Photocatalytic Activity of N-doped TiO2 Photocatalysts Prepared from the Molecular Precursor (NH4)2TiO(C2O4)2

用不同温度控制分解草酸氧钛铵制备N掺杂TiO₂光催化剂．利用XRD、IR、热分析、N₂吸-脱附等温线、XPS、紫外可见漫反射光谱和SEM表征了N-TiO₂光催化剂的结构．400～600 oC焙烧的N-TiO₂光催化剂为纯锐钛矿相,而700 oC焙烧的N-TiO₂光催化剂为锐钛矿和金红石混合相．N掺杂在TiO₂的间隙位使锐钛矿相TiO₂带隙变窄．在光降解甲基橙的反应中,600和400 oC焙烧的N-TiO₂催化剂分别在紫外光和全波长光照射下有最好活性;700 oC焙烧的N-TiO₂催化剂无论在紫外光和全波长光下都表现出最好的比活性,即最高的光量子效率,这可以归因于700 oC焙烧的N-TiO₂光催化剂良好的结晶程度和锐钛矿-金红石异相结的存在．     

双金属镍-锰/γ-Al2O3催化剂对甲烷二氧化碳重整反应的影响 (cited: 1)

用浸渍法制备γ-Al₂O₃负载的Ni-Mn双金属催化剂．在500～700 oC按照17:17:2的CO₂/CH₄/N₂比例,以36 mL/min的载气流速进行甲烷二氧化碳重整反应, 利用甲烷二氧化碳的转化率、生成的合成气H₂/CO比例以及长期稳定性等指标评价了催化剂的催化性能． 实验表明, 添加Mn提高催化性能并使双金属催化剂的稳定性更高, 比单金属催化剂更好地抑制焦炭生成,Mn最合适的添加量0.5wt％ ．通过BET、CO2-TPD、TGA、XRD、SEM、EDX和FTIR各种技术对催化剂进行了表征．     

掺杂Cs2O的12CaO·7Al2O3型发射材料的制备与特性

研究了掺杂Cs₂O的12CaO·7Al₂O₃(C12A7)型负离子存储发射材料的发射特性、离子发射分支比以及温度对发射强度的影响,同时对该材料的X射线衍射和电子顺磁共振的表征结果进行了分析. C12A7中Cs₂O的掺入不仅降低了发射温度,同时还增强了发射强度. 掺杂Cs₂O后,在800 V/cm的引出场下,发射温度由570 oC降低至500 oC,在700 oC时,发射强度由0.23 μA/cm<     

Superacid Catalyst SO42-/ZrO2-La2O3 Prepared by Ultrasonic Co-precipitation and Low Temperature Aging

低温陈化超声波共沉淀法制得SO₄^2-/ZrO^2-La₂O₃前驱体, 经H₂SO₄处理, 在不同温度下焙烧得到纳米晶催化剂SO₄^2-/ZrO^2-La₂O₃;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性.     

一维锰氧化物纳米棒在以O2为氧源的苯甲醇氧化反应中的催化性能

采用水热法合成MnOOH一维纳米线,通过MnOOH在不同气氛和温度中煅烧得到尺寸和形貌相似的不同锰氧化物,并用于以O₂为氧源的苯甲醇液相氧化反应. 结果表明,MnO₂对苯甲醇氧化反应具有较高的催化活性. 通过XPS、SEM、TEM和H₂-TPR等手段对催化剂的形貌和结构进行了表征,并讨论了可能影响反应活性的一些因素. MnO₂的良好催化性能可能与其晶格氧具有较高的迁移率以及氧化还原能力有关. 通过简单的焙烧处理,可以使MnO₂催化剂在苯甲醇氧化反应中具有良好的重复使用性.     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

针状纳米MnxNi0.5-xZn0.5Fe2O4的共沉淀法制备及表征

通过在碱液中共沉淀Mn²⁺、Ni²⁺和Fe²⁺后制备了棒状的前躯体,前躯体于不同温度煅烧后制得了Mn_xNi_0:5-xZn_0:5Fe₂O₄棒状体. 利用X射线衍射仪和透射电镜对棒状体的物相、形貌及粒径进行了表征,并利用振动样品磁强计对磁性能进行研究. 结果表明长径比大于15的棒状,随着x值的增加,Mn_xNi_0:5-xZn_0:5Fe₂O₄样品的直径增加,长度下降,长径比变小,当x=0.5时其直径在50 nm左右而长径比减小到7～8. 随着x值的增加,样品的矫顽力先增加后减少,x值达到0.4时样品的矫顽力再次增加,当煅烧温度为600 oC,x=0.5时样品的矫顽力最大为134.3 Oe. 饱和磁化强度随着x值的增加先增加后减少,当煅烧温度为800 oC和x=0.2时达到最大为68.5 Oe.     

