Pt纳米颗粒负载SrTiO3/TiO2异质结结构制备及制氢性能

本文以固定n(Sr)/n(Ti)摩尔比0.4的SrTiO_3/TiO_2(金红石相)异质结纳米颗粒,通过"光催化还原沉积方法"制备不同质量分数的纳米铂颗粒(0、1%、2%、5%),探究其催化活性的变化,采用XRD、SEM、UV-vis、XPS方法对其进行表征,并做了相关光催化分解水产氢性能测试.结果表明:负载贵金属Pt纳米颗粒量越大,对应的Pt晶粒平均尺寸为40.8 nm,1%Pt纳米颗粒SrTiO_3/TiO_2异质结构的BET比表面积在23.195 m~2/g处最高,并且介孔材料的特征是平均Barrett-Joyner-Halenda(BJH)孔径为13.60 nm,总孔体积为0.079 cm~3/g;高BET表面积和大的总孔体积强烈地支持SrTiO_3/TiO_2具有介孔结构的事实;相应的催化剂催化活性越高,其中负载5%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒光催化8 h产氢量为3.574 mmol,平均产氢效率为0.447 mmol/(gcat·h),但从性价比的角度来考虑,其催化效率远不及负载1%Pt纳米颗粒的SrTiO_3/TiO_2纳米颗粒催化效率的5倍,因此负载5%Pt的SrTiO_3/TiO_2纳米颗粒光催化效率最高.     

MoS2/g-C3N4复合催化剂的制备及CdSe量子点敏化产氢性能研究

太阳能光催化分解水制氢被认为是从根本上解决能源与环境问题较为理想的途径之一。在以尿素为原料制得石墨相氮化碳(g-C_3N_4)的基础之上,采用简单的低温溶液反应法将二硫化钼(MoS_2)与石墨相氮化碳(g-C_3N_4)复合得到复合催化剂MoS_2/g-C_3N_4,并利用透射电子显微镜(TEM)、X射线衍射(XRD)、紫外-可见漫反射(DRS)、傅里叶变换红外光谱(FT-IR)和荧光光谱等对该复合光催化剂的组成、形貌和光物理性能进行了表征;进而以CdSe量子点为光敏剂,三乙醇胺(TEOA)为牺牲剂,构建了不含贵金属的三组分光催化产氢体系,并对体系pH值、CdSe量子点浓度等对产氢性能的影响进行了研究。结果表明:将MoS_2纳米颗粒负载到g-C_3N_4上可使g-C_3N_4的光催化产氢性能得到显著提高。当MoS_2负载量为7%(质量比)时,在最佳的条件下(pH=9.0,CdSe量子点的体积为25mL),最大产氢速率达到了141.74μmol·h-1,6h的产氢总量达到了212.61μmol。最后,结合荧光猝灭实验,推测了该体系的产氢机理。     

3D Bi2WO6/TiO2异质结型光催化剂的制备以及增强的可见光催化性能

通过浸渍法合成了3D多组分Bi2WO6/TiO2异质结型复合光催化剂,多次浸渍使TiO2粒子层层沉积到花状Bi2WO6结构的表面。采用X射线粉末衍射(XRD)、扫描电镜(SEM)、光致发光光谱(PL)以及紫外-可见漫反射(UV-Vis)吸收光谱分别对所制备的复合光催化剂进行了表征,并以500W氙灯为光源,罗丹明B(RhB)为降解对象,进行了光催化活性测试,考察了不同TiO2复合量对Bi2WO6光催化剂反应活性的影响。结果表明,异质结型Bi2WO6/TiO2复合光催化剂的光催化活性明显优于纯Bi2WO6和TiO2。当复合15%(质量分数)TiO2时,所制备的复合光催化剂最有效促进电子和空穴的分离,并且光催化活性得到提高。活性提高的原因是所形成的异质结特殊的界面能够显著地降低光生电子和空穴的复合几率,并且具有较高的光吸收能力。     

