- 學位論文
鈷/二氧化鈦管奈米光觸媒降解有機物之光催化活性探討
Photocatalytic Activity of Cobalt-Doped Titania Nanotubes for Degradation of Organic Compound
摘要
本研究將商業化的二氧化鈦(P25)置於氫氧化鈉溶液中，經水熱法處理後再以硝酸及蒸餾水清洗可合成具有不同性質的奈米管凝團體，因為在酸洗過程中，板狀結構的表面電荷移除速率和最後的靜電荷狀態都會對板狀結構捲成奈米管產生影響。這說明了奈米管結構是可由酸洗的條件所控制，這說明了奈米管結構是可由酸洗時間及酸洗程度所控制，並找出最佳合成條件。 利用水熱法合成高空隙度之鈷/二氧化鈦管於可見光下分解甲基藍及BV 10兩種有機染料，此鈷/二氧化鈦管具有高的比表面積(289－379 m2/g)，其奈米管由板狀捲曲成中空管，外徑約10-15 nm，內徑約5-10 nm ，管長可達數微米。且鈷/二氧化鈦管為Anatase結晶結構，經由UV－Visible的分析顯示此奈米管具有可見光範圍的吸附及較窄的能隙值(1.8－2.4 eV)，根據，Kubelka-Munk 模式。 液相吸附甲基藍於奈米管中，其吸附表面覆蓋率(Θads)之值介於60－70 %。反之可見光光催化活性覆蓋率(ΘPhoto)之值介於20－40 %。另外，液相吸附BV 10於奈米管中其吸附表面覆蓋率(Θads)之值介於10－12 %，而可見光光催化活性覆蓋率(ΘPhoto)之值介於42－46 %。這結果顯示對於鈷/二氧化鈦奈米管的孔洞結構是扮演著最主要的因素，不但影響染料的吸附，也影響可見光光催化的效率。在本研究中，鈷(1 mol%)/二氧化鈦管擁有最佳的可見光光催化能力。
並列摘要
Titania nanotube aggregates with different porosities were prepared from hydrothermal treatment on commercial TiO2 particles in NaOH followed by HNO3 washing. In acid washing, both the charge-removal rate and final state of the electrostatic charges on TiO2 affects the rolling of TiO2 sheets into nanotubes. This demonstrates that the nanotube structure can be regulated by adjusting the washing condition. Thus, the optimal synthesis conditions can be finding. Highly porous Co-doped TiO2 nanotubes synthesized from a hydrothermal treatment were used to photodecompose methylene blue (MB) and Basic Violet 10 (BV 10) in liquid phase under visible irradiation. The titania nanotubes were found to have high specific surface areas of about 289–379 m2/g. These tubes were shown to be hollow scrolls with a typical outer diameter of about 10–15 nm, inner diameter 5–10 nm and length of several micrometers. The crystalline structures of titania nanotubes are of anatase-type. UV absorption confirmed that Co doping makes the light absorption of nanotubes shift to visible light region. With increasing the dopant concentration, the optical band gap of nanotubes became narrower, ranging from 2.4 eV to 1.8 eV, determined by Kubelka-Munk plot. The adsorptive surface coverage occupied by MB molecules was estimated to be 60–70 %, whereas only 20–40 % surface coverage can be utilized for visible photocatalysis. In additional, The adsorptive surface coverage occupied by BV 10 molecules was estimated to be 60–70 %, whereas only 20–40 % surface coverage can be utilized for visible photocatalysis. The pore structure of Co-doped TiO2 nanotubes plays as a major role in not only adsorbing MB molecules but also dominating the visible photocatalysis capability. In the present work, 1 mol. % of Co dopant concentration in titania crystallites is competence for visible photocatalysis.