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    题名: 氧化鎢/二氧化鈦之合成及其抗腐蝕 與光催化之應用
    作者: 吳佳穎;Wu,Chia-ying
    贡献者: 化學工程與材料工程學系
    关键词: 二氧化鈦;液相光觸媒;三氧化鎢;溶膠凝膠法;抗腐蝕;亞甲基藍降解;Titania;liquid photocatalyst;Tungsten oxide;sol-gel method;anticorrosion;the degradation of methylene blue
    日期: 2014-07-14
    上传时间: 2014-10-15 14:34:45 (UTC+8)
    出版者: 國立中央大學
    摘要: 本研究之目的在於發展於紫外光照射下有高效率光催化活性之光觸媒,並可以利用於抗腐蝕效果上,本研究運用了有機染料-亞甲基藍進行光降解反應,另外,將發展之液相光觸媒塗佈於不鏽鋼基材上,以便於測試其保護內層基材之抗腐蝕效果。利用摻雜過渡金屬化合物-三氧化鎢改質二氧化鈦,企圖將照光之後生成之光生電子由二氧化鈦之導帶傳導至三氧化鎢之導帶上儲存,並可在黑暗中持續有抗腐蝕的效果,另外,如果運用於光降解有機污染物反應上,則是利用三氧化鎢低能階與導帶位置較二氧化鈦低之特性,抑制電子電洞對的重組反應,增加其電荷分離的效率,以達成高光催化活性的目標。本研究係利用溶膠-凝膠法合成以三氧化鎢改質之液相二氧化鈦光觸媒,以浸鍍法的方式塗佈於基材上後,液相光觸媒可以回收再重複利用,大幅降低重新製作光觸媒的成本。本研究將不同製備條件(不同氧化鎢前驅物與添加不同氧化鎢之比例)製備出之光觸媒以不同鑑定方式鑑定其狀態,主要以單晶X光繞射儀、超高真空場發射掃描式電子顯微鏡、穿透式電子顯微鏡、高解析掃描穿透式電子顯微鏡與光電子能譜儀進行鑑定與分析。以循環伏安法進行抗腐蝕效果之分析,其循環可變電位範圍設定在-0.8 V 至0.6 V之間,電解液使用5 wt% 氯化鈉水溶液,並以20 瓦波長為254 nm的紫外光燈管為光源進行降解10 ppm亞甲基藍水溶液之光催化反應測試,而光降解反應之取樣樣品濃度可以藉由紫外可見光光譜儀進行分析。由單晶X光繞射儀分析圖顯示合成之光觸媒,其二氧化鈦奈米顆粒皆為銳鈦礦結構,由於添加之氧化鎢比例極少,故繞射圖中並未顯示出任何氧化鎢的繞射峰。由掃描式電子顯微鏡可知塗佈於玻璃基材上之光觸媒薄膜非常均一,其塗佈六次之薄膜厚度為348.84 nm左右。由穿透式電子顯微鏡之選區繞射圖可再次驗證二氧化鈦結構為銳鈦礦,而由高解析穿透式電子顯微鏡之晶格圖可知二氧化鈦之晶格間距為0.395 nm,其也符合銳鈦礦於(101)平面時之晶格間距。由穿透式電子顯微鏡亦可知二氧化鈦與以鎢改質之二氧化鈦奈米粒子之長短軸尺寸分別為30-77 nm和15-31 nm與33-53 nm和7-12 nm,摻雜氧化鎢粒子之後,其短軸尺寸明顯降低。由光電子能譜儀則可知二氧化鈦之鈦離子有兩種價態Ti3+和Ti4+,而氧化鎢之鎢離子也有兩種價態W5+和W6+,其分別為捕捉電洞之價態,另一則為抓取電子之價態,兩者的比例會影響電子電洞對重組的速率。在光催化活性之分析上,將塗佈有光觸媒薄膜之430型不鏽鋼基材浸入於5 wt% 硫酸水溶液中進行抗腐蝕效果之測試,結果顯示HT (1) 有較佳抗腐蝕效果,將相同塗佈條件之基材進行循環伏安法分析,亦可得相同結果,添加氧化鎢與二氧化鈦重量比為1比100之改質光觸媒有較低的電荷密度與電荷量,代表抗腐蝕效果較好。光反應活性以10 ppm亞甲基藍水溶液進行分析時,發現則是NT (4)與HT (4)之光催化活性較好。兩種氧化鎢前驅物之光催化活性則是以NT為最好,NT是利用鎢酸納為反應前驅物。本研究揭示了以氧化鎢改質二氧化鈦之光觸媒會受其添加氧化鎢比例多寡而影響光催化活性。;The purpose of this study was focused on preparing a photocatalyst with high photoactivity under UV light illumination and could be utilized on corrosion protection. This study used organic dye such as methylene blue to carry out photocatalytic reaction. Moreover, we coated as-prepared liquid photocatalyst onto stainless steel so as to analyze the anticorrosion effect about protecting interior metal substrate. Due to using WO3 to modify TiO2, the photoinduced electrons could be transferred from the conduction band of TiO2 to the conduction band of WO3 and stored on the storage system- WO3. Thus, it could be applied to dark condition and still had great effect of anticorrosion. If applied to the photocatalysis of degrading methylene blue, it could be take the advantage of lower band gap and lower conduction band of WO3 to inhibit the recombination of electron-hole pairs and enhance the separation rate of electron-hole pairs to increase the photoactivity. The literature used sol-gel method to synthesize W-modified TiO2 in liquid phase