Influence of Structure Parameters and Crystalline Phase on the Photocatalytic Activity of TiO2 Nanotube Arrays

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Abstract:

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 μm. 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 °C, respectively. The PC activity of TiO2–NTAs initially increases with calcination temperature from 250 to 500 °C and then decreases at higher calcination temperature. The enhanced PC activity observed from the samples annealed at 250-450 °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 °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 °C exhibits diminished PC activity because the NTs become shorter due to conversion of the bottom of anatase NTs into rutile film.

Keywords: CRYSTALLINE PHASE; LENGTH; NANOTUBE ARRAYS; PHOTOCATALYSIS; PORE SIZE; TIO2

Document Type: Research Article

DOI: http://dx.doi.org/10.1166/jnn.2011.4074

Publication date: December 1, 2011

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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