酸碱度调控氧化锌纳米材料形貌及其光催化还原CO2研究

利用水热法合成了形貌可控的氧化锌(ZnO)微纳材料。利用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),紫外-可见(UV-Vis)分光光谱和比表面积分析(BET)等技术对所制备的ZnO材料进行了表征。不同酸碱度(pH值)条件下,经过500 ℃退火2 h制备的ZnO均为纤锌矿结构。随着前驱液pH值的增加,所得ZnO从片状晶体变为棒状晶体。片状ZnO主要暴露极性晶面,棒状ZnO主要暴露非极性晶面。从生长角度考虑,在溶液为弱酸性条件下(pH 6.5),溶液中游离的氯离子(Cl^-)抑制了ZnO在锌极性面({Zn²⁺}_{crystal surface})的生长,水热反应产物为片状Zn₅(OH)₈Cl₂·H₂O,退火后得到微孔片状ZnO;当溶液中添加氢氧根(OH^-)后,锌离子(Zn²⁺)被络合为四羟基锌络合离子(Zn(OH)₄^2-),该络离子促进了ZnO在{Zn²⁺}_{crystal surface}的生长,从而得到棒状晶体。利用上述催化剂,在氙灯照射下进行光催化还原二氧化碳实验,发现极性面较多的片状ZnO具有更高的光催化性能。     

Zn2+ release from zinc and zinc oxide particles in simulated uterine solution

Zn²⁺ release from Zn and ZnO particles with different sizes in simulated uterine solution were investigated by absorbance measurements. The effects of pH and human serum albumin (HSA) on Zn²⁺ release were also studied. The morphology of Zn and ZnO particles was observed by scanning electron microscopy, and the corrosion products of zinc nanoparticles were analyzed by XRD. The results indicate that the maximum release ratios of Zn²⁺ from Zn and ZnO nanoparticles are higher than those from Zn and ZnO microparticles. Zn²⁺ release ratio depends not only on the pH of the simulated uterine solution but also the presence of human serum albumin. It decreases as the pH of the uterine solution increases. The trends of Zn²⁺ release ratios are almost the opposite for solutions with and without HSA. XRD analysis results indicate that zinc oxide is the main corrosion product of zinc particles.     

IN situ Confocal Microprobe Raman Spectroscopic Studies on Defective La-based Complex Oxides

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Hydrothermal Synthesis,Structure and Property of Transition Metal(Mn,Zn, Cd or Pb) Coordination Frameworks Using Quinoline-8-oxy-acetate Acid and Dicarboxylic Acid as Ligands

Five transition metal coordination compounds, [Mn₂(8-qoac)₂(bdc)(H₂O)₄](1)(8-qoacH=quinoline-8-oxy- acetate acid, H₂bdc=benzene-1,4-dicarboxylic acid), [Zn₄(8-qoac)₄(bdc)₂]_n(2), {[Cd₂(8-qoac)₂(Hip)₂(H₂O)₂]· (H₂O)₄}_n(3)(H₂ip=benzene-1,3-dicarboxylic acid), [Pb₃(8-qoac)₂(bdc)_1.5(H₂O)Cl]_n(4) and [Zn₂(8-qoac)(8-ql)(bdc)]_n (5)(8-Hql=8-hydroxyquinoline), were synthesized by hydrothermal syntheses of metal salts with benzenedicarboxy- lic acid and 8-qoacH. Compound 1 possesses a discrete dimer bridged by bdc^2- ligand. Compound 2 presents a 2D layer network constructed from bdc^2- linkers and 1D infinite ribbons, in which Zn(II) centers are bridged by 8-qoac^- with a tetradentate binding mode. Compound 3 displays a 1D zigzag chain, with adjacent chains further connected via extensive O-H···O hydrogen bonds to generate a 3D supramolecular structure. Compound 4 shows a 3D framework containing trinuclear lead secondary building units and bdc^2- linkers, in which a new coordination mode of 8-qoac^- ligand is observed. In compound 5, Zn(II) ions are simultaneously bridged by 8-qoac^-, 8-ql^- and bdc^2- ligands to form tetranuclear zinc units, which are further interlinked by bdc^2- linkers to yield a 2D wave-like layer. Based on intraligand(IL)(π-π^*) fluorescent emission, compounds 1―5 possess strong purple fluorescent emissions. In addition, the thermal stabilities of compounds 1―5 were studied.     

