CO2在纳米SiO2/TiO2悬浮体系中的光催化还原

用水热法合成了氧化硅改性的具有高比表面积、高催化活性的锐钛型二氧化钛, 并在其悬浮体系中将CO₂光催化还原合成甲醇. 采用XRD, TEM, 物理吸附, UV-Vis吸收光谱和FTIR等表征手段对催化剂结构特征进行了研究. 结果表明: 添加氧化硅后, 氧化硅和二氧化钛之间形成Si—O—Ti键, 抑制了TiO₂晶粒生长, 提高了锐钛型TiO₂的比表面积, 且随着含硅量的增加, SiO₂/TiO₂的UV吸收逐步蓝移, 禁带宽度增加. 还原反应结果表明: SiO₂/TiO₂具有光催化还原活性, 且随着含硅量的增加先增加后减小, 当SiO₂质量分数为3.5%时, SiO₂/TiO₂复合催化剂反应活性最强, 5 h内甲醇产量可达到21.0 mg/L, 并有少量甲醛生成.     

K-MnO/γ-Al2O3和Cu/SiO2催化剂应用于苯甲酸甲酯连续加氢合成无氯苯甲醇

以K-MnO/γ-Al₂O₃和Cu/SiO₂为催化剂, 利用固定床串联反应器实现了苯甲酸甲酯连续加氢合成无氯苯甲醇反应过程. K-MnO/γ-Al₂O₃和Cu/SiO₂催化剂对于苯甲酸甲酯连续加氢合成苯甲醇具有良好的加氢活性, 反应转化率可达89.2%, 苯甲醇的选择性为84.1%. 在苯甲酸甲酯加氢连续步骤中的氢醛比得到提高, 有效地抑制了副产物甲苯的生成. XRD, SEM和TPR表征结果表明: 采用吸附沉淀法制备的Cu/SiO₂-C15.2催化剂, 氧化铜在载体上具有良好的分散性能, 并且易于还原, 表现出最佳的苯甲醛加氢活性.     

Pt / InVO4 / TiO2可见光催化剂的制备及性能研究

采用溶胶-凝胶法制备了Pt / InVO₄ / TiO₂三元体系可见光催化剂。以乙烯为模拟目标分子，评价其光催化活性并与二元体系催化剂Pt / TiO₂ 和InVO₄ / TiO₂进行比较。用DRS，XRD对催化剂的吸收带边和晶型进行了表征。结果表明：Pt / InVO₄ / TiO₂在可见光区（λ>450 nm）的光催化比活性比Pt / TiO相似文献   

微乳法制备纳米TiO2 /SiO2的结构及光催化研究

Nanosized TiO₂ and TiO₂/SiO₂ particles were prepared by hydrolysis of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS) in the TX-100 reverse microemulsion. These particles were characterized by TG-DSC, XRD, FTIR, TEM，N₂ adsorption-desorption. Their photocatalytic activity was tested by degradation of methyl orange. The result shows that TiO₂/SiO₂ nanoparticles are with a monodispersed spherical phase and a uniform size distribution，and TiO₂ particles are dispersed on the surface of SiO₂. The band for Ti-O-Si vibration in FTIR was observed, the Ti-O-Si bond increased the stability of anatase TiO₂, suppressed the phase transformation of titania from anatase to rutile. And due to the addition of SiO₂, the average size of titania decreased from 38 nm in pure TiO₂ to 5 nm in TiO₂/SiO₂. It was found, under UV light irradiation, TiO₂/SiO₂ particles showed higher activity than pure TiO₂, and TiO₂/SiO₂(1/1) particles showed the highest photocatalytic activity on the photocatalytic decomposition of methyl orange, which was influenced by crystal structure, particle size, crystallinity and Surface area Characteristics.     

