Synthesis And Photoelectrochemical Properties Of The Nanomaterials Based On ZnO

In recent years, nanosemiconductor materials are used to the photocatalysis,solar cell and gas sensor, et al. Zinc oxide （ZnO） as an emerging semiconductormaterial has been applied to the photocatalysis, madicine, gas sensor, guided-waveoptical device and transparent conducting electrode, due to its wide direct bangap,large exciton binding energy of60meV, non-toxic, low cost, a high radiationresistance and perfect electromechanical coupling performance. However, as a widebangap semiconductor, ZnO has some disadvantages hinding its practicalapplication to some extent. First, the high recombination probability ofphotogenerated electrons and holes, and the low utilization efficiency of photon.Second, the powder catalysts are not easy to recycle and reuse. Therefore, theresearchers have devoted themselves to exploring photocatalysts to improve thephotocatalytic activity. On the one hand, they modify the surface of ZnO to extendZnO photoresponse from the UV region into the visible light region. So far, Surfacemodification with transition metal oxide, doping, noble metal deposition,photosensitization and reduction of surface treatment have been considered possiblesolutions to improve the quantum yield and photocatalytic activity. On the otherhand, an external electric field is required to facilitate the separation of thephotogenerated carriers and minimize the charges recombination reations. Thus, theprepared conducting thin films by the different methods served as the workingelectrode in the photoelectrocatalytic process with the constant potential or constantcurrent, to enhance the photocatalytic efficience for degradation of organicpollutants.In this thesis, we studied the difference from the photoelectric-chemical and photocatalytic properties of prepared pure ZnO nanorod arrays films on Zinc sheetsby the electrochemical method at first. Then the ZnO/FTO films on FTO wereprepared by the different method. And then, In₂O₃-sensitized ZnO nanorod arrayfilms were successfully prepared. We compared the photoelectrocatalytic activity ofthe In₂O₃-sensitized ZnO nanorod array films and the ZnO/FTO nanorod array filmsand discussed the behaviors of photogenerated electrons and holes by FISPVtechnique and electrochemical station. We also synthesized the Ag/ZnO nanorodarray films by noble metal deposition to change electron distribution on the surfaceof ZnO nanorod array, and the photocatalytic activity was enhanced. We haveevaluated the photoelectrocatalytic activity and photocatalytic activity of Ag/ZnOfilms by degradation of MB, and it provides the theoretical basis for the practicalapplication of photoelectrocatalyst.The main works of this thesis are studied as follows:1. Dense ZnO nanorod arrays were grown on zinc sheets by a simplehydrothermal method. We studied the photoelectrochemical property of pure ZnOnanorod arrays by the electrochemical workstation. And we also tested thephotocatalytic activity of ZnO nanorod arrays under different condition （differentapplied potential and with UV light or not）.The results indicated that when theapplied potential was-0.5V （vs. SCE）, the catalytic activity was highly enhanced.The effect of degradation MO was different under the different applied potential.Under the same condition, the degradation rate of MO solution in thephotoelectrocatalytic process was the highest among the photocatalytic,electrocatalytic and photoelectrocatalytic process, which suggests the synergeticeffect between PC and EC process.2. Based on the ZnO nanorod arrays on the FTO conducting glass by a simplehydrothermal method, we prepared In₂O₃-sensitized ZnO nanorod array films by afacile two-step process and get a series of In₂O₃-sensited ZnO nanorod array.Westudied the photoelectric property of them by FISPV technology and electrochemicalworkstation, to find the optimal value of the content of In₂O₃.We have evaluated the photoelectrocatalytic activity of ZnO nanorod array and In₂O₃-sensitized ZnOnanorod array by degradation efficiency of RhB. We studied the effect ofIn₂O₃-sensitized ZnO heterostructure construction for the performance of thephotoinduced electrons by using the electrochemical workstation and therelationship between photoinduced electrons behavior and the photoelectrocatalyticprocess. The results demonstrate that RhB in aqueous solution is more efficientlydegraded by using In₂O₃-sensitized ZnO nanorod array under visible light with aapplied bias in2hours, and also show the efficiency of In₂O₃-sensitized ZnOnanorod array is1.4times higher than that of pure ZnO.3. Based on ZnO/FTO, the Ag/ZnO nanorod array films were prepared byphoto deposition method. The amounts of Ag were different by controlling theconcentration of AgNO₃. The photoelectrochemical property of Ag/ZnO nanorodarrays by the electrochemical workstation was studied. And we also tested thephotocatalytic activity of Ag/ZnO nanorod arrays by degradation MB. The resultsshow that when the concentration of AgNO₃was0.05M, the photocurrent density ofAg/ZnO nanorod array film was the highest. The moderate of Ag serve electronsinks accumulation of the photogenerated electrons, and then facilitate the chargeseparation. As a result, the photocatalytic activity would increase. We have evaluatedthe photoelectrocatalytic activity of ZnO nanorod array and Ag/ZnO nanorod arrayby degradation efficiency of MB under visible light. The catalytic activity of Ag/ZnO nanorod array was the brightest. And we compared the photoelectrocatalyticand photocatalytic effect of Ag/ZnO nanorod array films showing the fact that theapplied potential can enhance the degradation efficiency of MB.