污染物甲胺为电子给体可见光下Pt/ZnIn2S4光催化制氢

用水热法制备了ZnIn2S4固溶体,并通过XRD和UV-vis漫反射光谱进行了表征.研究了一甲胺、二甲胺和三甲胺为给电子体,在Pt/ZnIn2S4上的可见光光催化制氢及自身的降解反应.3种甲胺都能显著提高光催化分解水制氢活性,同时自身得到很好的降解.电子给体的放氢活性顺序为:TMADMAMMA.通过红外衰减全反射(ATR-IR)法检测电子给体在ZnIn2S4表面的吸附行为,吸附强度大小依次为MMADMATMA.光催化活性与分子结构和在催化剂表面的吸附行为有关.3种污染物浓度对放氢活性的影响都符合Langmuir-Hinshelwood动力学模型.讨论了可能的化学反应机理.     

污染物甲醛为电子给体Pt/TiO2光催化制氢

研究了甲醛为电子给体在Pt/TiO2上光催化生成氢的反应。甲醛经光催化降解产生CO2和甲酸，甲酸可进一步被氧化；甲醛的光催化降解与放氢同时发生，催化剂的最佳Pt负载量为0．5％，甲醛浓度对反应的影响，表观上符合Langmuir-Hinshelwood关系式；碱性条件有利于该反应；在甲醛浓度较低时，甲醇的存在能部分地提高放氢速率，并讨论了可能的反应机理。     

污染物乙醇胺Pt/TiO2光催化制氢

研究了以污染物乙醇胺为电子给体在Pt/TiO2上光催化生成氢的反应.结果表明,三种乙醇胺都能显著地提高光催化放氢效率,且污染物也被很好降解.研究了反应时间、起始浓度、pH值对光催化放氢和污染物降解的影响.制氢和污染物降解都是在弱碱性(pH为8~9左右)时活性最好.三种乙醇胺浓度对放氢反应的影响,表观上符合Langmuir-Hinshelwood关系式.乙醇胺光催化降解最终产物主要是CO2,H2O和NH3,检测到了中间产物一乙醇胺和甲醛.探讨了可能的反应机理.     

利用甘油废水Pt/TiO2光催化制氢

研究了以甘油为电子给体在Pt/TiO2上光催化生成氢的反应.结果表明甘油能显著地提高光催化放氢效率,并且其自身的降解活性也很好.研究了反应时间、甘油起始浓度、溶液pH值、甘油废水中共存物对光催化放氢的影响.甘油光催化降解最终产物是H2O和CO2,检测到了甘油醛、羟基乙醛、羟基乙酸、甲醛等中间产物.探讨了可能的反应机理.     

草酸盐对甲醛光催化氧化降解过程促进作用的研究

采用漫反射红外光谱（DRIFTS）技术和循环伏安法对TiO2光催化剂上甲醛光催化氧化过程中催化剂表面吸附、降解行为进行了考察．研究了草酸盐对甲醛光催化氧化降解行为的影响，结果表明低浓度草酸钠的加入提高了甲醛的降解效率，这个结果归因于草酸根离子的存在能够清除吸附位上积聚的甲酸及类似中间产物．光电化学实验进一步证实了草酸钠对甲醛光催化氧化中间产物的清除作用．     

Pt/TiO2光催化分解甲酸制氢反应的原位红外光谱研究

用原位红外光谱研究了无氧条件下Pt/TiO2光催化甲酸制氢反应机理.结果表明,物理吸附的甲酸物种在光催化反应过程中向甲酸根离子转化,而甲酸根离子则逐渐向碳酸盐物种转化.水蒸气的添加显著促进了甲酸在Pt/TiO2上光催化反应的进行,并提高了产氢效率.提出了该光催化反应的可能机理.     

原位红外光谱法研究三氯乙烯在TiO2表面的光催化降解

通过原位红外光谱技术在线研究了三氯乙烯的直接光降解以及三氯乙烯在TiO2表面的气相光催化降解. 研究结果表明, UV/TiO2体系比UV体系具有更强的降解能力. 在三氯乙烯的光催化降解过程中, 发现有二氯乙酰氯、二氧化碳、一氧化碳、水、氯化氢和光气等中间产物生成. 根据反应结果, 分析了三氯乙烯在TiO2表面的气相光催化降解机理: 三氯乙烯在羟基自由基等作用下生成中间产物二氯乙酰氯, 二氯乙酰氯进一步发生自由基反应, 最终降解为二氧化碳、一氧化碳、水、氯化氢和光气.     

