电极在酸性溶液和间-硝基苯酚溶液中的氧化还原行为和电催化活性。结果表明,纳米TiO2掺杂SnO2电极的氧化峰电流达到143×10-3A/cm2,氧化还原峰电位差明显减小,催化降解间-硝基苯酚的COD去除率达到86.1%,具有较高的电催化活性。     

高活性Ti基纳米TiO_2膜催化电极的制备

采用“牺牲阳极法”恒槽压电解含有 0 .0 0 5mol·L- 1四乙基溴化铵的乙醇溶液 ,加入微量乙酰丙酮作稳定剂 ,电合成TiO2 前驱体钛酸乙酯Ti(EtO) 4 ,经水解、涂膜、煅烧制备Ti基纳米TiO2 膜电极 (Ti/nano_TiO2 ) .TEM、SEM、XRD测试表明 :TiO2 颗粒尺寸在 10～ 35nm ,膜厚达 0 .5μm ,主要为锐钛矿晶型 ,膜为多孔三维网状结构 .循环伏安法研究了纳米TiO2 膜电极对草酸还原为乙醛酸、硝基苯还原为对氨基苯酚反应的电催化活性 ,结果发现纳米膜中的Ti(Ⅳ ) /Ti(Ⅲ )氧化还原电对起一种中介作用 ,可使有机物如草酸和硝基苯间接电还原 ,且电极催化活性高 ,性能稳定     

煅烧温度对纳米TiO2光电响应的影响

自从Graetzel及其合作者在液结太阳能电池研究方面取得重大突破以来,纳米晶多孔膜电极越来越引起人们的兴趣。TiO2纳米结构电极是由纳米粒子烧结在一起的三维海绵状结构,电解液可渗透到电极内部,因而电荷的传输较复杂。如何提高纳米结构电极的光电转换效率是一个值得大力研究的问题。本文探索了煅烧温度对TiO2纳米结构电极电荷传输特性的影响,旨在为提高太阳能转换中光电转换效率而寻找有效途径。     

十八硫醇自组装膜对TiO2光电氧化甲醇的敏化作用

纳米电极;甲醇光电氧化;十八硫醇自组装膜对TiO2光电氧化甲醇的敏化作用     

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%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.