Pd/Mg(OH)2 Heterogeneous Nanocatalysts Synthesized by a Facile One-Pot Hydrothermal Method for CO Direct Esterification to Dimethyl Oxalate

Catalysis Letters - Pd-based heterogeneous nanocatalysts have wide application in chemical industry. However, the traditional synthesis process contains multi-steps such as impregnation, dry,...     

Photobreeding Heterojunction on Semiconductor Materials for Enhanced Photocatalysis

Construction of heterojunctions to photocatalysts is one of the most promising approaches to improve charge separation efficiency; however, the established constructing processes usually require high-temperature conditions and/or the adding of highly concentrated or expensive exotic species, and the improvement of effective contact and charge exchange between heterojunction components remains a problem. This work proposes an unprecedented “photobreeding” method and realizes the direct growth of Zn nanowires and Mott–Schottky heterojunctions from ZnS or viologen-coated ZnS microspheres through a photochemical reaction at room temperature without external species, while demonstrating the hypothesis proposed 140 years ago on the formation of Zn in the photochromic process of ZnS. After photobreeding of the heterojunctions, the hydrogen production efficiency of the photocatalysts increases by 2 orders of magnitude. This inexpensive, facile and efficient synthetic method will find applications in H₂ production, organic synthesis, CO₂ reduction, nitrogen fixation, and so on.     

A novel stair-like lithium coordination polymer constructed from 4,4′-bipyridine

A novel stair-like lithium coordination polymer Li₂(4,4′-bpy)₂(NO₃)₂, 1, has been synthesized by using standard Schlenk techniques. X-ray diffraction shows the 2D stair-like framework contains an approximately perpendicular 1D “Z” type Li-4,4′-bpy chain and an unprecedented Li–NO₃ chain.     

Syntheses and single-crystal structures of La3AgSnS7, Ln3MxMS7 (Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2)

In our investigation of non-centrosymmetric rare earth sulfides in the La₃AgSnS₇/KBr, LaAlGeS₅/NaBr, HoAlGeS₅/KBr, ErAlGeS₅/NaBr, Er₃AgGeS₇/KBr and La₃NaSnS₇/NaBr systems, five compounds belonging to the R₆B₂C₂Q₁₄ family have been obtained. These compounds crystallize in the P6₃ space group, and the crystal data are as follows—La₃AgSnS₇: a = 10.3780(15) Å, c = 5.9900(12) Å, Z = 2; La₃Ge_0.25GeS₇: a = 10.2970(15) Å, c = 5.8120(12) Å, Z = 2; Ho₃Ge_0.272(10)GeS₇: a = 9.6480(14) Å, c = 5.7920(12) Å, Z = 2; Er₃Ge_0.330(10)GeS₇: a = 9.5930(14) Å, c = 5.8490(12) Å, Z = 2; La₃Sn_0.25SnS₇: a = 10.2770(15) Å, c = 6.0030(12) Å, Z = 2. Single-crystal analysis indicated that the crystal structures consist of three types of building block: LnS_n, MS₄, and AgS₃ (for La₃AgSnS₇) or MS₆ units (for Ln₃M_xMS₇, Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2), as any other compounds belonging to the R₆B₂C₂Q₁₄ family. Ln₃M_xMS₇ (Ln = La, Ho, Er; M = Ge, Sn; 1/4 ≤ x ≤ 1/2) are deficient compounds with the B sites occupied partly by M(II), and/or M(IV).     

Preparation and photocatalytic activities of two new Zn-doped SrTiO3 and BaTiO3 photocatalysts for hydrogen production from water without cocatalysts loading

Sr_2/3Zn_1/3TiO₃ (1) and Ba_5/6Zn_1/6TiO₃ (2) with perovskite structure have been prepared by a facile sol–gel method, among which the A sites (Sr and Ba for 1 and 2, respectively) were partially replaced by zinc ions. The photocatalysts were characterized by powder X-ray diffraction, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results of photocatalysis experiment showed that both 1 and 2 exhibited good activity for water reduction to form H₂ without cocatalysts loading under ultraviolet light irradiation. Compared with pure SrTiO₃ and BaTiO₃, 1 and 2 showed remarkable improvement in H₂ production efficiency, respectively. And the photocatalytic mechanisms of them were investigated by the theoretical method. This study demonstrated that the substitutional doping of appropriate ions could change the crystal and band structures and significantly promote electron transport in catalysts, which result in their good photocatalytic activities.     

