Preparation Of ZnO Nanorod And Its Photocatalytic Performance

As a new multifunctional inorganic material,ZnO is widely used in many fields,such as gas sensing,pressure sensing,catalysis,and optics.Zn?OAc?₂ shows excellent catalytic activity for methyl N-phenyl carbamate?MPC?synthesis from the reaction of aniline and dimethyl carbonate?DMC?.But it is easily to be deactivated and can't be reused.In this paper,the preparation of nano-rod ZnO from deactivated Zn?OAc?₂ was investigated.Using Zn₄O?OAc?₆ as raw material,ZnO nanorods with uniform morphology?S-1?are prepared at 200°C for 24 h by hydrothermal method without acid,base or template.The length of ZnO nanorods was 1?m⁶?m and the diameter was between 150 nm and 250nm.The formation of ZnO nanorods was due to the combined action of Zn₅?OH?₈?OAc?₂·2H₂O?LHZA?and Zn?OAc?₂·2H₂O,which are formed by the addition of water to Zn₄O?OAc?₆.Using Zn₄O?OAc?₆ as raw material,hexagonal ZnO?S-2?with self-assembled hexagonal faces were prepared by adding 2wt%PEG-1500 as template at 180°C for 24 h.Zn?OAc?₂ has excellent catalytic activity for MPC synthesis from the reaction of aniline and DMC.The conversion of aniline and the yield of MPC were 97.3%and 97.2%respectively at 130?for 3 h catalyzed by Zn?OAc?₂.The catalyst after reaction,which almost had no catalytic for MPC synthesis,contained LHZA and a small amount of Zn?OAc?₂ and ZnO.The deactivated Zn?OAc?₂ was served as precursor to prepare nano-ZnO.The water content of DMC has a significant effect on the morphology of ZnO prepared by hydrothermal method;when DMC?H₂O content of 0.044 wt%?was used as raw material for the synthesis of MPC,a rod-like ZnO?S-3?with a relatively uniform can be obtained using deactivated Zn?OAc?₂ as precursor with the addition of PEG-400 during crystallization.The length and diameter of the ZnO rod is approximately 3⁸?m and0.3¹.0?m respectively.Without PEG-400 addition,flower-like ZnO?S-4?constituted by the cluster of short rod-like ZnO was prepared.Using Zn?OAc?₂?2H₂O as catalyst at 130°C for 3 h,the conversion of aniline and the yield of MPC were 92.5%and 91.7%respectively.The catalyst after reaction contained LHZA,a small amount of Zn?OAc?₂ and ZnO.ZnO nanowires?S-5?were obtained by using catalyst after reaction as precursor without template addition.The different morphologies of ZnO?S-1,S-2,S-3,S-4,S-5?was characterized by PL and UV-vis absorption spectrum.The PL spectrum results show that ZnO products have a strong luminescence peak centered at wavelength of 500 nm,it indicates that the prepared samples have many defects and oxygen vacancies.The photocatalytic activity of ZnO was studied by photodegradation of RhB as probe reaction and 365 nm UV light as light source.The photocatalytic activity of S-5 was better than other catalysts.RhB was almost completely degraded at 150 min.