从可溶性单源分子前驱体采用溶胶凝胶法制备ZnO/TiO2 纳米复合物

合成了单源分子前驱体Cl₂TiZn(dmae)₄ (dmae为2-二甲基乙醇胺),并以乙醇为溶剂,加入等摩尔量的水对其进行可控水解得ZnO/TiO₂纳米复合凝胶,经pH=9沉淀,在200、400和600 oC 烧结得到不同的产物T₂₀₀、T₄₀₀、T₆₀₀. XRD分析表明未烧结产物为无定形粉末并随着烧结温度升高晶型改善. ZnO呈纤锌矿结构(六方晶系),TiO₂呈板钛矿型结构(正交). BET分析和扫描电镜表明颗粒的大小随着烧结温度的提高而增加. 红外光谱证明Zn-O和Ti-O的特有的振动频率,OH基团烧结后的产物中被去掉. 所有的样品都显示良好的光催化活性, 且T₆₀₀活性最高.     

电流对苯甲醚电催化重整过程的影响

用电催化重整方法和NiCuZn-Al₂O₃催化剂进行生物油模型化合物苯甲醚的水蒸气重整制氢研究,结果表明,在700 oC和4 A条件下,获得的最高碳转化率和氢产率分别为98.3%和88.7%,电催化重整过程中发现的电流促进效应主要归结于重整反应床中温度分布的改变和电阻丝发射的热电子影响. 利用X射线衍射方法分析了反应前后的NiCuZn-Al₂O₃催化剂结构变化. 实验导出的苯甲醚重整反应表观活化能为99.54 kJ/mol,明显高于乙醇、乙酸和生物油轻质组分的重整反应表观活化能.     

高比表面积TiO2与g-C3N4复合材料的光催化性能及机理研究

本文通过简单的溶剂热法制备了g-C₃N₄与高比表面积的TiO₂复合材料,该方法操作简单且能耗低. 甲基橙降解实验结果表明,高比表面积的TiO₂有效提高了光催化活性. 光电化学测试结果表明,与g-C₃N₄复合后,TiO₂的电荷载流子迁移速率得到明显改善. g-C₃N₄/高比表面积-TiO₂的光催化活性很强,在100分钟内,6%-g-C₃N₄/高比表面积-TiO₂对甲基橙的降解程度可达92.44%. 6%-g-C₃N₄/高比表面积-TiO₂不仅具有良好的光催化降解性能,还具有较高的稳定性. 本文对6%-g-C₃N₄/高比表面积-TiO₂的光催化机理也进行了系统的研究.     

Au在Zr掺杂的CeO2(110)面吸附的第一性原理研究

采用基于广义梯度近似的投影缀加平面波(projector augmented wave)雁势和具有三维周期性边界条件的超晶胞模型，用第一性原理方法，计算并分析了Au在CeO₂(110)和Zr掺杂的CeO₂(110) 面的吸附能，吸附结构和电子结构等特征.从而得出Zr掺杂对Au/CeO₂(110)吸附体系的影响.结果表明：Zr的掺杂增大了Au在CeO₂(110) 面的吸附能，并改变了最强吸附位置，且导致了吸附体系中衬底结 关键词： Au Zr掺杂 2')" href="#">CeO₂ 吸附     

The surface properties and the activities in catalytic wet air oxidation over CeO2-TiO2 catalysts

