Zhang Xuming, Huo Kaifu, Wang Hairong, Zhang Wenrui, Chu Paul K
The Key State Laboratory Breeding Base of Refractories and Ceramics, School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China.
J Nanosci Nanotechnol. 2011 Dec;11(12):11200-5. doi: 10.1166/jnn.2011.4074.
Titanium oxide nanotube arrays (TiO2-NTAs) with different diameters and lengths are prepared by anodization of titanium foils in a water/ethylene glycol solution (5:95 V/V) containing 0.3 wt% NH4F. The effects of the diameters, lengths and crystalline phases of the NTAs on the photocatalytic (PC) activity are systematically evaluated. Larger pore diameter results in higher PC activity. The PC activity increases initially and then decreases with lengths for TiO2-NTAs and the optimal length that yields the highest PC activity is observed to be 6.2 microm. The crystalline phase and corresponding PC activity depend on the calcination temperature and their relationship is also investigated. The amorphous-to-anatase and anatase-to-rutile phase transitions initially occur at 300 and 500 degrees C, respectively. The PC activity of TiO2-NTAs initially increases with calcination temperature from 250 to 500 degrees C and then decreases at higher calcination temperature. The enhanced PC activity observed from the samples annealed at 250-450 degrees C is attributed to the better anatase crystalline structure at higher calcination temperature. The highest PC activity with regard to photodecomposition of methyl orange is observed from TiO2-NTAs calcined at 500 degrees C, which coincides with the anatse-to-rutile phase transformation. The synergistic effect of the anatase TiO2-NTAs and rutile barrier layers facilitate interfacial electron transfer consequently enhancing the PC activity. Further elevation of the calcination temperatures to 550 and 600 degrees C exhibits diminished PC activity because the NTs become shorter due to conversion of the bottom of anatase NTs into rutile film.
通过在含有0.3 wt% NH4F的水/乙二醇溶液（体积比5:95）中对钛箔进行阳极氧化，制备出了具有不同直径和长度的二氧化钛纳米管阵列（TiO2-NTAs）。系统评估了纳米管阵列的直径、长度和晶相对光催化（PC）活性的影响。较大的孔径会导致更高的光催化活性。对于TiO2-NTAs，其光催化活性随长度先增加后降低，观察到产生最高光催化活性的最佳长度为6.2微米。晶相及其相应的光催化活性取决于煅烧温度，同时也对它们之间的关系进行了研究。非晶态到锐钛矿相以及锐钛矿到金红石相的转变最初分别发生在300℃和500℃。TiO2-NTAs的光催化活性最初随煅烧温度从250℃升高到500℃而增加，然后在更高的煅烧温度下降低。在250 - 450℃退火的样品中观察到的光催化活性增强归因于较高煅烧温度下更好的锐钛矿晶体结构。在500℃煅烧的TiO2-NTAs对于甲基橙光分解表现出最高的光催化活性，这与锐钛矿到金红石相的转变相吻合。锐钛矿TiO2-NTAs和金红石阻挡层的协同效应促进了界面电子转移，从而提高了光催化活性。将煅烧温度进一步提高到550℃和600℃时，光催化活性降低，这是因为由于锐钛矿纳米管底部转化为金红石膜，纳米管变短。
