热处理温度对La-Y-Ni合金相结构和电化学性能的影响

采用磁悬浮感应熔炼法制备了组分为LaY_2Ni_(9.7)Mn_(0.5)Al_(0.3)的合金,在不同温度(1 073～1 373 K)下对合金进行热处理,利用X射线衍射法(XRD)、电子探针(EPMA)和电化学性能测试等方法,系统地研究了热处理温度对合金相结构和电化学性能的影响。结果表明,热处理可以显著提高合金的相均匀度,随着热处理温度的升高合金中的主相Ce_2Ni_7相先增加后减少。电化学研究表明,合金电极的最大放电容量、倍率性能和循环稳定性随着热处理温度的升高均呈现先升高后降低的趋势,与Ce_2Ni_7相含量的变化一致。电化学压力-组成-温度(P-C-T)测试表明,合金具有2个放氢平台,且随着热处理温度的升高合金的放氢坪台压增加。当热处理温度为1 273 K时,合金的Ce_2Ni_7相含量最高为86.53%(w/w),电化学性能最佳,最大放电容量为386.80 mAh·g~(-1)(60mA·g~(-1)),在电流密度为900 mA·g~(-1)时的高倍率性能HRD_(900)=89.45%,循环300周后的容量保持率S_(300)=72.18%(300 mA·g~(-1))。     

MoS2/管状g-C3N4复合光催化剂的光催化海水产氢性能

采用溶剂热法制备了具有二维/一维(2D/1D)纳米结构的MoS_2纳米片/管状g-C_3N_4(MS/TCN)复合光催化剂,并在可见光照射下用于光催化海水产氢。实验结果表明MS/TCN复合材料的光催化活性优于纯相TCN。此外,MS/TCN-0.5样品(含有0.5%(w/w)的MoS_2)显示出最佳的析氢活性,其产H_2速率为85.1μmol·h~(-1),且在进行循环性测试后,活性没有明显降低。     

Mg_2Ni_(1-x)Co_x合金相的固溶烧结法制备及结构和储氢性能

采用固溶烧结法制备了Mg_2Ni_(1-x)Co_x(x=0.10,0.15,0.20)合金,利用X射线衍射仪和压力-组成-温度测试仪等研究了Co含量对合金相结构和储氢性能的影响.结果表明,合金由Mg_2Ni型Mg_2(Ni,Co)主相及少量Mg和Mg Ni3Co新相组成.Mg2(Ni,Co)具有良好的可逆储氢性能,吸氢形成Mg_2Ni_(0.9)Co_(0.1)H_4型四元氢化物,其具有与父系氢化物HT-Mg_2NiH_4相近的放氢焓变(ΔHd=63.9 k J/mol H2).Mg_2Ni_(1-x)Co_x(x=0.10,0.15,0.20)合金具有良好的放氢动力学性能,二维相界面迁移为放氢过程的控制步骤.随着Co含量的增加,合金的放氢活化能(Ea)降低,其中,Mg_2Ni_(0.8)Co_(0.2)的Ea降低到54.0 k J/mol.     