Zn(Ⅱ)与5-氨基四氮唑和1,4-对苯二甲酸配位聚合物的溶剂可控合成

以5-氨基四氮唑（HATz）、1,4-对苯二甲酸（H₂BDC）和Zn（NO₃）₂为反应物,在水热条件下得到了1个二维层结构的Zn（Ⅱ）配位聚合物{[Zn₂（ATz）₂（BDC）（H₂O）₂] ·H₂O}_n（1）,而在N,N’-二甲基甲酰胺（DMF）溶剂热条件下得到了1个三维结构的Zn（Ⅱ）配位聚合物{[Zn₂（ATz）₂（BDC）（DMF）₂] }_n（2）. 通过元素分析、红外光谱、单晶X射线衍射和粉末X射线衍射等对它们的组成和结构进行了表征. 单晶结构分析结果表明,配合物1是以Zn（Ⅱ）离子作连接点、μ₂-ATz^-和μ₂-BDC^2-作连接子形成的3-连接（6,3）蜂窝型二维层结构,二维层之间再通过氢键作用形成三维超分子结构. 配合物2是以两羧基桥连的双核Zn（Ⅱ）单元[Zn₂（CO）₂] 作连接点、μ₂-ATz^-和μ₄-BDC^2-作连接子形成的6-连接简单立方格子的三维金属-有机框架结构. 室温固体荧光实验表明,在350 nm的光激发下,配合物1和2分别在451和466 nm处出现强烈的荧光发射.     

OXIDATIVE COUPLING OF METHANE OVER Na_2CO_3 DOPED ZIRCONIUM DIORIDE

Na_2CO_3/ZrO_2 catalyst shows a high activity of oxidative coupling of methane. It possesses stronger electron donor ability than that of ZrO_2 catalyst. The activation of methane is supposed to relate to the O_2~- or O_2~(2-) and O~- species.     

SOFC中干甲烷浓度对Ni-YSZ阳极上反应的影响

为探讨固体氧化物燃料电池(solid oxide fuel cell, SOFC)中干甲烷浓度对反应的影响,采用色谱在线测量阳极尾气,总结阳极尾气的变化规律。在此基础上,分析干甲烷在固体氧化物燃料电池Ni-YSZ阳极上的反应,寻找干甲烷浓度与电流对电池阳极反应影响的数学关系。结果表明,随着电流密度的增加,低浓度甲烷按顺序发生CH₄+O^2- → CO+2H₂+2e^-、CH₄+2O^2- → CO+H₂O+H₂ +4e^-、CH₄+3O^2- → CO+2H₂O + 6e^-、CH₄+4O^2- → CO₂+2H₂O+8e^-反应,高浓度甲烷只发生甲烷的第一个氧化反应,中浓度甲烷发生前两个或前三个反应。依据法拉第第一定律及反应物之间的关系,确定甲烷的低、中、高浓度的判定依据分别为:q_v(CH₄)≤I/(4F)、I/(4F)≤q_v(CH₄)≤I/(2F)、q_v(CH₄)≥I/(2F)。     

电解液对水系可充电池MnO2正极电化学性能的影响

研究了水系电解液中Li⁺、Zn²⁺和Mn²⁺阳离子对具有不同晶型结构和形貌的MnO₂正极电化学性能的影响,探讨其储能机理。结果表明,在不含Mn(II)离子的水溶液中,MnO₂电极所表现的电化学性能趋同,容量低,衰减快。含有Zn²⁺离子的水溶液中,MnO₂电极因二价锌离子的嵌入-脱出,容量明显提升,但衰减严重。当溶液中同时含有Zn²⁺、Mn²⁺离子时,基于Mn²⁺和Zn²⁺离子之间的协同作用和Mn²⁺离子氧化/还原反应过程的作用,有效抑制MnO₂颗粒的聚集和结构塌陷,削弱碱式硫酸锌杂质不利的影响,保持了锌离子在MnO₂电极中嵌入-脱出的高容量特性(200 mAh·g^-1,电流密度：100 mA·g^-1),及良好的循环稳定性。     

