【作者】 宋娟娟；

【导师】 黄唯平；

【作者基本信息】 南开大学 ， 无机化学， 2013， 博士

【摘要】 纳米Ti02因其无毒、价格低廉、化学稳定性好和优异的催化性能等特点被广泛用作净化环境的光催化材料、光电材料和催化剂载体等。与Ti02纳米颗粒相比,Ti02纳米管具有更大的比表面积,因此更适合做催化剂或催化剂载体。但是,作为光催化剂,由于Ti02具有较大的带隙能,对太阳光的利用率较低；此外,光激发产生的电子-空穴对易复合,导致其光量子效率很低。而作为热催化剂,水热法制备的Ti02纳米管的热稳定性较差。降低Ti02的带隙能、抑制光生电子-空穴对的复合,以及提高TiO2的热稳定性来提高Ti02的催化性能,一直是科研工作者关注的研究课题。针对以上问题,本文采用不同的制备方法,合成了一系列在紫外和可见光区具有高催化活性的修饰Ti02纳米管光催化材料,以及结构性能稳定的热催化剂。在光催化实验中,以甲基橙为目标降解物研究催化剂的光催化性能。本论文的具体研究内容主要包括以下方面：以钛酸丁酯为前躯体,廉价易得的蔗糖为碳源,采用溶胶-凝胶法和水热法相结合的方法制备了掺碳量不同的TiO2纳米管光催化剂(C/TiO2NTs)。通过EA、XRD、TEM、UV-vis-DRS等手段对所制备的催化剂进行表征分析。研究了C/TiO2NTs在紫外光及模拟日光条件下光催化降解甲基橙的活性,还讨论了焙烧温度和碳含量对催化性能的影响。结果表明：碳修饰TiO2光催化剂的禁带宽度变窄,在可见光区吸收增强；TiO2在紫外和可见光下的光催化活性明显提高,而且当焙烧温度为400℃、碳含量为0.90wt.%时,C/TiO2NTs样品的光催化活性最好。以钛酸纳米管为载体、Ru3(CO)12和C5H5Mn(CO)3为前躯体,采用浸渍-沉积一步法分别制备了Ru-C共修饰和Mn-C共修饰的TiO2光催化剂(Ru-C/TiO2, Mn-C/TiO2NTs)。通过XRD、TEM、UV-vis和XPS对催化剂进行表征,探讨了共修饰元素对提高TiO2光催化活性所起的协同作用。结果表明,在Ru-C/TiO2催化体系中,Ru-C/TiO2催化剂在500℃焙烧时,TiO2纳米管的管状结构被破坏,但锐钛矿型TiO2结晶度增大,且出现了少量的金红石型TiO2,其混晶型结构利于催化活性的提高；在TiO2的表面均匀分布着3-7nm的Ru02纳米颗粒；Ru-C/TiO2催化剂中的碳主要是以活性炭和碳酸盐的形式存在,有利于可见光的吸收,修饰的钉是以RuO2的形式沉积在TiO2的表而,有利于光生电子-空穴对的分离；Ru和C元素共修饰时,两者的协同效应使Ti02的带隙变得更窄,易激发产生更多的光生电子和空穴。而且Ru、C的修饰量、焙烧温度及焙烧气氛对催化剂的光催化活性都有一定的影响。在N2气氛下焙烧温度为500℃, Ru/C摩尔比为1.65的Ru-C/TiO2在紫外光和模拟可见光下的光催化活性最好,且优于P25的活性。在Mn-C/TiO2NTs催化体系中,比表面积随着焙烧温度的升高而减小,400℃焙烧的催化剂中,Ti02纳米管多数以管束聚集的状态存在；修饰的碳和锰分别以碳酸盐和MnxOy/Mn的形式存在于TiO2表面；降低了TiO2的带隙能。另外,锰、碳共修饰的协同效应大大提高了TiO2在紫外光和可见光下的催化性能,在N2气氛下焙烧温度为400℃,Mn、C含量分别为0.15wt.%和1.08wt.%时,Mn-C/TiO2NTs在紫外和可见光下的光催化活性最高。所用制备方法比较简单,而且都是在不额外引用碳源的条件下直接利用前躯体来实现金属与碳元素的共修饰,为金属与非金属共修饰TiO2的制备提供了新的思路。利用两步溶胶-浸渍法制备了结构稳定的C-Fe共修饰稳定TiO2纳米管催化剂(C-Fe/TiO2NTs)。由TEM图片得知,当焙烧温度达到400℃时TiO2还能保持较好的管状结构。通过XPS数据显示,修饰的碳没有取代TiO2中的晶格氧,大部分是以碳酸盐类物质吸附在TiO2的表面；通过UV-vis分析可知,C-Fe共修饰的协同效应使TiO2纳米管的带隙能降低,提高了对太阳光的利用率。催化性能测定结果表明：C-Fe共修饰稳定TiO2NTs的光催化性能优于纯TiO2NTs、C或Fe单独修饰TiO2NTs的催化性能,当焙烧温度为400℃、碳含量为1.45wt.%时,C-Fe/TiO2NTs具有最佳的光催化活性。以稳定TiO2纳米管为载体,IrCl3·3H2O以及蔗糖和IrCl3·3H2O为前躯体,采用一步直接浸渍-沉积法分别得到铱修饰(Ir-TiO2)及碳、铱共修饰的纳米TiO2光催化剂(C-Ir/TiO2)。通过表征、测试分析可知,铱修饰及碳、铱共修饰都拓宽了Ti02在可见光区的响应范围,降低了Ti02的带隙能,而且都提高了Ti02在紫外和可见光下降解甲基橙的催化活性。当焙烧温度为400℃、铱含量为2.77wt.%时,Ir/TiO2的光催化活性最好；碳、铱共修饰的协同效应使其光催化性能优于C或Ir单独修饰TiO2NTs,当焙烧温度为400℃、碳含量为1.24wt.%时,C-Ir/TiO2的光催化活性最好。以钛酸纳米管为载体,利用氢氧化铜水溶胶浸渍修饰法制备了结构稳定的CuO修饰Ti02纳米管催化剂(CuO/TiO2NTs)。通过XRD、TEM和XPS等手段对催化剂进行表征。初步探讨了焙烧温度和铜钛不同原子比对催化氧化CO的活性影响。研究表明：铜钛原子比及焙烧温度对催化剂的活性有明显影响,当焙烧温度为300℃、Cu/Ti原子比为1：2时,CuO/TiO2NTs的活性最高。对催化剂活性的其它影响因素及催化原理等还需进一步研究。更多还原

【Abstract】 Titania (TiO2) has received considerable attention due to its nontoxicity, low cost, high chemical stability and high photoactivity, and was widely used in many applications such as photocatalytic materials, photolectric materials and catalyst support. Compared with TiO22nanoparticles, TiO2nanotubes were more suitable to be utilized as catalyst or catalyst support due to their nanotubular morphologies and higher surface areas. However, wide bandgap, low utilization rate of solar energy, quick recombination of photogenerated electron-hole pairs resulted in low light quantum efficiency of TiO2nanotubes. Moreover, TiO2nanotubes obtained by hydrothermal process had bad structure stability for thermal catalysts. It had been a long-term issue for researchers to improve catalytic performancs