摘要
The photocatalytic ability of ZnO is improved through the addition of flower‐like Bi2WO6 to prepare a Bi2WO6/ZnO composite with visible light activity.The composite is characterized by X‐ray diffraction,transmission electron microscopy,scanning electron microscopy with UV–vis diffuse reflectance spectroscopy,X‐ray photoelectron spectroscopy and N2 adsorption‐desorption isotherms.After modification,the band gap energy of Bi2WO6/ZnO is reduced from 3.2 eV for ZnO to 2.6 eV.Under visible light irradiation,the Bi2WO6/ZnO composite shows an excellent photocatalytic activity for degrading methylene blue(MB)and tetracycline.The photo‐degradation efficiencies of(0.3:1)Bi2WO6/ZnO for MB and tetracycline are approximately 246 and 4500 times higher than those of bare ZnO,respectively,and correspondingly,the photo‐degradation rates for the two pollutants are approximately 120 and 200 times higher than those with bare ZnO,respectively.Moreover,the photocatalyst of(0.3:1)Bi2WO6/ZnO exhibits a higher transient photocurrent density of approximately 4.5μA compared with those of bare Bi2WO6 and ZnO nanoparticles.The successful recombination of Bi2WO6 and ZnO enhances the photocatalytic activity and reduces the band gap energy of ZnO,which can be attributed to the effective separation of electron–hole pairs.Active species trapping experiments display that[O2]-is the major species involved during photocatalysis rather than·OH and h+.This study provides insight into designing a meaningful visible‐light‐driven photocatalyst for environmental remediation.
印染废水具有水量大、色度高、难生化降解、有毒有害物质多等特点;另外抗生素废水的大量排放对水生和陆地生态系统带来了危害.光催化可有效降解有机物,因而被广泛研究和应用,其多以半导体作为光催化剂.ZnO因价廉、无毒、来源广、光催化活性高而广受关注.但是,由于其带隙较宽,只能被紫外光激发,对太阳光的利用率低,且易发生光腐蚀,光稳定性较差,从而大大降低了光催化活性,不利于其应用.将ZnO与其他半导体复合是改善其光催化活性的最有效方法之一.铋基光催化剂一直是光催化领域的研究热点,作为无机半导体纳米晶之一,Bi_2WO_6具有无毒性、适当的带隙和优异的光催化性能,因而得到广泛关注.本文将Bi_2WO_6复合到ZnO上以降低ZnO带隙能,提高其对太阳能的转换,降低电子-空穴的复合几率,促进电荷转移的有效分离,从而提高ZnO的光催化性能.本文采用两步水热法合成了一种异质结的花状Bi_2WO_6/ZnO复合材料.通过降解亚甲基蓝(MB)和四环素,研究了其光催化性能.结果表明,该Bi_2WO_6/ZnO复合材料对MB和四环素具有优异的光催化活性,对它们的光降解效率分别是纯ZnO的246和4500倍,相应地,对这两种污染物的光降解率分别是纯ZnO的120和200倍.活性因子捕获实验结果显示,超氧自由基在光催化降解过程中起主要作用,其次是羟基自由基和光生空穴.采用X射线衍射、透射电镜、扫描电镜、紫外-可见漫反射、N_2吸附脱附、X射线光电子能谱、荧光光谱、光电流等方法对材料的形态结构、孔结构、化学组成、带隙能、光吸收性质、载流子复合效率等进行了分析.复合后Bi_2WO_6/ZnO的形貌为微米尺寸纳米结构的花状绒球,直径约为4μm,带隙能量从3.2 eV降为2.6 eV.Bi_2WO_6/ZnO为介孔结构,复合后比表面积为原来的4.98倍.所制备的Bi_2WO_6/ZnO光催化剂比纯Bi_2WO_6和ZnO颗粒具有更高的瞬态光电流密度(约为4.5μA).综上,Bi_2WO_6和ZnO成功复合形成了异质结,降低了ZnO的禁带宽度,促进了电子和空穴的有效分离,从而提高了其光催化活性.
基金
supported by the National Natural Science Foundation of China(51578354)
Six Talent Peaks Program(2016-JNHB-067)
Suzhou Science and Technology Bureau(SS201667)
Qing Lan Project and Research Innovation Project for College Graduates of Jiangsu Province(KYCX17_2067)~~
作者简介
通讯联系人:郭永福.电话:(0512)68092987,电子信箱:yongfuguo@163.com;通讯联系人:白仁碧.电子信箱:ceebairb@live.com
