Fe掺杂TiO_2和Fe_2O_3量子点共负载催化剂:吸附与光催化协同作用高效降解有机染料（英文）

摘要:光催化作为节能、清洁的环境处理技术,被广泛应用于污染物处理领域,如室内气体净化、尾气VOCs处理和水体有机污染降解等.在众多光催化剂中,Ti O_2以其良好的化学稳定性、无二次污染、无刺激性和安全无毒等优势得到广泛研究.然而Ti O_2是宽禁带材料,仅能吸收太阳光谱的紫外光部分,通常需要用紫外光源来激发,光生电子-空穴易复合,这限制了其应用.过渡金属离子掺杂能在Ti O_2价带之上形成新的掺杂能级,从而提高其光谱响应范围,提高全光谱反应活性;与体相Ti O_2相比,纳米尺寸的Ti O_2具有更高的光催化活性,尤其小于10 nm的量子点尺寸Ti O_2有着高活性面积、较短的光生电子-空穴迁移路径和独特的量子尺寸效应;Fe_2O_3作为吸附材料与Ti O_2构建复合材料能够发挥吸附与光催化协同作用,从而提高污染物处理效率.我们以构建Fe掺杂Ti O_2和Fe_2O_3量子点共负载催化剂为目标,以钛酸四丁酯(TBT)和硫酸亚铁为前驱体,采用常温水解方法将Fe掺杂的Ti O_2量子点生长在MCM-41分子筛表面,并通过调节硫酸亚铁加入量合成了MCM-41负载的Fe掺杂Ti O_2和Fe_2O_3量子点催化剂.采用透射电子显微镜和X射线衍射研究了复合晶体结构,采用X射线光电子能谱、紫外-可见光谱和傅里叶变换红外光谱等表征手段研究了复合量子点材料生长机理和能带结构.结合吸附过程和光降解过程建立了吸附与光催化协同作用与污染物处理效率之间的关联关系.表征结果表明,硫酸亚铁水溶液加速TBT水解成功地在MCM-41表面生长了Fe掺杂Ti O_2量子点,并且量子点粒径随Fe前驱体量的增加而变大;前驱体比例Ti/Fe≤3.0时,过量的硫酸亚铁会析出并在焙烧过程中在MCM-41上分解为Fe_2O_3量子点,Fe_2O_3量随着硫酸亚铁加入量提高而增多.通过调节Fe前驱体的量,一方面Fe掺杂在二氧化钛价带之上形成了掺杂能级,减小了带隙,拓宽了光响应范围,另一方面引入适量Fe_2O_3量子点,实现了Fe掺杂Ti O_2和Fe_2O_3量子点共负载催化剂的构建.复合材料实现了吸附过程与光催化降解过程的协同作用,Fe_2O_3将污染物富集于催化剂表面,Fe掺杂Ti O_2将其有效降解,大大提高了污染物处理能力,其中FT/M-3.0处理效率最高,并在10次循环处理后依然维持较高的吸附能力和光催化降解能力.该工作为高效光催化水处理催化剂的设计和构建提供了新思路和策略.     

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.     

Fe3+掺杂TiO2光催化降解聚乙烯薄膜的研究

以快速溶胶-凝胶法制备了纳米TiO2光催化剂,并用Fe3 对其掺杂改性,在室温条件下,用于固相光催化降解聚乙烯(PE)包装薄膜的研究.对催化剂和薄膜进行了X衍射分析(XRD)、傅立叶红外光谱分析(FT-IR)、扫描电子显微镜(SEM)形貌观察.结果表明,60W紫外光辐射240h后,PE失重为8.43%,锐钛矿型纳米TiO2光催化剂使PE失重30.66%;用Fe3 掺杂后,0.5?2O3/TiO2、1.0?2O3/TiO2和2.0?2O3/TiO2分别使PE失重35.91%、20.72%和13.30%.光催化剂加速了PE的失重,碳链的断裂和光氧化腐蚀,在薄膜表面形成大量的坑洞,降解产物中的小分子量的石蜡含量明显增高.Fe3 掺杂有一个最佳量,0.5?2O3/TiO2光催化降解PE的活性最高.     

