| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 103 === In this study, the sol-gel and spin coating methods are used to fabricate α-Fe2O3-based thin films on fluorine-doped SnO2 (FTO) glass substrates which is used as a photoelectrode for photoelectrochemical (PEC) water splitting. In the first part, effects of polyvinylpyrrolidone (PVP) concentrations and spin-coating times on the microstructural, morphological, optical and electrochemical and PEC properties of pure α-Fe2O3 thin films are investigated. In the second part, we attempted to prepare Sn-doped α-Fe2O3 thin films for PEC water splitting via two types of impurity-doping (i.e., re-annealed at higher temperature or directly added tin chloride to our precursor solutions). The results from scanning electron microscope showed that the pure α-Fe2O3 thin films revealed a porous films on the surface of sample. After annealing at 550 oC in air ambient, all samples belonged polycrystalline hematite structure and no secondary phase via X-ray diffraction patterns and Raman spectra. From PEC performance, the sample deposited via PVP/Fe concentration ratio of 2 and spin-coating times of 8 times which has a higher photocurrent of 0.015 mA/cm2 than other samples. In the section of Sn-doping, we found that the specimen with re-annealing at 750 oC has a better PEC response due to the high temperature of re-annealing allowed the tin ion diffused from the substrate into iron oxide crystalline which increased the carrier concentration leading a higher PEC performance. On the other hand, we found that the 7.5% Sn-doped α-Fe2O3 thin films has a higher PEC response than other samples which prepared via directly added tin chloride to our precursor solutions. It is noticed that no matter whether added divalent or tetravalent tin ion, after annealing, they all became tetravalent tin ion and bonding with iron which were analyzed by X-ray photoelectron spectroscopy.
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