Study On Preparation And Photocatalytic Performance Of Various Shapes Of ZnO And Its Composite Catalyst

ZnO is widely used in photocatalytic environment cleaning,energy conversion,hydrogen production and antibacterial materials due to its good thermal stability,low cost and direct band gap.In recent years,researchers have prepared ZnO particles with specific morphologies in order to obtain semiconductor materials with high photocatalytic activity.Due to the difference in morphologies,different crystal planes will be exposed,leading to the difference in photocatalytic properties.Researchers have proposed a lot of methods to fabricate ZnO with different active crystal planes.However,how to prepare highly active ZnO with highly active planes through a simple,efficcient and environmental friendly method is the key to current research.In this paper,ZnO with different morphologies were prepared by atmospheric pressure hydrothermal method.The growth mechanism and photocatalytic properties of ZnO are studied in detail.Furthermore,the nano metal particles are deposited on the surface of ZnO with high activity crystal surface to prepare nano materials with much better photocatalytic performance.The mechanism of synthesis and photocatalytic performance were studied.The main research content is as follows:1.Through atmospheric hydrothermal method,the urchin-like、rod-like、fusiform-like、starfish-like and flower-like ZnO were prepared by adjusting the reaction conditions.The results show that the OH-and NH4+ ionized in different alkaline environments will be selectively adsorbed on different crystal planes of the ZnO during the growth process,which results in the difference in growth rate of each crystal face,further leading to the difference in ZnO morphologies.That is why ZnO with different morphologies show different exposed crystal planes.Urchin-like ZnO has{1010}and{1011}as the main exposed crystal planes while the rod-like ZnO has side {1010} and top {0001} as exposed crystal planes.Fusiform-like ZnO takes{1010}as the main exposed crystal plane while starfish-like and flower-like are ZnO particles assembled into a lamellar structure with {2110} as the main exposed crystal plane.2.The influence of morphological differences on the photocatalytic performance was studied.Flower-like ZnO particles with {2110} as the main exposed crystal plane showed the highest photocatalytic activity,while urchin-like ZnO exbited the lowest photocatalytic activity.Through comparative experiments,it can be concluded that most hydroxyl radicals as well as superoxide anions were generated by the flower-like ZnO,whose value is 47.83μmol/L and 102.78 μmol/L,respectively.The main reason for the difference of photocatalytic performance is the difference of active oxygen production caused by different exposed crystal faces.3.In order to further improve the photocatalytic activity of ZnO,Ag nanoparticles were prepared by depositing on the surface of flower like ZnO.The results show that Ag nanoparticles are uniformly distributed on the surface of ZnO and the absorption of the material in visible light band is enhanced.Further research shows that Ag@ZnO has higher photogenerated electron and hole separation efficienc and higher specific surface area comparing pure ZnO.MB is used as a simulated pollutant to detect the photocatalytic performance of the composite material.The results show that the photocatalytic degradation efficiency of Ag@ZnO increases first and then decreases with the increase of Ag amount.With the Ag loading around 4%,the MB degradation efficiency reaches the highest 98.6%within 2 h,which is 32.4%higher than pure ZnO.