No-noble metal CeO₂-TiO₂ catalysts prepared by sol-gel method were developed and examined for catalytic wet air oxidation (CWAO) of acetic acid. The structure of the catalysts was measured by BET, SEM, XRD, XPS and DTA-TG. We investigated the effect of the interactions of Ce and Ti on the structure of CeO₂-TiO₂ catalysts. The mechanisms of the relationships between the different content of Ti and the activity of CeO₂-TiO₂ catalysts were discussed. The results showed that the average crystal size of CeO₂ decreased and the surface areas increased; the low valence of Ce³⁺ increase, and the chemisorbed oxygen slightly decreased with the increase of Ti content on the surface of CeO₂-TiO₂ catalysts. The order of the activity in CWAO of acetic acid followed: Ce/Ti 1/1 > Ce/Ti 3/1 > Ce/Ti 1/3 > Ce/Ti 5/1 > CeO₂ > TiO₂ > no catalyst. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO₂-TiO₂ catalysts was observed in our study.     

Effect of combination of noble metals and metal oxide supports on catalytic reduction of NO by H2

We investigated the effects of combination of noble metals M (Rh, Pd, Ir, Pt) and metal oxide supports S (Al₂O₃, SiO₂, ZrO₂, CeO₂) on the NO + H₂ reaction using planar catalysts with M/S two layered thin films on Si substrate. In this study, NO reduction ability per metal atom were evaluated with a specially designed apparatus employing pulse valves for the injection of reactant molecules onto catalysts and a time-of-flight mass spectrometer to measure multiple transient products: NH₃, N₂ and N₂O simultaneously as well as with an atomic force microscopy to observe the surface area of metal particles. The catalytic performances of Rh and Ir catalysts were hardly affected by a choice of a metal oxide support, while Pd and Pt catalysts showed different catalytic activity and selectivity depending on the metal oxide supports. This assortment is consistent with ability to dissociate NO depending on metals without the effect of any support materials. There, the metals to the left of Rh and Ir on the periodic table favor dissociation of NO and those to the right of Pd and Pt tend to show molecular adsorption of NO. Therefore, the catalytic property of noble metals could be assorted into two groups, i.e. Rh and Ir group whose own property would mainly dominate the catalytic performance, and Pd and Pt group whose interaction with metal oxides supports would clearly contribute to the reaction of NO with H₂. NO reduction activity of Pd and Pt was found to be promoted above that of Rh and Ir, provided that Pd and Pt were supported by CeO₂ and ZrO₂.     

Characterization and catalytic performance of pure and Li2O-doped CuO/CeO2 catalysts

Pure and Li₂O-doped CuO/CeO₂ catalysts calcined at 500 °C were prepared by impregnation method. The catalysts are characterized by DTA, TG-DTG, XRD, IR, TEM, nitrogen adsorption at −196 °C and the catalytic decomposition of hydrogen peroxide at 30 °C.The effects of molar ratio, heat treatment time and the doping on the structural, surface and catalytic properties of nanocrystalline Cu/Ce-mixed oxides system have been studied. It was found that the catalytic activity of ceria-supported copper oxide catalysts increased by increasing both the heat treatment time and dopant content. However, the pure Cu/Ce-mixed oxide solids containing 10 wt.% CuO exhibited the best performance. The characterization results indicated that the higher surface area, the formation of solid solution between copper and cerium oxides, and the high dispersion of copper species on the ceria were responsible for the high catalytic activity of the CuO/CeO₂ catalysts.     

Selective CO oxidation in hydrogen-rich gas over CuO/CeO2 catalysts

A series of CuO/CeO₂ catalysts with different Cu-Ce compositions were synthesized by co-precipitation method and characterized by X-ray diffraction, H₂-TPR, CO-TPD, SEM and X-ray photoelectron spectroscopy (XPS) techniques. The effects of Cu-Ce composition and water vapor on the catalytic properties for the selective CO oxidation in the hydrogen-rich gas were investigated. The results indicated that CuO (10%)/CeO₂ catalyst remained the maximum CO conversion and selectivity at 140 and 160 °C, while the performance of CuO/CeO₂ catalysts deteriorated with the CuO molar ratio further increased. The interfacial CuO and CeO₂ interaction and synergistic effect enhanced the redox properties of CuO/CeO₂ catalyst and the highly dispersed copper species were proposed as the active sites for the selective CO oxidation. The blockage of catalytic active sites by absorbed water and the formation of CO-H₂O surface complexes reduced the activity of CuO (10%)/CeO₂ catalyst. The decreasing of surface lattice oxygen and absorbed oxygen species and the agglomeration of copper particles were the plausible interpretations for the deactivation of CuO (10%)/CeO₂ catalyst.     

Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

利用沉积沉淀法制备出了La改性Al₂O₃催化剂,研究不同焙烧温度对La改性Al₂O₃催化剂用于乙炔气相氢氟化合成氟乙烯反应性能的影响．利用NH₃-TPD、Pyridine-FTIR、XRD和Raman等技术对不同温度焙烧的催化剂进行表征,发现焙烧过程能改变催化剂结构的同时也能调变催化剂表面的酸量．经400 °C焙烧的催化剂显示出最高的乙炔转化率(94.6%)、最高的氟乙烯选择性(83.4%)和较低的积炭选择性(0.72%)．催化剂的高活性与其表面的高酸量有关,同时积炭的选择性也与其表面的酸中心数量有关．     

Pd与CeO2(111)面的相互作用的第一性原理研究

采用基于广义梯度近似的投影缀加平面波(projector augmented wave) 赝势和具有三维周期性边界条件的超晶胞模型，用第一性原理计算方法，计算并分析了Pd在CeO₂(111)面上不同覆盖度时的吸附能，价键结构和局域电子结构. 考虑了单层Pd和1/4单层Pd两种覆盖度吸附的情况. 结果表明：1)在单层吸附时，Pd的最佳吸附位置是O的顶位偏向Ce的桥位；在1/4单层吸附时，Pd最易在O的桥位偏向次层O的顶位吸附.2) 单层覆盖度吸附时，吸附原子Pd之间的作用较强；1/4单 关键词： 三元催化剂 Pd 2')" href="#">CeO₂ 吸附 密度泛函理论     

Effects of CeO2-ZrO2 present in Pd/Al2O3 catalysts on the redox behavior of PdOx and their combustion activity

The ceria-zirconium-modified alumina-supported palladium catalysts are prepared using impregnation method with H₂PdCl₄ as Pd source, hydrazine hydrate as reducing agent. The physicochemical properties of these catalysts are characterized by BET surface area (BET), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (H₂-TPR) and temperature programmed oxidation (O₂-TPO) techniques, and their catalytic activities for the combustion of methane are examined. The results show that the palladium mainly exist in a highly dispersed PdO species on Ce-Zr-rich grains as well as Al₂O₃-rich grains surfaces, and a stable PdO species due to the strong interaction between PdO and CeO₂-ZrO₂ on the Ce-Zr/Al₂O₃ surfaces. The catalytic activity is strongly related to the redox behavior of PdO species highly dispersed on Ce-Zr-rich grains and Al₂O₃-rich grains surfaces, and the higher the reducibility of the PdO species, the higher the catalytic activity. The presence of Ce-Zr in Pd/Al₂O₃ catalyst would inhibit the site growth of PdO_x particles and decomposition of PdO to Pd⁰, and the reoxidation property of Pd⁰ to PdO_x is significantly improved, which obviously increases thermal stability and catalytic activity of Pd/Ce-Zr/Al₂O₃ catalyst for the methane combustion.     

Effect of substrate temperature on microstructure and optical properties of single-phased Ag2O film deposited by using radio-frequency reactive magnetron sputtering method

Using a radio-frequency reactive magnetron sputtering technique,a series of the single-phased Ag2O films are deposited in a mixture of oxygen and argon gas with a flow ratio of 2:3 by changing substrate temperature(T s).Effects of the T s on the microstructure and optical properties of the films are investigated by using X-ray diffractometry,scanning electron microscopy and spectrophotometry.The single-phased Ag2O films deposited at values of T s below 200℃ are(111) preferentially oriented,which may be due to the smallest free energy of the(111) crystalline face.The film crystallization becomes poor as the value of T s increases from 100℃ to 225℃.In particular,the Ag2O film deposited at T s = 225℃ loses the 111 preferential orientation.Correspondingly,the film surface morphology obviously evolves from a uniform and compact surface structure to a loose and gullied surface structure.With the increase of T s value,the transmissivity and the reflectivity of the films in the transparent region are gradually reduced,while the absorptivity gradually increases,which may be attributed to an evolution of the crystalline structure and the surface morphology of the films.