Large-scale preparation of ordered titania nanorods with enhanced photocatalytic activity.pdf

Large-Scale Preparation of Ordered Titania Nanorods with Enhanced Photocatalytic Activity Jin-Ming Wu* and Tian-Wei Zhang Department of Materials Science Engineering, Zhejiang University, Hangzhou 310027, China Yue-Wu Zeng Analytical Measurement Center of Zhejiang University, Xixi Campus, Hangzhou 310028, China Satoshi Hayakawa,? Kanji Tsuru,?,? and Akiyoshi Osaka?,? Faculty of Engineering and Research Center for Biomedical Engineering, Okayama University, Tsushima, Okayama-shi, 700-8530, Japan Received January 5, 2005. In Final Form: May 8, 2005 A titania layer with ordered nanostructures is expected to be of high photocatalytic activity due mainly to its high specific surface area. In the present work, large-area films with ordered titania nanorods were deposited on titanium substrates through a solution approach. The nanorods, with the phase composition of a mixture of anatase and rutile, grew on top of a condensed anatase interlayer along mainly the rutile [001]-axis. The photocatalytic activity was evaluated by decomposing rhodamine B in water and compared with the general sol-gel derived titania films and a commercial DP-25 titania coating. It is found that the as-deposited titania nanorods exhibited extremely high initial photocatalytic activity but declined to a poor value after the consumption of beneficial oxidative peroxo complexes coordinated to Ti(IV). A subsequent thermal treatment eliminated such complexes but at the same time improved the crystallinity of the titania nanorods. The photocatalytic activity of the thermally treated titania nanorods was stable and significantly higher than that of the sol-gel derived film and commercial DP-25 coating. Introduction Ever since the discovery of the photocatalytic splitting of water on titania electrodes by Fujishima and Honda in 1972,1 numerous papers have appeared on titania as a photocatalyst to degrade trace organics in water.2-11 The photodegradation process involves ultraviolet (UV) light to excite a