Sm2O3掺杂TiO2光催化剂的制备和性能

 采用溶胶-凝胶法制备了Sm2O3掺杂TiO2光催化剂,通过X射线衍射、程序升温脱附和漫反射紫外-可见光谱等手段对催化剂进行了表征,并以苯酚为光催化降解反应模型化合物考察了光催化剂的活性,测定了苯酚在TiO2和Sm2O3掺杂TiO2光催化剂上的吸附常数. 结果表明,Sm2O3掺杂TiO2光催化剂具有较强的紫外光吸收性能. Sm2O3掺杂使TiO2粒径减小,比表面积增大,同时导致氧脱附温度提高及脱氧量增大. Sm2O3掺杂有利于反应底物在催化剂表面的吸附,Sm2O3的最佳掺入量为Sm/Ti摩尔比=0.8%.     

Fe2O3掺杂TiO2薄膜对甲基紫溶液光催化降解

光降解;Fe2O3掺杂TiO2薄膜对甲基紫溶液光催化降解     

Fe3+掺杂TiO2光催化纤维材料的制备及表征

以棉花纤维为模板制备了一系列Fe3+掺杂的、具有中空纤维结构的TiO2光催化材料(Fe3+/TiO2), 利用热重分析(TG)、扫描电子显微镜(SEM)、X射线衍射(XRD)、zeta电位、红外光谱(IR)和紫外-可见光谱(UV-Vis)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. 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Fe3+掺杂量的样品在太阳光下的光催化性能. 结果表明, 用模板法制备的Fe3+/TiO2中空纤维结构材料表面存在大量纳米微粒(平均尺寸约12 nm); Fe3+可能均匀分散于锐钛矿结构的TiO2中, 部分取代Ti4+的晶格位置, 既拓宽了TiO2的光谱响应范围, 又形成了TiO2晶体结构的缺陷, 使其表面带负电荷. 在太阳光条件下, 该纤维结构材料较纯TiO2对MB溶液具有更好的光催化脱色降解效果, 且Fe3+的掺入量显著影响该纤维材料的催化性能; 当Fe3+掺杂量为0.15%(w), 在500 ℃焙烧2 h所得中空纤维材料的催化性能最好, 2 h即可使MB溶液的脱色降解率达93%; 重复使用5次仍可使MB溶液的脱色降解率保持在90%以上, 且该催化剂材料易于离心分离去除. 因此, 以该模板合成法, 通过Fe3+的掺杂有望使TiO2成为一种低或无能耗、高活性的绿色环保型催化材料.     

金属离子掺杂的TiO2薄膜的制备及其光催化降解甲苯的性能

 采用溶胶-凝胶法制备了负载于铝板上掺杂金属离子的TiO2薄膜光催化剂,并通过空气中甲苯光催化降解实验评价了其光催化活性. 结果表明,Pt和Fe的掺杂对TiO2薄膜的光催化活性起促进作用,甲苯降解率分别提高了17%和6%; Ag的掺杂引起催化剂失活; Mn的掺杂未对TiO2薄膜的光催化活性起明显促进作用. XRD结果表明,掺杂金属离子前后TiO2均为锐钛矿相; TEM观察到薄膜催化剂微观结构为球形颗粒,粒径分布均匀,平均粒径为19 nm; 紫外漫反射光谱表明,Pt-TiO2薄膜催化剂的反射率几乎为0,表明其对光的吸收能力很强,因而Pt掺杂的TiO2薄膜光催化降解甲苯的活性最高.     

