Photocatalytic degradation of volatile chlorinated organic compounds on CuffiO_2 films prepared by size-controlled Cu deposition

在甲酸钠存在下，通过光还原Cu（II）制备了Cu沉积的TiO_2（Cu/TiO_2）薄膜。随着初始Cu（II）的浓度小于50毫克L-1，薄膜的透射率随照射时间的增加而下降。辐照6小时后，扫描电子显微镜（SEM）观察表明，薄膜表面的Cu颗粒主要为0.51±0.04 μm。另一方面，当在100或150 mg·L-1 <-1>Cu（II）溶液中进行照射时，在透射率降低之前观察到诱导期。扫描电子显微镜（SEM）分析表明，在诱导期内，Cu颗粒呈孤立沉积，尺寸为2.6±0.5 μm，且有较大的空隙。这些事实提出了两种制备Cu/TiO_2薄膜的方法。负载在膜上的Cu量可以通过改变初始Cu（II）浓度小于50 mg/L<-1>（方法A）或在Cu（II）浓度高于100 mg/L（方法B）下改变诱导期内的照射时间来验证<-1>。比较了两种方法制备的Cu/TiO_2薄膜在500℃焙烧后对亚甲基蓝溶液的光催化降解活性。方法B制备的薄膜在不经空气吹扫的条件下，光催化活性高于纯TiO_2。这一发现归因于较高的透射率的膜和功能的Cu颗粒作为电子陷阱，导致抑制空穴和电子之间的复合。采用B方法制备的Cu/TiO_2薄膜对三氯乙烯（TCE）进行了气相光催化降解实验。然而，TCE转化率急剧下降，随着照射时间的增加。这一事实表明，副产物的积累显着影响Cu/TiO_2薄膜的性能。

Cu-deposited TiO_2 (Cu/TiO_2) films were prepared by photoreduction of Cu(II) in the presence of sodium formate. With the initial Cu(II) concentrations less than 50 mg L 1, the transmittance of the films decreased with an increase in the irradiation time. After the irradiation for 6 hrs, the scanning electron microscopy (SEM) indicated that the most of the Cu particles on the films were 0.51±0.04 μm. On the other hand, when irradiation was conducted in 100 or 150 mg L^<-1> Cu(II) solution, induction periods were observed before the transmittance decreased. The SEM images of the films indicated that Cu particles of 2.6±0.5 μm were deposited isolatedly with much open space in the induction periods. These facts proposed two methods to fabricate the Cu/TiO_2 films. The Cu amounts loaded on the film can be verified by changing the initial Cu(II) concentration less than 50 mg L^<-1> (method A), or changing the irradiation time within the induction period under the Cu(II) concentration above 100 mg L^<-1> (method B). The photocatalytic activities of the Cu/TiO_2 films prepared by both methods followed by calcination at 500℃ were compared in the degradation of methylene blue in aqueous solutions. The films prepared by method B showed a higher photocatalytic activity than a pure TiO_2 under no purging with air. This finding is attributable to higher transmittance of the films and function of the Cu particles as the electron trap which leads to suppression of the recombination between holes and electrons. Photocatalytic degradation of trichloroethylene (TCE) in the gas phase was also performed on the Cu/TiO_2 films prepared by method B. However, the TCE conversion decreased drastically with an increase in the irradiation time. This fact suggests that the accumulation of the by-products significantly affected the performance of the Cu/TiO_2 films.