Lee Wai Hong, Lai Chin Wei, Hamid Sharifah Bee Abd
Nanotechnology & Catalysis Research Centre (NANOCAT), Institute of Postgraduate Studies (IPS), University of Malaya, Kuala Lumpur 50603, Malaysia.
Materials (Basel). 2015 Aug 28;8(9):5702-5714. doi: 10.3390/ma8095270.
WO₃-decorated TiO₂ nanotube arrays were successfully synthesized using an anodization method in ethylene glycol electrolyte with dissolved H₂O₂ and ammonium fluoride in amounts ranging from 0 to 0.5 wt %. Anodization was carried out at a voltage of 40 V for a duration of 60 min. By using the less stable tungsten as the cathode material instead of the conventionally used platinum electrode, tungsten will form dissolved ions (W) in the electrolyte which will then move toward the titanium foil and form a coherent deposit on the titanium foil. The fluoride ion content was controlled to determine the optimum chemical dissolution rate of TiO₂ during anodization to produce a uniform nanotubular structure of TiO₂ film. Nanotube arrays were then characterized using FESEM, EDAX, XRD, as well as Raman spectroscopy. Based on the FESEM images obtained, nanotube arrays with an average pore diameter of up to 65 nm and a length of 1.8 µm were produced. The tungsten element in the samples was confirmed by EDAX results which showed varying tungsten content from 0.22 to 2.30 at%. XRD and Raman results showed the anatase phase of TiO₂ after calcination at 400 °C for 4 h in air atmosphere. The mercury removal efficiency of the nanotube arrays was investigated by photoirradiating samples dipped in mercury chloride solution with TUV (Tube ultraviolet) 96W UV-B Germicidal light. The nanotubes with the highest aspect ratio (15.9) and geometric surface area factor (92.0) exhibited the best mercury removal performance due to a larger active surface area, which enables more Hg to adsorb onto the catalyst surface to undergo reduction to Hg⁰. The incorporation of WO₃ species onto TiO₂ nanotubes also improved the mercury removal performance due to improved charge separation and decreased charge carrier recombination because of the charge transfer from the conduction band of TiO₂ to the conduction band of WO₃.
采用阳极氧化法，在含有0至0.5 wt%溶解过氧化氢和氟化铵的乙二醇电解液中成功合成了WO₃修饰的TiO₂纳米管阵列。阳极氧化在40 V电压下进行60分钟。通过使用稳定性较差的钨作为阴极材料，而非传统使用的铂电极，钨会在电解液中形成溶解离子（W），然后这些离子会向钛箔移动并在钛箔上形成连贯的沉积物。控制氟离子含量以确定阳极氧化过程中TiO₂的最佳化学溶解速率，从而制备出均匀的TiO₂膜纳米管结构。然后使用场发射扫描电子显微镜（FESEM）、能量色散X射线光谱仪（EDAX）、X射线衍射仪（XRD）以及拉曼光谱对纳米管阵列进行表征。基于获得的FESEM图像，制备出了平均孔径高达65 nm、长度为1.8 µm的纳米管阵列。EDAX结果证实了样品中的钨元素，其显示钨含量在0.22至2.30原子百分比之间变化。XRD和拉曼结果表明，在空气气氛中于400 °C煅烧4小时后，TiO₂呈现出锐钛矿相。通过用TUV（灯管紫外线）96W UV - B杀菌灯对浸入氯化汞溶液中的样品进行光照射，研究了纳米管阵列的汞去除效率。具有最高长径比（15.9）和几何表面积因子（92.0）的纳米管表现出最佳的汞去除性能，这是由于其更大的活性表面积，使得更多的汞能够吸附到催化剂表面并还原为Hg⁰。由于电荷从TiO₂的导带转移到WO₃的导带，改善了电荷分离并减少了电荷载流子复合，因此在TiO₂纳米管上引入WO₃物种也提高了汞去除性能。
