Study On The Preparation And Properties Of Photocatalyst MnO₂ Nanocomposites

Photocatalytic technology is a green technology which has an important application prospect in the field of environmental remediation and energy crisis.The semiconductor photocatalytic technology as a simple and efficient oxidation reduction technology,is use the sunlight will organic pollutants degrade into carbon dioxide and water,and there was no consumption,has the advantages of simple equipment,low cost,short reaction time,green environmental protection,energy consumption is very low and so on,therefore,it has potential application value in controlling environmental pollution and alleviating energy crisis.MnO₂is an important narrow band gap semiconductor photocatalyst,which has a wide range of applications in air purification,antifogging and self-cleaning.Generally,the photoelectric properties and photocatalytic activity of MnO₂nanomaterials can be effectively improved by optimizing microstructure,doping,surface modification and building heterojunction.This paper mainly by surface modification and construct heterojunction two processes to prepare MnO₂nanocomposite materials,by field emission scanning electron microscopy,X ray powder diffraction and UV diffuse reflectance spectroscopy study the morphology,composition and optical properties of MnO₂nanocomposites,evaluate its photocatalytic performance by using methylene blue model pollutant.The main contents of the work are as follows:First,used K₂MnO₄and concentrated HCl as raw material,through the hydrothermal prepared MnO₂nanowires,and then used Cu?AC?₂?H₂O as raw materials and C₆H₁₂O₆as surfactant,Cu²⁺would load on the surface of MnO₂nanowires by water bath method,under the protection of N₂,CuO_x/MnO₂nanocomposites ware prepared by high temperature calcination method.The photocatalytic activity of the composite was investigated by methylene blue as a simulated pollutant.Compared with pure MnO₂nanowires,the specific surface area of CuO_x/MnO₂nanocomposites increased significantly.The larger specific surface area provided more reactive sites,promoted the photocatalytic reaction,enhanced the utilization of photogenerated electron-hole,and accelerated the separation and transfer of photogenerated electron-hole pairs,and enhanced the efficiency of photocatalytic degradation of organic compound.Second,we choosed AgNO₃,PVP and?CH₂OH?₂as raw materials to prepare Ag nanowires,then mixed Ag nanowires and MnO₂nanowires uniformly,and got the mechanical mixture of Ag nanowires and MnO₂nanowires,that is the production of Ag/MnO₂.The visible photocatalytic activity of the Ag/MnO₂mechanical mixture was evaluated through the photodegradation experiment of methylene blue.The experiment showed that the Ag/MnO₂mechanical mixture showed higher visible photocatalytic activity than the pure MnO₂nanowires.Third,by using K₂MnO₄,concentrated HCl,C₆H₁₂O₆and Cu?AC?₂?H₂O as raw material,by followed hydrothermal synthesis,surface loading and calcination technique,MnO₂nanowires which the surface was loaded by CuO were successfully prepared,named CuO/MnO₂hetero-nanostructures.The experiment of photocatalytic degradation of methylene blue showed that,compared with pure MnO₂nanowires,CuO/MnO₂hetero-nanostructures exhibited higher photocatalytic activity and stability,this was possible because the CuO and MnO₂composite could improve the separation rate of the photogenerated electron-hole pairs,so enhanced the ability of photocatalytic degradation of organic substance.