锐钛矿SO42-/TiO2纳米光催化剂的制备及其性能

采用溶胶-凝胶-浸渍法制备了锐钛矿型SO42-/TiO2纳米光催化剂,并通过X射线衍射(XRD)、BET比表面积测量和透射电镜(TEM)对其进行了表征。以对苯二甲酸作为探针分子,结合化学荧光技术研究了光催化剂表面羟基自由基的生成;在紫外和可见光的照射下,以甲基橙为光催化反应的模型化合物,研究了锐钛矿型SO42-/TiO2纳米光催化剂的光催化活性。结果表明:SO42-负载使锐钛矿TiO2的比表面积增加,吸附量增加,光催化活性提高;SO42-/TiO2纳米光催化剂的羟基自由基的生成速率越大,催化剂的催化活性越高;浸渍液H2SO4的浓度对SO42-/TiO2纳米光催化剂的吸附量、羟基自由基的生成速率和催化活性有一定的影响,H2SO4的最佳浓度为0.2mol/L。     

Ru掺杂TiO2和TiO2/SiO2光催化剂的制备及可见光分解水制氢性能研究

采用溶胶-凝胶法制备了系列Ru/TiO2和Ru/TiO2/SiO2可见光活性光催化剂。通过TEM、XPS、XRD、UV-Vis漫反射和电化学对样品进行了表征。发现Ru和Si的存在可以抑制TiO2的相转变和晶粒生长;Ru掺杂使TiO2和TiO2/SiO2对可见光的吸收增强,也提高了光生电子和空穴的分离,因而,提高了催化剂可见光分解水制氢活性。当Ru在TiO2和TiO2/SiO2中的掺杂量分别为0.014%和0.021%(质量分数)时,光催化剂的可见光活性最高,且Ru/TiO2/SiO2活性为Ru/TiO2的5倍。     

尖晶石型CoFe2O4/TiO2磁性光催化剂的制备及其性能

首先采用化学共沉淀法制备尖晶石型CoFe2O4,然后采用溶胶-凝胶法与钛酸丁四酯复合制备不同CoFe2O4载量(质量分数,下同)的CoFe2O4/TiO2磁性光催化剂。再利用X射线衍射(XRD)、透射电子显微镜(TEM)、振动样品磁强计(VSM)、同步热分析仪(TG-DSC)和紫外可见吸收光谱(UV-Vis)分别对物相、形貌、磁学性能等进行了分析和表征。最后在300 W紫外灯(主波长为253.7nm)照射下降解一定浓度的甲基橙溶液,研究不同CoFe2O4载量的CoFe2O4/TiO2磁性光催化剂在相变温度下对甲基橙溶液降解效果。结果表明,合成的CoFe2O4结晶度高,粒径为10～20nm,具尖晶石结构。CoFe2O4能较为均匀地负载于TiO2表面,CoFe2O4/TiO2磁性光催化剂具有超顺磁性。CoFe2O4/TiO2磁性光催化剂对甲基橙降解性能随CoFe2O4载量增加而降低。     

镧掺杂TiO2/膨润土复合光催化材料的制备及性能

以钠基膨润土为载体,钛酸丁酯和硝酸镧为原料,采用溶胶-凝胶法制备镧掺杂TiO2/膨润土复合光催化剂,采用X射线衍射(XRD)和红外光谱(IR)对复合催化剂进行了表征,在紫外光照射下,通过对TNT废水的光催化降解,考察其光催化活性。实验结果表明,掺杂镧与未掺杂镧的TiO2/膨润土复合光催化剂中TiO2主要以锐钛矿型存在;掺杂镧的TiO2/膨润土复合光催化剂的光催化性能明显优于未掺杂镧的TiO2/膨润土复合光催化剂,当镧的掺杂量为1%(原子分数),焙烧温度为500℃时,其光催化活性达到最佳效果。     

