制备工艺对NiFe2O4分解CO2活性的影响

随着大气中CO2浓度的增加,温室效应日趋严重,促使人们对大气中CO2的转化与消除这一课题更加重视。1990年Yutaka Tamaura[1]发现氧缺位磁铁矿几乎可以100%分解CO2后,为解决温室效应提供了一条新的探索途径。通过对不同铁酸盐MFe2O4(M=Fe,Mn[2],Co[3],Zn[4],Ni[5]等)分解CO2活性的考察,发现铁酸镍在300℃分解CO2的活性比其它铁酸盐都好。NiFe2O4的制备最常采用的是共沉淀法、柠檬酸溶胶凝胶法和水热法,3种方法由于制备     

Structural models for intergrowth structures in the phase system Al2O3-TiO2

The phase system Al₂O₃-TiO₂ was investigated in the compositional range from 48:52 to 62:38 mol% Al₂O₃:TiO₂. The samples were prepared by melting the binary oxides in an arc-imaging furnace and the obtained samples were examined by powder X-ray diffraction. The recorded powder patterns could be interpreted in terms of intergrowth structures consisting of two basic building blocks, which were deduced from the known crystal structures of β-Al₂TiO₅ and Al₆Ti₂O₁₃. The structure of a new ordered compound with the formula Al₁₆Ti₅O₃₄ is proposed. The thermal stability was estimated from DTA and tempering experiments and showed that all prepared samples decompose at temperatures around 800 °C into the binary oxides corundum and titania.     

Bulk and surface structures of V2O5/ZrO2 catalysts for n-butane oxidative dehydrogenation

The present investigation focuses on the structural properties and reactivity of zirconia-supported vanadium oxide catalysts, prepared by equilibrium adsorption in basic (pH 10) or in acid (pH 2.7) conditions with vanadium content up to 6 wt.% (pH 10) and up to 11.6 wt.% (pH 2.7). The samples, heated at 823 K for 5 h in air, were characterized by X-ray diffraction, Raman spectroscopy and TPR, both as prepared and after leaching with an ammonia solution to remove species not anchored to the zirconia surface. Some representative samples were also tested for the n-butane oxidative dehydrogenation (ODH) reaction. Depending on vanadium content, various vanadium species were identified by Raman spectroscopy that reacted differently on exposure to H₂. At similar loading, the fraction of vanadium in a dispersed state and thus interacting with the support was higher in samples prepared at pH 10 than in those at pH 2.7. Samples prepared at pH 2.7 contained a higher fraction of large polymeric structures in addition to ZrV₂O₇ and V₂O₅.In line with literature data for propane ODH on similar catalysts, our catalytic results suggested that the active sites for the ODH reaction are associated with the V–O–V bonds of the polymeric exposed structures, whereas the Zr–O–V sites favour alkane combustion.     

Synthesis and Characterization of TiO2/YFeO3 and Its Photocatalytic Oxidation of Gaseous Benzene

YFeO₃ was prepared by coprecipitation method and citric acid method, and TiO₂/YFeO₃ heterosystem photocatalysts were synthesized by loading TiO₂ sol on the surface of YFeO₃via sol-gel method. Their photocatalytic activities were evaluated by the decomposition of gaseous benzene under UV light illumination. The prepared photocatalysts were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectroscopy. Results revealed that the heterosystem photocatalysts prepared by coprecipitation method showed higher activity, and the maximum conversion of benzene could reach 44.7% within 180 min. The YFeO₃ samples prepared from coprecipitation method and citric acid method were absolutely in orthorhombic phase. The deposited titania was dispersed on the surface of carrier and a certain interaction existed between TiO₂ and YFeO₃. The two heterosystems photocatalysts had narrow band-gap energies.     

Preparation and photocatalytic activity of high-efficiency visible-light-responsive photocatalyst SnSx/TiO2

Visible-light-responsive composite photocatalysts SnS₂/TiO₂ and SnS/TiO₂ with different mass ratios were prepared by in-situ synthesis technology in solution with commercial TiO₂. The junction-based materials SnS_x (x=1, 2)/TiO₂ were found to have high visible-light photocatalytic performance and possess much better activity than the single-phase SnS_x or TiO₂. The greatly enhanced photocatalytic activity of the SnS_x/TiO₂ composites was mainly attributed to the matching band potentials and efficient charge transfer and separation at the tight-bonding interface between SnS_x and TiO₂. The fact was confirmed by the comparison of photocatalytic activities of the SnS₂/TiO₂ samples prepared by physical mixing method and in-situ synthesis technique.     

