二氧化鈦納米管陣列： 管長度對百草枯的光催化降解的影響

Abstract

中文摘要

(1) 目的：

高序性的TiO2奈米管因光催化去除有機污染物而備受關注。而管形態在光催化作用中具有良好的效果。但是尚未有研究來解釋最佳光催化活性與管長度的關係。而本篇觀察陽極生長過程中管形態的變化情形，並對光催化活性進行分析。

(2) 過程及方法：

我們透過陽極氧化法製作奈米管陣列並且觀察在陽極生長過程中管的形態演變的狀況，並透過SEM、XRD等儀器來分析相應的光催化活性與管長度之間的關係。

(3) 結果：

TiO2奈米管陣列的光催化活性大多數取決於陽極氧化時間。小內徑的短管光催化活性較差，是因為污染物擴散困難，而長管具有薄壁，因此光在更長距離被吸收，並且污染物必須進一步擴散以到達由電子電洞對產生的氧化物質才可以產生反應，而最佳管長度由這兩個結果之間折衷給出。

Abstract Highly ordered TiO2 nanotubes have attracted a lot of attention for the photocatalytic removal of organic pollutants. A few studies demonstrated that the tube morphology plays a key role on the photocatalytic activity. However, no studies have been performed to explain the optimal photocatalytic activity observed for a precise tube length. Here we studied how the morphology of the tubes evolves during anodic growth and we evaluated the corresponding photocatalytic activity. In our conditions, the optimal activity was found for 7 µm long tubes. The SEM study reveals that short tubes have a small pore opening thus hindering pollutant diffusion into the tubes. On the other hand, tubes longer than 7 µm have thinner walls due to etching by the fluoride ions. Consequently the volume of TiO2 decreases strongly in the upper part of the tubes as the tube length increase and light should travel a longer pathway before absorption and production of electron-hole pairs. Hence the organic species have to diffuse further and the photocatalytic activity decreases.