鐵酸鉍與二氧化鈦核殼奈米結構之壓電觸媒活性在有機染料分子之研究

Study on Piezocatalytic Activity of BiFeO3/TiO2 Core-Shell Nanostructures for Degradation of Organic Dye Molecules

劉奕伶(Yi-Ling Liu)

指導教授 ： 吳志明

國立清華大學/工學院/材料科學工程學系/碩士(2018年)

摘要

本研究利用水熱法合成具R3c結構之鐵酸鉍微米顆粒並將其球磨至奈米尺度，接著運用一被許多文獻採用的溶膠凝膠法合成鐵酸鉍-二氧化鈦核殼奈米結構。在降解染料實驗中，固定其他條件下，具有核殼結構的效果優於鐵酸鉍粉末;經過外加電場極化後的降解效率明顯高於未經極化之對照組: 經極化後的奈米核殼結構，其光觸媒降解程度約為未極化對照組之300 % 、 協同作用下壓電/光觸媒降解程度約為未極化對照組之200 %； 而在壓電催化及光催化之協同作用下，增強極化之鐵酸鉍-二氧化鈦奈米複合材料可在兩小時內降解10 ppm甲基紫溶液幾近完全，效果遠高於單獨壓電降解或光降解: 協同之壓電/光觸媒降解程度約為壓電降解之220 %、光降解之160 %，反應速率常數更是提升至壓電降解及光降解之500 %。利用螢光效應光譜儀(FL)的分析鑑定，也發現氫氧自由基的訊號隨著初始粉末量的及反應時間的提升而提升，因此我們可以確認在降解過程中確實存在氫氧自由基並且具有降解染劑之能力。外加電場極化步驟使得晶體內鐵電域轉為一致方向因此增強極化;加上具有高比表面積的異質結構形成合適能帶結構，加速表面載子的轉移;以及超音波週期性的震盪防止樣品表面電荷趨於中和，上述方法皆可降低再結合率驅使電子電洞對和溶液反應產生具高度氧化力的自由基，進而降解甲基紫染料溶液，可望其在高效能觸媒領域的潛在能力及應用。

關鍵字

鐵酸鉍 ； 異質結構 ； 壓電觸媒 ； 光觸媒 ； 極化 ； 染料降解

並列摘要

BiFeO3 microparticles with space group of R3c were prepared by hydrothermal process and ball-milled into nanoparticles to proceed with the synthesizing step for heterostructure. BiFeO3/TiO2 core-shell heterostructure was synthesized through a well-adapted sol-gel method. Under synergistic ultrasonification and light irradiation, polarization-enhanced BiFeO3/TiO2 core-shell structured nanocomposites almost achieved 100 % piezo/photo-catalytic degradation ratio for methyl violet dye solution of 10 ppm within 2 h. The synergy of piezo/photo-catalysis outperformed the piezocatalysis by 160 % and the photocatalysis by 220 %. Moreover, the rate constant of it is about 500 % of the piezocatalysis and photocatalysis. The enhanced polarization was realized through the polling process, which took good use of the inherent ferroelectricity. Suitable band structure from the core-shell nanocomposites with high surface area boosts the surface charge transfer and the ultrasonic vibration keeps the field from saturation. These means were employed so as to reduce the recombination probability of the induced carriers, which could subsequently react with the solution to generate powerful oxidizing radicals and further dissociate organic dyes. In the flourescence photoluminescence (FL) analysis, the signals associated to hydroxyl radicals elevate with the increase of both the amount of catalysts and catalytic times. This well corroborates the importance of the powerful oxidizing agents in the degradation process. This work reveals more efficient dye degradation, utilizing polarization enhancement and synergy of mechanical vibration and light irradiation, which provides a new strategy for high performance catalytic applications.

並列關鍵字

BiFeO3 ； nanocomposite ； piezocatalysis ； photocatalysis ； polling

參考文獻

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