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

在甲酸钠存在下，采用光还原Cu（II）法制备了Cu/TiO_2沉积膜。当Cu（II）初始浓度小于50 mg L 1时，膜的透过率随辐照时间的增加而降低。辐照6 h后，扫描电子显微镜（SEM）显示，膜上的Cu颗粒大部分为0.51±0.04 μm。另一方面，当在100或150 mg L^<-1> Cu（II）溶液中辐照时，在透射率下降之前观察到诱导期。扫描电镜（SEM）结果表明，在诱导过程中，Cu颗粒大小为2.6±0.5 μm，呈孤立沉积，且有较大的开放空间。这些事实提出了两种制备Cu/TiO_2薄膜的方法。通过改变初始Cu（II）浓度小于50 mg L^<-1>（方法A），或改变诱导期内Cu（II）浓度大于100 mg L^<-1>的辐照时间（方法B），可以验证膜上负载的Cu量。比较了两种方法制备的Cu/TiO_2膜在500℃下煅烧后对水溶液中亚甲基蓝的光催化活性。B方法制备的膜在不吹扫的情况下比纯TiO_2具有更高的光催化活性。这一发现是由于薄膜具有较高的透过率和Cu粒子作为电子陷阱的功能，从而抑制了空穴和电子之间的复合。方法b制备的Cu/TiO_2膜也进行了气相光催化降解三氯乙烯（TCE），但随着照射时间的增加，TCE转化率急剧下降。这表明副产物的积累对Cu/TiO_2薄膜的性能有显著影响。

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.