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  • 學位論文

奈米級含氮鐵二氧化鈦之可見光光催化活性機制探討

Photocatalytic study of nanocrystalline Fe N co-doped titania under the visible light

指導教授 : 陳孝行

摘要


本研究添加零價鐵與氯化銨製備含氮鐵二氧化鈦,藉由氮鐵元素摻雜於二氧化鈦表面,發揮其兩者優點大幅提升二氧化鈦的光催化活性,此外藉由氮鐵元素之特性,同時縮短二氧化鈦之能隙,提升可見光觸媒未來實場之應用性;本研究製備奈米級含氮鐵二氧化鈦之可見光光催化活性機制探討分為兩主軸:1.製備含氮鐵二氧化鈦之物性分析。2. 含氮鐵二氧化鈦之可見光光催化活性測試。 製備含氮鐵二氧化鈦之物性分析部分,本研究結果顯示,藉由ESCA能譜圖與XRD晶相分析可得知,添加零價鐵與氯化銨於高溫缺氧製備過程內,氯化銨於高溫下會分解成NH3與HCl,而NH3¬會摻雜於二氧化鈦表面;零價鐵於高溫缺氧製備過程與二氧化鈦中氧元素產生反應形成Fe2O3,且鐵元素與鈦元素同為3d軌域與易產生鍵結之特性,生成Fe2TiO5,而鐵摻雜量會隨加藥量呈正相關增加,含氮量則是有一最適加藥比例,於固定零價鐵加藥量,提升二氧化鈦與氯化銨重量比時,二氧化鈦與氯化銨重量比1:6擁有最高的含氮量。此外,藉由UV/Visible分析得知,本研究製備之Fe/N-TiO2(2.21eV)之能隙遠低於Degussa P-25(3.2eV)與TiOxNy(2.95eV)。 含氮鐵二氧化鈦之可見光光催化活性測試部分,本研究製備之Fe/N-TiO2擁有最佳光催化活性之樣品,製備條件為零價鐵添加0.01g,二氧化鈦與氯化銨重量比1:6,其光催化反應速率為0.066h-1,於最佳製備條件下Fe/N-TiO2之光催化反應速率遠優於TiOxNy(Fe 0 1:6)的0.028 h-1與Degussa P-25的0.018 h-1。此外,研究製備Fe/N-TiO2在氮鐵含量摻雜過量時,光催化反應速率會隨之遞減,因此,改質Fe/N-TiO2最適摻雜氮、鐵量分別為1.5~2.5 mole%與1.9~3.5 mole%。能隙變化與光催化活性部分,Fe/N-TiO2 能隙為2.81eV,擁有最佳光催化反應速率,雖氮鐵摻雜量增加,有助於縮短能隙,然而當能隙低於2.8eV,則無法產生氫氧自由基,降低了二氧化鈦光催化活性,如樣品Fe 0.05 1:6能隙為2.21 eV,反應速率則為0.022 h-1時,則遠低於樣品Fe 0.01 1:6能隙為2.81 eV,反應速率為0.066h-1。

並列摘要


Photochemical reactions catalyzed by semiconductors have been investigated extensively in the degradation of toxic organic pollutants, in organic synthesis and in energy conversion and storage. Titania is a semi-conducting photocatalyst. It can decompose the organic pollutant by irradiation under UV light. This study is divided to prepare TiO2-xNx by calcined Degussa P-25 and NH4Cl. The final propose is decreased the bandgap of TiO2, and let it can be catalyzed in the visible light. This study demonstrates a simple route for the preparation of nanocrystalline N-doped titania by calcined with ammonia chloride. This study have two important parameters: calcined temperature(T) and the ratio of TiO2 to NH4Cl(R). The N-doped titania we made was characterized by ESCA, XRD, BET and TEM etc. The wavelength of absorption of N-doped we prepared by calcination with ammonia chloride was shifted to the range of visible light.The ESCA measurement showed that nitrogen was surely doped in the titanium oxide, and the highest nitrogen content in TiO2-xNx is 11.83%. the sample is RT-1:6-400. The XRD measurement showed that Anatase phase easily transformed to Rutile phase at 500℃ and above. The crystalline transformed rate become higher by the higher calcined temperature and higher ratio of TiO2 to NH4Cl. The best photocatalytic activity in the degradation of methylene blue is obtained at the N loading about 11.83at%. The film exhibits the degradation of methylene blue with a rate-constant(k) about 0.0512 h-1 and decrease 150 hours to remove the methylene blue. Final, the RT-1:6-400 have the best efficiency photacatalisis is. It is sure the the NH4Cl is a nice material to be the N source by HCl(g) produce in the high calcined temperature with TiO2 and NH4Cl.

參考文獻


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