of TiO2by reducing the bandgap, inhibiting the recombination of photogenerated electron-hole pairs and increasing the thermal stability of TiO2nanotubes. To overcome the drawbacks of TiO2mentioned above, a series of high catalytic activity and high thermal stability of doped TiO2nanotubes were prepared with different preparation methods in this thesis. The photocatalytic performances of products were evaluated by monitoring their catalytic activities for degradation of methyl orange solution under UV light and simulated sunlight irradiation in the photocatalysis experiments. The primary work was as follows:Using tetrabutyl titanate and sucrose as precursors, carbon-modified TiO2nanotubes (C/TiO2NTs) with various carbon contents were prepared by the combination of sol-gel process with hydrothermal treatment. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectroscopy. The influences of calcination temperature and carbon content on catalytic performance of C/TiO2NTs were also discussed. The results indicated that TiO2in the catalysts was anatase. The doped carbon narrowed the band-gap width and increased absorption in the visible range. Compared with pure TiO2nanotubes, C/TiONTs could significantly enhance the photocatalytic efficiency, and the0.90wt.%C/TiO2NTs calcined at400℃exhibited the best photocatalytic activity.Using TiO2NTs as support, Ru3(CO)12and C5H5Mn(CO)3as modification precursor, Ru-C co-modified TiO2nanotubes (Ru-C/TiO5NT5) and Mn-C co-modified TiO2nanotubes (Mn-C/TiO2NTs) were prepared respectively via impregnation-deposition method. The products were characterized with TEM, XRD, UV-vis and XPS, and the synergistic effect comodification elements how to increase the photocatalytic activities were discussed. In the Ru-C/TiO2catalytic system, the conclusions were listed as follows:XRD results showed that although the tubular structure was destroyed calcined at500±, the crystallinity of anatase phase was increased, and appeared the phase transition of small amount anatase to rutile, which was beneficial to improve the catalytic activity. TEM images revealed RuO2nanoparticles with a diameter of3-7nm were uniformly deposited on the surface of TiO2. XPS results revealed that the carbon in Ru-C/TiO2existed as active carbon and carbonate, which benefit the visible light absorbtion, and ruthenium existed as RuO2, which benefit the photo generation electron-hole pairs separation. To the ruthenium and carbon co-modified TiO2, the Ru-C synergistic effect could largely narrow the band gap of TiO2and easily energize more photogenerated electrons and holes. The influences of calcination temperature, calcination atmosphere and contents of C and Ru on the photocatalytic activity of the samples were investigated. Obtained results showed that Ru-C/TiO2NTs exhibited higher photocatalytic activity than P25under UV or simulated sunlight irradiation when Ru and C mole ratio was1.65and calcinated at500±in N2atmosphere.In the Mn-C/TiO2catalytic system, the conclusions were listed as follows:TEM images revealed the specific surface area of TiO2NTs were decreased with the increase of calcinations temperature and exist nanotubes structure with bundles gather state. XPS results revealed that the carbon existed as carbonate, and manganese existed as MnxOy/Mn on the surface of TiO2respectively. UV-vis results revealed that the badgap of TiO2were decreased. To the manganese and carbon co-doped TiO2, the Mn-C synergistic effect could largely enhance the photocatalytic performance under UV light and simulated sunlight irradiation. When the manganese and carbon content were0.15wt.