TiO2/SiO2/γ-Fe2O3-SiO2磁性光催化剂的制备与表征

 A γ-Fe2O3-SiO2 composite was prepared by sol-gel method followed by calcination at 700 ℃ for 30 min starting from tetraethoxysilane and iron nitrate. Upon further coating with SiO2 and TiO2, a TiO2/SiO2/γ-Fe2O3-SiO2 magnetic photocatalyst was obtained. XRD results show that Fe in the composite converts to the γ-Fe2O3 phase up to a processing temperature of 700 ℃, and further increase in temperature results in the formation of the α-Fe2O3 phase. The TiO2/SiO2/γ-Fe2O3-SiO2 samples obtained are monodisperse spherical particles with 200～250 nm diameter, well coated firstly by an amorphous SiO2 layer and then by an anatase TiO2 layer. The TiO2/SiO2/γ-Fe2O3-SiO2 particles retain their magnetic property well and show high activity for the photocatalytic degradation of salicylhydroxamic acid.     

硫和银共掺杂介孔TiO2的制备、表征及其对染料的光催化降解活性

以P123为模板,以钛酸四正丁酯、硝酸银和硫脲为原料采用模板法制备了一系列硫和银共掺杂介孔TiO₂光催化材料．利用SEM、XRD、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征．以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能．结果表明,用模板法制备的共掺杂介孔TiO₂光催化材料在紫外和可见光条件下较纯介孔TiO₂和单掺杂介孔TiO₂对甲基橙溶液具有更好的光催化降解效果, 且硫和银的掺杂量及样品焙烧温度显著影响该材料的催化性能．当硫掺杂量为2mol%和银掺杂量为1mol%,在500 oC 焙烧2 h所得光催化材料的催化性能最佳,4 h即可使甲基橙的降解率达98.8%,重复使用4次仍可使甲基橙的降解率保持在87.5%以上     

DFT calculations for Au adsorption onto a reduced TiO2 (110) surface with the coexistence of Cl

Residual chlorines, which originate from HAuCl₄, enhance the aggregation of gold (Au) nanoparticles and clusters, preventing the generation of highly active supported Au catalysts. However, the detailed mechanism of residual-chlorine-promoted aggregation of Au is unknown. Herein to investigate this mechanism, density functional theory (DFT) calculations of Au and Cl adsorption onto a reduced rutile TiO₂ (110) surface were performed using a generalised gradient approximation Perdew, Burke, and Ernzerhof formula (GGA–PBE) functional and plane-wave basis. Although both Au and Cl atoms prefer to mono-absorb onto oxygen defect sites, Cl atoms have a stronger absorption onto a reduced TiO₂ (110) surface, abbreviated as rTiO₂ (110) in the following, than Au atoms. Additionally, co-adsorption of a Cl atom and a Au atom or Au nanorod onto a rTiO₂ surface was investigated; Cl adsorption onto an oxygen defect site weakens the interaction between a Au atom or Au nanorod and rTiO₂ (110) surface. The calculation results suggest that the depletion of interaction between Au and rTiO₂ surface is due to strong interaction between Cl atoms at oxygen defect sites and neighbouring bridging oxygen (O^B) atoms.     

化学镀镍-高磷合金的微观结构及晶化行为研究

分别以SnCl2.2H2O和SnCl2.5H2O为锡源,采用胶溶晶核法,经沉淀和胶溶过程,在液相中一步合成了金红石型TiO2。详细考察了各种胶溶条件对产物结构的影响,并通过两种锡源实验结果的比较对异相晶核法中两种锡源的成晶机理进行了分析,所合成的金红石型TiO2晶粒度为20－50nm,两种方法获得完全红金石型TiO2所需引入SnO2的最低物质的量的分数分别为10％和8％。     

Selective catalytic reduction of nitric oxide with ammonia: A theoretical ab initio study

Ab initio quantum chemical studies at the HF/Lanl2dz level were carried out to investigate the interaction of ammonia, NO, and a mixture of the two with vanadia/titania. It was found that the replacement of Ti_6c by V_6c is the only feasible way to form highly dispersed vanadia over the titania. The V?O species thus formed will be in octahedral symmetry with the axial distortions, and no tetrahedrally coordinated V species can be formed. Ammonia fully covers the catalyst surface either through the associative interaction with the Lewis acid site of Ti_5c or the dissociative adsorption channels. The dissociation of ammonia on the O site bridging the Ti_6c and V_6c octahedra and on the V?O group can proceed with the highest gain in energy. The formation of an adsorbed ammonium ion was found to be an energetically highly unfavorable process. The V?O group is no longer expected to play a major role in the stabilization of the surface ammonium ion. NO can be activated on the Ti_5c site of the catalyst containing predissociated ammonia on the bridging O site and V?O group. It can be expected that the SCR reaction products are formed through the reactions of both adsorbed NO and NH₂ or the desorbed NH₂ group with NO in the gas phase. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Silica - Titania Support for HVOC''s Combustion Catalysts

Preparation of support series for catalysts of combustion of halogenated volatile organic compounds (H-VOC's) was carried out. It was stated that all they allow preparing active catalysts however their main drawback is the lack of hardness against products of H-VOC's combustion e.g. hydrogen chloride and chlorine. Laboratory tests showed that titania and silica - titania supports were characterized by the highest hardness against chlorine derivatives. In comparison to the titania supports, low content (ca. 10 wt.%) silica-containing supports have better mechanical properties, i.e. mechanical strength and attrition resistance. In this paper the method of preparation, composition and physicochemical properties of silica - titania support are presented. This revised version was published online in June 2006 with corrections to the Cover Date.     

