有机胺柱类钙钛矿型钽酸盐的制备与表征

采用分步交换法，合成了新型的正丙胺、正丁胺柱层状类钙钛矿型钽酸盐C3H7NH3-Sr2Ta3O10与C4H9NH3-Sr2Ta7O10，采用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(IR)对该类化合物的结构与形貌进行了表征，并测定了其比表面积。     

Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta3O10 (M = Cs, Na, H, and C6H13NH3)

The Dion-Jacobson series of triple-layered perovskite tantalates (MCa2Ta3O10, M = Cs, Na, H, and C6H13NH3) were synthesized to evaluate their photocatalytic activity for overall water splitting to evolve H2/O2 under UV irradiation. The photocatalytic activity was susceptible to the hydration of interlayer space. The hydrous Na phase exhibited much higher activity (H2: 308 micromol.h(-1)) compared to the anhydrous Cs phase (24 micromol.h(-1)) and the hydrous H phase (22 micromol.h(-1)) in the presence of 0.5 wt % Ni impregnated. H2O/D2O isotopic experiment suggested that the hydrated interlayer plays as an active site for water splitting, where the high mobility of water molecule in the interlayer should correlate with the total photocatalytic activity. The FLAPW electronic structure calculation demonstrated that the terminating oxygen site, O4, which faces to the interlayer space, contributes largely to the top of the valence band. Judging from comparison with the double-layered tantalates, MLaTa2O7, in our previous study, the contribution of terminating oxygen site to the band structure is supposed to depend on the number of perovskite layers.     

五氧化二钽纳米柱的水热合成和光催化性能

以聚乙烯醇(PEG)为结构导向剂,利用水热法合成了形貌可控的Ta2O5纳米柱.采用X射线衍射、扫描电镜、透射电镜、漫反射紫外-可见光谱和光致发光光谱对所制备样品进行了表征.考察了结晶时间和Ta2O5/Sr(OH)2摩尔比等合成参数对样品形貌的影响,并在此基础上对Ta2O5纳米粒可能的生长机理进行了推测.结果表明,在PEG和Sr(OH)2存在条件下可以合成形貌可控的Ta2O5纳米柱.研究了紫外光下Ta2O5纳米柱降解罗丹明B的光催化性能,发现Ta2O5的形貌对光催化性能有很大影响, Ta2O5纳米柱的光催化性能与其长度和直径比成线性关系.催化降解反应的表观速率常数最高可达0.156 min–1,且经多次循环使用后,样品仍然保持较高的催化性能.     

类钙钛矿结构新钽酸盐KSr2Ta3O10的合成、结构与层间特性

类钙钛矿结构氧化物是由钙钛矿结构基元与其它类型结构基元组合而成的一种超结构复合氧化物.     

Photocatalytic activity of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) for water splitting into H2 and O2

The photocatalytic activities of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) strongly depended on the crystal structure. Overall, photocatalytic water splitting into H2 and O2 proceeded over La3TaO7 and La3NbO7, which have an orthorhombic weberite structure, Y2Ti2O7 and Gd2Ti2O7, which have a cubic pyrochlore structure, and La2Ti2O7, which has a monoclinic perovskite structure. All of these materials are composed of a network of corner-shared octahedral units of metal cations (TaO6, NbO6, or TiO6); materials without such a network were inactive. The octahedral network certainly increased the mobility of electrons and holes, thereby enhancing photocatalytic activity.     

The effect of group IIIA metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6·H2O

A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an 'extra step' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows the highest photocatalytic activity.     

Synthesis of hexagonal BaTa2O6 nanorods and influence of defects on the photocatalytic activity

Hexagonal barium tantalate (BaTa2O6) nanorods were synthesized by a hydrothermal method based on the reaction of concentrated Ba(OH)2 solution and Ta2O5. BaTa2O6 samples show a uniform cylindrical structure with diameters of 5-30 nm and the lengths of 50-200 nm. The formation of BaTa2O6 nanorods follows a dissolution-recrystallization mechanism and is governed by hydrothermal temperature and time. BaTa2O6 nanorod samples prepared at 270 degrees C for 72 h have exhibited the highest photocatalytic activity in the degradation of Rhodamine B (RhB) in aqueous solution under UV radiation. Hydrogen-related defects were detected in BaTa2O6 nanorods, which originate from the oxygen octahedron. The number of defects was dependent on the hydrothermal temperature, and the photocatalytic activities of BaTa2O6 nanorods increase with the decrease of defect amounts. On the basis of the experiment results, the difference in photocatalytic activities for samples is mainly caused by lattice defects, which can act as inactivation centers.     

