氟离子掺杂和吸附对二氧化钛光催化活性的影响

已有文献报道,在二氧化钛的体相和表面分别掺杂和吸附氟离子,都能加快水中有机化合物的光催化降解.前者归结于表面形成的三价钛离子促进光生载流子分离,后者归结于双电层中的氟离子促进羟基自由基脱附.但是,有关它们之间的活性差异未见有文献报道.本文采用水热法,以钛酸丁酯和氟化铵为原料,合成出具有不同氟离子掺杂量的光催化剂.通过苯酚降解反应,研究氟化钠和硝酸银外部加入对这些催化剂光催化性能的影响.结果表明:无论是处于二氧化钛的体相,还是处于二氧化钛的双电层外层和内层,这些氟离子都能促进苯酚的光催化降解.但是,它们的相对活性依次降低.此外,在催化剂的水悬浮液中,同时加入硝酸银和氟化钠,能进一步加快苯酚的光催化降解,且该反应的速率远远大于单独加入氟化钠或硝酸银时的速率总和.这说明将导带电子的还原过程和价带空穴的氧化过程耦合起来,是提高二氧化钛光催化量子效率的有效途径.     

氟掺杂纳米 TiO2 薄膜的低温制备及其光催化性能

 以氟化铵为氟源, 采用水热法制得氟掺杂 TiO2 (FTO) 溶胶, 并通过浸渍提拉法在低温下制备了 FTO 薄膜. 其中在 120 oC 下水热处理 10 h 所得的 TiO2 溶胶制备的薄膜均匀透明, 具有较高的光催化活性. 氟掺杂后的 TiO2 晶粒尺寸并未发生明显变化, 但薄膜的光催化活性显著升高. F/Ti 摩尔比为 0.01 时, FTO 薄膜的光催化活性最高, 比 TiO2 薄膜的活性升高了 23%. X 射线光电子能谱结果表明, 氟掺杂 TiO2 中的氟离子存在晶格取代掺杂和表面化学吸附两种形式. 这两种氟离子的共同作用是 FTO 薄膜光催化活性升高的主要原因.     

氟掺杂提高纳米二氧化钛光催化活性的研究进展

纳米二氧化钛(TiO2)具有光催化活性高、无毒、化学性质稳定、成本低等优点,是目前最具发展前景的光催化剂。但TiO2的宽禁带和低量子效率限制了它的实际应用。因此,对TiO2进行改性研究,实现TiO2的可见光响应和提高其量子效率成为研究的热点。氟掺杂不仅能够使TiO2具有可见光催化活性,而且可提高其紫外光催化活性。本文综述了氟掺杂TiO2的制备,氟掺杂提高TiO2光催化活性的机理、氟与其他元素共掺杂TiO2的研究进展。     

负载贵金属光催化剂的光催化活性研究

在注入V离子的二氧化钛光催化剂上负载贵金属,制备了在可见光照射下具有高光催化活性的功能型光催化剂,研究在可见光和太阳光照射下丙炔的光催化水解反应，利用这些改性的二氧化钛构筑太阳能到化学能的转换系统.研究结果发现了V/Pt光催化剂在丙炔和水的光催化水解反应中，由于贵金属的存在，有利于促进发生加氢反应；导致丙烯的生成量增加.在可见光下的光催化活性也和负载贵金属所处的氧化状态有着密切的关系，贵金属完全被还原到0价是提高光催化活性的必要条件.     

