Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst

Preparation and Photocatalytic Properties for Water Decomposition of Titanate Photocatalyst

Author YinYongZhe
Tutor ChenGang
School Harbin Institute of Technology
Course Chemical Engineering and Technology
Keywords Bi4Ti3O12 Doping Loading Sol-gel reaction Photocatalytic
CLC O643.36
Type Master's thesis
Year 2008
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In this paper, a series of Bi4Ti3-xMxO12(M=Cr、Fe、Co) single phase polycrystalline samples were synthesized by the sol-gel reaction method, and the effect of NiOx-loading on photocatalystic activities was also investigated. Besides, the structures and photocatalytic activity of these compounds were studied by X-ray diffraction(XRD), Fourier Transform Infrared(FT-IR), Differential Thermal Analysis(DTA), Brunaure-Emmett-Teller Analysis(BET), Ultraviolet Visible DiffuseReflectance Spectra(UV-vis), and the measurement of photocatalytic activities.The influence of co-catalyst such as NiOx and CoO on photocatalytic activity was further investigated. Many new data and results of them were obtained here, which will help us do the further reseaches, development and applications.Bi4Ti3-xMxO12(M=Cr、Fe、Co) belong to the layered perovskite structure. UV-vis diffuse reflectance spectra of Bi4Ti3-xMxO12(M=Cr、Fe、Co) show that the as-obtained samples have obvious absorption in visible light region(>420nm) with increasing of the amount of dopant. The band gaps of Bi4Ti3-xMxO12 were influenced by the doping of Cr, Fe, Co and decreased with the increasing of the x. The band gaps were affected mostly by the doping of Co. So these photocatalysts might response in the visible light region. The BET results suggest that the surface areas of the samples prepred by the sol-gel method were very relatively big and it was increased with increasing of the amount of dopant. SEM images show that the crystallinity of the samples becomes stronger with the increase of dopant content, resulting in the decrease of photocatalytic activity under visible light irradiation. The photocatalytic experiment results indicated that the crystallinity was the key factor to determine the photocatalytic activities of the samples. Because as the improvement of the crystallinity, the defacts was decresed, so it can prevent electron–hole recombination, which is assumed to be the reason for the improved photocatalytic property. The present research provides useful information for designing new photocatalysts for water splitting.The photocatalytic property was increased after the doping of Cr and Co, and it could be also improved by NiOx-loading, among of which Bi4Ti2.6Cr0.4O12 shows the highest photocatalytic activities. Although Bi4Ti3-xFexO12(x=00.5) also belongs to the layered perovskite structure and has obvious absorption in visible light region(>420nm) with increasing of the amount of dopant, particularly it has an obivious absorption in the region of 420480nm. However, the doping of the Fe makes the activity lower. This is because the distortion of the lattice. From the IR spectra, the absorbence at 800cm-1 belongs to TiO6 are not obeserved. So, chosing the siutable elements for doping is very important. We studied the influence of amounts of NiOx co-catalyst on photocatalytic activity and found that the most optimum amount of the co-catalyst was around 0.2 mass% as Ni metal particles on the Bi4Ti3O12 photocatalyst.

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