锌掺杂TiO_2的制备及其可见光催化性能

以钛酸纳米管[H2Ti2O2(OH)2,NTA]作为钛的前驱体、ZnCl2为锌源,采用水热法制备了锌掺杂的TiO2光催化剂;采用X射线衍射仪和透射电镜分析了催化剂产物的晶体结构和微观形貌;同时以亚甲基蓝为模型反应物,研究了锌掺杂量和水热温度对催化剂可见光光催化性能的影响.结果表明,水热温度为130℃,锌掺杂量为0.5%时,所得样品的光催化性能最佳.     

Photocatalytic oxidation of organic dyes with visible-light-driven codoped TiO2 photocatalysts

A novel copper (II) and zinc (II) codoped TiO₂ photocatalyst was synthesized by a modified sol-gel method using titanium (IV) isopropoxide, Zn(NO₃)₂ · 6H₂O and copper(Il) nitrate as precursors. The samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and photo-luminescence spectra (PL). The XRD results showed undoped and Zn, Cu-codoped TiO₂ nanoparticles mainly including anatase phase and a tiny amount of Zn- and Cu-oxides exist in the mixed system, which is attributed to the decomposition of copper and zinc nitrates in the TiO₂ gel to form CuO and ZnO and randomly dispersed on the TiO₂ surface. On the basis of the optical characterization results, we found that the codoping of copper (II) and zinc (II) resulted a red shift of adsorption and lower recombination probability between electrons and holes, which were the reasons for high photocatalytic activity of Zn, Cu-codoped TiO₂ nanoparticles under visible light (λ > 400 nm). The photocatalytic activity of samples was tested for degradation of methyl orange (MO) in solutions. The results indicated that the visible-light driven capability of the codoped catalyst were much higher than that of the pure TiO₂ catalyst under visible irradiation. Because of the synergetic effect of copper (II) and zinc (II) element, the Zn, Cu-codoped TiO₂ catalyst will show higher quantum yield and enhance absorption of visible light. In the end, a key mechanism was proposed in order to account for the enhanced activity.     

新钽酸盐Ba2LnTi2Ta3O15(Ln=Y、La)的结构与介电性能

通过固相反应法合成了四方钨青铜结构新钽酸盐Ba2LaTi2Ta3O15与Ba2YTi2Ta3O15,分别进行了X射线衍射分析与介电性能测试.结果表明, Ba2LaTi2Ta3O15室温时晶胞参数为a=1.242 64(5) nm, c=0.391 57(2) nm,为四方钨青铜结构顺电相；Ba2YTi2Ta3O15室温时晶胞参数为a=1.236 46(4) nm, c=0.388 60(2) nm,为四方钨青铜结构铁电相,铁电相与顺电相转变温度为180 ℃.频率为1 MHz时, Ba2LaTi2Ta3O15陶瓷的室温相对介电常数为194,介电损耗也降低至8×10－4. Ba2YTi2Ta3O15陶瓷的室温相对介电常数为107.     

Cu2O/ZnO的形貌可控制备及光催化性能

以CuSO₄和ZnCl₂为原料, 采用温和的液相还原法制备得到Cu₂O/ZnO微米结构高效光催化剂. 研究了不同[Cu²⁺]/[Zn²⁺]比条件下所得Cu₂O/ZnO复合物的形貌和光催化活性. 通过5.5 h的光照, Cu₂O/ZnO光催化剂对甲基橙染料的降解率为(77.5±0.1)%. 将多形貌Cu₂O/ZnO复合物作为阳极, 铂片作为对电极, 中间注入甲基橙溶液, 组装“三明治”结构拟电池, 研究了复合物的光降解机制.     

