【作者】 陈友三；

【导师】 李旦振； 王绪绪；

【作者基本信息】 福州大学 ， 物理化学， 2005， 硕士

【摘要】 光催化技术是一种最理想的环境污染治理技术,近二十年来受到国内外的广泛关注。然而,普遍使用的TiO₂或改性的TiO₂光催化剂存在太阳能利用率低和光量子效率不高的弊端,这严重制约了光催化技术的大规模应用。此外,大量研究表明,对难降解环境污染物,如芳烃类化合物,TiO₂ 基光催化剂还存在光催化氧化活性低和极易失活的问题。因此,开发新型高效光催化剂,提高催化剂对芳烃化合物的光催化降解效率,特别是活性稳定性,成为当今环境光催化研究的焦点和热点问题,对光催化学科的可持续发展具有重大的理论和实际意义。本论文采用超声解胶技术合成了半导体纳米晶In（OH）₃和In₂O₃光催化剂。运用热重-差示扫描、X 射线粉末衍射、比表面、紫外-可见漫反射吸收光谱、低分辨透射电镜、傅立叶变换红外光谱、X 射线光电子能谱等测试手段详细表征了其晶相结构、形貌和光电特性;以挥发性的有机污染物（VOCs）,如苯、甲苯、丙酮蒸气为模型污染物,采用连续流动或间歇式光催化反应器对其光催化活性和稳定性进行了评价,并与国际标准P25-TiO₂催化剂进行了比较。论文得到如下主要结果和结论:（1）采用超声解胶技术可以得到粒子直径10～20nm 的In（OH）₃ 立方型晶体,该晶体在160℃可以稳定存在,高于这个温度会缓慢分解,到250℃完全转变为In₂O₃晶体。（2）In（OH）₃和In₂O₃对氮气的吸附-脱附等温线均为IV 型,且具有相近的BET 比表面积,分别为125 和126 m²/g。经120℃制得的In（OH）3 半导体的直接和间接带隙分别为5.48 和5.02eV;（3）与P25-TiO₂ 相比,In（OH）3 对苯表现出很高光催化活性和活性稳定性。在254 nm 的紫外光照射下,2 h 后反应便可达到稳态,苯的转化率接近32%,有接近56%的苯分子被完全矿化,反应30 小时活性仅略有降低;而在相同条件下,P25-TiO₂对苯的转化率只有9%,且反应6 小时完全失活。对甲苯也得到类似的结果。（4）引入水蒸气可以使In（OH）₃对苯和甲苯的活性保持长时间稳定,且随水蒸气含量的增大,矿化率也随之增大。（5）In（OH）₃与P25-TiO₂相比,光催化活性高和活性稳定的原因可能与其高的空穴氧化能力和表面不易结碳有关。论文的创新点:（1）采用超声解胶技术合成出了多孔大比表面In（OH）3纳米晶体,并对其结构和性能进行了详细表征;（2）首次发现In（OH）₃是一种良好的光催化剂,证明其对苯和甲苯有比TiO2高得多的活性及活性稳定性,并对其原因进行了初步探讨。该研究为消除芳烃类的污染提供了一种优良的光催化剂,同时拓宽了光催化剂的开发思路,也为新型催化剂的开发提供了良好的基体材料。更多还原

【Abstract】 Over the past two decades, there has been growing attention in the photocatalytic oxidation technology which is regarded as a perfect method for pollution destruction in home and abroad. However, widely used TiO₂ or modified TiO₂ catalysts had some defects, for example, low solar energy utilization and poor quantum efficiency, which seriously limited the large-scale application of photocatalytic technology. Moreover, a comparative study of literature data revealed that TiO₂-based catalysts had low photooxidation activity and were often deactivated during non-degradative environmentally hazaerdous compounds such as aromatic hydrocarbons degradation. Hence, The development of a novel photocatalyst with high efficiency and durability for photocatalytic degradation of aromatic hydrocarbons, is a hot and focus problem in environmental photocatalytic field, which had a great significance for development of photocatalytic science. In this paper, we reported In（OH）₃ and In₂O₃ semiconductor nanocrystal photocatalysts which were synthesized by peptization of colloidal precipitates under ultrasound radiation and characterized by thermogravitery-differential scanning calorimetry analysis （TG-DSC）, X-ray diffraction （XRD）, N₂ adsorption analysis applying BET method, UV-Visible diffuse reflectance spectroscopy （DRS）, low resolution transmission electron microscopy （TEM）, Fourier-transform infrared spectroscopy （FTIR）, X-ray photoelectron spectroscopy （XPS）, which confirmed the morphological structure, image and photoelectric properties. Benzene, toluene and acetone were used as a model VOCs to investigate the gas-phase photocatalytic performance over In（OH）₃ nanoparticles in a recirculating reactor and a closed bath reactor, and the results were compared with that obtained over the degussa P25-TiO2 catalyst. The results showed that: （1） In（OH）₃ particle size is between 10 and 20 nm, it belongs to nanocubic which was stable at temperature lower than 160℃and converted into In2O3 at 250℃. （2） The adsorption/desorption isotherms of In（OH）₃ and In₂O₃ were IV type, further more, they had similar BET areas which were 125 and 126m²/g, respectively. The direct and indirect band gap of In（OH）₃ semiconductor which was dried at 120oC were 5.48 and 5.02eV. （3）Under the same conditions, In（OH）3 exhibits much higher photoactivity and durability than Degussa P25-TiO2 for benzene oxidation and mineralization. For example, the conversion of benzene was about 32% after 2h over In（OH）3 catalyst, that is to say, about 56% of benzene molecule was mineralized, furthermore, catalyst was very slowly deactived in 30h under 254nm UV irradiation. On the contrary, P25-TiO2 catalyst had only 9% conversion of benzene and completed deactived in 6h. In（OH）3 exhibited similar result for toluene photooxidation. （4） When the photocatalytic oxidation of benzene and toluene over In（OH）3 were performed in the present of water vapor, it enhanced the catalyst durability, moreover, with the increase in water vapor content, both the conversion and mineralization of benzene were increased at the steady state. （5） Compare with P25-TiO2 catalyst, the reason of high photoactivity and durability over In（OH）3 catalyst may be due to the high hole oxidation potential and uneasy to carbon deposited on catalyst surface. The innovations of this study are: （1） The porous indium hydroxide nanocrystal with a high BET area was prepared by peptization of colloidal precipitates under ultrasound radiation, moreover, its characteristic and properties were studied in detail （2） In（OH）3 was first time used in photooxidation of organic pollutions and was proved that it had a higher photocatalytic activity and longer durability for aromatic hydrocarbons degradation than P25-TiO2, then the reason was primally studied. This study provided a novel high effective photocatalyst for elimination of aromatic hydrocarbons. At the same time, it extended the ideas of exploring photocatalyst and provided a novel catalyst development with based material.更多还原