Enhanced Adsorption Capacity and Photo-Catalytic Oxidative Activity of Dyes in Aqueous Medium by Hydrothermally Treated Titania Pillared Clay

Titania pillared montmorillonite clay was prepared by two different routes viz. 1) conventional ion exchange method and 2) modified method wherein the post hydrothermal treatment after ion-exchange was employed. The influence of the post hydrothermal treatment on the textural properties of titania-pillared clays was studied. The calcined clay was characterized by different physico-chemical techniques such as XRD, EDX, low temperature (77 K) nitrogen adsorption and UV-Vis diffuse reflectance spectroscopy. The content of pillared titania remained unchanged irrespective of the method of preparation. The method of preparation and severity of the conditions employed for the hydrothermal treatment resulted in alteration of the crystallinity and crystallite size of the anatase. The changes in the average pore diameter was found to comensurate with the changes in crystallite size of anatase phase. The increase in total pore volume as a function of the severity of the post hydrothermal treatment resulted in the decrease in micropore volume. The severity of the post hydrothermal treatment governed the extent of the blue shift in UV-Vis DRS spectra.The behaviour of titania pillared clays in adsorptive capacity and in photo-catalytic oxidation of methylene blue and victoria pure blue in aqueous medium was studied as a function of their physico-chemical characteristics. The titania pillared clays prepared by post hydrothermal route has shown enhanced adsorption capacity and photo-catalytic oxidation.     

Photocatalytic Effects of Rutile Phase TiO2 Ultrafine Powder with High Specific Surface Area Obtained by a Homogeneous Precipitation Process at Low Temperatures

The photocatalytic characteristics of nanostructured TiO₂ ultrafine powder with rutile phase produced using the homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 TiO₂ powder by flame hydrolysis. The TiO₂ powder by the HPPLT showed much higher photoactivity in the removal rate, showing lower pH values in the solution than the P-25 powder when eliminating metal ions such as Pb and Cu from the aqueous metal-EDTA solutions. This can be inferred as the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of an electron-hole pair formed on the surface of the TiO₂ particles under UV light irradiation. Also, in the view of the TiO₂ particle morphology, compared to the well-dispersed spherical P-25 particles, the agglomerated TiO₂ secondary particles by the HPPLT consist of acicular typed primary particles with a thickness in the range of 3–7 nm and the primary particles radialize in all directions, which would be more effective to photocatalytic reactions without the large electron-hole recombination on the surface of the TiO₂ particle under UV light irradiation. It can be, therefore, thought that the higher photoactivity of the rutile TiO₂ powder by the HPPLT in the aqueous solutions results mainly from having a larger surface area by the acicular shaped primary particles with very thin thickness and radialization in all directions.     

Ti-HMS介孔分子筛的制备及其在一氧化氮催化分解反应中的活性

 在常温下制备了具有不同钛含量的大比表面积和孔体积的介孔分子筛HMS．XRD谱表明,这些Ti－HMS样品呈现出很好的六方晶形．经焙烧后,Ti－HMS样品的UV吸收光谱和XAFS谱结果表明,在Ti－HMS（1）和Ti－HMS（2）骨架中的钛离子以四配位存在,而在Ti－HMS（10）中至少有部分钛是以六配位存在．在NO存在的情况下,在273K下光催化剂Ti－HMS受紫外光照射后,导致NO分解生成N2,O2和N2O．实验结果表明,具有高分散四配位钛的Ti－HMS（1）使NO以高效率、高选择性分解生成N2和O2;随着钛含量的增加,其光催化活性反而降低．     

TiO2光催化降解4-氯苯酚过程中的电分析监测

采用循环伏安法和紫外光谱法对有机物的光催化降解进行机理研究和在线监测.以标准光催化剂DegussaP25在紫外光照射下催化降解4-氯苯酚,发现在降解过程中至少有两对氧化还原中间产物对苯二酚-苯醌和羟基氢醌-羟基苯醌.由4-氯苯酚及中间产物的电极响应,可以观测到它们在光催化降解过程中的含量变化,从而对整个过程实现在线监测,并由此全面了解光催化反应机理.从不同反应时间后测得的紫外光谱可以看到,苯环特征峰逐渐消失.这表明4-氯苯酚的苯环逐渐被打开,直至被彻底降解.