制备方法对Nd_2O_3上过氧物种光诱导生成的影响

分别采用水解、水热和燃烧法制备了三种主要物相均为立方Nd_2O_3的样品。以325 nm激光为激发源,在室温和空气气氛下对上述样品上过氧物种的光诱导生成情况进行了比较考察。经Raman光谱仪的激光束照射后,三种样品上均可检测到过氧物种的生成,但燃烧法制备的样品上过氧的生成速率显著大于其他两种样品。O_2-和CO_2-TPD(程序升温脱附)的表征结果表明,与水解和水热法制备的立方Nd_2O_3相比,燃烧法制备的样品表面含有更多的低配位晶格氧物种,晶格氧的碱性也更强,因而更有利于在光诱导下与分子氧反应生成过氧物种。     

Hydrothermal Synthesis and Luminescent Properties of Flowerlike Zn2GeO4 and Mn2+-Doped Zn2GeO4 Hierarchical Architectures

Three-dimensional(3D) flowerlike hierarchical Zn₂GeO₄ and Mn²⁺-doped Zn₂GeO₄ microstructures have been prepared by a facile hydrothermal approach. X-Ray diffraction(XRD), field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM) and photoluminescence(PL) spectrometry were employed to characterize the samples. Such flowerlike hierarchical Zn₂GeO₄ microstructures with an average diameter of 3―4 μm were found to be constructed by abundant single crystalline nanorods of about 90 nm in diameter. The luminescent properties of Zn₂GeO₄:xMn phosphors with different contents of Mn²⁺ as an activator were investigated. The Mn²⁺-doped samples showed green luminescence corresponding to the d-d transition of Mn²⁺ under the irradiation of UV light. The red shift(from 531 nm to 538 nm) in λ_em with increasing Mn²⁺ content was observed in the luminescent spectra, which should be attributed to a weak crystal field because of the substitution of Zn²⁺ by Mn²⁺ at a distorted tetrahedral lattice site.     

Sol-gel Derived Silicate Phosphor Films

Mn²⁺-doped Zn₂SiO₄ and Mg₂Gd₈(SiO₄)₆O₂ phosphor films were deposited on silicon and quartz glass substrates by sol-gel process (dip-coating). The results of XRD and IR showed that the Zn₂SiO₄:Mn films remained amorphous below 700℃ and crystallized completely around 1000℃ From AFM studies, it was observed that the grains with 0.5-0.8 μm size packed closely in Zn₂SiO₄:Mn films, which were uniform and crack free. The luminescence properties of Zn₂SiO₄:Mn films were characterized by absorption, excitation and emission spectra as well as luminescence decay. These properties were, discussed in detail by a comparison with those of Mn²⁺ (and Pb²⁺)-doped Mg₂Gd₈(SiO₄)₆O₂ phosphor films.     

SO_2对Mn-Ce/TiO_2低温SCR催化剂的毒化作用研究

考察了SO_2对Mn-Ce/TiO_2低温脱硝催化剂活性的影响,利用XRD、BET、SEM和XPS对其毒化作用的原因进行分析。结果表明,SO_2对催化剂活性有明显的抑制作用,使NO_x去除率由84%降至42%左右。主要是SO_2的加入造成催化剂比表面积减小,孔径为5-10 nm的孔数量减少,且催化剂晶相由锐钛矿型转化成金红石型结构,活性组分MnO_x发生晶化现象,破坏了Mn-Ti间的强相互作用。催化剂理化性质的变化造成吸附态氧转化为晶格氧的路径受阻、MnO_2含量减少和CeO_x储氧功能减弱,并且产生氧阻效应而使NO吸附和解吸受阻,造成催化剂活性降低。同时生成的硫酸铵盐在催化剂表面沉积,覆盖了催化剂表面的Lewis酸性位,使其对NH_3吸附能力减弱。     

Cu+/SiO2-ZrO2催化剂的制备及其催化甲醇氧化羰基化性能

采用溶胶-凝胶法制备了SiO₂-ZrO₂复合氧化物载体,通过和CuCl₂进行离子交换制备了Cu⁺/SiO₂-ZrO₂催化剂,并研究其催化甲醇液相氧化羰基化合成碳酸二甲酯性能。结果表明,Zr以离子形式进入无定型SiO₂骨架结构中形成Si－O－Zr键,同时产生较强的B酸中心。CuCl₂通过热处理自还原为CuCl分散在SiO₂-ZrO₂载体表面,并与载体表面B酸发生离子交换形成Cu⁺物种,从而保留了活性金属组分Cu,脱除大部分的Cl元素,改善催化剂失活和设备腐蚀等问题。当焙烧温度为450℃时,催化剂表现出良好的催化活性,CH₃OH转化率、DMC选择性和时空收率分别达到10.0%、79.4%和1.45g/(g·h)。
     

