鈦鋯混合氧化物的合成與光催化反應活性探討

為了達到更好的光催化效果，本實驗合成含有大表面積與規則孔洞的不同比例鈦鋯混合氧化物。當鈦的含量在70% Ti/(Ti+Zr)莫耳百分比以下，則初合成的結構就可以維持在二維六角堆積；當樣品鍛燒到400°C 時，含60% Ti/(Ti+Zr)莫耳百分比以下的樣品還可以維持如本實驗室之前所發表的純ZrO2 的二維六角堆積結構。Ti/(Ti+Zr)莫耳百分比在50%左右表面積最大可以到達約400m2 g-1，但更高鈦含量的樣品，由於只是顆粒堆積的結構，所以表面積下降到大約只有150m2 g-1。在300nm 紫外光為光源作光降解phenol 活性結果的探討，發現二氧化鈦的含量比例越多，催化效果越好，但是含有少部分二氧化鋯對催化效果也有顯著的幫助，所以含有90% Ti/(Ti+Zr)莫耳百分比之樣品在紫外光下光降解phenol 效果是最好的，比相同製成方法的純二氧化鈦更佳。另外在當鍛燒溫度越高，紫外光光降解 phenol 活性會顯著提升，但在樣品鍛燒到1000°C 時開始下降。所以在300nm 波長範圍下的催化，最好的90% Ti/(Ti+Zr)莫耳比的樣品鍛燒到900°C 可以在60 分鐘將反應幾乎完成, 略慢於商業催化劑Degussa P25 的45 分鐘。反觀419nm 可見光的光降解phenol 效果卻是相反的, 雖然90% Ti/(Ti+Zr)莫耳百分比混合的比例依然是最好的，但是鍛燒溫度越低，反應活性卻是越好，當低於400°C 時，樣品在可見光的活性可以略快於Degussa P25。對於觸媒表面因鍛燒溫度的高低也會顯現出極性大小的差異，實驗上利用極性較小的農藥物種加保伏(carbofuran)來與極性大的phenol 來作反應物比較探討，另外也利用aniline、benzaldehyde 與benzoic acid 一些苯環上不同官能基的衍生物當做反應物來觀察對光催化反應的影響。

關鍵字

二氧化鈦；二氧化鋯；光催化；苯酚；混合氧化物

並列摘要

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.

並列關鍵字

TiO2 ； ZrO2 ； phtocatalysis ； phenol ； mixed metal oxides

參考文獻

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鈦鋯混合氧化物的合成與光催化反應活性探討

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