TiO2/Cu2O/Pt复合空心微球的制备及其光催化性能

以锐钛矿相TiO₂溶胶为基底,采用沉淀法和液相沉积法制备了TiO₂/Cu₂O/Pt复合空心微球,通过改变n₍Ti⁴⁺)∶n_Cu2+和H₂Pt Cl₆·6H₂O溶液的加入量对TiO₂的形貌和结构进行调控,采用不同的方法对不同样品的物相及结构、微观形貌和光学性能进行了对比分析。分析结果表明,复合材料中Pt与Cu₂O的引入产生协同效应,不仅在一定程度上阻止了电子-空穴的复合,还降低了禁带宽度,在可见光区域光吸收明显增强。与TiO₂、Cu₂O和TiO₂/Cu₂O光催化剂相比较,TiO₂/Cu₂O/Pt降解有机污染物的能力显著增强,首次光照120 min可降解93%的甲基橙(MO)溶液,4次循环后降解率为71%,具有良好的光催化...     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

溶胶-喷雾干燥法制备纳米Li3V2(PO4)3/C及其电化学性能

本文以LiOH.H2O、NH4VO3、H3PO4和柠檬酸为原料,采用溶胶-喷雾干燥法制备Li3V2(PO4)3/C正极材料,对比了喷雾前驱体直接煅烧与机械活化后煅烧的样品的结构、形貌及其电化学性能。采用XRD、SEM、BET和振实密度测试等对样品的结构、形貌等进行了表征;采用恒流充放电、CV和EIS等手段考察了材料的电化学性能。结果表明,溶胶-喷雾干燥得到的样品为多孔球壳形,其壳体由厚度为100 nm左右的纳米片组成,经机械活化后煅烧保持保持了其纳米片结构,其结晶度与振实密度改善较明显,电化学性能较优异。0.1C放电比容量为123.6 mAh.g-1,10C和20C高倍率放电比容量还高达107.8和106.0 mAh.g-1。电化学阻抗结果表明,由该方法制备的样品具有较小的电荷转移阻抗。     

Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles

Diol capped γ-Fe₂O₃ nanoparticles are prepared from ferric nitrate by refluxing in 1,4-butanediol (9.5 nm) and 1,5-pentanediol (15 nm) and uncapped particles are prepared by refluxing in 1,2-propanediol followed by sintering the alkoxide formed. X-ray diffraction (XRD) shows that all the samples have the spinel phase. Raman spectroscopy shows that the samples prepared in 1,4-butanediol and 1,5-pentanediol and 1,2-propanediol (sintered at 573 and 673 K) are γ-Fe₂O₃ and the 773 K-sintered sample is Fe₃O₄. Raman laser studies carried out at various laser powers show that all the samples undergo laser-induced degradation to α-Fe₂O₃ at higher laser power. The capped samples are however, found more stable to degradation than the uncapped samples. The stability of γ-Fe₂O₃ sample with large particle size (15.4 nm) is more than the sample with small particle size (10.2 nm). Fe₃O₄ having a particle size of 48 nm is however less stable than the smaller γ-Fe₂O₃ nanoparticles.     

Parameters controlling the photocatalytic performance of ZnO/Hombikat TiO2 composites

Commercial TiO₂ (Hombikat, UV-100) was impregnated with different loadings of zinc nitrate solution and subsequently calcined at different temperatures in order to obtain a stable homogeneous solid composite of ZnO/TiO₂. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), UV-vis and Raman spectroscopy, inductively coupled plasma mass spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS) as well as N₂ adsorption and desorption measurements. Results show that ZnO was incorporated within the TiO₂ crystals and did not form a separate bulky phase or metallic zinc. Moreover, the calcination temperature dramatically modifies the texture properties of the prepared samples compared with original Hombikat TiO₂. The photocatalytic performance of the prepared samples was evaluated by monitoring the degradation of methyl orange dye under black light illumination. Three main parameters were studied; ZnO loading, surface area and initial pH of the methyl orange solution. The variation in ZnO loading appears to have less influence on the catalytic activity than either the surface area or the pH.     