Pillaring of Zn2Al Layered Double Hydroxide by Dawson Polyoxometalate Anions

Zn2Al layered double hydroxide pillared with Dawson polyoxometalates, P₂W₁₇ZO₆₁^8-(Z=Mn²⁺, Co ²⁺, Ni²⁺, Cu²⁺, Zn²⁺) was prepared. A basal space of ca. 16 nm indicates the intercalated Dawson ions to be oriented with their C₂ axis perpendicular to the double hydroxide layers(with the exception of P₂W₁₇Zn-LDH). The IR and¹³P MASNMR spectral reveal that the Dawson ions retain their integrity in the interlayer space of LDH. A preliminary study shows that these compounds are highly active catalysts for the oxidation of cyclohexene with molecular oxygen.     

锅炉结渣初始沉积层微观沉积机理研究

选取矾土Al₂O₃和赤铁矿Fe₂O₃,对这两种矿物做弹性常数的微观分析、对比,X射线衍射分析表明,煤灰与初始沉积层中的矿物种类相同,但两者中矾土Al₂O₃和赤铁矿Fe₂O₃的含量相差很大。采用第一性原理(first-principles)的超软赝势平面波方法,对Al₂O₃和Fe₂O₃的电子结构、弹性常数进行了计算。结果表明,从两种物质的结构角度分析,Al₂O₃晶体中Al³⁺、O^2-的堆积排列相对于Fe₂O₃中Fe³⁺、O^2-要稀疏,这是它们性质不同的结构原因;对于两晶体在<100>方向和切向上的化学键, Fe-O键比Al-O键更容易变形或者断裂,从而导致Fe₂O₃极易沉积在清洁水冷壁上;对Fe₂O₃,切向面对其沉积起了关键性的作用。     

Synthesis, spectral and structural characterization of three zinc(II) azide complexes with aminopyrazine

The reaction between zinc(II) azide, Zn(N₃)₂ and aminopyrazine (ampyz) afforded the complexes: [Zn(N₃)₂(ampyz)₂] (1), [Zn(N₃)₂(ampyz)]_n (2) and [Zn₃(N₃)₆(ampyz)₂]_n (3). These complexes are characterized by spectroscopic and crystallographic methods. The IR spectra of these compounds are measured and discussed. The structure of 1 consists of isolated tetrahedral zinc atom surrounded by two mono-dentate N-ampyz and two terminal azido ligands. Complex 2 features a zigzag chain of zinc centers in which each zinc is surrounded by alternate di-EO (end-on) and di-EE (end-to-end) azide bridges, the chain thus contains alternate four-membered Zn₂N₂ and eight-membered Zn₂(NNN)₂ rings. The two ampyz ligands are located in cis-arrangement and each of them further binds another zinc atom giving rise to a 3D network. Complex 3 contains two structurally different zinc atoms; the six-coordinate Zn(1) center links two di-EO azido bridges and two trans ampyz, thus having ZnN₆ chromophore. The five-coordinate Zn(2) center binds two di-EO bridging azido groups and the fifth position is occupied by an N atom from a bridging ampyz molecule. Both zinc centers, therefore participate in the formation of a 1D chain of cyclic Zn₂N₂ units. Each ampyz ligand binds another zinc atom via the second pyrazinic N atom giving another cross-chain and thus the structure consists of 2D sheets. In these three complexes the azido ligands of all types are asymmetric and linear within the experimental error.     