温和条件下甲醛在 Pt/TiO2 上催化氧化反应的原位漫反射红外光谱研究

 采用原位漫反射红外光谱研究了温和条件下 1%Pt/TiO2 催化剂上甲醛的吸附和氧化反应, 并对催化剂的失活进行了分析. 结果表明, Pt/TiO2 催化剂在室温条件下即可将甲醛氧化成 H2O 和 CO2, 100 oC 以下甲酸根的分解为决速步骤, 低温下催化剂失活是由于表面未能及时分解的甲酸根占据了催化剂的活性位, 升温至 100 oC 即可将甲酸根完全分解并恢复催化剂的活性.     

MCM-41分子筛担载纳米TiO2复合材料光催化降解罗丹明B

采用溶胶-凝胶法将TiO2担载在介孔MCM-41分子筛上, 制备了不同TiO2含量的系列TiO2/MCM-41复合材料, 利用X射线衍射、N2吸附、紫外-可见光谱和透射电镜等方法对其进行表征. TiO2的晶型为锐钛矿相, 复合材料的比表面积和孔体积随其中TiO2担载量(复合材料中TiO2与MCM-41的质量比)的增加而减小, TiO2的平均粒径随其担载量的增加而增大. 以罗丹明B的光催化降解为探针反应, 评价了TiO2/MCM-41复合材料的光催化降解活性. 结果表明, 在紫外光照射下, 罗丹明B在该复合材料上的光催化降解反应遵循一级反应动力学, 复合材料对罗丹明B的光催化降解活性明显高于商用TiO2 (P-25), 复合材料的光催化降解活性由复合材料的吸附能力和所含TiO2的光催化活性共同决定.     

MCM-41分子筛担载纳米TiO2复合材料光催化降解罗丹明B

采用溶胶.凝胶法将TiO2担载在介孔MCM-41分子筛上,制备了不同TiO2含量的系列TiO2/MCM-41复合材料,利用X射线衍射、N2吸附、紫外-可见光谱和透射电镜等方法对其进行表征.TiO2的晶型为锐钛矿相,复合材料的比表面积和孔体积随其中TiO2担载量(复合材料中TiO2与MCM-41的质量比)的增加而减小,TiO2的平均粒径随其担载量的增加而增大.以罗丹明B的光催化降解为探针反应,评价了TiO2/MCM-41复合材料的光催化降解活性.结果表明,在紫外光照射下,罗丹明B在该复合材料上的光催化降解反应遵循一级反应动力学,复合材料对罗丹明B的光催化降解活性明显高于商用TiO2(P-25),复合材料的光催化降解活性由复合材料的吸附能力和所含TiO2的光催化活性共同决定.     

甲酸存在下硝酸根在二氧化钛表面光催化还原成氨

用甲酸作空穴清除剂,研究了ＴｉＯ２水悬浮体系中硝酸根光催化还原氨的反应。与草酸作空穴清除剂相比,甲酸加速硝酸根的还原更显著。研究了硝酸根和甲酸根的浓度效应及ｐＨ效应。实验结果表明,硝酸根在ＴｉＯ２表面的吸附是加附是加速该光催化还原反应的重要因素。     

Pt—TiO2光催化还原罗丹明B

报道了罗丹明B（RhB)在TiO2催化剂上的吸附过程及加氢反应结构。当草酸作为电给体时,光催化反应产生的氢气,可使RhB发生快速地氢反应,生成无色的加氢产物。该加氢过程与催化剂的种类、表面化学状态和担载催化剂的种类有密切关系。     

Kinetics of adsorption of oxalic acid on different titanium dioxide samples

FTIR-ATR kinetic studies on the adsorption of oxalic acid on different TiO(2) films were performed. The particulate films were obtained through the evaporation of TiO(2) suspensions. The evolution of the IR bands followed a pseudo-first-order behavior, as previously observed. Systematic studies as a function of the oxalic acid concentration afforded the specific rate constant for adsorption (k(a)) and desorption (k(d)). The influence of physical parameters of the samples, i.e., specific BET area, crystalline domain size, TiO(2) load, film area, and pore size, on the kinetic parameters k(a) and k(d) was analyzed. A mechanism in which the adsorption and desorption processes are controlled by the diffusion through the pores of the films is proposed (intraparticle diffusion). It is concluded that all the samples behave in the same way. Thicker films or those with smaller particle size (higher specific surface area, smaller pores) show the slowest rates of adsorption and desorption. These results are relevant for the design of efficient heterogeneous catalysts and sensors, and for the interpretation of pollutant adsorption.     

