Ag@AgBr光催化剂的制备及其可见光催化降解亚甲基蓝反应性能

采用沉积-沉淀及光还原法制备了Ag@AgBr等离子体光催化剂,利用X射线衍射、扫描电镜和紫外-可见漫反射光谱对其进行了表征,并考察了该等离子体光催化剂在可见光(λ420nm)下的催化性能,探讨了催化剂用量、pH值、亚甲基蓝初始浓度、H2O2添加量、循环使用及捕获剂对Ag@AgBr催化性能的影响.结果表明,当亚甲基蓝的初始浓度为10mg/L,催化剂用量为1g/L,pH=9.8时,光照12min后,亚甲基蓝的降解率高达96%,且样品经5次循环使用后活性基本保持不变;而少量H2O2的添加对光催化活性影响不大,过量的H2O2会降低光催化活性;乙二胺四乙酸捕获空穴后比异丙醇捕获·OH后的光催化活性降得更低.同时,对Ag@AgBr等离子体光催化剂可见光降解亚甲基蓝的催化机理进行了分析.

Synthesis of Ag@AgBr Photocatalyst and Its Performance for Degradation of Methylene Blue under Visible-Light Irridiation

Ag@AgBr plasmon photocatalyst was prepared by the deposition-precipitation and photo-reduction method. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse spectroscopy. The photocatalytic activity and stability of the prepared samples were evaluated by the degradation of methylene blue (MB) under the visible light (λ > 420 nm) irradiation. Several parameters, such as catalyst concentration, pH value, initial MB concentration, H2O2 content, recycling runs, and scavengers, were examined. The results show that the photocatalytic activity of Ag@AgBr reached 96% in MB aqueous solution (10 mg/L) containing 1 g/L catalyst at pH = 9.8 under visible-light irradiation, and it almost kept unchanged after five-cycle photocatalytic test. The degradation efficiency of MB had little variation in the presence of a small amount of H2O2 but reduced in the presence of excessive H2O2. MB photodegradation was greatly suppressed by ethylenediaminetetraacetic acid while slightly decreased by isopropanol. The photocatalytic mechanism for MB degradation by Ag/AgBr under visible light irradiation was also presented.