NaZSM-5分子筛磷酸改性对TiO2/ZSM-5光催化剂的影响

以不同浓度磷酸改性的HZSM-5为载体,采用溶胶-凝胶法制备得到TiO2/HZSM-5光催化剂,通过XRD、SEM、BET、FT-IR和XPS进行表征。结果表明,磷酸处理没有改变分子筛的晶体结构,对分子筛的表面形貌改变不大,负载后的TiO2包覆在分子筛表面。负载前后的TiO2表现为锐钛矿晶型,钛以四价钛的形式存在,氧化物的组成为TiO2。TiO2与HZSM-5没有发生化学键合作用,负载型光催化剂的比表面积随着磷酸浓度的增加而显著提高。活性艳红X-3B的降解率随磷酸浓度的增加而变化,最佳磷酸处理浓度为0.5mol/L。50%TiO2/0.5HZSM-5较TiO2有更高的光催化活性,紫外光照射2h可使活性艳红X-3B降解93.4%,而染料在TiO2上的降解率只有61.0%。     

纳米Ni-TiO2光催化剂的制备及其性能研究

采用溶胶-凝胶法制备了过渡金属Ni掺杂纳米TiO2光催化剂(Ni-TiO2),采用XRD、纳米粒度、UVVis和PL对其进行了表征和分析,并以亚甲基蓝(MB)作为目标降解物,研究了Ni掺杂量以及热处理温度对NiTiO2性能的影响。结果表明:当pH=2.5、n(Ni)∶n(Ti)=1%、热处理温度为500℃时制备的样品在普通日光灯下、5h内对MB的光催化降解率达到92.54%,明显优于Degussa P25在相同条件下的降解率(50.69%)。     

磷酸处理HZSM-5负载TiO2光催化降解活性艳红X-3B

以磷酸改性的HZSM-5分子筛为载体,采用溶胶-凝胶法制备TiO2/HZSM-5光催化剂,通过XRD,SEM,BET,FT-IR和XPS进行表征。结果表明:TiO2均匀地分散在HZSM-5表面,没有发生TiO2颗粒的聚集。负载后的TiO2保持了锐钛矿晶体结构,TiO2的晶粒尺寸在负载后有所减小。TiO2/0.5HZSM-5的比表面积和对活性艳红X-3B的吸附量都随HZSM-5含量的增加而增加。负载后的TiO2光催化活性均高于纯TiO2,50%(质量分数)TiO2/0.5HZSM-5具有最高的活性,经紫外光照射2h可使活性艳红X-3B降解93.4%,而染料在纯TiO2上的降解率只有61.0%。     

Crystal Structure of (H3O)2[(UO2)2(SeO4)3(H2O)2](H2O)3.5

Crystals of (H₃O)₂[(UO₂)₂(SeO₄)₃(H₂O)₂](H₂O)_3.5 were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 11.9402(11), b = 13.6452(14), c = 13.7271(12) Å, β = 109.436(7)°, V = 2109.1(3) ų] was solved by the direct method and refined to R ₁ = 0. 048 (wR ₂ = 0. 082) for 3677 reflections with |F _hkl |F _hkl |. The structure consists of [(UO₂)₂(SeO₄)₃(H₂O)₂]₂₋ layers arranged parallel to the (010) plane. The layers are formed by uranium and selenium coordination polyhedra sharing common vertices and are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups arranged between the layers. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 412–414. Original Russian Text Copyright ? 2005 by Krivovichev, Kahlenberg.     

Crystal Structure of (H3O)6[(UO2)5(SeO4)8(H2O)5](H2O)5

Crystals of (H₃O)₆[(UO₂)₅(SeO₄)₈(H₂O)₅](H₂O)₅ were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 13.835(2), b = 13.4374(16), c = 14.310(3) Å, β = 108.004(14)°, V = 2530.1(7) Å ³] was solved by the direct method and refined to R ₁ = 0.090 for 4409 reflections with |F _hkl ≥ 4σ|F _hkl |. The structure is based on [(UO₂)₅(SeO₄)₈(H₂O)₅]⁶⁻ layers arranged parallel to the (101) plane; these layers have a unique topological structure. The U(1)O₆(H₂O) and U(3)O₆(H₂O) linked through selenate groups form chains running along [ [`1]\bar 1 01] direction. The chains are combined in layers by U(2)O₆(H₂O) bipyramids. The layers are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups located between the layers.     