K1.9Na0.1Ta2O6·2H2O的形貌可控合成及光催化性能

钽酸盐光催化材料往往具有较高的光催化活性.近年报道的钽酸盐光催化剂主要采用传统高温固相法制备,该方法不可避免地导致高温烧结,使合成的钽酸盐颗粒较大,比表面积较小,而且该方法具有不可克服的晶体转变、结晶度差、分解、挥发和纯度低等缺点,使制备的光催化剂活性较低.而纳米材料由于粒径小,提高了电子和空穴的扩散速度,大大降低了电子和空穴在材料内的复合几率,从而使光催化材料活性大幅提高.此外,粒径减小也使表面原子迅速增多,减小了光的漫反射,同时也使光吸收不易达到饱和,有利于提高光吸收效率.因此,制备纳米材料是提高半导体光催化剂活性的有效手段.目前,采用湿化学的溶液合成方法能在较低温度下获得粒度小且均匀、计量比准确的光催化剂粉末,但是合成钽酸盐光催化剂的水溶性钽前体即乙醇钽(或氯化钽)价格昂贵,而且对潮湿极端敏感易水解,使产物纯度降低,不适合工业化生产.近年来,尽管有文献报道以Ta2O5为原料利用水热、溶胶-凝胶和共沉淀等方法制备钽酸盐,但其合成条件苛刻,合成步骤复杂,合成周期较长,耗能大,产物产量较低且不均匀,很难实现产物的形貌控制来筛选出适合光催化反应的材料.目前关于纳米钽酸盐光催化材料形貌控制方面的研究鲜有报道,主要是由于Ta2O5极难溶解,很难实现液相合成.因此,纳米钽酸盐光催化材料的可控制备是研究的难点.我们发展了熔盐-水热制备钽酸盐新方法,实现了K1.9Na0.1Ta2O6·2H2O的可控制备.利用熔盐法制备一种可溶性钽酸盐前驱体,再通过水热法在液相进一步反应制得纳米钽酸盐光催化材料K1.9Na0.1Ta2O6·2H2O,通过控制反应条件实现了纳米钽酸盐K1.9Na0.1Ta2O6·2H2O的形貌调控,得到了纳米球、微球、去顶八面体形貌和类似榴莲形貌等不同形貌,而利用其它制备方法很难控制钽酸盐的形貌.另外,研究了制备材料吸附和光催化降解罗丹明B的性能,发现该材料光催化活性与形貌直接相关.表征结果表明,制备样品的X射线衍射(XRD)谱图尖锐,结晶较好,其各衍射峰位置均与K2Ta2O6一致,为纯相烧绿石结构,属于立方晶系,空间群为Fd3m.通过分析合成材料的元素组成及含量,确定K：Na：Ta比例近似为1.9：0.1：2.为了进一步研究属于烧绿石型化合物K1.9Na0.1Ta2O6·2H2O的结构,对不同形貌材料进行了红外光谱测试,所有样品在450–1000 cm–1的谱峰可归属于(K, Na)–O和Ta–O键的振动,3300 cm–1左右为晶体结构中水的羟基伸缩振动峰,1720 cm–1左右是晶体结构中水的弯曲振动峰.可以看出,不同形貌材料的红外谱图吸收带宽度和位置十分相似,只存在小的偏移和变化,进一步表明不同形貌的材料具有相似的晶体结构,与XRD结果一致.差热-热重分析确定了结构中所含结晶水数量近似为2.光催化性能测试结果表明,具有纳米球形貌的材料比表面积较大,因而光催化活性最高.     

Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7复合层状钙钛矿的合成及光催化分解水产氢性能(英文)