MO(M=Cu和Ni)/TiO2/γ-Al2O3催化剂在CO+O2反应中的活性

采用X射线衍射(XRD)，程序升温还原(TPR)等表征手段考察了TiO₂改性对CuO(或NiO)在γ-Al₂O₃表面上分散以及还原性能的影响，同时检测了这些改性的催化剂在CO+O₂反应中的活性。结果表明:TiO₂的改性使得CuO和NiO在γ-Al₂O₃载体上的分散复杂化，产生了多种状态的氧化铜(氧化镍)物种。当负载量低于其在γ-Al₂O₃上的分散容量(0.56 mmol Ti⁴⁺/100 m² γ-Al₂O₃)时，TiO₂的加入主要是抑制了CuO和NiO在γ-Al₂O₃载体上的分散;而当负载量远大于其分散容量时，出现了CuO和NiO在晶相TiO₂(锐钛矿)上的分散。无论其负载量如何，TiO₂的加入促进了CuO的还原。因此，在250 ℃的CO+O₂反应中，改性的催化剂中具有更多的活性位，因而显示出更高的活性;相反，TiO₂的改性则抑制了NiO的还原。因此，在350 ℃的CO+O₂反应中，可还原的氧化镍的量明显少于未经改性的催化剂，导致改性催化剂的活性降低。     

核壳结构TiO2@SiO2催化碳酸二甲酯与苯酚酯交换合成碳酸二苯酯

以反相微乳液法和沉淀法相结合制备了核壳结构TiO₂@SiO₂,首次用于碳酸二甲酯与苯酚酯交换合成碳酸二苯酯反应,显示较好的催化活性. 采用200 ℃焙烧的TiO₂@SiO₂,用量0.20 g,反应9 h,苯酚转化率达41.8%,酯交换选择性为100%. 透射电镜显示TiO₂@SiO₂核厚壳薄,TiO₂核直径220-300 nm,SiO₂壳厚度40-60 nm,具有介孔结构. TiO₂@SiO₂对碳酸二甲酯与苯酚酯交换反应有好的重复使用性,使用4次苯酚转化率仍保持在40%以上. TiO₂与SiO₂发生相互作用,Ti进入骨架形成Ti-O-Si键,骨架Ti的形成提高了TiO₂@SiO₂的催化性能.     

吸附相反应技术制备MnOx/CeO2/SiO2催化剂及其低温选择性催化还原Nox

采用吸附相反应技术制备得到了MnO_x/CeO₂/SiO₂催化剂,通过X 射线衍射（XRD）、透射电子显微镜（TEM）、高分辨透射电子显微镜（HRTEM）、紫外激光拉曼（Raman）等手段对催化剂进行了表征. HRTEM分析表明活性组分MnO_x与CeO₂都均匀分布在载体SiO₂表面;XRD分析表明Mn₃O₄特征峰随着CeO₂含量的增加逐渐减小至完全消失,CeO₂的加入降低了MnO_x的结晶程度,增加了MnO_x的分散性;Raman光谱表明催化剂表面的Mn离子能够进入CeO₂晶格,激发出空穴氧,随着CeO₂负载量的增加,催化剂氧空穴浓度先升高后降低.以NH₃为还原剂,考评催化剂的NO_x低温选择性催化还原（SCR）性能,催化剂催化活性随CeO₂负载量增加先升高后降低,与催化剂氧空穴浓度变化规律一致,说明催化剂活性受氧空穴浓度影响,氧空穴浓度升高,催化剂催化活性升高.     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

气相燃烧合成纳米复合粒子的形态与结构

在气相燃烧反应器中成功地合成了TiO₂-SiO₂、TiO₂-SnO₂复合粒子。TiO₂-SiO₂复合粒子中TiO₂以金红石型和锐钛型存在，SiO₂以无定型的形式存在。复合结构为SiO₂附着于TiO₂的外部，在Ti∶Si的进料比较大时SiO₂附着于TiO₂的表面，Ti∶Si比值减小到1∶4时，SiO₂包覆全部TiO₂表面。包覆层的厚度大约为6～7nm。TiO₂-SnO₂的复合粒子中同时存在着三种晶体结构SnO₂、金红石型和锐钛型的TiO₂。在复合粒子的表面，TiO₂和SnO₂两种组分分布均匀。通过改变进料方式可以调整复合粒子的结构。     

球形TiO2-Al2O3的制备、结构和理化性能研究

将Ti(SO₄)₂溶于稀盐酸合成酸性钛溶胶，再将其与铝溶胶和六次甲基四胺溶液混合后采用油柱成型法制备了球形TiO₂-Al₂O₃复合氧化物。通过XRD、低温氮吸附-脱附与NH₃-TPD等手段对样品进行表征，结果表明600 ℃焙烧得到的球形TiO₂-Al₂O₃中TiO₂以无定型形式存在;随TiO₂含量的增加，球形TiO₂-Al₂O₃的比表面积、孔容和平均孔径呈增加趋势;TiO₂的引入没有对球形TiO₂-Al₂O₃的强酸和弱酸中心的强度产生影响，弱酸中心数量显著增加，强酸中心数量稍有增加;球形TiO₂-Al₂O₃的堆密度和压碎强度随TiO₂含量的增加而减小，颗粒直径基本保持不变。     