TiO2/BixTiyOz气相光催化降解苯的动力学模型及反应机理

在密闭不锈钢反应器内考察了TiO2/BixTjyOz催化剂气相光催化降解苯的性能.结果表明,TiO2负载于Bi12TiO20,Bi2Ti2O7和Bi4Ti3O12上制成的催化剂,光催化活性得到很人的提高,TiO2最佳负载量为2.0%;其中,TiO2/Bi12TiO20的光催化活性最高,苯最高转化率是纯TiO2的2倍,催化剂使用寿命也延长了1倍.在本文实验条件下,TiO2/Bi12TiO20上苯气相光催化降解符合Lang-muir-Hinshelwood动力学模型,光催化反应速率常数k和Langmuir吸附常数K分别为0.006 4mg/(L·min)和9.670 2L/mg.采用红外光谱对失活的催化剂进行表征,结果表明催化剂表面出现了羰基与羟基等的振动峰,同时检测到主要的中间产物是2,6-二叔丁基-4-甲基苯酚,它吸附在催化剂表面活性化上而导致催化剂失活.最后推测了苯在催化剂表面气相光催化降解的反应机理.     

Fe、N共掺杂TiO2纳米管阵列的制备及可见光光催化活性

应用电化学阳极氧化法结合浸渍和退火后处理制备了Fe和N共掺杂的TiO2纳米管阵列光催化剂,并用场发射扫描电镜(FESEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和俄歇电子能谱(AES)仪对其进行了表征.结果表明,Fe、N共掺杂对TiO2纳米管阵列的形貌和结构没有明显影响,Fe和N均掺入了TiO2晶格.紫外-可见(UV-Vis)漫反射光谱显示Fe和N共掺杂TiO2纳米管阵列的吸收带边较纯TiO2纳米管阵列和单一掺杂TiO2纳米管阵列红移,可见光吸收增强.以可见光催化降解罗丹明B(RhB)考察了材料的光催化活性,Fe和N共掺杂TiO2纳米管阵列对RhB的降解速率较纯TiO2纳米管阵列和单一掺杂TiO2纳米管阵列明显提高,证明了Fe、N共掺杂产生的协同效应提高了TiO2纳米管阵列在可见光照射下的光催化活性.     

Spontaneous vesicles, disks, threadlike and spherical micelles found in the solubilization of DMPC liposomes by the detergent DTAC

Iron oxide/MCM-41 nanocomposites, Fe(2)O(3)/MCM-41, containing 5%, 10%, and 20% (w/w) iron oxide, were prepared via a direct nonhydrothermal method at room temperature. The preparations were preformed by using iron(III) nitrate, tetra-ethoxysilane (TEOS), and cetyltrimethylammonium bromide (CTAB) mixed or unmixed with dodecyltrimethylammonium bromide (DTAB). The produced materials were dried and calcined at 550 °C for 3 h. Test materials were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), N(2) gas adsorption/desorption isotherms, small angle and wide angle X-ray diffraction (XRD). Results indicate that mixing of CTAB with DTAB does not harm the formation of blank MCM-41 structure. For the composite Fe(2)O(3)/MCM-41 materials, results showed formation of more stable MCM-41 structure with higher surface area and improved porosity in the presence of mixed (CTAB+DTAB) than in the presence of single (CTAB) surfactants for up to 10% Fe(2)O(3)/MCM-41 (w/w). This was explained in terms of the effect DTAB on contraction of the template micellar size to compensate for the expected size expansion upon the addition of ionic iron(III) nitrate precursor. Highly dispersed Fe(2)O(3) nanoparticles were formed in all cases even with the highest iron oxide percentage. Formation of the nanocomposites was postulated to be determined by fast nucleation and slow growth of iron oxide species, which facilitated formation of well dispersed iron oxide nanoparticles inside and on the wall of the MCM-41 material.     

Facile synthesis of the cubic mesoporous material MCM-48. Detailed study of accompanying phase transformations

The synthesis of cubic mesoporous material MCM-48 has been simplified and can be accomplished via facile hydrothermal synthesis using convenient commercial reagents. The cubic structure evolves from the initially formed hexagonal MCM-41 and undergoes slow conversion to the lamellar MCM-50 precursor. The system was sampled at 1 hr intervals and the intermediate products characterized by elemental analysis, X-ray powder diffraction and adsorption. The results are discussed from the standpoint of possible mechanisms of MCM-48 generation.     

