Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu, 30013, Taiwan.
Sci Total Environ. 2010 Jul 15;408(16):3334-41. doi: 10.1016/j.scitotenv.2010.03.032. Epub 2010 May 6.
The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO(2) nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO(2) and to enhance the photocatalytic activity of TiO(2) towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO(2), respectively. Results showed that the particle size of metal-deposited TiO(2) was larger than that of Degussa P25 TiO(2). Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k(obs)) for MB photodegradation by Degussa P25 TiO(2) was 3.94 x 10(-2) min(-1) and increased by 1.4-1.7 times in k(obs) with metal-deposited TiO(2) for MB photodegradation compared to simple Degussa P25 TiO(2). The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k(obs) for MB degradation increased from 3.94 x 10(-2) min(-1) in the absence of metal ion to 4.64-7.28 x 10(-2) min(-1) for Ag/TiO(2) and to 5.14-7.61 x 10(-2) min(-1) for Cu/TiO(2). In addition, the electrons generated from TiO(2) can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO(2).
采用负载金属的 Degussa P25 TiO2 纳米粒子光辅助还原金属离子和有机染料，研究了金属离子对 TiO2 表面性质的修饰和对 TiO2 光催化降解亚甲基蓝（MB）活性的增强作用。采用 X 射线粉末衍射（XRPD）、X 射线光电子能谱（XPS）和透射电子显微镜（TEM）分别对负载金属的 TiO2 的结晶度、化学物种和形貌进行了表征。结果表明，负载金属的 TiO2 的粒径大于 Degussa P25 TiO2。基于 XRPD 图谱和 XPS 谱图，观察到添加甲酸盐可通过降低金属离子的氧化态来促进其光还原，从而提高 MB 的光降解效率和速率。Degussa P25 TiO2 光降解 MB 的拟一级速率常数（kobs）为 3.94×10-2 min-1，而负载金属的 TiO2 光降解 MB 的 kobs 比单纯 Degussa P25 TiO2 提高了 1.4-1.7 倍。金属离子的质量负载增加显著提高了 MB 的光降解效率；在不存在金属离子的情况下，MB 降解的 kobs 从 3.94×10-2 min-1 增加到 Ag/TiO2 的 4.64-7.28×10-2 min-1 和 Cu/TiO2 的 5.14-7.61×10-2 min-1。此外，在缺氧条件下，TiO2 产生的电子可以有效地同时还原金属离子和 MB。然而，金属离子和有机染料会从被光照的 TiO2 中争夺电子。
