博碩士論文 973204049 完整後設資料紀錄

DC 欄位 值 語言
DC.contributor化學工程與材料工程學系zh_TW
DC.creator陳怡利zh_TW
DC.creatorI-li Chenen_US
dc.date.accessioned2010-6-9T07:39:07Z
dc.date.available2010-6-9T07:39:07Z
dc.date.issued2010
dc.identifier.urihttp://ir.lib.ncu.edu.tw:444/thesis/view_etd.asp?URN=973204049
dc.contributor.department化學工程與材料工程學系zh_TW
DC.description國立中央大學zh_TW
DC.descriptionNational Central Universityen_US
dc.description.abstract本研究之目的在於發展具有高催化活性之核殼結構光觸媒，並將其應用於有機汙染物之分解。利用貴金屬如金、銀等改質二氧化鈦光觸媒已被廣泛研究；而貴金屬中的金、鉑和鈀的成本昂貴，難以被一般工業所接受。本研究主軸在於利用成本相較為低的銀來改質二氧化鈦。將貴金屬沉積於二氧化鈦表面可以提高光催化效率，由於金屬在表面形成電子活性點以促進界面電荷轉移，此種觸媒結構雖然活性好，但易造成暴露在外的金屬與其他表面介質產生作用，使金屬容易溶解或腐蝕，導致觸媒無法長久使用。核殼結構可用來克服此項缺點，將貴金屬置於內核，而半導體氧化物如二氧化鈦當做殼層。 本篇論文分成兩個部份，第一部分探討核殼結構之銀/二氧化鈦的製備，及活性，主要前驅物為硝酸銀、聯胺、十六烷基三甲基溴化銨及醇氧鈦。銀於內核層的量係利用感應偶合電漿質譜分析儀(ICP)與化學分析影像能譜儀(ESCA)測定。奈米銀顆粒的大小約為5-10nm，殼層之二氧化鈦厚度約為10-20nm。以 10 ppm 亞甲基藍水溶液為光反應標準物，以兩支1.5W波長254nm的紫外燈管當為光源，光降解樣品取樣利用紫外可見光光譜儀(UV–vis)分析濃度，進行光反應活性之鑑定。結果顯示經由水熱法後的核殼結構銀/二氧化鈦光觸媒活性優於未經水熱法之觸媒，其主要由於經由水熱法處理，會增加其二氧化鈦結晶性，而晶型結構明顯的二氧化鈦，可增加光子進入內核的量子效率。 在化學沉積法中，所製備之銀改質二氧化鈦其前驅物為Evonik Degussa 公司的P25二氧化鈦、十六烷基三甲基溴化銨、硼氫化鈉、硝酸銀，銀擔載量係利用感應偶合電漿質譜分析儀(ICP)進行測定，結果顯示，幾乎所有的銀前驅物都能夠擔載在二氧化鈦表面而不流失。其奈米銀顆粒大小約為 5-10 nm，以 10 ppm 亞甲基藍水溶液為光反應標準物，以兩支1.5W波長254nm的紫外燈管當為光源，光降解樣品取樣利用紫外可見光光譜儀(UV–vis)分析濃度，進行光反應活性之鑑定。結果顯示擔載銀重量比為1 wt.%的光降解效果最好，由此可見銀擔載量並非越多越好，擔載量太多會產生遮蔽效應，過多的銀顆粒會阻擋進入二氧化鈦表面的光子而降低光反應的量子效率，造成其光催化活性並不與銀擔載量成正比。 將銀擔載於二氧化鈦上之光觸媒與前述之核殼結構銀/二氧化鈦光觸媒做比較，可發現兩者在短時間內活性以銀擔載於二氧化鈦上之光觸媒能有較顯著的效果，以長時間而言兩者的活性差距不大，其可能原因為在短時間內，銀沉積於二氧化鈦上能夠有效地捕捉光子所激發之電子，增加了二氧化鈦表面活性位置，而提高了反應活性。而長時間後，表面的金屬可能會腐蝕或溶解，而核殼結構銀/二氧化鈦光觸媒可有效避免此問題。 電子與所吸附的氧分子與水分子反應分解成氧離子與氫氧自由基，這些高活性物質會與亞甲基藍分子反應而分解成小分子如二氧化碳與水分子。從實驗結果得知，銀擔載量的多寡並不是影響活性的主要因素，而是與奈米銀顆粒的分散性、顆粒大小、附著方式和結晶性有關。 zh_TW
dc.description.abstractThe purpose of this study was to develop a catalyst with high photocatalytic activity and had core/shell structures. It could be applied to the decomposition of organic pollutants under UV light irradiation. The literature shows that the use of precious metals such as gold or silver modified titanium dioxide photocatalyst has been widely studied. Noble metals such as gold, platinum and palladium are too expensive to be used in industrial application. In order to find an efficient way to improve the quantum efficiency of photocatalyst, silver was chosen to modify titanium dioxide in this study. The noble metal deposition on the surface of titanium dioxide can increase the photocatalytic activity since the metal can form active sites to promote the electronic charge transfer in the interface of metal and TiO2. Although the activity of this kind of structure is high, the exposed metal is easy to dissolve or corrosive, therefore the catalyst cannot use for a long time. Core/shell structure can be used to overcome this shortcoming, the noble metals located in the core, while the semiconductor oxide such as titanium dioxide is in the shell. This thesis is divided into two parts, the first part is on the preparation of Ag/TiO2 with core/shell structure and its activity. The precursors were the silver nitrate, hydrazine, cetyltrimethylammonium bromide and titanium tetraisopropoxide (TTIP). The amount of silver in the inner core was determined by inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS). Nano-silver particle size was about 5-10nm, the shell thickness of titanium dioxide was about 10-20nm. The photoreaction was carried out in a 10 ppm methylene blue solution with two 1.5 W 254 nm UV light as the light source. The concentration of MB in the degradation samples were measured by UV-visible spectrometer (UV-vis). The results showed that Ag/TiO2 after hydrothermal treatment had higher photocatalytic activity than the one without treated by hydrothermal method. Which was mainly due to treatment by hydrothermal would increase the crystallinity of TiO2. The high crystallinity of titanium dioxide can increase the quantum efficiency of photons into the nucleus. In the chemical deposition method, the precursors were Evonik Degussa P-25 titanium dioxide, cetyltrimethyl ammonium bromide, sodium borohydride, and silver nitrate. The silver loading was determined by inductively coupled plasma-mass spectrometry meter (ICP-MS). The results show that almost all of the silver precursor could load on the support. The silver particle size was about 5-10 nm. The reaction was carried out in a 10 ppm methylene blue solution with two 1.5 W 254 nm wave length UV light as the light source. The concentration of methylene blue in the degradation samples was measured by UV-visible spectrometer (UV-vis). The results showed that the 1 wt.% Ag/TiO2 had the highest photodegradation activity. It shows that the silver loading was not the only reason to influence the photoactivity. Too much silver loading would block access the surface of titanium dioxide and decreased quantum efficiency of photoreaction. The photocatalytic activity was not proportional to silver loading. The activity of silver/TiO2 photocatalyst was compared with Ag@/TiO2 with core-shell structure. Ag/TiO2 had a higher activity in the initial reaction period. It was possible because the silver deposited on TiO2 could effectively capture the photons. After a long time reaction, the surface of the metal may corrode or dissolve, and the core-shell Ag@TiO2 photocatalyst can effectively avoid this problem. Silver nanoparticles increase the actives sites and make electrons easily act with the adsorbed substances such as O2 and OH– to form O2– and OH radicals. These highly active substances reacted with methylene blue molecules and formed small molecules such as carbon dioxide and water molecules. en_US
DC.subject奈米銀zh_TW
DC.subject核殼結構光觸媒zh_TW
DC.subject化學沉積法zh_TW
DC.subject光觸媒zh_TW
DC.subject亞甲基藍降解zh_TW
DC.subject銀改質二氧化鈦zh_TW
DC.subject二氧化鈦zh_TW
DC.subjectnanoparticleen_US
DC.subjectmethylene blue degradationen_US
DC.subjectchemical depositionen_US
DC.subjectcore/shell structure photocatalysten_US
DC.subjectsilveren_US
DC.subjecttitanium dioxideen_US
DC.title核殼結構及金屬擔載結構之Ag/TiO2光觸媒及在亞甲基藍之光催化性質zh_TW
dc.language.isozh-TWzh-TW
DC.titleThe phohtocatalytic activity of Ag/TiO2 photocatalyst with core shell and metal doping structure toward methylene blue decompositionen_US
DC.type博碩士論文zh_TW
DC.typethesisen_US
DC.publisherNational Central Universityen_US

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