Cu掺杂BiVO4微米片的水热合成和光催化性能

以Bi(NO3)3.5H2O、NaVO3和Cu(NO3)2.3H2O为原料并以十六烷基三甲基溴化铵(CTAB)为结构导向剂通过水热法制备了Cu/BiVO4微米片晶体。采用XRD、XPS、SEM、HRTEM、UV-Vis、比表面积测试等对产品进行了表征。结果表明,2.0 g CTAB辅助水热法能够合成结晶度高且形貌规整的单斜白钨矿Cu/BiVO4微米片晶体,其长度为1.0～2.0μm,宽度为0.5～2.0μm,厚度在200～300 nm内。相比BiVO4颗粒,片状Cu/BiVO4样品的紫外–可见光吸收边发生了稍许红移,具有较小的能带隙。光催化结果说明,5.0wt%Cu/BiVO4微米片表现出最好的光催化活性,其速度常数k为5.89×10–2/min,可见光照射10 mg/L亚甲基蓝溶液60 min的光解率达100%。     

SiO2-TiO2自清洁防反光薄膜的制备与表征

采用溶胶-凝胶浸渍-提拉法,通过改变镀膜顺序和镀膜速率制备了TiO2/SiO2(ST)和SiO2/TiO2(TS)型的一系列SiO2改性TiO2双层薄膜.薄膜的形貌、光透性、光催化活性、亲水性等分别用场发射扫描电镜(FESEM)、分光光度计、光降解甲基橙等表征方法进行了分析.结果表明:SiO2膜层因其低反射指数,在ST...     

Synthesis, crystal and band structures, and optical properties of a new framework mercury pnictides: [Hg4As2](InBr3.5As0.5) with tridymite topology

A new framework compound, [Hg₄As₂](InBr_3.5As_0.5) (1), has been prepared by the solid-state reaction of Hg₂Br₂ with elemental In and As at 450 °C. Compound 1 crystallizes in the space group P₆₃/mmc of the Hexagonal system with two formula units in a cell: a = b = 7.7408(6) Å, c = 12.5350(19) Å, V = 650.47(12) Å³. The crystal structure of 1 features a novel 3D framework, [Hg₄As₂]²⁺ with tridymite topology. The optical properties were investigated in terms of the diffuse reflectance and infrared spectra. The electronic band structure along with density of states (DOS) calculated by DFT method indicates that the present compound is semiconductor, and the optical absorption is mainly originated from the charge transitions from Br-4p and As-4p states to Hg-6s and In-5p states.     

La掺杂TiO2介孔微球的超声水热合成和光催化性能

以钛酸四丁酯为钛源、硝酸镧为镧源、十二胺为模板剂,采用超声?水热法合成了La3+掺杂介孔TiO2微球,并利用XRD、XPS、TEM、BET、UV-Vis、IR、FL等手段表征了材料的结构、形貌、比表面积、孔径分布及光学性能.研究结果表明,适量La3+离子掺杂不仅能使介孔TiO2晶粒细化,比表面积增大,荧光强度减弱.La3+/TiO2的光吸收边红移,并具有比商业P25更好的光催化活性,其中介孔La3+/TiO2(2.0at%)的比表面积和平均孔径分别为132.7 m2/g和8.67 nm,光催化降解初始浓度为40 mg/L的亚甲基蓝溶液120 min时,其降解率达到98.5%,表现出最强的光降解能力.     

钙钛矿结构La(1-x-y)CaxSryMnO3陶瓷的制备及研究

采用溶胶-凝胶法制备了纳米La(1-x-y)CaxSryMnO3系列粉体,经压片后烧结成陶瓷.用振动样品磁强计测量样品的磁化强度随温度的变化,结果表明各样品的居里温度在250～330K温度范围内,|(e)M/(e)T|最大值在1.353～3.392A·m2/kg·K范围内变化.用差示扫描量热仪(DSC)测定了各样品相变温度和相变潜热,得出各样品的相变潜热在0.852～2.381J/g范围内,相变潜热较大的样品其|(e)M/(e)T|最大值也较大;另外,La0.8-xCao.20SrxMnO3(x=0.05、0.08、0.10)样品的|(e)M/(e)T|最大值较大,并且居里温度在室温附近,有可能成为室温附近的磁制冷材料.