非贵金属助剂Ni_2P修饰类石墨碳氮化物光催化剂增强可见光光催化产氢性能（英文）

随着化石燃料的日益枯竭,能源危机已经成为一个严重的全球性问题。开发氢气等环境友好型的可再生能源来替代化石燃料已迫在眉睫。光催化水解制氢被认为是解决这一问题最有效的技术之一,贵金属(如Pt)可以作为助催化剂提高光催化体系的制氢性能,但高昂的成本限制了该技术的进一步应用。因此,开发新型、高性能、低成本的非贵金属助催化剂以替代贵金属助催化剂,对于将光催化产氢技术付诸实践具有重要意义。在此,我们以共轭聚合物(SCN)n为前驱体成功地合成了Ni_2P/类石墨碳氮化物光催化剂(Ni_2P/CN),在可见光照射下具有优异的光催化产氢性能。使用各种表征技术、光学和光电化学测试研究了这些材料的结构组成、形貌特征以及光学性质。X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)结果表明了合成的Ni_2P/CN纳米复合材料具有良好的晶体结构。扫描电镜(SEM)和透射电镜(TEM)结果显示,Ni_2P/CN样品具有典型的二维层状结构,Ni_2P纳米颗粒均匀地负载在CN表面。紫外-可见漫反射光谱(DRS)结果表明,负载Ni_2P纳米颗粒有效地增强了CN对可见光的吸收能力。光致发光光谱(PL)和光电流测试结果表明,Ni_2P的负载有利于促进光生载流子的迁移和分离效率。光催化产氢实验是在可见光照射下进行的,以三乙醇胺为牺牲剂。结果表明,Ni_2P/CN复合光催化剂具有良好的光催化还原性能。性能最优的Ni_2P/CN复合材料产氢效率达到了623.77μmol·h~(-1)·g~(-1),优于以贵金属Pt作助催化剂的CN样品的产氢效率(524.63μmol·h-1·g-1)。此外,通过一系列表征、光学以及光电化学测试的分析表明,Ni_2P纳米粒子均匀地附着在CN的表面上,并且它们之间存在很强的界面效应,从而形成了抑制光生载流子重组并促进电子迁移的电子传输通道,促进电子从CN迁移至Ni_2P。此外,根据实验和表征,提出了一种可能的光催化机理。这项工作对于非贵金属取代贵金属作为光催化产氢助剂的发展具有重要意义。     

CTAB辅助合成纳米复合材料Ag/ZnO-TiO2及其紫外光催化性能

在模板剂溴化十六烷基三甲基胺(CTAB)的辅助作用下,按nAg∶nZn∶nTi=0.1∶2∶1的物质的量的比,采用溶胶-凝胶再结合程序升温溶剂热法制备了一系列纳米复合材料Ag/ZnO-TiO2(CTAB),并经X射线衍射(XRD)、紫外-可见漫反射吸收光谱(UV-Vis/DRS)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、扫描电子显微镜配合X射线能量色散谱仪(SEM-EDS)和N2吸附-脱附测定等测试手段对不同温度(500、600、700℃)和不同时间(5、7 h)下煅烧得到各产物的组成、结构及形貌等进行了表征。结果表明,该系列复合材料不仅含有ZnO纤锌矿和TiO2锐钛矿结构,同时有部分Zn2TiO4生成,其Ag还以单质形式存在。在CTAB作用下改变煅烧温度和时间可使各产物分别呈现纳米线、纳米球等多种形态,且颗粒分布较均匀。上述各复合材料在紫外光作用下对罗丹明B(RB)的光催化降解结果显示,样品煅烧温度和煅烧时间不同,其活性会发生明显的变化。     

纳米复合材料CdS/TiO_2制备与不同模式光催化降解多种染料

采用化学水浴沉淀法再结合溶胶-凝胶和程序升温溶剂热两步法制备了一系列不同比例的CdS/TiO2纳米复合材料。通过X-射线衍射(XRD)、X-射线光电子能谱(XPS)、扫描电镜(SEM)、紫外-可见漫反射吸收光谱(UV-Vis/DRS)和氮气吸附-脱附测试等手段对所合成纳米复合材料的组成、结构和形貌进行了表征。结果表明,该系列CdS/TiO2纳米复合材料为锐钛矿TiO2和六方相CdS的混合晶相,其对可见光有较强吸收,并且随着复合材料中TiO2比例的增加,BET值明显增大。另外,所合成的CdS/TiO2复合材料呈圆球形,颗粒比较均匀。紫外光催化降解甲基橙的实验结果表明,摩尔比为1∶4的CdS/TiO2复合材料的活性明显高于CdS、P25以及其他不同比例的CdS/TiO2。同时,1∶4 CdS/TiO2纳米复合材料在紫外光、可见光和微波辅助光催化等不同模式下对多种结构的染料均有较好的降解效果。     

