g-C3N4量子点修饰球形Bi2WO6及其光催化活性增强机制

g-C3N4 quantum dots decorated spherical Bi2WO6 photocatalyst and its enhanced photocatalytic activities mechanism

采用水热法制备三维分级结构Bi2WO6,在此基础上采用浸渍-焙烧法将g-C3N4量子点成功沉积在Bi2WO6的表面,获得Z-型结构g-C3N4/Bi2WO6光催化剂。采用XRD,FE-SEM,TEM,UV-Vis-DRS测试手段对催化材料的组成、形貌和光吸收特性进行表征。以亚甲基蓝(MB)和对硝基苯酚(p-NPh)为模型污染物,考察g-C3N4量子点表面修饰对Bi2WO6光催化活性的影响。结果表明:所得Bi2WO6为三维分级多孔结构,孔尺寸约为10nm,浸渍-焙烧法可将尺寸约5nm的g-C3N4量子点沉积在其二级结构纳米片表面。Z-型结构g-C3N4/Bi2WO6光催化剂的催化活性优于纯Bi2WO6的,且10%g-C3N4/Bi2WO6(质量分数)异质光催化剂对MB的降解表观速率常数(kapp)分别为纯Bi2WO6和g-C3N4的4.5倍和5.8倍,对p-NPh的kapp分别为纯Bi2WO6和g-C3N4的2.6倍和1.6倍。O2·是光催化过程中的主要活性物种。g-C3N4量子点与Bi2WO6形成异质结,有利于拓宽光响应范围的同时有效抑制了Bi2WO6光生电子与空穴的复合,从而提高了催化剂的活性。

Three-dimensional(3 D) Bi2WO6 architecture was successfully synthesized via a hydr-othermal process. The g-C3N4 quantum dots(QDs) were deposited on the surface of as-synthesized 3 D Bi2WO6 hierarchical structure to construct the novel Z-scheme g-C3N4/Bi2WO6 heterojunctions via a simple impregnation-calcination method. The morphology, composition and visible-absorptive properties of as-synthesized samples were characterized by XRD, FE-SEM, TEM, UV-Vis-DRS techniques. Methylene blue(MB) and p-nitrophenol(p-NPh) were selected as model pollutant to investigate the effect of g-C3N4 QDs on the photocataytic activity of Bi2WO6 nanoarchitecture. The results reveal that as-prepared Bi2WO6 exhibits the 3 D architecture with the pore size of about 10 nm via a simple impregnation-calcination method. g-C3N4 QDs with the size of about 5 nm can be deposited on the surface of secondary nanoplate of Bi2WO6. The photocatalytic activity of Z-scheme g-C3N4/Bi2WO6 is superior to the pure g-C3N4 and Bi2WO6, and 10%g-C3N4/Bi2WO6 exhibits the best photocatalytic activity for MB and p-NPh. The apparent rate constant(kapp) for the degradation of MB is as high as 4.5 and 5.8 times, 2.6 and 1.6 times for p-NPh compared to that of pure g-C3N4 and Bi2WO6, respectively. The O2· is the main reactive species during the photocatalytic process. The catalytic efficiency enhancement of g-C3N4/Bi2WO6 relative to Bi2WO6 or g-C3N4 can be attributed to the formation of heterojunction between g-C3N4 QDs and Bi2WO6, which suppresses the recombination of photogenerated electron/hole pairs as well as broaden the light absorption.