Study On Preparation Of CeO₂-based Composites And Their Photocatalytic Properties

Cerium oxide has become a new kind of photocatalytic material due to the chemical stability,non-toxic and simple preparation However,the band gap of CeO₂ is 2.79 eV,which can only absorb light with wavelength range less than 444 nm and can not make full use of sunlight.The electron and hole are easy to recombine,which leads to low photocatalytic efficiency of cerium oxide.These problems limit the photocatalytic application of the cerium oxide.In order to improve the photocatalytic activity of the photocatalysts we constructed heterojunction and deposited precious metals.This paper includes the following two aspects:The photocatalysts of cerium oxide and bismuth oxide heterojunction were synthesized by simple hydrothermal method.The structure and properties of Bi₂O₃,CeO₂,Bi₂O₃/CeO₂ were characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FESEM）,UV-vis,X-ray photoelectron spectroscopy（XPS）and transmission electron microscopy（TEM）.The photocatalytic activity of Bi₂O₃/CeO₂ composite photocatalyst is higher than that of single CeO₂ photocatalyst.When the amount of Bi/Ce is 4: 6,the degradation effect of methylene blue and phenol is the best.The photocatalytic activity of Bi₂O₃/CeO₂ is due to the formation of an effective heterojunction structure in Bi₂O₃/CeO₂ composite photocatalyst synthesized by hydrothermal method.The heterojunction structure is helpful to separate electron-hole pairs and improve CeO₂ photocatalytic activity.At the same time,the synthesized Bi₂O₃/CeO₂ contains more oxygen defects which provided the more active sites,increased photocatalytic activity.The Ag/CeO₂ composite was synthesized by hydrothermal and photoreduction method.The structures and the photocatalytic properties of CeO₂ nanorods,CeO₂ nanocubes,Ag/CeO₂ nanorods and Ag/CeO₂ nanocubes were measured by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and UV-vis（UV-vis）.The CeO₂ nanorods have a length of 30-70 nm and a width of 7-13 nm.The CeO₂ cube has a side length of 15-40 nm.The degradation of phenol and methylene blue by CeO₂ NRs in visible light is better than that of CeO₂ NCs.This is because the exposedcrystal face of CeO₂ NRs is（110）and the exposed crystal face of CeO₂ NCs is（100）.And the photocatalytic activity of crystal surface（110）is better than the crystal surface（100）.The degradation of methylene blue and phenol in Ag/CeO₂ NRs was better than that in CeO₂ NRs.This was due to the fact that Ag produced a plasma resonance effect,which enhanced the visible light absorption of CeO₂ NRs and promoted the separation of electrons and holes.