直接硼氢化物燃料电池（DBFC）阳极材料及反应机理*

以碱金属硼氢化物为燃料的直接硼氢化物燃料电池（DBFC）,是一种有发展潜力的移动电源。DBFC阳极过程是一个复杂的H^--H0*-H⁺之间价态转化的电极反应体系,涉及BH₄^-的电氧化反应、BH₄^-的水解释氢反应与氢的电氧化反应,该过程不仅与电极材料有关,也与反应条件有关。研发能有效抑制释氢的廉价阳极催化材料,是DBFC实用化的关键。因此,本文对近年来报道的DBFC阳极催化材料、以及BH₄^-在不同阳极材料上的电化学氧化反应机理进行了综述,并归纳出需要深入研究的主要问题。     

氧化镧作为直接硼氢化物燃料电池阴极催化剂的研究

通过采用线性电势扫描(LSV)和恒电流计时电势扫描方法对氧化镧作为直接硼氢化物燃料电池阴极催化剂的电化学性能进行了研究.实验结果表明:在单室燃料电池体系中,氧化镧对氧还原具有良好的活性,同时在强碱溶液中对硼氢根离子具有很强的稳定性且对硼氢根的水解没有任何促进作用.以镍基储氢合金作为电池的阳极催化剂组装成简单的单室燃料电池,电池的开路电压达到1.052 V,在常温下(21℃),电池于0.491 V获得最高功率密度65.25 mW·cm-2,电池运行稳定.     

氧化铈作为阴极催化剂在直接硼氢化物燃料电池中的应用

研究以氧化铈(CeO2)作为直接硼氢化物燃料电池(DBFC)阴极催化剂的性能.结果表明:氧化铈对氧还原具有良好的催化效能,但对BH4-离子水解没有明显的促进作用,而且还能抑制它在正极的氧化.以氧化铈为阴极催化剂组装成的模拟单室燃料电池在常温下的最高功率密度为67.8mW·cm-2,运行稳定.     

直接硼氢化物燃料电池

直接硼氢化物燃料电池是一种新型的燃料电池,具有理论比能量高,产物清洁无污染,燃料易于储存和运输等特点,可广泛应用于小型便携式电子产品和移动电源,近年来受到越来越多研究者的关注。本文在介绍了直接硼氢化物燃料电池工作原理的基础上讨论了阳极催化剂、阴极催化剂的研究进展,并探讨了电解液和温度等条件对电池性能的影响,简要分析了发展直接硼氢化物燃料电池面临的主要问题。     

层状水滑石结构包覆钴硼合金的电化学产氧性能

电解水制氧是一种非常有吸引力的转化储存间歇式能源的技术.本文着重研究了非晶态钴硼合金的电解水产氧性能.非晶态钴硼合金可以通过硼氢化钠直接还原钴盐来获取,并表现出较高的电化学活性.对钴硼合金的弱氧化,产生了类水滑石结构的钴氢氧化物,可进一步提高该类催化剂的整体催化活性,达到接近商业催化剂水平.     

层状水滑石结构包覆钴硼合金的电化学产氧性能（英文）

电解水制氧是一种非常有吸引力的转化储存间歇式能源的技术.本文着重研究了非晶态钴硼合金的电解水产氧性能.非晶态钴硼合金可以通过硼氢化钠直接还原钴盐来获取,并表现出较高的电化学活性.对钴硼合金的弱氧化,产生了类水滑石结构的钴氢氧化物,可进一步提高该类催化剂的整体催化活性,达到接近商业催化剂水平.     

双核双金属酞菁(FeCoPc_2)阴极催化直接硼氢化物燃料电池

研制一种无膜型直接硼氢化物燃料电池(DBFC).循环伏安测试发现FeCoPc2在碱性溶液中对氧还原具有催化作用.稳态极化曲线表明,由于FeCoPc2结构具有较强的共轭效应以及Fe、Co在催化中的协同作用使它比FePc、CoPc具有更强的氧还原能力,并获得了110mW/cm2的功率密度.恒电流放电测试表明该燃料电池性能具有良好的稳定性.     

直接硼氢化物燃料电池阴极催化剂的研究进展

缓慢的阴极氧还原动力学和催化剂稳定性是制约直接硼氢化物燃料电池商业化的关键因素之一。为此,研究者在提高催化剂的催化活性与稳定性和降低催化剂成本方面开展了大量的研究工作。本文在简要介绍直接硼氢化物燃料电池的工作原理和阴极氧还原反应机理的基础上,从催化剂性能和反应机理角度综述了近年来直接硼氢化物燃料电池中贵金属和非贵金属两类阴极催化剂的主要研究进展,指出了阴极催化剂研究所面临的问题,同时提出了阴极催化剂研究的新的发展方向。     

提高AB_5型贮氢电极合金低温电化学性能研究

采用优化稀土成分并添加适量的硼改善AB5型贮氢合金的低温性能 .实验表明 ,含富Ce稀土及添加适量硼的AB5型合金 ,其低温电化学性能优良 ,能满足Ni/MH电池在低至 - 35℃小倍率电流密度放电的要求 .贮氢合金低温性能的改善与合金的微结构、热力学和动力学性能相一致     

PtCr合金的溶液制备及其电化学性质分析

催化剂性能的高低直接决定了燃料电池性能的好坏. 采用Pt基合金不仅能够降低催化剂Pt的载量, 而且往往能够提高催化剂的性能. 本工作用Cr作为合金化元素, 通过液相共沉淀的方式制备了不同比例的碳载PtCr合金催化剂. 采用高分辨透射电镜(HRTEM), 扫描电镜(SEM)等技术对合金催化剂的物理性质进行了测试. 结果表明, 获得的PtCr/C催化剂均匀地分散在Vulcan XC-72碳载体上, 粒度小于4 nm. 通过电化学测试, 研究了不同比例PtCr合金的电化学催化性能. 循环伏安测试表明, 本实验条件合成的合金催化剂在Pt/Cr原子比为2/1的时候, 对氧还原动力学有最佳的催化性能.     

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.