CO2 adsorption over Si-MCM-41 materials having basic sites created by postmodification with La2O3

Moderate basic sites could be created onto mesoporous Si-MCM-41 materials by postsynthesis modification with highly dispersed La2O3. The La2O3-modified MCM-41 materials (designated here as LaM) have been characterized by Fourier transform infrared spectroscopy, temperature-programmed desorption, X-ray photoelectron spectroscopy, X-ray diffraction (XRD), and N2 adsorption/desorption and have been tested as model adsorbents for CO2 adsorption. XRD and N2 adsorption results showed that all LaM materials still maintained their uniform hexagonal mesoporous structure even after postsynthesis modification with La2O3 loading up to 20 wt %. Although the surface area, pore size, and pore volume of LaM materials decreased with increasing La2O3 loading, their capacity for CO2 storage could be significantly improved when La2O3 loading was increased from 0 to 10 wt %. Unidentate and bidentate carbonates have been identified by in situ FTIR as the two types of CO2 species adsorbed on LaM surface. The LaM material also possesses good thermal stability, allowing the model adsorbent to be regenerated at high temperature and recyclable.     

基于MCM-41模板制备β-MnO_2纳米纤维及其催化降解亚甲基蓝染料

以介孔氧化硅材料MCM-41为模板,硝酸锰为锰源,通过浸渍、450℃焙烧4 h得到Mn-MCM-41,用NaOH溶液溶解除去氧化硅模板得到锰氧化物,采用XRD,HRTEM和N2吸附-脱附等测试技术对产物进行了表征.结果表明,所得产物是纯相的β-MnO2纳米纤维,直径小于3 nm.纳米纤维之间有序排列组成类似MCM-41模板的介孔结构,其比表面积达到136.5 m2/g.将所制备的β-MnO2纳米纤维用于催化过氧化氢氧化分解质量浓度为60 mg/L的亚甲基蓝(MB)模拟染料废水,经100 min反应后,亚甲基蓝水溶液脱色率达到97.59%.所制备的催化剂对降解处理高浓度亚甲基蓝溶液,具有降解脱色率高和反应速度快等优点.     

Formation Process of MCM-41 Precursor and Porous Texture of MCM-41

The formation process of the MCM-41 precursors (silicate/surfactant complex) was investigated on the basis of the pH titration curves of Na(4)SiO(4) in the presence of [C(16)H(33)N(CH(3))(3)]Cl. Measurements of the pH titration curves were carried out using the computer-controlled gravimetric titrator constructed in our laboratory. The white precipitate (MCM-41 precursor) was abruptly formed at pH 11.1 (298 K) and at pH 9.9 (343 K). Formation of the MCM-41 precursor can be explained by coagulation of the rod-like micelle colloids whose surface is covered by the condensed silicate anions of (HSiO(3))(n)(n-). The porous texture of the MCM-41 samples whose precursors were synthesized under different conditions was analyzed on the basis of the adsorption isotherms of nitrogen at 77 K. It has been shown that the MCM-41 sample whose precursor was prepared at pH 9.9 and 343 K shows one sharp peak (r(p) = 1.65 nm) in the pore size distribution curve, but the MCM-41 samples whose precursors were prepared at pH 6.5-5.0 and 343 K give two peaks (r(p) = 1.66 nm and r(p) = 2.12-2.36 nm). The appearance of the second peak (r(p) = 2.12-2.36 nm) has been considered to be in connection with the destruction of the MCM-41 precursor into small fragments in acidic medium. Copyright 2000 Academic Press.     

Atomistic model of micelle-templated mesoporous silicas: structural, morphological, and adsorption properties