自从分解水产氢被首次报道以来,许多光催化剂被开发出来并用于光催化分解水产氢.然而,由于光生电子和空穴的复合率普遍较高,大部分的光催化剂分解水产氢效率都很低.因此,开发新型高效的光催化材料至关重要.具有(Bi_2O_2)~(2+)(A_(m-1)M_mO_(3m+1))~(2-)通式的Aurivillius相层状钙钛矿材料因具有独特的层状结构、元素可调性以及优异的电荷传输和分离能力而广泛应用于光催化分解水和去除有机污染物.此外,当该类层状钙钛矿被剥离成超薄纳米片时,其光催化性能进一步提高.为了进一步提高层状钙钛矿的载流子分离能力,将客体(如贵金属,半导体等)通过化学反应的途径插入到层状钙钛矿的层间区域,从而合成出复合层状钙钛矿被广泛发展和应用.然而,引入的客体主要是贵金属和半导体,这类客体的高成本和不均匀分布制约了其进一步的应用.由于廉价、无毒和稳定等优点,镍基材料如Ni,NiO,Ni_2O_3,NiS,NiS_2,Ni(OH)2和Ni(OH)x等被广泛用作增强电极材料的光电性能和催化剂的光催化分解水产氢性能的助催化剂.本文采用简单的原位化学反应法制备出镍基配合物Ni-CH_3CH_2NH_2(Ni-EA)插层的Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7(Ni-EA/HSNNs)复合层状钙钛矿;然后采用X-射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、X-射线光电子能谱(XPS)、紫外-可见漫反射光谱等手段对Ni-EA/HSNNs光催化剂进行了系统的研究.XRD结果表明,引入Ni~(2+)后,HSNNs层间距减小并且平行于钙钛矿层的晶面结晶度增强,证明HSNNs沿垂直于钙钛矿层的方向出现了层层组装.FTIR和XPS结果表明,引入的Ni~(2+)与HSNNs层间和表面的乙胺分子之间存在较强的相互作用,结合高分辨透射电镜图可知,Ni的存在形态可能为配合物Ni-EA.由此可见,当向HSNNs中引入Ni~(2+)时,Ni~(2+)和HSNNs层间和表面的乙胺分子反应生成带正电的配合物Ni-EA,由于Ni-EA与HSNNs的钙钛矿层带有异种电荷,两者之间存在较强的静电相互作用力,从而引起钙钛矿纳米片HSNNs的层层组装,最后形成Ni-EA/HSNNs复合层状钙钛矿.光催化分解水产氢性能测试结果表明,当引入0.5 wt%Ni时,复合层状钙钛矿表现出最优的光催化性能.与HSNNs(241.58μmol/h)相比,0.5%Ni-EA/HSNNs的光催化分解水产氢速率(372.67μmol/h)提高了0.54倍,表现出与0.5%Pt/HSNNs可比拟的光催化活性,可见,非贵金属Ni具有替代贵金属Pt的能力.进一步的研究表明,镍基配合物Ni-EA显著增强了催化剂的光生载流子的传输和分离能力,从而提高了其光催化分解水产氢性能.该文为光催化分解水产氢提供了一种简便的合成非贵金属配合物助催化剂的方法.     

碳修饰钨酸铋光催化降解水体中的邻苯二甲酸酯

以Bi(NO3)3.5H2O、Na2WO4.2H2O为反应物,采用水热法,经由葡萄糖炭化合成了碳修饰Bi2WO6(C-Bi2WO6)催化剂;考察了C-Bi2WO6光催化降解3种邻苯二甲酸酯(PAEs)的催化性能.结果表明:C-Bi2WO6对PAEs的降解效果优于Bi2WO6,特别是在葡萄糖与Na2WO4.2H2O质量比约10∶100条件下得到的催化剂的催化性能最优.与此同时,当PAEs的pH=6时,降解效果最好;而PAEs的浓度也对PAEs的光催化降解有一定的影响.     

11-钨铜三元杂多阴离子层状材料的制备及其光催化性能

采用离子交换法将杂多酸盐K₈［Co(H₂O)W₁₁CuO₃₉］镶嵌到Zn₂Al粘土当中,制得层状材料LDH［Co(H₂O)W₁₁CuO₃₉］^8-(2),其结构经IR, XRD, SEM, EDS和N₂吸附-脱附与孔径分析表征。并以2为光催化剂,研究其对孔雀石绿溶液光降解的催化活性,最佳实验条件为：孔雀石绿溶液的初始浓度为20 mg·L^-1,初始pH为2, 2用量为0.08 g,脱色率98.32%。     

Crystal growth of two new photoluminescent oxides: Sr3Li6Nb2O11 and Sr3Li6Ta2O11

Single crystals of Sr3Li6M2O11 (M = Nb, Ta) were grown out of a high-temperature Sr(OH)2/LiOH/KOH flux. The single crystal X-ray diffraction data were indexed to the orthorhombic Pmma system, with a = 10.5834(15) A, b = 8.3103(13) A, c = 5.8277(8) A, V = 512.55(13) A(3), and Z = 2 for Sr3Li6Nb2O11 and a = 10.5936(6) A, b = 8.3452(5) A, c = 5.8271(4) A, V = 515.15(6) A(3), and Z = 2 for Sr3Li6Ta2O11. The crystal structure consists of sheets of interconnected SrO8 polyhedra that are separated by M-O layers and an intervening LiO(x) polyhedral framework, representing a new structural type. The M-O layers exhibit a rare occurrence of both five- and six-coordinated M(5+) ions in the same structure. The oxides, upon excitation at 250 nm, exhibit violet emission at room temperature.     

