球状TiO₂薄膜的制备、改性及光电化学性质研究

【作者】 张姝娟；

【导师】 李洁；

【作者基本信息】 中南大学 ， 物理化学， 2011， 硕士

【摘要】 在众多的半导体材料中,TiO2具有无毒、稳定、高催化活性和高折射率等优良特性。但由于其光生电子-空穴对的复合几率较高,对太阳光能利用率低等缺点而严重阻碍了TiO2的工业化应用。本文以钛酸四丁酯[Ti(OC4H9)4]、冰乙酸、聚乙烯吡咯烷酮(PVP)、尿素和硝酸铁为原料,采用溶胶凝胶法和脉冲电沉积法制备了表面由球状颗粒组成的TiO2薄膜、N-TiO2薄膜以及Fe修饰的N-TiO2薄膜(Fe/N-TiO2薄膜)。利用TG-DSC、XRD、SEM、紫外可见吸收以及光电化学测试等检测手段对制备出的各种TiO2薄膜进行了表征。主要研究成果如下：首先考察了PVP用量和热处理温度对TiO2薄膜电极形貌及光电化学性质的影响。当PVP为1g时,经500℃热处理1 h制备出由球形颗粒组成TiO2的薄膜,颗粒尺寸为100-200 nm。400℃时,薄膜球形颗粒尺寸达到250 nm左右,表面较光滑,随着热处理温度的上升表面球形颗粒有变小的趋势,并且颗粒表面也变得较粗糙。另外,光电流随热处理温度先上升后下降,在500℃时,光电流达到最大值。在施加偏压为1.0V(vs Ag/AgCl),热处理温度为400℃、500℃和600℃时的光电流密度分别为0.23、0.42和0.31 mA/cm2。其次,在上述基础上,以尿素[CO(NH2)2]为氮源,成功实现TiO2薄膜电极的N掺杂。研究表明,N的引入对薄膜形貌没有影响,当尿素含量为4%时,N-TiO2薄膜样品的光响应范围扩展到600 nm以上的可见光区,在电位为1.0V(vs Ag/AgCl)时,光电流密度比未掺杂薄膜提高了1倍。最后,为进一步提高TiO2薄膜电极的光电转换效率,本文采用脉冲电沉积法对球状N-TiO2薄膜电极进行表面修饰,研究了Fe修饰对薄膜光电性能的影响。结果表明,通过调节沉积电流可实现Fe负载量的控制,沉积铁后样品光电流密度在1.4 V下达到1.55 mA/cm2,相比沉积前提高了50%。更多还原

【Abstract】 Among various oxide semiconductors, titanium dioxide (TiO2) has properties of non-toxic, high catalytic activity, optimum chemical stability and high refractive index. However, fast recombination rate of photogenerated electron-hole pairs in the bulk TiO2 and the low quantum yield of photochemical conversion for solar severely hinder the industrial applications of TiO2 semiconductor material. In this study, five chemical materials, i.e., tetrabutylortitanate, ice acetic acid, polyvinylpyrrolidone (PVP), urea and ferric nitrate, were used as raw material. The TiO2 film, N- TiO2 film and Fe/N- TiO2 film with spherical particles on surface were prepared by sol-gel method and pulse electrodeposition. The TG-DSC, XRD, SEM, UV-Vis absorption spectroscopy and photocurrent spectroscopy analysis were performed to characterize the morphology, crystalline phase, photo-absorption ability and photoelectrochemical property of the sample. The main results are outlined as following:Firstly, the effects of PVP contents and sintering temperature on microstructure and photoelectrochemical properties of TiO2 films were investigated. The TiO2 films with spherical particles of size about 100-200 nm were synthesized after heat treatment at 500℃for 1 hour by adding 1 g PVP. Spherical particle size reached～250 nm and the surface was smooth when films were prepared at 400℃. The grain size becomes smaller and the surface of the grain is rougher with the increase of heat treatment temperature. In addition, photocurrent becomes higher firstly and then becomes lower with the increase of heat treatment temperature. The photocurrent reached the maximum value when treated at 500℃. The photocurrent of N-TiO2 films calcined at 400℃,500℃,600℃are 0.23,0.42 and 0.31 mA/cm2 respectively.Furthermore, the nitrogen-doped TiO2 film was fabricated by sol-gel method using urea as N source. The result indicates that inducing of N has no effect on morphology of film. Optical response of TiO2 sample with 4% N extended to over 600 nm in visible light area. In comparison to undoped TiO2, the N-doped samples show a significant enhancement in photoresponse with photocurrent increase of 1 time at 1.0 V (vs Ag/AgCl).Finally, to further improve photoelectric conversion efficiency, we have fabricated Fe-doped N-TiO2 film by pulse voltage electrodeposition. The effects of Fe content on photoelectrochemical properties of N-TiO2 films were investigated. The results show that ferric can be doped successfully onto TiO2 photoelectrodes by controlling deposition current, and the Fe/N-TiO2 film show significant enhancement in photoresponse with photocurrent increase of 50%.更多还原