MgH_2+20%(w)MgTiO_3复合材料的吸/放氢性能(英文)

为了降低MgH2的吸放氢温度,提高其吸放氢动力学性能,本文通过球磨方法制备了MgH2+20%(w)MgTiO3复合储氢材料,并研究了其储氢性能.X射线衍射(XRD)结果表明,MgTiO3在与MgH2球磨过程中生成Mg2TiO4和TiO2,并且Mg2TiO4和TiO2在体系的吸放氢过程中保持稳定,能够对MgH2的吸放氢过程产生催化作用.程序升温脱附和吸/放氢动力学测试结果表明,添加MgTiO3后MgH2的初始放氢温度从389°C降至249°C.150°C下的吸氢量从0.977%(w)提高到2.902%(w),350°C下的放氢量从2.319%(w)提高到3.653%(w).同时,MgH2放氢反应的活化能从116kJ·mol-1降至95.7kJ·mol-1.与MgH2相比,MgH2+20%(w)MgTiO3复合材料的热力学与动力学性能均有显著提高,这主要是由于球磨和放氢过程中原位生成的TiO2和Mg2TiO4具有良好的催化活性.     

血小板状Ru掺杂Ni2P纳米催化剂的合成及其双功能电催化析氢和析氧性能

采用简单的一锅法制备了血小板状Ru掺杂Ni_2P纳米片催化剂。金属Ru的引入不但显著增强了催化剂的电子传输性能,而且导致血小板状纳米片表面产生了大量阶梯/位错缺陷;此外,电催化活性位点测试表明Ru和Ni_2P均是电催化的有效活性组分。这些因素共同促进了电催化析氢(HER)和析氧反应(OER)过程。对于HER,该催化剂表现出明显优于单一Ni_2P和Ru且接近商用20%(w/w)Pt/C催化剂的初始电位(35 mV)和Tafel斜率(34 mV·dec~(-1))以及长久的稳定性(3 000圈)。对于OER,该催化剂表现出优于Ni_2P、Ru、20%Pt/C且接近商用IrO_2催化剂的初始电位(1.54 V)和过电势η10(0.49 V)。     

储氢材料新合成方法的研究--Ⅲ.置换-扩散法合成Mg2Ni0.75Cu0.25

本文用置换-扩散法合成了三元储氢合金材料Mg_2Ni_(0.75)Cu_(0.25),并对合成的样品进行了吸、放氢性能测试。结果表明,它与氢的反应是可逆的,氢化产物的热分解温度较Mg_2NiH_4有明显的降低。本法合成的样品与冶炼法合成的样品相比较,具有易于活化,吸、放氢速度明显加快等优点。     

Ni2P@CoP3核壳纳米球的制备、表征及其用于超级电容器性能

利用水热技术先后获得Ni纳米球和Ni@Co(OH)_2海胆状核壳纳米球前驱体,通过高温煅烧法获得NiO@CoO核壳纳米球,再以次磷酸钠为原料,通过高温磷化法最终获得Ni_2P@CoP_3核壳纳米球。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高角度环形暗场像扫描透射电子显微镜(HAADF-STEM)、X射线粉末衍射仪(XRD)、能谱仪(EDS)及X射线光电子能谱(XPS)对产物的形貌、结构和组成进行表征。采用循环伏安(CV)、恒电流充放电(GCD)以及循环稳定性实验探索了电极材料的电化学性能。结果表明,Ni_2P@CoP_3核壳纳米球的直径约为400 nm,由六方系Ni_2P纳米核和立方相CoP_3纳米壳构成。相比单纯的Ni_2P或CoP_3纳米球,Ni_2P@CoP_3核壳纳米球发挥了复合结构的协同效应,更加有利于电解液的质子传递,促进了赝电容反应,表现出更高的比容量、稳定性和更长的循环寿命。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.