La-doped titania nanocrystals with superior photocatalytic activity prepared by hydrothermal method

Abstract

Potassium titanate (KTO) nanobars were synthesized by a hydrothermal method and used as a precursor to synthesize TiO 2 nanocrystals. La doping of the TiO 2 nanocrystals was achieved by introducing La 3+ into the hydrothermal media. The hydrothermal transition of KTO to TiO 2 was investigated under various conditions, finding that the pH of the hydrothermal media, the temperature, and the pre-treating procedure play important roles in the phase transition. X-ray diffraction and transmission electron microscopy were used to characterize the crystal phase and morphology of the samples and the transition process of the hydrothermal reaction. The content of La 3+ in the samples was measured by inductively coupled plasma atomic emission spectroscopy. The photocatalytic activity of the La-doped TiO 2 (LaT) was measured under UV light with the degradation of methyl orange (MO, 10 mg/L). The results showed that the photocatalytic activity of TiO 2 was enhanced remarkably by La-doping. LaT hydrothermally prepared with 0.15 mol/L La 3+ at under 180 °C showed the optimal reaction constant of 0.11 min −1 for the degradation of MO, about 9.20 and 3.69 times than those of bare TiO 2 and P25, respectively. 采用水热法合成钛酸钾 (K 2 Ti 8 O 17 ) 纳米棒, 并将它作为前驱体水热转晶合成 TiO 2 纳米晶, 同时通过在水热体系中引入稀土元素 La 3+ 实现对 TiO 2 的 La 掺杂. 考察了不同条件下钛酸盐向 TiO 2 的转晶过程, 发现水热溶液的 pH 值、温度以及预处理步骤对转晶过程有很大的影响. 利用 X 射线衍射以及透射电子显微镜对样品的晶相和形貌进行了表征. 利用电感耦合等离子体原子发射光谱测量了所合成的 La 掺杂 TiO 2 样品中的 La 含量. 通过在紫外光下降解甲基橙 (MO, 10 mg/L) 测试了 La 掺杂 TiO 2 样品的光催化性能. 结果表明 La 掺杂后 TiO 2 的光催化活性大大提高. 在 0.15 mol/L La 3+ 浓度下 180 oC 水热合成的 La 掺杂 TiO 2 样品显示了最佳的光催化活性. 其对 MO 的光催化降解反应常数高达 0.11 min -1 , 大约是空白 TiO 2 样品的 9.20 倍, P25 TiO 2 的 3.69 倍. La 3+ doped TiO 2 was prepared by treating K 2 Ti 8 O 17 in acidic solution. TiO 2 doped with 0.15 mol/L La 3+ gave the optimal reaction constant of 0.11 min-1 for methyl orange degradation, about 9.20 times that of bare TiO 2 .