多功能Na2WO4-离子液体催化体系催化环己醇一锅合成己内酰胺

己内酰胺是合成尼龙-6和工程塑料的关键中间体.工业上己内酰胺的合成工艺分三步:以环己醇为原料合成环己酮,环己酮氨肟化合成环己酮肟,环己酮肟重排生成己内酰胺.该工艺存在工艺流程长、重排过程中使用发烟硫酸腐蚀设备、形成大量低值副产物硫酸铵等问题.随着人们对环境保护意识的提高,发展环境友好、经济效益高的直接合成己内酰胺工艺已经迫在眉睫.多步串联反应具有设备投资少、中间分离步骤少、反应效率高等优点,其关键问题之一是多功能催化剂的开发.环己醇作为环己烷氧化反应的副产物,能够直接用于己内酰胺的合成,具有理论研究价值和工业应用意义.本文构建了以环己醇氧化、环己酮肟化和环己酮肟重排反应构成的串联反应系统,可缩短己内酰胺合成工艺流程,降低能耗,减小环境污染.合成了九种离子液体,并与Na2WO4组成催化体系,以环己醇、过氧化氢和羟胺为原料,催化环己醇直接合成己内酰胺.首先研究了不同Na2WO4-离子液体催化体系对环己醇直接氧化合成环己酮反应的影响.反应介质的酸性和离子液体水油两相中的相转移功能是影响氧化过程的两个主要因素.Na2WO4-磺酸基功能化的离子液体催化剂具有较高的氧化活性.这是由于磺酸基的引入提高了催化剂酸性,另外磺酸基功能化的离子液体随碳链的增长,催化剂的亲油性增强,即该催化剂相转移功能增强.考察了九种离子液体对氧化过程的影响,其中Na2WO4-[BSTma]HSO4在氧化过程中催化活性最高,因此将其用于催化环己酮与羟胺合成己内酰胺的反应,并考察了环己酮与[BSTma]HSO4的摩尔比对该反应的影响,发现该摩尔比为1:0.08时,反应效果最好.最后,将Na2WO4-[BSTma]HSO4体系用于催化环己醇直接合成己内酰胺的反应.考察了反应温度、反应时间和环己醇与[BSTma]HSO4摩尔比的影响.在氧化时间为300 min,肟化和重排时间为150 min,反应温度为80℃,环己醇:H2O2:(NH2OH)2·H2SO4:Na2WO4·2H2O:[BSTma]HSO4的摩尔比为1.00:1.50:0.50:0.06:0.08的条件下反应效果最好,环己醇转化率为97.3%,己内酰胺收率为76.0%.Na2WO4-[BSTma]HSO4催化体系活性较高的原因是离子液体阳离子的相转移作用,以及在氧化过程中离子液体与过氧钨酸盐的配位作用和对Beckmann重排过程中中间产物的稳定作用.研究了Na2WO4-[BSTma]HSO4催化体系的普适性,发现该催化体系对所考察的脂肪醇和芳香醇直接合成酰胺均具有较好的催化活性.另外,回用的Na2WO4-[BSTma]HSO4催化剂仍具有较好的催化活性.因此,该催化体系具有高效易回收、操作简单和反应条件温和的优点.     

光电流法研究TiO2薄膜表面吸附氧对光催化活性的影响

采用溶胶-凝胶法制备了锐钛矿型和金红石型TiO2薄膜, 利用光电流和XPS技术研究了薄膜表面吸附氧对不同晶型TiO2光催化活性的影响. 并通过降解纯的环己烷溶液的实验来评估不同晶型TiO2的光催化活性. 结果表明, 在相同条件下, 锐钛矿型TiO2比金红石型具有明显的光催化活性. 这是由于锐钛矿型TiO2比金红石型TiO2具有较强的吸附氧的能力, 同时其光生电子与空穴的复合率相对较小所致.     

多功能Na_2WO_(4-)离子液体催化体系催化环己醇一锅合成己内酰胺（英文）

己内酰胺是合成尼龙-6和工程塑料的关键中间体.工业上己内酰胺的合成工艺分三步:以环己醇为原料合成环己酮,环己酮氨肟化合成环己酮肟,环己酮肟重排生成己内酰胺.该工艺存在工艺流程长、重排过程中使用发烟硫酸腐蚀设备、形成大量低值副产物硫酸铵等问题.随着人们对环境保护意识的提高,发展环境友好、经济效益高的直接合成己内酰胺工艺已经迫在眉睫.多步串联反应具有设备投资少、中间分离步骤少、反应效率高等优点,其关键问题之一是多功能催化剂的开发.环己醇作为环己烷氧化反应的副产物,能够直接用于己内酰胺的合成,具有理论研究价值和工业应用意义.本文构建了以环己醇氧化、环己酮肟化和环己酮肟重排反应构成的串联反应系统,可缩短己内酰胺合成工艺流程,降低能耗,减小环境污染.合成了九种离子液体,并与Na_2WO_4组成催化体系,以环己醇、过氧化氢和羟胺为原料,催化环己醇直接合成己内酰胺.首先研究了不同Na_2WO_(4-)离子液体催化体系对环己醇直接氧化合成环己酮反应的影响.反应介质的酸性和离子液体水油两相中的相转移功能是影响氧化过程的两个主要因素.Na_2WO_(4-)磺酸基功能化的离子液体催化剂具有较高的氧化活性.这是由于磺酸基的引入提高了催化剂酸性,另外磺酸基功能化的离子液体随碳链的增长,催化剂的亲油性增强,即该催化剂相转移功能增强.考察了九种离子液体对氧化过程的影响,其中Na_2WO_(4-)[BSTma]HSO_4在氧化过程中催化活性最高,因此将其用于催化环己酮与羟胺合成己内酰胺的反应,并考察了环己酮与[BSTma]HSO_4的摩尔比对该反应的影响,发现该摩尔比为1:0.08时,反应效果最好.最后,将Na_2WO_(4-)[BSTma]HSO_4体系用于催化环己醇直接合成己内酰胺的反应.考察了反应温度、反应时间和环己醇与[BSTma]HSO_4摩尔比的影响.在氧化时间为300 min,肟化和重排时间为150 min,反应温度为80 ℃,环己醇:H_2O_2:(NH2OH)2·H_2SO_4:Na_2WO_4·2H_2O:[BSTma]HSO_4的摩尔比为1.00:1.50:0.50:0.06:0.08的条件下反应效果最好,环己醇转化率为97.3%,己内酰胺收率为76.0%.Na_2WO_(4-)[BSTma]HSO_4催化体系活性较高的原因是离子液体阳离子的相转移作用,以及在氧化过程中离子液体与过氧钨酸盐的配位作用和对Beckmann重排过程中中间产物的稳定作用.研究了Na_2WO_(4-)[BSTma]HSO_4催化体系的普适性,发现该催化体系对所考察的脂肪醇和芳香醇直接合成酰胺均具有较好的催化活性.另外,回用的Na_2WO_(4-)[BSTma]HSO_4催化剂仍具有较好的催化活性.因此,该催化体系具有高效易回收、操作简单和反应条件温和的优点.     

