摘要
二氧化钛具有独特的湿敏、气敏、紫外光吸收、光电转化及光催化性能,在传感器、介电材料、自清洁材料、有机-无机太阳能电池、光催化降解污染物等领域有着广阔的应用前景。TiO_2纳米管因其特殊的结构而表现出更加优异的性能。若将TiO_2纳米管(或多孔)膜高质量地转移至透明导电基底FTO上,制备出多孔TiO_2/FTO纳米薄膜,则其可直接作为光电极,以便在光电转换等领域得到更好的应用。本论文以“TiO_2/FTO纳米管有序阵列光电极的制备、CdS修饰及其光学特性的研究”为题,主要述及以下几方面的研究工作:
1.以金属钛片为基底(0.2 mm),采用连续三步阳极氧化法,在含有NH4F的乙二醇溶液内,成功制备出大面积(18 mm×11 mm)自持多孔TiO_2纳米管阵列膜(管长≤1.5μm)。通过进一步研究发现,该自持薄膜不仅具有较高的晶化程度、较高的透射率(400~2500 nm),而且不同的阳极电压对薄膜的透射强度及光学能隙(Eg)都有明显的调制作用。
2.利用实验室配制的TiO_2溶胶,成功将自持TiO_2纳米管阵列膜转移粘结至FTO导电玻璃上,经退火处理后形成TiO_2/FTO纳米管阵列膜光电极。
3.采用序贯化学浴沉积方法,对TiO_2/FTO纳米管阵列膜光电极做CdS纳米颗粒修饰。实验发现,经CdS纳米颗粒修饰的TiO_2/FTO光电极,其帯隙宽度由原来的3.22 eV减小至2.43 eV,光吸收带边也由原来的380 nm红移至554 nm。研究表明,这种转移粘结法制备的TiO_2/FTO半透明光电极经CdS纳米颗粒修饰后,具有很宽的光谱响应特性,这是光电转换应用研究所期待的。这项研究对基于TiO_2纳米管阵列的光催化及光伏太阳电池的应用研究将是非常有益的。
TiO_2 nanomaterials have been widely studied due to their unique electrical and electrochemical properties which are suitable for sensing, catalysis and solar cells. In recent years, TiO_2 nanotubes with high surface-to-volume ratios have received considerable attention because of their potential applications of highly efficient photocatalysis and photovoltaic cells. If the TiO_2 nanotube membranes could be transferd onto the FTO substrates, the transparent and conductive TiO_2/FTO photoelectrode would have a better application in the photoelectric conversion filed. This dissertation titled“Highly ordered TiO_2/FTO nanotube array photoelectrode:fabrication, modification of CdS and its optical properties”mainly describes the following work and results:
1. The large-scale (18 mm×11 mm), highly-ordered, vertically-oriented free-standing TiO_2 nanotube membranes were fabricated by three-step anodization Ti foils(0.2 mm) in ethylene glycol containing 0.25 wt.% NH4F. It is found that the optical energy gap (Eg) of TiO_2 nanotube membranes could not only have high transmissivity (400~2500 nm), but also be effectively modulated by different anodic voltage. Obviously, this work would be beneficial to apply in organic-inorganic photovoltaic devices.
2. Then the as-prepared free-standing membranes were transferred to FTO-coated glass substrates with TiO_2 sol, and the semitransparent TiO_2/FTO photoelectrode was obtained after annealing treatment.
3. The TiO_2/FTO photoelectrode was modified with CdS by the sequential-chemical bath deposition (S-CBD) method in order to extend the optical absorption range of bare TiO_2/FTO. The measurement results show that the band-gaps decrease from 3.22 eV for bare TiO_2/FTO to 2.43 eV for CdS-modified TiO_2/FTO. Meanwhile, the optical absorption band-edges of CdS-modified TiO_2/FTO have efficiently shifted from 380 nm to 554 nm, which could lead to an extended optical absorption range from the ultraviolet to the visible.
引文
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