在本研究中，採用兩極式陽極氧化電化學法在含氟蝕刻液中，藉由改變工作偏壓(5V~30V)、電解液氟離子濃度(0.1M~0.7M)、蝕刻液pH值(pH1~pH7)、蝕刻液溫度(20~80℃)、蝕刻液添加甘油量(0~10M)，來探討製程參數對二氧化鈦奈米管管徑之影響。結果顯示：二氧化鈦奈米管之管徑會隨工作偏壓(5V~20V)、蝕刻液中氟離子濃度(0.1M~0.7M)及蝕刻液溫度(20~40℃) 增加而增大，其直徑範圍在65~134 nm。但直徑會隨蝕刻液中之pH值(pH1~pH7)及甘油添加濃度(0M~10M)增加而減小。 陽極氧化所得之二氧化鈦奈米管經為非晶態，經480℃、3小時熱處理後成為銳鈦礦(anatase)為主和金紅石(rutile)為副晶體之混合，經浸泡於0.2M硝酸銀溶液中15、30、45與60分鐘用以擔載不同濃度之銀，或浸泡0.5g SnCl2+0.56M HCl 浸泡5分鐘，接著再以0.05M PdCl2+0.5M HCl 浸泡1分鐘，以擔載鈀，分別於0.5 M硫酸溶液中進行氧還原(oxygen reduction reaction ,ORR)催化反應，藉以比較其ORR催化反應之活性。結果顯示：非晶質二氧化鈦奈米管不具活性，經480℃、3小時熱處理後，結晶性二氧化鈦奈米管開始具有活性，其活隨奈米管孔徑由100縮小至65nm而增加活性。若奈米管擔載銀，其ORR之起始電位(Eonset)上升至較正值，表示催化活性增大，還原電流隨銀含量之增多而增大，表示增加銀擔載量，有增進催化速率之結果，管徑在65nm之奈米管經1小時之紫外光(λ=254nm)還原銀觸媒可得最高之催化反應電流(242μA/cm2)。在相同中擔載量下，鈀擔載於二氧化鈦奈米管中比擔載銀的活性更高、催化速率更快。 Self-organized titanium dioxide nanotube was fabricated on titanium foils by electrochemical anodization in fluoride solution at room temperature. The effect of voltage employed, fluoride concentration, pH of the bath and the temperature of the bath on the diameter of the nanotubes was of interest. The result revealed that the diameter of nano tubes increases (from 30 to 100 nm) with increasing the voltage from 5 to 20 V. It also increases (from 70 to 134 nm) with an increase of the fluoride concentration from 0.1 to 0.7 M. The diameter of the nano tubes increases with increasing the bath temperature (from 20 to 80℃), whereas it decreases (from 100 to 45 nm) with increasing the pH value of the bath (from 1 to 7). The addition of glycerol causes a decrease in the diameter of the nano tubes, with increasing glycerol from 0 to 5.0 M, the diameter of the tubes decreases from 100 nm to 87 nm. The anodized nanotubes were amorphous and they turned out to be a mixture of anatase and rutile after exerting a heat-treatment at 480 ℃ for 3 h. The heat-treated nano tubes were immersed in 0.2M silver nitrate for 15、30、45 and 60 minutes to be loaded with various silver contents. And they were immersed in a mixture of 0.5M SnCl2+0.05M PdCl2 for 5 minutes to be loaded with Pd. All kinds of nano tubes were put in 0.5 M sulfuric acid solution to conduct oxygen reduction reaction (ORR) and compare their onset potential (Eonset) and cathodic current density. The results revealed that amorphous TiO2 is inactive to ORR, heat-treated at 480℃ for 3 h turning the amorphous nano tubes into crystalline to become active. The reactivity of the nano tubes increases with decreasing the diameter from 100 to 65nm. In the presence of Ag loading, the onset potential (Eonset) of ORR becomes more positive so that the catalytic activity is higher, and the cathodic current density increases with increasing the Ag-loading. Obviously, Ag-load on the crystal TiO2 nano tubes enhances the catalytic activity. For instance, For nano tubes with diameter at 65nm illuminated by UV-light(λ=254nm) for 1 h to be loaded with silver leads to highest cathodic current density (242μA/cm2) for ORR。At the same loading level, Pd-loaded nano tubes are better than Ag-loaded nano tubes to reveal higher catalytic activity.