%and1.08wt.%respectively and calcinated at400 ℃, Mn-C/TiO2NTs exhibited the good photocatalytic activities under UV and simulated sunlight irradiation. The preparation method was simple, and achieved the metal and carbon codoping with the modification precursor and without additional carbon source. The method would provide new thought for preparing metal and nonmetal co-modified TiO2.The target product C-Fe co-modified TiO2nanotubes (C-Fe/TiO2NTs) with high thermal stability were successfully synthesized via two-step sol-impregnation method. TEM images showed the better tubular structure of TiO2calcinatied at400℃. XPS results revealed that carbon did not substitute oxygen atom in the lattice of anatase TiO2and the most carbon existed as carbonate. The results revealed that the synergistic effect of C and Fe co-modified could not only decrease the band-gap energy of TiO2nanotubes, but also inhibit recombination of photo generation electron-hole pairs. The photocatalyic performance of C-Fe/TiO2NTs was superior to the activities of TiO2NTs, C-TiO2NTs and Fe-TiO2NTs. When the carbon content was1.45wt.%and calcinated at400℃, C-Fe/TiO2NTs exhibited the best photocatalytic activity.Using stable TiO2NTs as support, IrCl3·3H2O, sucrose and IrCl3·3H2O as modification precursor, Ir modified TiO2(Ir-TiO2) and C-Ir co-modified TiO2(C-Ir/TiO2NTs) were prepared respectively via impregnation-depbsition.The products were characterized with TEM, XRD, UV-vis and XPS. UV-vis results revealed that Ir modified TiO2and C-Ir comodifed TiO2both could broaden the light response range, reduce the bad gap, and enhance the photacatalytic activities to degrade methyl orange solution under UV light and simulated sunlight irradiation. The2.77wt.%Ir-TiO2NTs calcinated at400℃exhibited the best photocatalytic activity. The photocatalytic performances of C-Ir/TiO2were superior to C-TiO2and Ir-TiO2because of the synergistic effect of carbon and Irdium comodified TiO2. When the carbon content was1.24wt.%and calcinated at400℃, the C-Ir/TiO2NTs exhibited the best photocatalytic activity.By using hydrogen titanate nanotubes as support, CuO modified-TiO2nanotubes (CuO/TiO2NTs) with high thermal stability were prepared by impregnation method. The prepared materials were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Their catalytic performances for low-temperature CO oxidation were preliminary discussed. The atomic ratio between Cu and Ti and calcination temperature were also investigated. When the atomic ratio of Cu and Ti was1:2and calcined at300℃, the CuO/TiO2NTs exhibited the best catalytic performance. Other influence factors for catalytic performance and the catalytic principle need to be further researched.更多还原