and then utilize dip-coating to coat as-prepared sol onto substrate. Because of liquid photocatalyst could be reused again and again, the cost of preparing photocatalyst could be decreased significantly. Moreover, the structure of different photocatalyst on different preparing conditions could be analyzed by XRD, SEM, TEM, HRTEM and XPS. The cycle potential range of cyclic voltammetry to analyze anticorrosion effect was set from -0.8 V to 0.6 V. The electrolyte used 5 wt% NaCl(aq). The photocatalytic reaction was carried out with methylene blue destruction by 20 W UVC light illumination and the concentration of every sample could be analyzed with UV-visible spectrophotometer. From the figures of XRD, the as-prepared TiO2 nanoparticles were all in anatase phase. Then, there were no peaks corresponding to WO3 due to the low amount of WO3. From SEM images, the as-prepared thin film of photocatalyst was very uniform and the thickness of thin film was around 348.84 nm. As shown in the SAED from TEM and the lattice space from HRTEM, both could be verified that the TiO2 nanoparticles were all anatase. Seen by the figures of TEM and HRTEM, the major and minor axis of pure TiO2 and W-modified TiO2 nanoparticles were 30-77 nm, 15-31 nm, 33-53 nm and 7-12 nm, respectively. It could be indicated that doping WO3 into TiO2 could decrease the minor axis obviously. From the data of XPS next, the chemical states of Ti and W were Ti3+, Ti4+, W5+ and W6+. Ti3+ and W5+ could gather holes; however, Ti4+ and W6+ could trap photoinduced electrons. The amount of these chemical states affected the recombination of electron-hole pairs. In the analysis of photoactivity, placing coated stainless steel substrates with photocatalyst thin film into 5 wt% sulfuric solution could be tested the anticorrosion effect. The results demonstrated that HT (1) exhibited great effect of corrosion protection. If using the same coated substrates to do cyclic voltammetry analysis, the results also indicated the same result, that is, the sample with the weight ratio of TiO2:WO3 = 100 : 1 could have lowest current density and the amount of charge. It could be showed the best effect of anticorrosion. The other photocatalysis with destruction organic dye illustrated NT (4) and HT (4) performed the best photoactivity on degrading methylene blue solution. Among the two different W precursors, NT, which was used Na2WO4 as precursor, exhibited the best photoacivity no matter in anticorrosion or in degradation. This study revealed W-modified TiO2 could be influenced by the amount of adding W and different W precursors.
    显示于类别:[化學工程與材料工程研究所] 博碩士論文

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