贵金属负载光催化剂在丙炔光催化水解反应中的研究(Ⅲ)

利用三种不同负载方法制备了含有不同贵金属的TiO2光催化剂,通过测试其XPS和光催化活性和选择性发现,TiO2光催化剂在丙炔和水的光催化水解反应中,由于贵金属的存在,有利于促进发生加氢反应,导致丙烯的生成量增加.Pt,Ru,Rh,Pd和Ag负载在TiO2上,在紫外线照射下(λ>270nm),Pd负载的TiO2光催化剂表现出最高的光催化活性.光催化活性和负载贵金属所处的氧化状态有密切的关系,贵金属完全被还原到0价是提高光催化活性的必要条件.     

三氯化钌催化下环己烷和环己醇在离子液体中的氧化反应研究

在三氯化钌催化下，使用叔丁基过氧化氢在离子液体中可将环己烷和环己醇氧化为环己酮，结果表明环己醇的氧化具有较高的转化率和选择性．离子液体(bmim)^ PF6^-和催化剂三氯化钌均有一定的重复使用性．     

Fe~(3+)离子对二氧化钛光电化学催化性能的影响

应用电化学阳极氧化法制备Ti上多孔状纳米晶TiO2薄膜,以及不同Fe3+离子掺杂量的二氧化钛薄膜.研究了Fe3+离子掺杂对二氧化钛薄膜吸收光谱和光催化活性的影响,发现Fe3+的掺杂使薄膜的吸收带边发生红移,在可见光照射下其光催化活性也有一定的提高.     

Selective photocatalytic oxidation of alcohols to aldehydes in water by TiO2 partially coated with WO3

Semiconductor TiO₂ particles loaded with WO₃ (WO₃/TiO₂), synthesized by impregnation of tungstic acid followed by calcination, were used for photocatalytic oxidation of alcohols in water with molecular oxygen under irradiation at λ>350 nm. The WO₃/TiO₂ catalysts promote selective oxidation of alcohols to aldehydes and show higher catalytic activity than pure TiO₂. In particular, a catalyst loading 7.6 wt % WO₃ led to higher aldehyde selectivity than previously reported photocatalytic systems. The high aldehyde selectivity arises because subsequent photocatalytic decomposition of the formed aldehyde is suppressed on the catalyst. The TiO₂ surface of the catalyst, which is active for oxidation, is partially coated by the WO₃ layer, which leads to a decrease in the amount of formed aldehyde adsorbed on the TiO₂ surface. This suppresses subsequent decomposition of the aldehyde on the TiO₂ surface and results in high aldehyde selectivity. The WO₃/TiO₂ catalyst can selectively oxidize various aromatic alcohols and is reusable without loss of catalytic activity or selectivity.     

