近幾年來，自發現光催化原理與廣泛應用後，為空氣與水的二次淨化帶來一大突破。二氧化鈦因其化學穩定性佳、無毒與適當之半導體能隙，居光催化研究重要地位；為進一步改善二氧化鈦光催化性質，常以p-n接面之複合材料作為光催化性質應用。p-n接面可藉由降低電子-電洞對復合，增加可見光波段吸收，提升光催化效率。
本研究採用陽極化製程直接於鎳-鈦合金表面成長二氧化鈦-氧化鎳複合奈米管陣列。除可簡化目前p-n複合光觸媒之製程，並可藉由奈米管陣列達到大表面積目標。主要以水、氟化銨及乙二醇溶液作為陽極化反應電解液，藉由改變電壓(20~60V)、氟化銨濃度(0.25~1wt%)、水含量(0.5~1wt%)與反應時間(5~90min)，探討二氧化鈦-氧化鎳奈米管陣列之成長特性。將陽極化後的奈米管陣列，經不同溫度(300~600oC)與時間(1hr~24hr)退火，形成銳鈦礦/金紅石與氧化鎳，量測其光催化性質。
在水含量0.5~1wt%與氟化銨含量0.25~1wt%溶液條件下，可得到奈米管陣列。隨氟化銨含量由0.25增加至1wt%，奈米管管徑由33nm降至9nm，管長則由550nm減至230nm。當電壓由20增加至60V，管徑隨之增加。在陽極化過程中同時存在場致溶解與化學溶解作用之競爭，氟化銨添加量在0.25與0.5wt%時，陽極化時間由5增加至90min時，奈米管長度分別由600增加至1200nm與710增至900nm。但當氟化銨添加量為1wt%時，化學溶解作用大於場致溶解，最終導致管長隨時間(5~90min)增加而由440縮短至180nm。將陽極化後之奈米管陣列經400oC退火3hr以上，可產生氧化鎳，5hr產生二氧化鈦銳鈦礦，8hr以上部分銳鈦礦轉化為金紅石結構。在不同相組成中，同時具有氧化鎳、銳鈦礦與金紅石二氧化鈦之奈米管陣列具有最佳光催化性質。而在不同表面形貌上，隨著表面積增加，光催化效率提升；但當管徑過小，亞甲基藍溶液流入受阻，光降解效率降低。本研究中，以奈米管徑39nm管長1200nm之氧化鎳-二氧化鈦奈米管獲得最佳光催化效率，於7hr內可分解72.1%亞甲基藍。

Ever since first reported in 70’s, research on photocatalysis has made a progress in improvement of water and air cleaning. Featuring chemical stability, non-toxicity and appropriate energy band gap, TiO2 has been highly attractive in research field of photocatalysis. Researchers found that p-n junction can reduce the possibility of e-h pair recombination and increase the absorption in visible light area of the photocatalyst, leading to higher photocatalytic efficiency. In this research, we fabricated NiO-TiO2 p-n junction photocatalysts by directly synthesizing nanotube arrays on Ni-Ti foils with an anodization method.
In this work, ethylene glycol with additional NH4F and water was chosen as the electrolyte. The growth behaviors of the anodic nanotubes were investigated by changing the voltage, NH4F concentration, water content and reaction time of the anodization processes. When Ni-Ti foils were anodized in electrolyte containing 0.5~1 wt% water, 0.25~1 wt% NH4F with an applied voltage of 40~60V, nanotubes were synthesized. Tube diameter increased with increasing potential, water content, and reduced NH4F concentration. Nanotubes were synthesized with 9~40 nm in diameter and 200nm~1.2μm in length. As a result of competition between field-assisted dissolution and chemical dissolution, extended reaction time did not always lead to a longer tube.
Various heat treatments were applied to nanotube arrays and different phase compositions were produced. When annealed at 400 oC, NiO crystallite and anatase TiO2 can be formed after 3hr and 5hr annealing respectively. However, after 8hr annealing at 400 oC, part of anatase transformed to rutile structure.
With photodegradation test of methylene blue, effects of the crystal phase and surface morphology of NiO-TiO2 nanotube arrays on their photocatalytic efficiency were discussed. The best photocatalytic performances were obtained using samples with crystalline phases composed of NiO, anatase and a little rutile TiO2. Among samples with various surface morphology, the nanotube array with 39 nm diameter and 1.2μm tube length had the best photocatalytic efficiency, which degraded 72.1 % methylene blue in 7hr.

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