Computational study of interaction of bromine ions with clusters (O2)6(H2O)50 and (O3)6(H2O)50

Interaction of bromine ions with water clusters that have absorbed the molecules of oxygen and ozone is studied using a molecular-dynamics simulation of flexible molecules. The cases of location of Br⁻ ions on the surface and in the bulk of the cluster are described. Water clusters with ozone molecules remain stable during their interaction with the Br⁻ ions, while oxygen molecules are found to evaporate from the cluster when Br⁻ ions appear in its bulk. In the presence of Br⁻ ions, the infrared spectra of systems with O₃ molecules are observed to be intensified. The intensities of the IR spectra with O₂ molecules may both increase and decrease depending on the arrangement of the Br⁻ ions. The Raman spectra are sensitive to the appearance of Br⁻ ions only for systems that contain oxygen molecules. As a result of interaction with the Br⁻ ions, the power of IR radiation emitted by the clusters can not only increase, but also decrease.     

Syntheses and structures of Ta2(WO2)0.87H0.26(PO4)4 and Ta2(MoO2)(PO4)4

Tantalum hydrogen phosphate, β-TaH(PO₄)₂, has a three-dimensional structure that is stable to remarkably high temperature (∼600 °C) presumably due to the presence of strong hydrogen bonds. Impedance measurements indicate a low conductivity, 2.0 × 10⁻⁶ S/cm at 200 °C in 5% H₂. In further studies aimed at enhancing the conductivity by aliovalent doping, we have investigated systematically the synthesis of compounds in the TaH(PO₄)₂-W₂P₂O₁₁ system at 380 °C. As a result, a new phase, Ta₂(WO₂)_0.87H_0.26(PO₄)₄, was identified and subsequently the molybdenum analog Ta₂(MoO₂)(PO₄)₄ was also prepared. The structures were determined by single crystal X-ray diffraction techniques. The structures of Ta₂(WO₂)_0.87H_0.26(PO₄)₄ and Ta₂(MoO₂)(PO₄)₄ can be formally derived from the structure of β-TaH(PO₄)₂ by the replacement of two P-OH protons with an MO₂²⁺ (M = Mo and W) group together with a change in the orientation of some phosphate tetrahedra.     

Crystal Structure of Tl2[(UO2)2(MoO4)3] and Crystal Chemistry of the Compounds M2[(UO2)2(MoO4)3] (M = Tl, Rb, Cs)

A new compound, Tl₂[(UO₂)₂(MoO₄)₃], was prepared by a solid-phase reaction. The compound crystallizes in a rhombic system, space group Pna2₁, a = 20.1296(9), b = 8.2811(4), c = 9.7045(4), V = 1617.69(13) ų, Z = 4. The crystal structrue was solved by the direct method and refined to R ₁ = 0. 04 for 4884 unique reflections. The structural motif is a framework consisting of UO₇ pentagonal bipyramids and MoO₄ tetrahedra. The Tl coordination polyhedra are irregular, with seven and eight vertices. Large channels of the size 6 × 10.8 Å, occupied by Tl⁺ cations, are arranged parallel to the [001] direction. The compound is isostructural to the previously described α-Cs₂(UO₂)₂(MoO₄)₃ and Rb₂(UO₂)₂ (MoO₄)₃. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 408–411. Original Russian Text Copyright ? 2005 by Nazarchuk, Krivovichev, Burns.     

Comparison between SiO2 films deposited by atomic layer deposition with SiH2[N(CH3)2]2 and SiH[N(CH3)2]3 precursors

Thin SiO₂ layers were deposited by atomic layer deposition (ALD) using either Bis-dimethylamino-silane (BDMAS: SiH₂(N(CH₃)₂)₂) or Tris-dimethylamino-silane (TDMAS: SiH(N(CH₃)₂)₃) precursors. The purpose of this study is to evaluate these precursors for their suitability for ALD of hafnium (Hf)-silicate gate dielectrics. The advantages of these precursors are that the melting points and vapor pressures are moderate. The thickness of SiO₂ deposited using ALD process is controlled by the number of growth cycles and the growth rate was different for each precursor, that for BDMAS being 1.5 times that for TDMAS at the same reactor pressure. The carbon impurity in the SiO₂ film deposited using BDMAS was about half an order of magnitude less than that using for TDMAS. Furthermore, the carbon impurity was reduced to about the detection limit of secondary ion mass spectrometry after high temperature annealing at 1000 °C during 5 s.     

