| Titanium dioxide (TiO2), as core material in photocatalytic technique, has been received great attention and extensively studied in recent years. However, there are some problems in large-scale application, which make photocatalytic technique in wastewater application stagnant. The recombination of photo-generated carriers leads to a low quantum efficiency. The narrow range of its photoresponse is unfavorable to the effective utilization of sun light. The immobilization of the catalyst is also a serious problem.Based on the existing problems, the objectives of this thesis are put forward. TiO2(undoped and doped) was prepared on ITO glass to form nanofilm electrode by metal-organic chemical vapor deposition method. The prepared film electrode has good transparency and high conductivity. The immobilization of the catalyst was achieved by depositing TiO2onto substrate forming film. The nanostructure of TiO2and its application in PEC system are favorable to lower the possibility of carrier recombination. The visible-light photocatalytic activity of catalyst was achieved by doping with B or Fe.The TiO2deposition process using MOCVD technology was numerically simulated by computational fluid dynamics method. The resultes showed that the growth rate of the films increased with the increase of deposition temprature, flow rate had a market influence on the concentration of TTIP near the substrate, and growth rate also increased with the increase of source temperature. The optimal ranges of main parameters were determinded:deposition temperature1023K, source temperature363K, flow rate6-7SLM, while the growth rate of the flim is about75nm/min under these condition. The sensitivity analysis of operating parameters showed that the deposition process was kinetically controlled under623K deposition temperature, the parameter with the most influence on both growth rate and uniformity was deposition temperature in this condition. Under823K depostion temperature, each parameters had a certain degree of influence on film growth rate and unformity with little differences. At1023K deposition temperature, the system was in the mass transport-limited regime. The growth rate influenced by both depositon temperature and flow rate, while film uniformity was mainly control by flow rate.The results on the study of film growth pattern and the catalytical activity of TiO2/ITO film showed that the prepared TiO2films were well-crystallized anatase with high uniformity, the growth mechanism of the film was S-K mode, the grain size was around26nm under650℃deposition temperature, the527nm thick film had the best photocatalytic activity under UV illumination, the degradation rate of MO was greatly improved in PEC process, especially under SE illumination. The degradation rate were upto97%within120min and the apparent reaction rate constant had doubled over the conventional photocatalytic process.Different amount of B were doped into TiO2by MOCVD method in preparation process. The doping of B can make TiO2has visible-light response by narrowing its bandgap to2.92eV.5at.%B-doped TiO2/ITO film can efficiently degrade MO under visible light illumination and its catalytic performance can be significantly improved in PEC process with the degradation rate of MO over80%in120min. The results of first-principle calculation showed that most of the doping B substituted the O in anatase lattice, while some of them entered the crystal lattice to form Ti-O-B bond and a small amount existed remain B2O3.The study on the doping of transition metal Fe showed that proper concentration of doping Fe enhanced the photocatalytic process of TiO2under UV illumination. Meanwhile the doped film had obvious visible light response and catalytic activity under visible light illumination. Compared with the doping of B, Fe-doped TiO2/ITO film electrode had higher photocatalytic activity under UV light due to the seperation of photogenerated carriers by substituted Fe3+in the lattic. Meanwhile the0.6eV redshift caused by Fe doping lead to the enhancement of film catalytic activity under visible light illumination. The results of first-principle calculation showed that the doping of Fe could induce intermediate state near CBM formed by partly hybridization of Fe3d and O2p orbital while part of Fe3d orbital formed acceptor level near VBM, which lead to a visible light driven activity. |
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