Behavioral Regulation And Properties Of Nano-Cu₂O Composite Thin Films

Cu₂O is a semiconductor material with a forbidden band width of about 2.0eV.It has the advantages of cheap,non-toxic and safe,and has potential applications in the treatment of photovoltaic devices and photocatalytic degradation of pollutants.Since its photocatalytic efficiency is largely restricted by the defects of recombination for photogenerated electron and hole,Cu₂O can be combined with noble metal or n-type semiconductor to improve the photocatalytic and photoelectric conversion efficiency.On the one hand so that you can make full use of the sun in the ultraviolet and visible light parts,which greatly enhance the utilization of sunlight conversion;the other hand can effectively reduce the electronic hole with the compound rate,in order to improve the photovoltaic device Conversion efficiency.In this paper,Cu₂O thin films and their modified Ag-Cu₂O and ZnO-Cu₂O composite films were prepared by electrodeposition on the ITO conductive glass by three-electrode electrochemical deposition.The films were characterized by XRD,XPS,SEM,UV-Vis and PL The microstructure,surface morphology and optical properties of the prepared films were characterized and analyzed.The electrochemical performance of the composite films was also studied.The mechanism and the application of photocatalytic degradation of methylene blue were also discussed.Get the following conclusions:（1）Preparation and characterization of Ag-Cu₂O composite films.The results show that the prepared Cu₂O thin films have high purity and high strength（111）crystal face,and have the crystal structure of high quality chalcopyrite under the condition of best preparation of nano-Cu₂O thin films.The Ag-Cu₂O composite films were obtained by oxidation-reduction reaction,and the films were regular and dense.The absorption boundary of Ag-Cu₂O film is about 600nm,and the absorption of light is the largest at 500nm,which is almost 2 times of visible light absorption of Cu₂O film.The band gap of Ag-Cu₂O composite film is about 1.98ev.At the same time,Ag-Cu₂O composite films have higher photocurrent and open circuit voltage than those of Cu₂O thin films,and their sizes are about-0.007 1A/cm 2 and 4.0mV,respectively.It is shown that Ag-Cu₂O composite films have the same Cu₂O The film has more excellent photoelectric properties.In addition,the carrier concentration of Ag-Cu₂O composite film is 1.3294x1026cm-3,which shows a high photo-generated electron-hole concentration,which is favorable for the absorption of ultraviolet light.（2）Mechanism and kinetics of photocatalytic degradation of methylene blue by Ag-Cu₂O composite thin films.The results show that the degradation of methylene blue by Ag-Cu₂O composite thin film is the first of the hydroxyl radicals by UV-Vis and GC-MS analysis and analysis of the intermediates in the reaction process and analysis of various spectra.Attack the methylene blue molecular chromophore,that is,nitrogen and sulfur heterocyclic ring,so that it was destroyed and decolorization;and then attack the degradation of methylene blue intermediates,and then through a series of reaction process was eventually catalyzed degradation of CO2 and H2O and other small molecules.The photocatalytic degradation of methylene blue by Ag-Cu₂O composite films was investigated by means of the first-order reaction kinetics model:c=cok=coexp（0.1257co-0.452）In addition,the photocatalytic activity of Ag-Cu₂O composite film is higher than that of pure Cu₂O film.The degradation rate of the Ag-Cu₂O composite film is 93.1%after 3h,and the photocatalytic degradation rate of methylene blue after repeated 8 but also to more than 75%.The results show that Ag-Cu₂O composite films exhibit better catalytic performance and reusability.（3）Preparation and characterization of ZnO-Cu₂O composite films.The results show that the ZnO-Cu₂O composite films prepared by electrodeposition are of high purity and the film morphology is fluffy and stacked.The thickness is about 50nm.At the same time,the ZnO-Cu₂O films show good absorption and stronger photoluminescence properties from the visible region to the ultraviolet region.It can be seen that the electrochemical reaction of ZnO-Cu₂O film is small in the dark state,the electrochemical resistance is large and the efficiency of photo-generated electron-hole is low.In the case of light,It can be seen that the spectral impedance of the AC impedance is significantly reduced,the carrier concentration in the film is increased,and the quantum efficiency is also increased,resulting in a decrease in the electrochemical resistance.（4）ZnO-Cu₂O composite thin films photocatalytic degradation of methylene blue.The results show that the photocatalytic degradation of methylene blue by ZnO-Cu₂O composite thin films is also the process of hydroxyl radicals attacking the methylene blue molecules by UV-Vis and GC-MS analysis of the intermediates in the photocatalytic reaction process.And then attack the degradation of the intermediate product,and then through a series of reaction process is eventually degraded to CO2 and H2O and other small molecules.The degradation rate of the ZnO-Cu₂O composite film was 91%after photocatalytic degradation.After 8 times of repeated use,the degradation rate of methylene blue could reach more than 75%.The results show that the ZnO-Cu₂O composite films exhibit better catalytic performance and reusability.