低温甲烷氧化偶联纳米SrTi_(0.975)Li_(0.025)O_(3-δ)催化剂的原位ESR和TPSR表征

采用溶胶-凝胶法制备纳米钙钛矿型复合氧化物催化剂SrTi1-xLixO3-δ(x=0、0.025、0.050),用微型催化反应评价装置结合XRD、TEM、原位ESR和程序升温表面反应(TPSR)等方法,研究甲烷氧化偶联(OCM)纳米SrTi1-xLixO3-δ催化剂结构和催化性能。结果表明,B位掺杂适量的低价Li+离子可优化纳米SrTiO3催化剂低温(~650℃)甲烷氧化偶联催化性能,Li+掺杂量为0.025时获得最高的甲烷转化率和C2选择性。与柠檬酸法制相同组成的常规催化剂相比,SrTi0.975Li0.025O3-δ纳米催化剂具有较优良的低温OCM催化性能和相同温度下更高的C2选择性。SrTi0.975Li0.025O3-δ纳米催化剂优良的催化性能与其表面原子配位不饱和存在F中心相关。     

一种多孔配位聚合物的氢键协同客体响应

由硝酸锌、 吡唑-3,5-二羧酸（H₃pzdc）和2-氨基对苯二甲酸（H₂abdc）在溶剂热条件下反应得到一种多孔配位聚合物(Me₂NH₂)[Zn₂(pzdc)(abdc)]·H₂O·DMF(1·g), 其中Me₂NH₂⁺由溶剂N,N-二甲基甲酰胺（DMF）水解得到, 1可视为平行排列的平整带状{Zn₂(pzdc)}⁺链被abdc^2-柱子交错支撑而成的三维多孔框架. 通过脱附/吸附溶剂分子, 中心对称的配位聚合物1·g可以可逆转变成手性的(Me₂NH₂)[Zn₂(pzdc)(abdc)](1′). 单晶结构分析表明, 在客体响应过程中, 基于框架、 抗衡离子和客体分子之间的氢键协作与竞争, 抗衡离子发生了显著的移动 和转动, 导致{Zn₂(pzdc)}⁺链扭曲和转动, 伴随着超过10%的晶胞体积和孔洞率变化. 气体吸附测试表明, 化合物1'对N₂和CO₂存在不同的结构响应行为.     

Synthesis and Characterization of Zinc Succinate, Zn(C4H4O4)

Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｕｃｃｉｎａｔｅｉｏｎ (Ｃ4Ｈ4Ｏ4) 2 -(—ＯＯＣＣＨ2 ＣＨ2 ＣＯＯ— )ｉｓａｖｅｒｓａｔｉｌｅｌｉｇａｎｄｓｉｎｃｅｅａｃｈｏｆｔｈｅｆｏｕｒｔｅｒｍｉｎａｌｃａｒｂｏｘｙｌｏｘｙｇｅｎｓｉｓａｂｌｅｔｏｐａｒｔｉｃｉｐａｔｅｉｎｃｏｏｒｄｉｎａｔｉｏｎｔｏｃｅｎｔｒａｌｍｅｔａｌａｔｏｍ(ｓ)ｉｎａｄｄｉｔｉｏｎｔｏｔｈｅｆｌｅｘｉｂｉｌｉｔｙｏｆｔｈｅＣ—Ｃｂｏｎｅ .Ｓｕｃｈｃｏｏｒｄｉｎａｔｉｎｇｖｅｒｓａｔｉｌｉｔｙｈａｓｂｅｅｎｒｅｆｌｅｃｔｅｄｉｎｓｅｖｅ…     

钛(Ⅳ)离子掺杂的氧化锌多壁纳米纤维结构材料的制备及光催化性能

借助棉花纤维模板、利用两步法制备了Ti⁴⁺/ZnO多壁纳米纤维结构材料,利用热重分析(TG)、X射线衍射(XRD)和扫描电子显微镜(SEM)等技术手段对其进行了表征;以亚甲基蓝(MB)的降解脱色为模型反应,考察了Ti⁴⁺掺杂量对ZnO多壁纳米纤维结构材料光催化性能的影响。 结果表明,利用模板辅助的两步法成功制备了Ti⁴⁺掺杂的ZnO多壁纳米纤维结构材料(Ti⁴⁺/ZnO);Ti⁴⁺的掺入影响ZnO材料的纳米结构,从而使Ti⁴⁺/ZnO的光催化性能明显高于ZnO;Ti⁴⁺/ZnO多壁纳米纤维结构材料良好的光催化性能可主要归于Ti⁴⁺/ZnO材料中活性中心-O^2--Ti⁴⁺-O^2--Zn²⁺-的形成和光生电荷e^--h⁺沿着颗粒间的有效传递。