本文選題：鋯酸鋇 + 鈣鈦礦結(jié)構(gòu)��； 參考：《南京大學(xué)》2015年碩士論文

【摘要】：現(xiàn)如今隨著化石能源的不斷消耗,大氣中的二氧化碳含量越來越高,其所帶來的能源污染問題和溫室效應(yīng)的影響越來越明顯。因此解決全球能源危機(jī)和應(yīng)對這全球化氣候問題是當(dāng)前科學(xué)界的重要任務(wù)。眾所周知,二氧化碳是大氣中最主要的溫室氣體。面對上述兩個(gè)問題,最理想的方式就是減少大氣層中CO2的含量的同時(shí)又能緩解或者解決能源危機(jī)。即利用太陽能將二氧化碳轉(zhuǎn)化為碳?xì)浠衔铩ｄ喫徜^是理想的鈣鈦礦結(jié)構(gòu),其空間群為Pm3m,晶格常數(shù)為a=4.19 A,目前已經(jīng)被廣泛研究和使用。具有以下優(yōu)點(diǎn)：熱膨脹系數(shù)小,導(dǎo)熱性差,良好的機(jī)械性,熱穩(wěn)定性和抗腐蝕性。被廣泛應(yīng)用于工程或其他領(lǐng)域中,如航空中超音速發(fā)動(dòng)機(jī)的隔熱涂層材料,電解質(zhì)材料和一些復(fù)合物工程材料中的界面材料等,是高溫超導(dǎo)材料的良好基底。BaZrO3的導(dǎo)帶位置在-1.8 eV左右,所以躍遷至導(dǎo)帶的光生電子足夠還原CH4/CO2, HCOOH/CO2, CO/CO2, HCHO/CO2, CH3OH/CO2。因此從能量的角度來說,BaZrO3中產(chǎn)生的光生電子和空穴有足夠的能力來還原CO2和氧化水。本文以探索半導(dǎo)體材料BaZrO3的光催化二氧化碳還原效率為目的,通過Pechini法低溫合成BaZrO3。通過X射線衍射(XRD)分析物相,BET測定比表面積,紫外可見分光光度計(jì)測定漫反射光譜,并通過Kubelka-Munk方程獲得其吸收光譜,從而得知其光學(xué)帶隙,通過理論計(jì)算得知其能帶圖和態(tài)密度,通過掃描電鏡(SEM),透射電鏡(TEM)獲得表面助催化劑的擔(dān)載情況,獲得當(dāng)光催化效率最高時(shí),最適宜的助催化劑及其擔(dān)載量。為進(jìn)一步深入開展理想鈣鈦礦型化合物的光催化還原CO2性能研究做準(zhǔn)備鋪墊工作。主要研究內(nèi)容和結(jié)論如下：鋯酸鋇的帶隙高達(dá)4.8eV,是間接帶隙半導(dǎo)體,價(jià)帶頂和導(dǎo)帶底分別位于3.0eV和-1.8eV (Versus NHE, PH=7.0),其價(jià)帶主要由02p軌道構(gòu)成,而導(dǎo)帶由過渡金屬Zr的4d電子空軌道構(gòu)成,這在很大程度上限制了其光吸收的范圍。在紫外條件之下,沉積在BaZrO3表面的納米Ag顆粒表現(xiàn)的光催化性能明顯要優(yōu)于擔(dān)載了其他貴金屬后的BaZrO3樣品。1273K下制備的BaZrO3樣品擔(dān)載0.3wt%銀單質(zhì)時(shí)表現(xiàn)的性能最高。因?yàn)锳g的費(fèi)米能級(EF)比BaZrO3的導(dǎo)帶位置要低,所以在銀單質(zhì)擔(dān)載的BaZrO3樣品的表面,受紫外光激發(fā)的光生電子,容易穿越界面,從而使電子在Ag處富集,而空穴則留在BaZrO3之中。這將會有效的促進(jìn)光生電子空穴對的分離效率,有效的降低了其復(fù)合的概率。這些研究將有效的為后續(xù)的研究打下基礎(chǔ)。
[Abstract]:Nowadays, with the consumption of fossil energy, the carbon dioxide in the atmosphere is increasing, and the energy pollution and the effect of Greenhouse Effect are becoming more and more obvious. Therefore, solving the global energy crisis and dealing with the global climate is an important task for the current scientific community. As we all know, carbon dioxide is the most important greenhouse gas in the atmosphere. In the face of these two problems, the ideal way is to reduce the CO2 content in the atmosphere while alleviating or solving the energy crisis. The use of solar energy to convert carbon dioxide into hydrocarbons. Barium zirconate is an ideal perovskite structure with a space group of Pm 3 m and a lattice constant of 4 19 A. Barium zirconate has been widely studied and used. It has the following advantages: small coefficient of thermal expansion, poor thermal conductivity, good mechanical properties, thermal stability and corrosion resistance. It is widely used in engineering and other fields, such as thermal insulation coating materials of supersonic engines in aviation, electrolyte materials and interfacial materials in some composite engineering materials, etc. It is a good substrate for HTS. The conduction band position of BaZrO3 is about -1.8 EV, so the photoelectron transition to the conduction band is sufficient to reduce Ch _ 4 / CO _ 2, HCOO _ H / CO _ 2, CO / CO _ 2, HCHOP / CO _ 2, Ch _ 3OH / CO _ 2. Therefore, the photogenerated electrons and holes produced in BaZrO3 have sufficient capacity to reduce CO2 and oxidized water from the point of view of energy. In order to explore the photocatalytic carbon dioxide reduction efficiency of semiconductor material BaZrO3, BaZrO _ 3 was synthesized by Pechini method at low temperature. The specific surface area was measured by X-ray diffraction (XRD) and the diffuse reflectance spectrum was measured by UV-Vis spectrophotometer. The absorption spectrum was obtained by Kubelka-Munk equation, and the optical band gap was obtained. The energy band diagram and density of states were obtained by theoretical calculation. The surface cocatalyst was supported by scanning electron microscope (SEM) and transmission electron microscope (TEM). The most suitable cocatalyst and its loading capacity were obtained when the photocatalytic efficiency was the highest. Preparation for further research on the photocatalytic reduction of CO2 of ideal perovskite compounds. The main research contents and conclusions are as follows: the band gap of barium zirconate is up to 4.8 EV, which is an indirect band gap semiconductor. The top and the bottom of the valence band are located in 3.0eV and -1.8 EV Versus NHEs, PH7. 0% respectively. The valence band of barium zirconate is mainly composed of 02p orbitals. The conduction band is composed of the transition metal Zr 4d electron empty orbit, which limits the range of light absorption to a great extent. The photocatalytic performance of the Ag nanoparticles deposited on the surface of BaZrO3 was obviously better than that of the BaZrO3 samples loaded with 0.3wt% silver at .1273K. The photocatalytic performance of the Ag nanoparticles deposited on the surface of BaZrO3 was better than that of the BaZrO3 samples loaded with other precious metals. Because the Fermi energy level of Ag is lower than that of BaZrO3, the photogenerated electrons excited by ultraviolet light on the surface of BaZrO3 samples supported by silver are easy to cross the interface, which makes the electrons enrich in Ag and the holes remain in BaZrO3. This will effectively promote the separation efficiency of photogenerated electron hole pairs and effectively reduce the probability of recombination. These studies will effectively lay the foundation for further research.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ132.35;O643.36

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相關(guān)期刊論文 前1條

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