锐钛矿型多孔TiO2薄膜的溶解法制备及性能表征

在具有锐钛矿晶粒的TiO₂溶胶中加入苯丙乳液粒子，使用该混合液浸渍提拉涂膜，然后利用甲苯将薄膜中的苯丙乳液粒子溶解去除，并通过重复涂膜，在室温下获得了具有良好多孔性的锐钛矿型TiO₂薄膜。考察了多孔薄膜的表面形貌、光学性能、吸附性能和光催化性能。结果表明：随薄膜涂膜次数的增加，TiO₂多孔薄膜的吸光度增大，透光率减小，光吸收边波长向长波方向移动。罗丹明B在TiO₂多孔薄膜上的吸附量随涂膜次数的增加先升高，后降低；多次涂膜会在薄膜中产生半封闭的孔洞，经过长时间的毛细渗透等作用能进一步增加薄膜对罗丹明B的吸附。TiO₂多孔薄膜通过吸附+光催化氧化的模式快速分解罗丹明B，其活性主要受到薄膜在光催化反应初期的吸附能力的影响。此外，TiO₂的负载量、光的利用效率、以及光生电荷迁移及其分离等也是影响薄膜光催化活性的因素。     

Effects of anatase TiO2 morphology and surface fluorination on environmentally relevant photocatalytic reduction and oxidation reactions

Aiming at clarifying the interplay on TiO₂ photoactivity between particle morphology and surface fluorination, the photocatalytic performance of anatase nanocrystals, characterized by a pseudo-spherical shape or a nanosheet structure, is investigated in both a reduction and an oxidation reaction, either in the absence or in the presence of added fluoride anions. Cr(VI) photocatalytic reduction is strongly favored by a large exposure of anatase {001} facets; however, surface fluorination leads in this case to a morphology-independent photoactivity decrease, due to the decreased adsorption of the reaction substrate. More interestingly, a beneficial synergistic effect between the platelet-like anatase morphology and TiO₂ surface fluorination is clearly outlined in Rhodamine B photocatalytic degradation, possibly resulting from the intrinsic ability of fluorinated {001} anatase facets of boosting ^?OH radical mediated oxidation paths, due to their larger amount of surface –OH groups, as revealed using Fourier-transform infrared spectroscopy.     

Study of the Efficiency of UV and Visible‐Light Photocatalytic Oxidation of Methanol on Mesoporous RuO2–TiO2 Nanocomposites

Mesoporous RuO₂–TiO₂ nanocomposites at different RuO₂ concentrations (0–10 wt %) are prepared through a simple one‐step sol–gel reaction of tetrabutyl orthotitanate with ruthenium(III) acetylacetonate in the presence of an F127 triblock copolymer as structure‐directing agent. The thus‐formed RuO₂–TiO₂ network gels are calcined at 450 °C for 4 h leading to mesoporous RuO₂–TiO₂ nanocomposites. The photocatalytic CH₃OH oxidation to HCHO is chosen as the test reaction to examine the photocatalytic activity of the mesoporous RuO₂–TiO₂ nanocomposites under UV and visible light. The photooxidation of CH₃OH is substantially affected by the loading amount and the degree of dispersion of RuO₂ particles onto the TiO₂, which indicates the exclusive effect of the RuO₂ nanoparticles on this photocatalytic reaction under visible light. The measured photonic efficiency ξ=0.53 % of 0.5 wt % RuO₂–TiO₂ nanocomposite for CH₃OH oxidation is maximal and the further increase of RuO₂ loading up to 10 wt % gradually decreases this value. The cause of the visible‐light photocatalytic behavior is the incorporation of small amounts of Ru⁴⁺ into the anatase lattice. On the other hand, under UV light, undoped TiO₂ shows a very good photonic efficiency, which is more than three times that for commercial photocatalyst, P‐25 (Evonik–Degussa); however, addition of RuO₂ suppresses the photonic efficiency of TiO₂. The proposed reaction mechanism based on the observed behavior of RuO₂–TiO₂ photocatalysts under UV and visible light is explored.     

Fluorinated Mesoporous Anatase TiO<Subscript>2</Subscript> Microspheres with High Surface and Enhanced Photocatalytic Activity for the Degradation of Methyl Orange

Highly crystalline mesoporous TiO₂ microspheres with areas up to 122 m²/g and tunable pore size have been prepared through a combined sol–gel and solvothermal processes. The concentration of NaF exhibits a great effect on the morphology, crystallinity, crystal size and photocatalytic activity of the TiO₂ microspheres. A higher NaF concentration results in an increase in the average crystal size and pore size, whereas whereas it caused a decrease in the specific surface areas. All fluorinated TiO₂ microspheres showed a higher photocatalytic activity than P25 and pure TiO₂ microspheres obtained in the absence of NaF due to the effect of surface fluorination on the photoactivity of TiO₂. The approach described in this study provides a simple method to synthesize the micrometer-sized hierarchical structure of mesoporous TiO₂ microspheres that are ready for practical applications such as environmental pollutants removal and solar cell because these high active materials can be easily separated.     