The structural, morphological, and adsorption properties of MCM-41 porous silicas are investigated using a realistic numerical model obtained by means of ab initio calculations [Ugliengo, P.; et al. Adv. Mater.2008, 20, 1]. Simulated X-ray diffraction, small angle neutron scattering, and electronic microscopy for the atomistic model are in good agreement with experimental data. The morphological features are also assessed from chord length distributions and porous volume and specific geometrical surface calculations, etc. The N(2), CO(2), and H(2)O adsorption isotherms in the atomistic model of MCM-41 are also in reasonable agreement with their experimental counterpart. An important finding of the present work is that water forms a film adsorbed on specific hydrophilic regions of the surface while the rest of the surface is depleted in water molecules. This result suggests that the surface of MCM-41 materials is heterogeneous, as it is made up of both hydrophilic and hydrophobic patches. While adsorption and irreversible capillary condensation can be described using the thermodynamical approach by Derjaguin (also known as the Derjaguin-Broekhoff-De Boer model), the Freundlich equation fits nicely the data for reversible and continuous filling in small pores.     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价, 并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3, PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能. 发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性. 实验结果表明, 纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原, 导致铂金属分散度和催化剂的丙烷脱氢活性较低. 用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用, 提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性. 并且, 积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度, 故具有较高的丙烷脱氢反应稳定性. PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能可能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关, 而且与Al2O3/MCM-41载体的介孔结构有关.     

高纯度中孔分子筛MCM-41的合成与表征

用不同pH值的混合物制备了不同孔径的全硅MCM-41和不同金属离子取代的M-MCM-41(M=Al,Mn,Fe和V)分子筛.这些试样均呈现MCM-41的X射线粉末衍射特征峰和Ⅳ型氮气吸附等温线,但混有不同含量的无定形氧化硅.样品中MCM-41晶体的含量与溶胶的pH值和所用表面活性剂的碳链链长有关.骨架硅的金属离子取代降低了MCM-41的有序度,并且(100)面衍射峰强度从Al到V依次减弱.     

Preparation of MnCo/MCM-41 catalysts with high performance for chlorobenzene combustion

MCM-41 was synthesized by a soft template technique. The specific surface area and pore volume of the MCM-41 were 805.9 m²/g and 0.795 cm³/g, respectively. MCM-41-supported manganese and cobalt oxide catalysts were prepared by an impregnation method. The energy dispersive X-ray spectroscopy clearly confirmed the existence of Mn, Co, and O, which indicated the successful loading of the active components on the surface of MCM-41. The structure and function of the catalysts were changed by modulating the molar ratio of manganese to cobalt. The 10%MnCo(6:1)/MCM-41 (Mn/Co molar ratio is 6:1) catalyst displayed the best catalytic activity according to the activity evaluation experiments, and chlorobenzene (1000 ppm) was totally decomposed at 270 °C. The high activity correlated with a high dispersion of the oxides and was attributed to the exposure of more active sites, which was demonstrated by X-ray diffraction and high-resolution transmission electron microscopy. The strong interactions between MnO₂, Co₃O₄, MnCoO_x, and MCM-41 indicated that cobalt promoted the redox cycles of the manganese system. The bimetal-oxide-based catalyst showed better catalytic activity than that of the single metal oxide catalysts, which was further confirmed by H₂ temperature-programmed reduction. Chlorobenzene temperature-programmed desorption results showed that 10%MnCo(6:1)/MCM-41 had higher adsorption strength for chlorobenzene than that of single metal catalysts. And stronger adsorption was beneficial for combustion of chlorobenzene. Furthermore, 10%MnCo(6:1)/MCM-41 was not deactivated during a continuous reaction for 1000 h at 260 °C and displayed good resistance to water and benzene, which indicated that the catalyst could be used in a wide range of applications.     

A new palladium nanoparticle catalyst on mesoporous silica prepared from a molecular cluster precursor

A promising approach to the controlled synthesis of supported nanoparticles involves the use of molecular carbonyl clusters as precursors. Molecular metal clusters consist of a defined number of structurally ordered atoms, and active monodisperse metal particles are formed after dispersing the molecules and removing the ligands. An octanuclear palladium cluster precursor with easily displaceable ligands was used to generate palladium nanoparticles on mesoporous MCM-41. The molecular cluster precursor, [Pd8(CO)8(PMe3)7], was directly adsorbed from solution onto MCM-41, followed by gentle thermolysis which yielded small metal nanoparticles. Compared to MCM-41-based catalysts prepared from palladium salts by conventional methods, this cluster-derived palladium catalyst has shown an efficient activity for liquid-phase hydrogenation of alkenes.