Preparation And Photocatalytic Properties Of Bi₂S₃/BiOX（X=Cl、Br、I） Composite Materials

Along with the rapid development of modern industry technology, pollution have seriously threaten the safety of human life. The photocatalytic technology is one kind of novel technology of the energy development and pollution control, which is widely paid attention by scientist. A lot of refractory materials or difficultly removing materials, such as organic phosphorus compounds, chloroform, polychlorinated biphenyls(PCBS) and polycyclic aromatic hydrocarbons, etc can be degraded by the photocatalytic technology. Because the reaction condition is not harsh, photocatalytic reaction can achieve at the room temperature and the organic pollutants can be degraded efficiently, the photocatalytic technology has become a hot research at home and abroad.In this study, BiOX(X=Cl, Br, I) and Bi2S3/BiOX(X=Cl, Br, I) composite were fabricated. The structure, morphology and properties of the composites prepared under different condition were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), ultraviolet-visible diffuse(UV-Vis) and Raman. The effect of Bi2S3/BiOX(X=Cl, Br, I) composites prepared under different conditions on the photocatalytic degradation properties of methyl orange was studied. At the same time, the mechanism of photocatalytic degradation of methyl orange was discussed preliminarily. The specific research contents are as follows:BiOX(X=Cl, Br, I) photocatalytic materials were prepared respectively by the ultrasonic assisted hydrolysis method with Bi(NO3)3 and KI as reaction materials. Bi2S3/BiOX(X=Cl, Br, I) composite photocatalytic materials were obtained by an anion exchange reaction with thioacetamide as sulfur source, which Bi2S3 were in situ growth on the surface of BiOX(X=Cl, Br, I). The particles on the surface of BiOX(X=Cl, Br, I) were proved to be Bi2S3 by Raman. The amount of Bi2S3 is few in the Bi2S3/BiOX(X=Cl, Br, I) composite prepared.Effect of different hydrolysis time, different the amount of deionized water on the structure and morphology of the BiOI materials was studied. The difference of the structure and morphology of the BiOI materials fabricated under different composite time and different feed ratio were studied. It can be found that all of BiOX(X=Cl, Br, I) are thin irregular flakes and the structure and morphology of the BiOX(X=Cl, Br, I) materials are hardly affected by different hydrolysis time and different amount of deionized water. The effect of different composite time and different feed ratio on the morphology of the Bi2S3/BiOX(X=Cl, Br, I) materials is less.Bi2S3 distributes on the surface of BiOX(X=Cl, Br) in the Bi2S3/BiOX(X=Cl, Br) materials, and on the edge of BiOI in the Bi2S3/BiOI materials. With the increase of composite time and feed ratio, the amount of Bi2S3 gradually increases. The dimension of Bi2S3 becomes large with the increase of composite time, and the dimension of Bi2S3 becomes small with the increase of feed ratio.The UV-Vis absorption performance of BiOI prepared at different hydrolysis time and different deionized water was studied. It can be found that the effect of hydrolysis time and amount of deionized water on the absorption performance of BiOI is less.The UV-Vis spectrum of Bi2S3/BiOX(X=Cl, Br, I) composite materials prepared at different composite time and different feed ratio was researched. It can be found that the ability of light absorption of Bi2S3/BiOX(X=Cl, Br, I) composite materials is higher than that of BiOX(X=Cl, Br, I), and exists red shift.It can be found that the photocatalytic efficiency of BiOCl is better under UV light, the degradation of methyl orange is 94.53% within irradiation 120 min. The photocatalytic efficiency of Bi2S3/BiOCl is hardly higher than that of BiOCl, the degradation of Bi2S3/BiOCl on methyl orange is 97.58% within the same time.The photocatalytic efficiency of Bi2S3/BiOX(X=Br, I) on methyl orange is significantly higher than that of BiOX(X=Br, I). The photocatalytic efficiency of Bi2S3/BiOBr, prepared at the ratio of 1:1 and composited 120 min, on methyl orange is best. the degradation of Bi2S3/BiOBr on 40mg/L methyl orange is 92.57% within UV light irradiation 100 min. The photocatalytic efficiency of Bi2S3/BiOI, prepared at the ratio of 1:1 and composited 60 min, on methyl orange is best. the degradation of Bi2S3/BiOI on 20mg/L methyl orange is 40.98% within visible light irradiation 180 min.The mechanism of degradation of the Bi2S3/BiOX(X=Cl, Br, I) composite photocatalyst on methyl orange was discussed preliminarily. The high photocatalytic properties of Bi2S3/BiOX(X=Cl, Br, I) composite materials are due to the synergy of heterojunction between Bi2S3 and BiOX(X=Cl, Br, I). The photo induced electron-hole pair can transfer between Bi2S3 and BiOX(X=Cl, Br, I), which lead to the decrease of the composite of electron-hole pair. With the increase of amount of Bi2S3, the defect on the interface and surface of composite will change, which affects the composite of electron-hole pair, hence lead to the change of photocatalytic properties of Bi2S3/BiOX(X=Cl, Br, I) composite materials.