Effect of TiO2 modification with fluorine on the physicochemical properties and activity in the photocatalytic oxidation of pollutants in air under UV irradiation

The influence of the modification of the TiO₂ surface with F^? ions on the physicochemical properties of the catalysts and efficiency in the photooxidation of gaseous molecules under atmospheric conditions and under UV irradiation was studied by IR spectroscopy. The fluorine-containing samples adsorb more water molecules than unmodified TiO₂. The amount of adsorbed water increases with increasing content of surface fluoride ions. The fluorination of the TiO₂ surface first leads to the substitution of the terminal OH groups by F^? ions and to an increase in acidity of the bridging acidic OH groups remained on the surface. The modification also results in the structural rearrangement of the surface involving defective and surface Ti⁴⁺ sites. Fluorine modification increases the activity of TiO₂ in the photocatalytic oxidation of ethanol, acetaldehyde, acetic acid, and acetone. At the same time, benzene and H₂S are oxidized more rapidly on unmodified TiO₂. The presence of fluorine on the TiO₂ surface exerts almost no effect on the oxidation rate of chlorine-containing substrates C₃H₇Cl and C₂H₄Cl₂.

     

Effect of Pt loading on the photocatalytic reactivity of titanium oxide thin films prepared by ion engineering techniques

Platinum-loaded titanium oxide thin-film photocatalysts were prepared by using an ionized cluster beam (ICB) deposition method and a RF magnetron sputtering (RF-MS) deposition method as dry processes. From the results of the photocatalytic oxidation of acetaldehyde with O₂ under UV light irradiation, small amounts of Pt loading (less than 10 nm film thickness) were found to dramatically enhance the photocatalytic reactivity. However, when TiO₂ thin films were loaded with relatively larger amounts of Pt (more than 30 nm as the film thickness), the photocatalytic reactivity became lower than for the pure TiO₂ thin films. Moreover, investigations of the ratio of Pt loaded onto the surface of the thin film catalysts by XPS measurements revealed that the small amounts of Pt loaded exist as very small clusters working to efficiently enhance the charge separation, whereas, large amounts of Pt covers the entire surface of the TiO₂ thin films, resulting in a decrease of the photocatalytic reactivity.     

Design of highly ordered Ag-SrTiO3 nanotube arrays for photocatalytic degradation of methyl orange

Ag-SrTiO₃ nanotube arrays were successfully prepared for the degradation of methyl orange (MO) under ultraviolet irradiation. In order to form highly ordered SrTiO₃ nanotube arrays, the preparation of TiO₂ nanotube arrays by anodic oxidation of titanium foil in different electrolytes was investigated. The selected organic solvents in electrolytes include glycerol, dimethyl sulfoxide and glycol. The results indicate that the morphology of TiO₂ nanotube arrays prepared in glycol containing ammonium fluoride electrolyte is more regular. Then SrTiO₃ nanotube arrays were synthesized by a hydrothermal method using TiO₂ nanotube arrays as the precursor. In order to further improve the photocatalytic activity of SrTiO₃ nanotube arrays, Ag nanoparticles were loaded on SrTiO₃ nanotube arrays by two sets of experiments. The loaded Ag results in an enhancement of photocatalytic activity of SrTiO₃ nanotube arrays. Moreover, the effect of pH on the photocatalytic degradation of MO was also studied.     

Photocatalytic decomposition of liquid-water on the Pt-loaded TiO2 catalysts: Effects of the oxidation states of Pt species on the photocatalytic reactivity and the rate of the back reaction

The photocatalytic decomposition of liquid water on Pt-loaded TiO₂ (Pt/TiO₂) catalysts was investigated. The results obtained by XPS and XRD measurements of the catalysts as a function of the calcination temperature as well as the photocatalytic decomposition reactions of H₂O clearly indicate that controlling the oxidation state of Pt as well as the amount of loaded Pt species are both important factors in the design of water-splitting photocatalysts having high efficiency and stoichiometry.     

阳极氧化法制备TiO2多孔薄膜

本文综述了制备TiO₂薄膜的各种方法,详细介绍了阳极氧化法制备TiO₂多孔膜的进展,在非含氟电解液体系中,对纯钛进行阳极氧化处理可制得表面呈无规则生长的多孔膜结构;在含氟电解液体系中,则可自组织形成高度有序的TiO₂纳米管阵列,并指出阳极氧化法是可在常温低压下进行、操作工艺简单、薄膜性能稳定、再现性好的一种最具工业化应用潜力的制备方法。