奈米銀改質二氧化鈦光觸媒

二氧化鈦(TiO2)是一種常見的光觸媒，因其穩定、無毒、便宜等特性而被廣泛使用於汙染處理及氫氣生產。TiO2的能隙(3~3.2 eV)使其只能吸收波長小於400 nm的紫外光，然而太陽光中紫外光比例很低，造成TiO2在陽光下效率不彰，必須使用人造光源，成為TiO2光觸媒的一大缺點。許多研究致力改善TiO2光觸媒的效率，混摻貴金屬奈米結構是其中一種。為釐清貴金屬奈米結構對TiO2效率的影響，本實驗共合成三種銀奈米結構，分別為小的銀奈米球(5~15 nm)、大的銀奈米球(15~30 nm)以及銀的三角板(平均75 nm)，銀奈米結構與商用TiO2粉末(P25)依不同濃度比例混合成漿料，並乾燥為粉末。光降解反應在自製的反應器中進行，光源為日光燈、紫外燈及LED燈；模擬汙染物為亞甲基藍染料；實驗溫度為25℃，照光開始前將光觸媒粉末與亞甲基藍預攪30分鐘以達粉末與染料間的吸附脫附平衡。實驗發現銀奈米結構的大小及形狀會影響TiO2效率的增益，其中以銀的三角板表現最佳，效率的提升主要來自銀奈米結構的侷域表面電漿共振(LSPR)效應，以及銀奈米結構做為電子陷阱能有效降低電子電洞結合率。

關鍵字

二氧化鈦；光觸媒；奈米銀

並列摘要

Phtocatalysis phenomenon of titanium dioxide (TiO2) has been widely investigated due to its potential application in degradation of pollutant and production of hydrogen. However, because of the large band gap, TiO2 shows low photocatalytic activity under the irradiation of the visible light. Constructing the hybrid system of noble metal nanostructures and TiO2 is one known way to enhance the photocatalytic activity of TiO2 under visible light irradiation. In our study, three kinds of silver nanostructures were synthesized: nanospheres with smaller size (5-15 nm), nanospheres with larger size (15-40 nm) and nanoprisms (~75 nm). While silver nanospheres were synthesized by the chemical reduction method, silver nanoprisms were synthesized by the following photo conversion process. The slurry was made by mixing silver solution with commercial TiO2 powder (P25) with certain weight percentage. It was then used as the photocatalyst to degrade the methylene blue solution, which is the assumed pollutant in our study. We found that silver nanostructures can enhance the TiO2 photocatalytic activity and the enhancement is a function of the shape and the size of nanostructures. The enhancement of the photocatalytic activity of these hybrid system might be attributed to the localized surface plasmon resonance (LSPR) of silver nanostructures. The formation of electronic state on the interface between semiconductor and metal nanoparticles might also help charge separation, which reduces the recombination rate of electrons and holes.

並列關鍵字

TiO2 ； photocatalysis ； silver nanostructures

參考文獻

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國際替代計量

奈米銀改質二氧化鈦光觸媒

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