部分还原氧化石墨烯/二氧化钛复合材料的水热合成及其光催化活性

采用水热法以Hummers氧化法制备的氧化石墨和钛酸四丁酯为原料制备了部分还原的氧化石墨烯/二氧化钛(RGO/TiO₂)复合光催化剂, 并研究了该复合材料在可见光以及紫外光下对亚甲基蓝的光催化降解活性.结果表明, 通过改变反应温度和氧化石墨加入量可以调控TiO₂的晶相组成及其在复合材料中的分散性; 在水热反应过程中氧化石墨烯发生了部分还原; 所制备的RGO/TiO₂复合材料的可见光和紫外光催化活性均高于纯TiO₂; 部分还原的氧化石墨烯在复合材料中担当载体和电子受体, 同时可以使TiO₂的初始吸收边向可见光区域红移, 增强了TiO₂在可见光区域的吸收, 能有效提高对目标污染物的吸附性和光催化降解活性.     

Electrochemically assisted photocatalysis on self-organized TiO2 nanotubes

In this work we investigate influence of an externally applied bias on the photocatalytic performance of self-organized TiO₂ nanotube layers. These layers were grown by anodization of titanium in fluoride containing electrolytes and have different geometric dimensions. Since the layers are grown directly on the Ti substrate, a very good electrical backside contact is directly provided. Therefore, we use the nanotube layers/Ti structures as photo-anodes for the UV light induced photocatalytic decomposition of acid orange 7. For comparison, we use TiO₂ nanopowder (Degussa P25) compacted also on a Ti sheet. The present results demonstrate that the photocatalytic activity of self-organized TiO₂ nanotube layers can significantly be increased by electrochemical bias.     

Photocatalytic oxidation of gaseous trichloroethylene by UV/TiO2 process

Summary The objective of this study was to investigate the reaction behavior of the photocatalytic oxidation of gaseous trichloroethylene (TCE) using titanium dioxide at room temperature. The experiments were carried out under various humidity levels and oxygen contents of carrier gas in an annular photoreactor. Experimental results indicated that the factors affecting the photocatalysis of TCE by UV/TiO₂ process are carrier gases and humidity. It was found that increasing the relative humidity in inlet gas flow under low humidity could improve the decomposition of trichloroethylene and the mineralization of organic intermediates at an irradiation UV light intensity of 2.82 W m^-2 by UV/TiO₂ process. The photocatalytic kinetics of gaseous trichloroethylene can be described by the Langmuir-Hinshelwood rate equation.     

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。     

光催化CO2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO₂引起的地球变暖和能源短缺已经成为一个严重的全球性问题. 利用太阳光和光催化材料将CO₂还原为碳氢燃料, 不仅可以减少空气中CO₂浓度, 降低温室效应的影响, 还可以提供碳氢燃料, 缓解能源短缺问题, 因此日益受到各国科学家的高度关注. 本文综述了光催化还原CO₂为碳氢燃料的研究进展, 介绍了光催化还原CO₂的反应机理, 并对现阶段报道的光催化还原CO₂材料体系进行了整理和分类, 包括TiO₂光催化材料, ABO₃型钙钛矿光催化材料, 尖晶石型光催化材料, 掺杂型光催化材料, 复合光催化材料, V、W、Ge、Ga基光催化材料及石墨烯基光催化材料. 评述了各种材料体系的特点及光催化性能的一些影响因素. 最后对光催化还原CO₂的研究前景进行了展望.     