TiO2/Cu2O/Pt复合空心微球的制备及其光催化性能

以锐钛矿相TiO₂溶胶为基底,采用沉淀法和液相沉积法制备了TiO₂/Cu₂O/Pt复合空心微球,通过改变n_Ti⁴⁺∶ n_Cu²⁺和H₂PtCl₆·6 H₂O溶液的加入量对TiO₂的形貌和结构进行调控,采用不同的方法对不同样品的物相及结构、微观形貌和光学性能进行了对比分析。分析结果表明,复合材料中Pt与Cu₂O的引入产生协同效应,不仅在一定程度上阻止了电子-空穴的复合,还降低了禁带宽度,在可见光区域光吸收明显增强。与TiO₂、Cu₂O和TiO₂/Cu₂O光催化剂相比较,TiO₂/Cu₂O/Pt降解有机污染物的能力显著增强,首次光照120 min可降解93%的甲基橙(MO)溶液,4次循环后降解率为71%,具有良好的光催化稳定性能。     

Thermal Stability of Pt/Al2O3 Catalysts Prepared by Sol-Gel

A series of Pt/Al₂O₃ catalysts were prepared using a sol-gel method. The influence of several parameters used in the synthesis including: metal content, identity of the metal precursor, and the water/alkoxide ratio on the structural properties of the fresh (dried) and calcined samples were studied. It was found that the BET surface area decreased with an increase in the platinum content. A surface area of 500 m²/g was obtained following calcination at 773 K. The structure of fresh samples as determined by FTIR corresponded to that of a pseudoboehmite structure. Samples prepared using a water/alkoxide ratio (H₂O/ATB) of 9 showed a well-defined, uniform pore size distribution following calcination at 773 K. Metal dispersions comparable to those obtained using impregnation methods were obtained. Aging studies (calcination at 873 K for 24 h) performed on these catalysts, exhibited sintering behavior which were similar to Pt/Al₂O₃ catalysts prepared by other methods. The sample prepared using a H₂O/ATB ratio of 9 had the highest surface area and was more thermally resistant towards metal sintering. A bimodal metal particle size distribution was observed: some particles exhibited sintering while others of similar size showed a greater thermal stability to sintering. The sample having the largest surface area and the highest thermal stability following thermal treatment was a consequence of a more condensed structure and a higher pore roughness obtained after drying the gel. This enabled the formation of an alumina structure which was more amorphous and limited aggregation of platinum particles due to surface diffusion within the pore structure.     

Preparation of Cu-doped Cd0.1Zn0.9S solid solution by hydrothermal method and its enhanced activity for hydrogen production under visible light irradiation

A series of Cu-doped Cd_0.1Zn_0.9S solid solution with various amounts of Cu dopant was successfully prepared by hydrothermal method. The properties and the photocatalytic activity of the prepared samples for hydrogen production under visible light irradiation were compared to those prepared by co-precipitation method. The Cu-doped Cd_0.1Zn_0.9S samples prepared by hydrothermal method showed both improved crystallinity and photoabsorption ability as compared to the undoped sample. On the other hand, even though Cu-doped Cd_0.1Zn_0.9S prepared by co-precipitation method also showed improved photoabsorption ability in the visible light region, the samples showed poor crystallinity compared to the undoped one. With the same amount of Cu dopant, all samples prepared by hydrothermal method were found to exhibit higher photocatalytic activity for hydrogen production than the samples prepared by co-precipitation method. It was revealed that the amount of Cu dopant, crystallinity and narrow band gap energy are important factors to obtain highly active and stable photocatalysts.     

Thermoelectric properties and microstructure of Mg3Sb2

Mg₃Sb₂ has been prepared by direct reaction of the elements. Powder X-ray diffraction, thermal gravimetric, differential scanning calorimetery, and microprobe data were obtained on hot pressed samples. Single phase samples of Mg₃Sb₂ were prepared and found to contain oxygen at the grain boundaries and to lose Mg and oxidize at temperatures above 900 K. Thermoelectric properties were characterized by Seebeck, electrical resistivity, and thermal conductivity measurements from 300 to 1023 K, and the maximum zT was found to be 0.21 at ∼875 K.     

