【作者】 钟雪春；

【导师】 潘湛昌； 魏志钢；

【作者基本信息】 广东工业大学 ， 化学工程， 2011， 硕士

【摘要】 TiO2由于具有化学性质稳定、抗光腐蚀、无毒和成本低等优点,在光转化和光催化领域具有广阔的应用前景。但是,Ti02的禁带宽度较大,需要在紫外光照射下才能表现出光催化活性。为了增强Ti02可见光吸收和提高Ti02光催化效率,本论文采用溶胶凝胶法制备了过渡金属第一过渡系24-30号过渡金属离子掺杂Ti02,利用X-射线衍射(XRD)、紫外-可见漫反射吸收光谱(UV-Vis)、比表面积测试等表征手段研究了Ti02晶体结构、光吸收性能,比表面积等性能。同时制备了泡沫镍负载型Mn掺杂Ti02作为正极,碳棒作为负极,以三价砷为目标氧化物,以紫外灯(主波长253.7nm)为光源,进行光电催化实验,测试催化剂的催化活性。Mn/TiO2的UV-Vis表征结果表明：催化剂制备过程,离子掺杂浓度取1.5%(摩尔含量),焙烧温度取500℃,焙烧时间均3h时光吸收性能得到最大改善。由过渡金属离子掺杂TiO2光谱吸收图可知,过渡金属离子掺杂Ti02后,可见光吸收相比于纯Ti02均有所增强,在500nm附近增强程度按Cr3+, Mn2+, Cu2+, Co2+, Ni2+, Fe3+, Zn2+)顺序递减。XRD测试结果表明：掺杂对催化剂晶型结构影响不大,掺杂前后催化剂都保持了锐钛矿晶型,掺杂后未出现掺杂离子的特征峰可能是掺杂量太小的原因。比表面测试结果表明各种催化剂比表面积的大小顺序为Cr/TiO2> Mn/TiO2> Ni/TiO2> Cu/TiO2>Co/TiO2>Zn/TiO2>Fe/TiO2。金电极溶出伏安法测三价砷所得标准曲线线性度较好,光催化活性测试结果表明：光电催化降解三价砷效果优于光催化降解,原因是通电可以阻碍光催化剂的光生电子和空穴复合；Mn掺杂TiO2后催化活性增强,原因是Mn掺杂后使Ti02比表面积增大,光吸收增强。用密度泛函理论方法计算研究了Mn、Cu掺杂Ti408,讨论了掺杂对Ti02晶体结构、能带结构、态密度、轨道和光学性质的影响。结果表明：Mn掺杂Ti02后价带变宽,导带发生较大下移,同时在价带和导带之间增加了杂质能级,使禁带宽度变小,电子激发需要的能量变小。同时进行了Mn掺杂Ti02的实验研究,实验测得的光谱吸收结果与理论计算结果一致,就是掺杂后可见光吸收增强,Cu掺杂后表现了和Mn掺杂类似的效果。过渡金属掺杂Ti16032超晶胞计算筛选出Mn为过渡金属最佳掺杂元素。更多还原

【Abstract】 Titanium dioxide(TiO2) has been considered as one of the most promising materials for its application in photocatalysis and photo conversion because of its high chemical stability, corrosion resistance, nontoxicity and low cost. However, it shows photo catalytic activity only under the UV irradiation due to its wide band gap(3.0-3.2eV). In order to improve the photocatalytic activity or extend the photo absorption to the visible light region, in this paper, transition metal(element 24 to 30) ion doped TiO2 had been prepared by sol-gel method. X-Ray diffraction, UV-Vis absorption spectrum, BET method were used to understand the crystallization behavior, optical property and specific surface area. By using Mn/TiO2 thin film deposited on porous nickel as positive electrode, carbon rod as negative electrode, arsenic as as target oxidation material, UV lamp(λ=253.7nm) as light source, experiments had been done to test the catalytic activity.The results of UV-Vis scanned by Mn/TiO2 indicated that catalysts showed the best optical properties when ion molar fraction was 1.5%, calcining temperature was 500℃, calcining time was 3h. UV-visible spectra of TiO2 doped with various transition metal ions showed that the absorption of the doped TiO2 had been improved in the visible-light range, the degree of improvement were decreasing by Cr3+, Mn2+, Cu2+, Co2+,Ni2+, Fe3+, Zn2+. The results of XRD showed that TiO2 and doping TiO2 were anatase crystal, and there were no typical characteristic diffraction peaks of doping ions because of the low doping rates. BET results showed that the display order of specific surface area was Cr/TiO2>Mn/TiO2> Ni/TiO2>Cu/TiO2> Co/TiO2>Zn/TiO2>Fe/TiO2.The standard curve of arsenite determined by electrochemical stripping voltammetry had the best linearity. Photocatalytic activity evaluation indicated that degradation of arsenite by photoelectrocatalytic method was better than photocatalytic method because electrifying could hinder the reuniting of photogenerated electron and photogenerated hole. Catalytic activity of Mn/TiO2 inhenced because of the increasment of BET and optical absorption.Using density function theory, pure TiO2, Mn/TiO2 and were calculated to investgate the geometry, the band structure, the electronic density of states, the orbit and the optical properties. The results indicated that the hybridization between O-2p and Mn-3d lead to some new bands between valence bands and conduction bands, besides, the valence bands become wider and the conduction bands shift downwards in Mn doped anatase TiO2, These changs lead to the narrowing of band gap and a red shift of the absorption band in Mri/TiO, experiments of Mn/TiO2 were also been done, the red-shift of Mn doped TiO2 in the experiments agreed with our calculation result. Calculated results of Cu/TiO2 are similar to Mn/TiO2. It was indicated that Mn was the best doping element by the caculation of transition metal ions doping Ti16O32 supercell.更多还原