Bi_(2)MoO_(6)/AgBr的制备及其光催化活性增强机制

Preparation of Bi_(2)MoO_(6)/AgBr and Its Photocatalytic Activity Enhancement Mechanism

采用水热法合成了Z型异质结Bi_(2)MoO_(6)/Ag Br光催化剂,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、比表面积测试仪(BET)、稳态/瞬态荧光光谱仪等对其微观形貌、物相组成以及光电性能等特性进行表征;通过对目标污染物罗丹明B(Rh B)的降解分析该催化剂的活性和降解机理。结果表明,该催化剂由立方相的Bi_(2)Mo O_(6)纳米片堆叠而成的纳米微球和负载在其表面的Ag Br纳米花簇构成,异质结的形成使得比表面积增加了7.2 m^(2)/g,光生电子对寿命延长。Bi_(2)Mo O_(6)与Ag Br复合后光催化活性明显提高,当Ag Br复合量为10%时效果最佳,光催化反应速率常数是Bi_(2)Mo O_(6)的1.6倍。当Rh B浓度为0.5×10^(-5)mol/L、Bi_(2)Mo O_(6)/Ag Br投加量为250 mg/L、p H值=7时,反应20 min后对Rh B的降解率可达到95.9%,且Bi_(2)Mo O_(6)/Ag Br经过5次循环实验后仍具有较高的光催化活性。自由基捕获实验结果表明,Bi_(2)MoO_(6)的主要活性基为·O_(2)^(-),Bi_(2)Mo O_(6)/Ag Br的主要活性基团为·O_(2)^(-)和h^(+)。根据以上实验结果,提出了一种由Ag^(0)粒子为通道的Z型电荷转移机理。

Z-type heterojunction Bi_(2)MoO_(6)/AgBr photocatalyst was synthesized by hydrothermal method,and its microscopic morphology,phase composition and photoelectric properties were characterized by SEM,XRD,BET,UV-Vis spectrophotometer and transient/steady fluorescence spectrophotometer.Meanwhile,the activities and degradation mechanism of the catalysts were analyzed by degradation of rhodamine B (Rh B).The catalyst was composed of stacked Bi_(2)MoO_(6) nanosheets in cubic phase and Ag Br nanoflower clusters loaded on its surface.The formation of heterojunction increased the specific surface area by 7.2 m^(2)/g and prolonged the lifetime of photogenerated electron pair.Photocatalytic activity of Bi_(2)Mo O_(6) loaded with AgBr was significantly improved.The best performance was obtained when the loaded amount of AgBr was 10%,and the rate constant of the corresponding photocatalytic reaction was 1.6 times higher than that of single Bi_(2)Mo O_(6) as the photocatalyst.When the RhB concentration was 0.5×10^(-5)mol/L,the Bi_(2)MoO_(6)/AgBr dosage was 250 mg/L and pH was 7,the degradation rate of Rh B reached 95.9% after 20 min of reaction,and the Bi_(2)MoO_(6)/AgBr still had high photocatalytic activity after 5 cycles of experiments.The radical trapping experiments indicated that themain active group of Bi_(2)MoO_(6) was·O_(2)^(-),and the main active groups of Bi_(2)MoO_(6)/AgBr were·O_(2)^(-) and h^(+).According to the above experimental results,a Z-type charge transfer mechanism with Ag^(0) particles aschannels was proposed.