Dielectric properties of Pb3 (PO4)2 | Pb3 (AsO4)2

The dielectric constants of Pb₃ (PO₄)₂ | Pb₃ (AsO₄)₂ at room temperature are intrinsic and fulfill the Lyddane - Teller - Sachs relation. At higher temperatures the specific conductivity increases with an activation energy of 0.56 eV leading to Maxwell - Wagner polarization effects thereby increasing the effective dielectric constant. Corresponding peaks in ∈' (T) are extrinsic and not attributed to structural phase transformations.     

Phase Separation in the Ternary Liquid System [Th(NO3)4(TBP)2]— [UO2(NO3)2(TBP)2]—Decane at Various Temperatures

The phase diagram of the ternary liquid system [Th(NO₃)₄(TBP)₂]— [UO₂(NO₃)₂(TBP)₂]—decane was studied within the 298.15–333.15 K range. The system has the area of homogeneous solutions and area of binary liquid subsystems (with separation); one phase (I) is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂·(TBP)₂] and the other phase (II), in decane. The temperature does not substantially affect the area of phase separation. In two-phase systems, [UO₂(NO₃)₂(TBP)₂] is mainly concentrated in phase I, in spite of the fact that the binary system [UO₂(NO₃)₂(TBP)₂]—decane is single-phase in the entire temperature range studied. Concentration of [UO₂(NO₃)₂(TBP)₂] in phase I results in redistribution of [Th(NO₃)₄(TBP)₂] into phase II. The points of the critical composition of the ternary system are compositions with similar content of the solvates [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂] at all the temperatures studied. __________ Translated from Radiokhimiya, Vol. 47, No. 6, 2005, pp. 520–522. Original Russian Text Copyright ? 2005 by Keskinov, Mishina, Pyartman.     

Phase equilibria in the liquid ternary system [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-Isooctane at different temperatures

The phase diagrams of the ternary systems [Th(NO₃)₄(TBP)₂]-[UO₂(NO₃)₂(TBP)₂]-isooctane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in isooctane. With increasing temperature from 298.25 to 333.15 K, the mutual solubility of Th(NO₃)₄(TBP)₂ and isooctane does not change noticeably, but the two-phase fields somewhat contract. In the two-phase systems [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂]-isooctane is single-phase over the entire temperature range examined. The preferential accumulation of [UO₂(NO₃)₂(TBP)₂] in phase I causes the redistribution of [Th(NO₃)₄(TBP)₂] and isooctane into phases II and I, respectively. The compositions of the ternary systems in the critical points at different temperatures were determined. The electronic absorption spectra of uranyl nitrate solvate with TBP in the homogeneous and two-phase systems were recorded and analyzed. Original Russian Text ? A.K. Pyartman, V.A. Keskinov, V.V. Lishchuk, Ya.A. Reshetko, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 420–422.     

Crystal structure of complexes of Np(VI) and Pu(VI) perchlorates with triphenylphosphine oxide, [NpO2(OP(C6H5)3)4](ClO4)2 and [PuO2(OP(C6H5)3)4](ClO4)2

Single crystals of [NpO₂(TPPO)₄](ClO₄)₂ and [PuO₂(TPPO)₄](ClO₄)₂ isostructural to the complex [UO₂(TPPO)₄](ClO₄)₂ [TPPO = OP(C₆H₅)₃] studied previously were prepared, and the structures of these compounds were determined. The coordination polyhedron of these compounds is a tetragonal bipyramid. The geometric characteristics of the tetragonal bipyramids in the compounds are practically the same despite the actinide contraction of the central atoms, whereas the unit cell volume decreases in the series U-Np-Pu. The equality of the volumes of the coordination polyhedra of the U, Np, and Pu atoms is attributed to the influence of TPPO containing phenyl radicals with negative effective charge. Original Russian Text ? I.A. Charushnikova, N.N. Krot, Z.A. Starikova, I.N. Polyakova, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 407–411.