| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === The present investigation mainly focused on the ilmenite structure materials, NiTiO3 and CoTiO3, which may be the potential materials for photocatalysis. In advanced, the silver ions were used to substitute for part of nickel or cobalt ions, so as to prepare the photocatalysts as (Ag1-XNiX)TiO3 and (Ag1-XCoX)TiO3 nano-sized powders. This research can be divided into five sections, including changing the parameters of the organic acid precursor method which was modified from the Pechini process, preparing NiTiO3 and CoTiO3 powders by the citric acid precursor method, and also investigating the photocatalytic properties of silver doped NiTiO3 and CoTiO3 powders for the degradation of methylene blue (MB). In the experiments, nano-sized NiTiO3 and CoTiO3 powders were successfully prepared by the citric acid precursor method and the crystalline temperature of NiTiO3 and CoTiO3 powders were 620�薡 and 588�薡. It is also found that NiTiO3 and CoTiO3 powders heated to 600�薡 for 3 hours in air would be the candidates for photocatalysts. Moreover, the crystalline activation energy of NiTiO3 and CoTiO3 was estimated as 383 and 251 kJ/mol; the activation energy of grain growth was also calculated as 8.84 and 13.23 kJ/mol for NiTiO3 and CoTiO3.
When silver ions were in substitution for nickel or cobalt ions, the ability for NiTiO3 and CoTiO3 to adsorb MB molecules was improved, and the photo-degradation of MB was also influenced by the dopants of silver ions. Silver-doped NiTiO3 and CoTiO3 photocatalysts shows the best photodegradation rate of MB up to 63.71% and 32.42% under the UV light irradiation for 12 hours, and also presents the best photodegradation rate of MB as 65.74% and 35.59% under the visible light irradiation for 60 hours. Including the degradation of MB from the adsorbability of NiTiO3 and CoTiO3 in the dark, the concentration of the reacted MB solution was mostly decreased about 97.48% and 99.84% of the initial MB concentration for Ag-NiTiO3 series, and also decreased about 57.05% and 57.28% for Ag-CoTiO3 series after the UV and visble light irradiation. Therefore, silver ions used to place nickel or cobalt ions can substantially improve the photocatalysis for the degradation of MB.
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