Synthesis and Photocatalytic Activities of Ti/Zr Mixed Metal Oxides
Date Issued
2007
Date
2007
Author(s)
Tsai, Huai-De
DOI
zh-TW
Abstract
Mesoporous Ti/Zr mixed metal oxides were prepared using zirconium sulfate and titanium oxysulfate as the zirconium and titanium precursors, respectively, and cetyltrimethylammonium (CTMA) ions as the pore-directing agent. The Ti/Zr atomic ratio was varied from 0 to 90%. For the as-made materials with the Ti/Zr atomic ratio up to 70%, the low-angle powder XRD patterns featured a strong diffraction peak at 2θ~2-2.5° indexed to the (100) plane and two weak peaks indexed to the (110) and (200) planes of 2D-hexagonal structure. After calcination at 400°C, the metal oxides with the Ti/Zr atomic ratio lower than 60% still retained a small diffraction peak at 2θ~3.5-4° in the low-angle XRD patterns, indicating the preservation of ordered mesoporous structures. Anatase TiO2 particles were formed in the as-made samples with the Ti/Zr atomic ratio greater than 60% evidenced by the appearance of diffraction peaks at higher angles (2θ = 25.38˚, 38.38˚, 48.15˚). These peaks grew stronger after the samples were calcined at 400°C. All the mixed metal oxides calcined at 400°C showed high surface areas, varying from 102 to 402 m2/g, and large pore volume in the range of 0.14-0.44 cm3/g. Among them, the one with 50% Ti/Zr atomic ratio has the highest surface area of 402 m2/g. The photocatalytic activities of the Ti/Zr mixed metal oxides were examined in photodegradation of phenol in aqueous solutions. The photocatalytical activity was found to improve with the increase in titanium content and the crystallinity of the anatase phase. When the Ti/Zr atomic ratio is over 70%, the photocalatytical activities of the mixed oxides would exceed that of mesostructured pure TiO2. The mixed oxide with 90% Ti/Zr atomic ratio calcined at 600°C gave the highest photocatalytic activity, and the phenol degradation rate was almost twice as fast as that over anatase TiO2. However, the low calcined temperature samples gave the better activities on the visible light induced photocatalysis. Under 419 nm visible light radiation, the materials with Ti/(Ti+Zr) ratio of 90 % calcined below 300 °C showed the best photocatalytic activity in phenol degradation, which is due to facile adsorption of phenol molecules on the surface of materials with rich hydroxyl groups. In addition, the photocatalytic rate is increased by increasing of the pKa value of the reactants.
Subjects
二氧化鈦
二氧化鋯
光催化
苯酚
混合氧化物
TiO2
ZrO2
phtocatalysis
phenol
mixed metal oxides
Type
thesis
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