Ta2O5/Si薄膜界面结构及光催化活性

利用溶胶-凝胶法和旋转镀膜法在单晶Si(110)基底上制备了Ta2O5光催化剂薄膜. 薄膜颗粒的晶粒度和大小随着热处理温度的升高而增加. 利用扫描俄歇电子能谱(AES)的表面成分分析、深度剖析和线形分析技术研究了热处理温度对Ta2O5/Si 样品膜层和基底的界面化学状态和相互作用的影响规律. 研究表明, 在700 ℃以下热处理时, Ta2O5/Si薄膜界面处以扩散作用为主;在800 ℃高温热处理时,在界面扩散的同时也引发界面反应, 生成了SiO2物种, 界面扩散和界面反应会对薄膜和基底元素的化学价态发生影响. 在紫外光下降解水杨酸的光催化活性的研究表明, 在600 ℃下焙烧制备的Ta2O5/Si薄膜具有与TiO2/Si薄膜相当的光催化活性.     

Synthesis and structure of new water-soluble and stable tantalum compound: ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)

The stable water-soluble tantalum complex with lactic acid (ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)), (NH4)4[Ta2(C3H4O3)4(O2)2O].3H2O, was prepared in the crystalline form. According to the single-crystal X-ray diffraction data, this compound forms a monoclinic cell with a = 13.85(2) A, b = 9.06(1) A, c = 12.32(2) A, and beta = 116.30 degrees , space group C2 (No. 2), and has Z = 2 molecules per unit cell. The solid-state 13C NMR data and low flack parameter are consistent with the determined structure. Appearance of the same vibration modes in Raman and IR spectra supports the choice of the space group without inversion symmetry. The solution of the tantalum complex was successfully applied for the synthesis of two photocatalytic materials, NaTaO3 and Sr2Ta2O7.     

复合半导体MoS_2/Cu_2O的制备及其光催化性能研究

采用两步法制备了MoS_2/Cu_2O催化剂,对其催化降解甲基橙(MO)性能进行了研究.首先,通过液相剥离和梯度离心获得少数层MoS_2纳米片,然后采用水热还原法在MoS_2纳米片上合成Cu_2O纳米颗粒,形成MoS_2/Cu_2O复合半导体,并分别通过扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、UV-Vis紫外可见漫反射光谱(DRS)等手段对催化剂的结构进行表征.在可见光下,MoS_2/Cu_2O复合半导体降解MO的效率明显高于纯MoS_2和Cu_2O.为了获得最佳光催化活性,探究了MoS_2质量分数(5%、10%、20%、30%、40%、50%)对MoS_2/Cu_2O复合半导体光催化降解MO的影响.最后,经过5次循环实验,MoS_2/Cu_2O降解率下降为82.5%,循环稳定性有待进一步提高.     

Syntheses and properties of zinc and calcium complexes of valinate and isovalinate: metal alpha-amino acidates as possible constituents of the early Earth's chemical inventory

We have studied the ligand behavior of racemic isovalinate (iva) and valinate (val) towards zinc(II) and calcium(II). The following solid metal amino acidates were obtained from aqueous solutions: Zn3Cl2(iva)4 (1), Zn3Cl2(val)4 (2). Zn(val)2 (3), Zn(iva)2 x 2H2O (4), Zn(iva)2 x 3.25H2O (5), Zn(iva)2 (6), Ca(iva)2x xH2O (7), and Ca(val)2 x H2O (8). Except for complex 3, these were hitherto unknown compounds. The conditions under which they formed, together with current ideas of the conditions on early Earth, support the assumption that alpha-amino acidate complexes of zinc and calcium might have belonged to early Earth's prebiotic chemical inventory. The zinc isovalinates 1, 4, and 5 were characterized by X-ray crystal structure analyses. Complex 1 forms a layer structure containing four- and five-coordinate metal atoms, whereas the zinc atoms in 4 and 5 are five-coordinate. Compound 5 possesses an unprecedented nonpolymeric structure built from cyclic [Zn6(iva)12] complexes, which are separated by water molecules. The thermolyses of solids 1. 3, and 8 at 320 degrees C in an N2 atmosphere yielded numerous organic products, including the cyclic dipeptide of valine from 3 and 8. Condensation, C-C bond breaking and bond formation, aromatization, decarboxylation, and deamination reactions occurred during the thermolyses. Such reactions of metal-bound a-amino acidates that are abiotically formed could already have contributed to an organic-geochemical diversity before life appeared on Earth.