硼铈共掺杂纳米TiO2光催化降解三氯杀螨醇和菊酯类农药

采用溶胶-凝胶法在钛酸丁酯水解过程引入硼酸、硝酸铈,制备具有光催化活性的硼铈共掺杂纳米二氧化钛（TiO2）,经XRD、TEM、FT-IR、UV-Vis-DRS表征晶体结构,在日光灯照射下,光催化降解三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯农药。结果表明：硼铈共掺杂的TiO2只有锐钛矿型,而纯的或掺铈的TiO2有含有锐钛矿型、金红石相和少量板钛矿型,UV-Vis-DRS测定结果表明硼铈共掺杂的TiO2禁带宽度变小,硼铈共掺杂的TiO2在可见光区吸光度高于掺杂铈和不掺杂的TiO2,在420nm~850nm有强的吸收;在同样光照下对三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯的降解试验证明硼铈共掺杂纳米TiO2的光催化活性高于不掺杂或只掺杂铈的TiO2。     

Surface Modification of a Magnetic SiO2 Support and Immobilization of a Nano-TiO2 Photocatalyst on It

This study presented an effective method to modify the surface chemical reactivity of a SiO₂/Fe₃O₄ support. The unmodified SiO₂/Fe₃O₄ support was prepared by the hydrolysis and condensation of tetraethoxysilane on the surface of hydrophilic Fe₃O₄ nanoparticles. These were then modified by a heat treatment in an ethanol/water solution under reflux. The resulting samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The immobilization of a TiO₂ nanocatalyst on both unmodified and modified supports was performed to investigate the effects of the modification of the magnetic silica support on the loading of a TiO₂ nanocatalyst and the photocatalytic activity. The loading of TiO₂ and the photocatalytic activity were both improved.     

Significant enhancement of the photoelectrochemical activity of TiO2 nanotubes

In the present work, we report on a facile and effective approach to significantly enhance the photocatalytic activity of TiO₂ nanotubes. The TiO₂ nanotubes prepared by the electrochemical oxidation of titanium in dimethyl sulfoxide (DMSO) with 2% HF were treated in a methanol solution under UV light irradiation. In comparison with the untreated TiO₂ nanotubes, the treatment resulted in a dramatic increase in the donor density of the TiO₂ nanotubes by approximately 3 orders of magnitude. The treated TiO₂ nanotubes exhibited a 15-fold enhancement in photocurrent and a 6.8-fold increase in the photoelectrochemical degradation of 4-nitrophenol, significant for hydrogen generation and wastewater treatment.     

SnO2/TiO2纳米管复合光催化剂的性能及失活再生

基于微波水热法和微乳液法合成SnO₂/TiO₂纳米管复合光催化剂. 通过X射线衍射（XRD）、配有能量色散X射线光谱仪（EDX）的透射电镜（TEM）和电化学手段对光催化剂进行表征. 以甲苯为模型污染物,考察光催化剂在紫外光（UV）和真空远紫外光（VUV）下的性能及失活再生. 结果表明,SnO₂/TiO₂纳米管复合光催化剂形成三元异质结（锐钛矿相TiO₂（A-TiO₂）/金红石相TiO₂（R-TiO₂）、A-TiO₂/SnO₂和R-TiO₂/SnO₂异质结）,促使光生电子-空穴对的有效分离,提高光催化活性. SnO₂/TiO₂表现出最佳的光催化性能,UV和VUV条件下的甲苯降解率均达100%,CO₂生成速率（k₂）均为P25的3倍左右. 但由于UV光照矿化能力不足,中间产物易在催化剂表面累积. 随着UV光照时间的增加,SnO₂/TiO₂逐渐失活,20 h 后k₂由138.5 mg·m^-3·h^-1下降到76.1 mg·m^-3·h^-1. 利用VUV再生失活的SnO₂/TiO₂,过程中产生的·OH、O₂^-·、O（¹D）、O（³P）、O₃等活性物质可氧化吸附于催化剂活性位的难降解中间产物,使催化剂得以再生,12 h后k₂恢复到143.6 mg·m^-3·h^-1. UV和VUV的协同效应使UV降解耦合VUV再生成为一种可持续的光催化降解污染物模式.     

Microwave-hydrothermal synthesis and photocatalytic properties of biomass charcoal/TiO2 nanocomposites

Biomass charcoal-doped titanium dioxide (C/TiO₂) composites were proposed by microwave-hydrothermal and calcination method using tetrabutyl titanate as the titanium source and lignin as the carbon source. TiO₂ crystals with different morphologies could be successfully adsorbed onto the surface of biomass charcoal. These products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), derivative thermogravimetric (DTG), UV–vis diffuser flection spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET). The photocatalytic activities of the as-obtained composites were checked under visible light irradiation. The results showed that both the microwave-hydrothermal temperature and time played an important role in the microstructure and photocatalytic activity of the samples. The rapid microwave-hydrothermal with the thermal post-treatment provides a promising route for the fabrication of biomass charcoal-doped nanocomposites materials.