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Visible-light response Cr-doped TiO2-XNX photocatalysts
No full textChromium (Cr) and nitrogen (N)-doped titania (TiO2) was prepared using sol–gel method and ammonia thermal treatment. TiO2 co-doped
with Cr and N showed intense absorption bands in the visible-light region. The X-ray photoelectron spectroscopy (XPS) detected chromium
and nitrogen ions on the surface of catalysts, but no diffractive peak of chromium oxide or titanium nitride was observed in X-ray diffraction
(XRD) spectra. The analysis of X-ray absorption near edge spectroscopy (XANES) indicated either Cr3+ or Cr4+ chemical status implying that
chromium either substituted Ti4+ site or locally was isolated on the surface of TiO2. The photocatalytic activity was evaluated by the degradation
of methylene blue (MB) and isopropyl alcohol (IPA) under visible-light (>460 nm) irradiation using blue-light emitted diode. The rate constants
of MB and IPA photodegradation with N-doped TiO2 were 7.7 and 80 mol l−1 h−1 g−1, which were much higher than those with pure TiO2, 0.15
and 0 mol l−1 h−1 g−1, respectively. The Cr and N co-doped TiO2 showed less photoactivity than either Cr or N-doped TiO2 due to the extra
imperfection of TiO2 lattice during preparation
Visible-Light Cr-doped TiO2-XNX Nano Photocatalysts
No full text為了能夠更有效率的利用太陽光或是室內光源，本研究致力於研發具有可見光應答催化活性之二氧化鈦光觸媒。利用改良式溶膠凝膠法合成二氧化鈦，並且在製程中摻雜鉻、氮元素。相較未經改質之本質二氧化鈦以及商用觸媒P25，摻質後的二氧化鈦成功的具備吸收波長小於550nm之可見光的能力，並且能夠有效的催化亞甲基藍染料水溶液的還原脫色反應、以及異丙醇水溶液的氧化分解反應。在亞甲基藍及異丙醇的催化反應中，改質觸媒在可見光下之反應速率常數分別為9、0.8(μmole/liter-hr-g)；比起純二氧化鈦1.1、0(μmole/liter-hr-g)皆高出許多。
在二氧化鈦中摻入鉻元素的改質製程，使價態與傳導帶間形成其他的獨立能階，進而降低電子電洞對分離所需激發光子之能量，始能達到改質可見光應答目的。而過量摻雜之鉻元素則會進入結構中的鑲嵌位置，扭曲本質結構的結果會造成二氧化鈦原本具有之良好光量子效益降低。
對二氧化鈦進行氨氣熱處理則能將氮原子取代結構中氧原子並生成微量氮化鈦成分，氮原子進入結構中取代位置能夠縮小能隙使得二氧化鈦具有可見光應答催化能力。氮元素摻入量超過最適值後亦會降低光量子效益，推論過量的氮元素摻雜位置、或是還原性氣氛下在結構中引入的氧缺陷會成為光觸媒中降低催化能力的電子電洞再結合中心。To use solar or interior light efficiently, we sought a photocatalyst titania with high reactivity under visible light. Titania powders were prepared and doped into chromium or nitrogen atoms via modified sol-gel method. Doped titania have revealed an improvement over pure titania or Degussa P25 photocatalys under visible light(wavelength<550nm) in UV-Vis absorption and photocatalytic activity such as photodegradations of methylene blue and isopropyl alcohol. The rate constants of MB and IPA catalytic reaction with doped titania are 9 and 0.8(μmole/liter-hr-g), which are much higher than those with pure titania, 1.1 and 0(μmole/liter-hr-g), respectively.
Chromium doped into the lattice of titania is responsible for the visible-light response photocatalytic activity because of the isolated narrow bands formed between the valence band and conduction band and lowering the photon energy required to excite the electrons. However excess doped chromium located the interstitial cites in the lattice distorted the original structure and consequently deteriorated the intrinsic photocatalytic activity of titania.
A few amount of nitrogen atoms substituted the lattice oxygen atom and titanium nitride was formed under ammonia-annealing process. Nitrogen doped into substitutional sites of titania has proven to be indispensable for band-gap narrowing and photocatalytic activity. Increasing the nitrogen-doped concentration more than optimum level lowered the quantum yields, indicating the doping sites and oxygen vacancy introduced under the reductive atmosphere could also serve as electron-hole recombination sites.誌謝
中文摘要 Ⅰ
英文摘要 Ⅱ
目錄 Ⅲ
表目錄 Ⅴ
圖目錄 Ⅵ
第一章 緒論 1
第二章 文獻回顧 2
2-1二氧化鈦簡介 2
2-2光催化反應原理 5
2-3 二氧化鈦可見應答之提升 8
第三章 實驗方法
3-1 TiO2觸媒之合成 20
3-1-1 藥品與儀器 21
3-1-2 Cr/TiO2之製備 21
3-1-3 TiO2-XNX之製備 22
3-1-4 Cr/TiO2-XNX之製備 22
3-2物性分析 26
3-2-1 儀器型號與規格 26
3-2-2 X光繞射法(XRD) 26
3-2-3 紫外-可見光吸收光譜(UV-Visible spectrophotometer)28
3-2-4 X射線光電子譜儀(X-ray photoelectron,XPS) 29
3-2-5氮氣吸附-脫附測定孔徑分佈與比表面積 32
3-2-6 X光吸收光譜術(X-ray absorption spectroscopy,XAS) 33
3-3 光催化活性檢測 36
3-3-1反應物及反應系統相關裝置 36
3-3-2 亞甲基藍（MB）脫色之光催化活性試驗 37
3-3-3 異丙醇（IPA）氧化之光催化活性試驗 41
第四章 實驗結果 43
4-1二氧化鈦之物性分析 43
4-1-1 XRD分析 43
4-1-2 UV-VIS吸收光譜分析 51
4-1-3比表面積與孔徑分析 57
4-1-4結構元素氧化價態分析 60
4-1-4-1 Cr/TiO2系列試樣之光電子能譜分析 61
4-1-4-2 TiO2-XNX系列試樣之光電子能譜分析 66
4-1-5 X光吸收光譜分析 70
4-1-5-1 Cr/TiO2系列試樣之XAS分析 71
4-1-5-2 TiO2-XNX系列試樣之XAS分析 75
4-2二氧化鈦光催化活性檢測 78
4-2-1 Methylene blue（MB）脫色反應 79
4-2-1-1以可見光反應器進行MB脫色反應 81
4-2-1-2以紫外光反應器進行MB脫色反應 87
4-2-2 Isopropyl alcohol（IPA）氧化分解反應 90
4-2-2-1以可見光反應器進行IPA氧化分解反應 93
4-2-2-2以紫外光反應器進行IPA氧化分解反應 95
第五章 結論與建 議 98
5-1 經Cr、N元素摻雜之二氧化鈦結構性質探討 98
5-2 光催化活性分析研究 100
5-3 結論與未來展望 104
參考文獻 106
個人小傳 11
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koamabayili/VECTRON-author-checklist: VECTRON author checklist
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Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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