二氧化鈦鍍銀及二氧化鈦鍍金之奈米複合材料 合成及光催化性質

Abstract

二氧化鈦具有化學穩定性，低成本，無毒性，是常見的光催化材料，然而由 於二氧化鈦受到照光激發產生的電子電洞對容易再結合，以及無法有效利用可見 光能量，因此二氧化鈦的光催化效率仍有待增進。文獻報導提到貴重金屬的添加 和二氧化鈦形成奈米複合材料後能提升二氧化鈦光催化效果。因此於本論文中， 我們製備二氧化鈦鍍銀以及二氧化鈦鍍金之奈米複合材料並研究光催化性質。 首先我們以市售二氧化鈦粉末與氫氧化鈉水溶液合成鈦酸鈉鹽奈米管，經由 稀酸溶液進行質子交換可得到鈦酸鹽奈米管。鈦酸鹽奈米管經由熱處理後可得到 具有光催化活性之鋭鈦礦二氧化鈦奈米線。因此在製備鋭鈦礦二氧化鈦奈米線過 程中可以得到鈦酸鈉鹽奈米管以及鈦酸鹽奈米管之中間產物。 我們使用鈦酸鈉鹽奈米管，鈦酸鹽奈米管以及鋭鈦礦二氧化鈦奈米線做為擔 體擔載銀粒子製備二氧化鈦鍍銀複合材料，而擔體的表面電荷以及表面積會影響 銀粒子的大小以及在擔體上的含量。二氧化鈦鍍金複合材料使用鋭鈦礦二氧化鈦 奈米線做為擔體擔載金粒子。而金粒子的粒徑大小及在二氧化鈦擔體上的含量隨 著金氯酸的濃度提高而增加。我們進一步測試了二氧化鈦鍍銀以及二氧化鈦鍍金 奈米複合材料的光催化性質，包含了光降解甲基藍和光分解水實驗。發現二氧化 鈦奈米線擔載的金屬粒子大小與含量會影響奈米複合材料的光催化性質。

Titanium oxides are common photocatalytic materials due to its chemical stability, low cost, and non toxicity. However, the photocatalytic efficiency is still improvable due to fast charge recombination and inability to utilize visible light. Noble metals have been reported to be very effective for enhancement of TiO2 photocatalysis. Thus in this study, we prepared the TiO2/Ag and TiO2/Au nanocomposites to study the photocatalytic properties. We have synthesized sodium titanate nanotubes from commercial RDH TiO2 powders in a sodium hydroxide solution, followed by proton exchange of sodium titanate nanotubes in dilute acid to form titanic acid nanotubes. After annealing, the titanic acid nanotubes have been converted into photoactive anatase TiO2 nanowires. Therefore, during the fabrication of anatase TiO2, we can obtain the intermediate compounds of sodium titanate nanotubes and titanic acid nanotubes. We have prepared TiO2/Ag nanocomposites by depositing Ag nanoparticles on the support materials such as sodium titanate nanotubes, titanic acid nanotubes and anatase TiO2 nanowires. The surface charge and the surface area of the support materials would affect the Ag nanoparticle sizes and Ag loading. TiO2/Au nanocomposites were prepared by using anatase TiO2 nanowires as the support material. The Au loading and the particle size of Au increased with HAuCl4 concentration. In addition, photocatalytic properties of TiO2/Ag and TiO2/Au nanocomposites were examined by the photodegradation of methylene blue and photoelectrochemical water splitting. The size and loading of the metal particles would affect the photocatalytic properties of the nanocomposites.