静电自组装制备纳米TiO2/SiO2光催化材料

采用静电自组装方法制备了纳米TiO2/SiO2光催化材料。采用巯丙基三甲氧基硅烷偶联剂对SiO2进行干法改性,采用双氧水/冰醋酸将偶联剂巯基基团氧化为磺酸基基团。在正负电荷的吸引下,带负电荷的SiO2与带正电荷的钛聚合阳离子自发地组装在一起,经一定温度热处理得到纳米TiO2/SiO2光催化材料。采用XRD、FTIR、PL、UV-Vis DRS、SEM和ICP等对材料进行了分析和表征。采用甲基橙溶液评价材料的光催化性能。结果表明:SiO2促使锐钛矿的形成,抑制锐钛矿向金红石的转变,减小TiO2的晶粒尺寸,使得TiO2光吸收波长发生蓝移。TiO2与SiO2通过Si-O-Ti键发生结合。采用静电自组装方法制备的材料中TiO2的含量高于传统方法,导致材料的光催化性能有所提高。     

四角星形BiVO4/Bi2O3催化剂的制备及性能

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO_4/Bi_2O_3催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射(UV-Vis DRS)等方法对样品进行表征。可见光下,BiVO_4/Bi_2O_3复合物的光催化降解罗丹明B性能及光电流响应均优于纯BiVO_4。这是由于BiVO_4/Bi_2O_3复合材料形成了异质结构,有效抑制了光生电子与空穴的复合效率。     

四角星形BiVO4/Bi2O3催化剂的制备及性能研究

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO₄/Bi₂O₃催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-射(UV-Vis DRS)等方法征。可见光下,BiVO₄/Bi₂O₃复合物的光催化降解丹明B性能及光电优于纯BiVO₄。BiVO₄/Bi₂O₃复合材料形成了异质结构,有效抑制了光电子与空穴的复合效率。     

Preparation and characterization of CoFe2O4/TiO2 magnetic composite films

CoFe₂O₄/TiO₂ magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on microstructures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature. Supported by the National Natural Science Foundation of China (Grant Nos. 50632030 and 10474077), and the Natural Science Foundation of Shaanxi Province (Grant No. 2006E135)     

g-C_3N_4/CaTi_2O_5复合材料制备及其光催化性能

利用类石墨氮化碳(g-C_3N_4)和亚稳相钙钛氧化物(CaTi_2O_5)固相法制备C_3N_4/CaTi_2O_5复合材料。利用X射线衍射(XRD)、金相显微镜、扫描电子显微镜(SEM)及附带能谱分析仪(EDS)和N2吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计(UV-Vis)测试了样品的光吸收性能,研究C_3N_4与CaTi_2O_5物质的量之比(nC_3N_4/nCaTi_2O_5)对C_3N_4/CaTi_2O_5复合样品的物相结构和微观形貌的影响,同时考察C_3N_4/CaTi_2O_5复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明:相比纯C_3N_4和CaTi_2O_5样品,C_3N_4/CaTi_2O_5复合样品在可见光下具有较高的光催化性能,随着nC_3N_4/nCaTi_2O_5增加,样品的光催化降解率随之增加而后降低,当nC_3N_4/nCaTi_2O_5=1∶1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

浸渍-分解法制备高可见光催化活性的Bi2O3/TiO2纳米管阵列

用浸渍-分解法将Bi₂O₃纳米颗粒沉积在TiO₂纳米管壁上, 制备了Bi₂O₃/TiO₂纳米管阵列. 用电感耦合等离子体发射光谱(ICP-AES)测定了Bi₂O₃/TiO₂ 纳米管阵列的化学组分, 利用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 通过在可见光下(λ>400 nm)降解甲基橙(MO)水溶液来评价样品的光催化活性. 结果表明, Bi₂O₃纳米颗粒均匀地沉积在TiO₂纳米管中. Bi₂O₃/TiO₂纳米管阵列具有比纯Bi₂O₃膜和N-TiO₂纳米管阵列高得多的可见光催化活性. Bi₂O₃/TiO₂纳米管阵列活性的增强是其强可见光吸收和Bi₂O₃与TiO₂之间形成的异质结的协同作用的结果.