以草酸为电子给体在Pt-TiO2上光催化生成氢

 以草酸为电子给体,研究了在Pt－TiO2上光催化生成氢的反应．草酸的存在明显促进了生成氢的反应;二氧化钛负载Pt也明显提高了反应速率,Pt的最佳负载量为w（Pt）＝0．5％．草酸浓度对氢生成反应的影响符合Lang－muir关系式．最佳pH值为2～4．     

以葡萄糖为电子给体光催化还原水制氢的研究

以葡萄糖为电子给体,研究了在M/TiO2(M=Pt,Pd,Au,Rh)催化剂上光催化还原水生成氢气的反应.重点考察了体系(或溶液)中溶解的气体和溶液的pH值对析氢速率的影响.实验结果表明,四种催化剂均能够有效地催化以葡萄糖为电子给体的光催化还原水制氢反应.溶液中溶解的一氧化碳和氧气对放氢反应有负面影响,析氢的最佳pH值约为5.本文还对可能的氧化反应机理进行了讨论,葡萄糖很可能经葡萄糖醛酸被氧化.     

Hydrogen production from water by visible light using zinc porphyrin-sensitized platinized titanium dioxide

The rate of H₂ evolution from aqueous suspensions of Pt/TiO₂ with deposited zinc porphyrin in the presence of an electron donor (EDTA, triethanolamine, ascorbic and oxalic acids) during irradiation by visible light (λ > 520 nm) was optimized with respect to the concentrations of platinum, zinc porphyrin and electron donor. The relationship between the rate of hydrogen evolution and pH has a maximum at pH 4–5 for EDTA, ascorbic and oxalic acids, as does the adsorption of these donors on TiO₂. In the case of triethanolamine, H₂ production increases sharply in alkaline solutions when the triethanolamine molecules are deprotonated. The photostability of the photosensitizer increases on the semiconductor. Turn-over numbers for the zinc porphyrins varied from 50 for water-soluble zinc porphyrin up to 150–185 for water-insoluble sensitizers.     

Density functional theory study of formic acid adsorption on anatase TiO2(001): geometries, energetics, and effects of coverage, hydration, and reconstruction

We present density functional theory calculations and first-principles molecular dynamics simulations of formic acid adsorption on anatase TiO(2)(001), the minority surface exposed by anatase TiO(2) nanoparticles. A wide range of factors that may affect formic acid adsorption, such as coverage, surface hydration, and reconstruction, are considered. It is found that (i) formic acid dissociates spontaneously on unreconstructed clean TiO(2)(001)-1 x 1, as well as on the highly reactive ridge of the reconstructed TiO(2)(001)-1 x 4 surface; (ii) on both the 1 x 1 and 1 x 4 surfaces, various configurations of dissociated formic acid exist with adsorption energies of about 1.5 eV, which very weakly depend on the coverage; (iii) bidentate adsorption configurations, in which the formate moiety binds to the surface through two Ti-O bonds, are energetically more favored than monodentate ones; (iv) partial hydration of TiO(2)(001)-1 x 1 tends to favor the bidentate chelating configuration with respect to the bridging one but has otherwise little effect on the adsorption energetics; and (v) physical adsorption of formic acid on fully hydrated TiO(2)(001)-1 x 1 is also fairly strong. Comparison of the present results for formic acid adsorption with those for water and methanol under similar conditions provides valuable insights to the understanding of recent experimental results concerning the coadsorption of these molecules.     

Adsorption of 2-chloropyridine on oxides--an infrared spectroscopic study

The adsorption of 2-chloropyridine on SiO(2), TiO(2), ZrO(2), SiO(2)-Al(2)O(3) and H-mordenite has been studied by IR spectroscopy. The different modes of interaction with oxide surfaces, i.e. hydrogen-bonding and adsorption at Br?nsted or Lewis acid sites, was modelled by ab initio calculations at the B3LYP/DZ+(d) level. Adsorption on SiO(2) results in hydrogen bonding to surface hydroxyl groups, whereas the spectra obtained following adsorption on TiO(2) and ZrO(2) display evidence for electron transfer at Lewis acidic surface sites. Protonation of 2-chloropyridine at Br?nsted acidic sites was detected only for adsorption on SiO(2)-Al(2)O(3) and H-mordenite, indicating the presence of Br?nsted acidic sites on these oxide surfaces with pK(a) values 相似文献   

ATR-FTIR measurements and quantum chemical calculations concerning the adsorption and photoreaction of oxalic acid on TiO2

The adsorption and photoreaction of oxalic acid on the surface of anatase and rutile TiO2 nanoparticles have been studied using a combined experimental and theoretical approach. In the dark, the experimental adsorption reaches an equilibrium state that can be described as a mixture of adsorbed water and oxalic acid molecules, with the latter forming two different surface complexes on anatase and one on rutile particles. When the system is subsequently illuminated with UV(A) light, the surface becomes enriched with absorbed oxalic acid, which replaces photo-desorbed water molecules, and one of the adsorbed oxalic acid structures on anatase is favoured over the other.