摻雜VA族元素之二氧化鈦作為可見光光觸媒之研究

Studies on Group VA Elements Doped TiO2 as Photocatalysts Using Visible Light

楊政晁(Cheng-Chao Yang)

指導教授 ： 鄭淑芬

國立臺灣大學/理學院/化學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.10373

摘要

本論文以共沉澱法和沉積沉澱法，將VA族元素之P、Sb及Bi摻雜於二氧化鈦中，製備可利用可見光波長進行有機汙染物催化降解之光觸媒。
共沉澱法製備之二氧化鈦，以P、Sb及Bi之稀酸或鹽類溶液與TiOCl2一起迴流反應而得，其晶相會受到摻雜元素莫耳比例增加的影響，由完全金紅石(rutile)晶相而逐漸呈現包含銳鈦礦(anatase) 的混相二氧化鈦。樣品中摻雜10~12% Bi的二氧化鈦在50 ℃烘乾後得到初合成觸媒，以波長419nm可見光之光源照射時，對於苯酚溶液的催化降解活性和礦化成二氧化碳的能力最高，而且優於商業化觸媒Degussa P25二氧化鈦，但是對於苯甲醛的催化降解活性和礦化成二氧化碳的能力則遠低於商業化Degussa P25二氧化鈦。隨著熱處理溫度的升高，觸媒顆粒變大，催化活性都會逐漸降低。此外，比較溶液之酸鹼性對光降解的影響，發現酸性環境有助於光催化降解苯酚反應的進行；相反的，對於苯甲醛溶液的光催化降解，活性並不會受到pH值的影響。
沉積沉澱法製備二氧化鈦，先分別製備金紅石和銳鈦礦晶相的二氧化鈦，再將Bi溶液以1N氫氧化鈉溶液調整pH值到6~7之間，使氧化鉍沉積於二氧化鈦的表面。XRD圖譜顯示，二氧化鈦的晶相皆為純相，無其他雜相出現。UV-Vis吸收光譜則顯示銳鈦礦晶相的二氧化鈦於可見光波長範圍內，沉積Bi後在400~ 600 nm之間會有肩帶（shoulder）吸收，沉積Bi於P25的吸收光譜則會有清楚的紅位移。對於苯酚的光催化反應，沉積1% Bi的金紅石晶相二氧化鈦，催化活性和礦化能力亦大於商業化P25和沉積Bi之銳鈦礦晶相二氧化鈦。其中，以 200℃溫度熱處理摻雜1% Bi的金紅石晶相二氧化鈦，能夠得到最佳的催化活性。
為了利用孔洞材料高表面積可吸附有機汙染物的特性，以提高有機汙染物的降解率，嘗試將摻雜Bi的二氧化鈦膠體(sol)負載於孔洞材料MCM-41和SBA-15表面，所得樣品將檢測IR、表面積、XRD、TEM、UV-Vis吸收光譜及催化活性。

關鍵字

二氧化鈦 ； 金紅石 ； 銳鈦礦 ； 光催化

並列摘要

The synthesis methods of coprecipitation and deposition-precipitation were used in this thesis. The elements of P, Sb, and Bi were doped in titanium dioxide for application as photocatalyst to degrade organic pollutants.
The phosphoric acid, antimony(III) chloride and bismuth nitrate were as source of P, Sb, and Bi and diluted or solved in acid, respectively. The solution was mixed with 4M TiOCl2 and refluxed together to get doped titanium dioxide. The crystal phase of titanium dioxide was affected by the dopants. The phase was changed from pure rutile to become mixed phase (anatase and rutile) if more dopant was added. The best photocatalyst is as-made Bi-doped titanium dioxide and mole ratio is 10~12% when phenol solution was photocatalyzed by doped titanium dioxide by 419nm wavelength light source. In addition, photocatalytic activity of Bi-doped TiO2 is better than commercial Degussa P25. But, the photocatalytic activity of Bi-doped titanium dioxide is less than Degussa P25 when used to degrade benzaldehyde solution. The particle size of catalyst may be larger and causes photocatalytic activity gradually decreased when treated at higher temperature. The pH effect is also an effect factor of photocatalytic activity. The photocatalytic degradation of phenol solution is helpful in acidity, but benzaldehyde is not affected by this factor.
For deposition-precipitation method, the rutile and anatase phase of titanium dioxide must be made before bismuth loaded on the surface. Then, bismuth solution was added and pH adjusted between 6 and 7 by 1M sodium hydroxide solution. From the patterns of XRD, all of the catalysts are single phase, that is, the dispersion of bismuth on the surface of TiO2 is homogenerous. After Bi loaded, the UV-Vis spectra showed a shoulder between 400nm and 600nm. The absorption spectra of loaded P25 had clearly red-shift. The results of degradation of phenol solution, 1% mole ratio bismuth precipitated on rutile phase titanium dioxide which photocatalytic activity and mineralization ability are better than loaded P25 and anatase TiO2. In addition, the 1% bismuth loaed TiO2.had best photocatalytic activity when treated at 200℃ for 2 hours.
Using the characteristic of high specific surface area of mesoporous materials to adsorb organic pollutants in order to increase organic pollutants degraded ratio. The Bi-doped TiO2 was supported on MCM-41 and SBA-15. The samples were measured IR, specific surface area, XRD, TEM and photocatalytic activity.

並列關鍵字

titanium dioxide ； rutile ； anatase ； photocatalysis

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