覆載鎳奈米顆粒於二氧化鈦薄膜表面對光催化之影響

Abstract

本研究採用電弧蒸鍍、雙極式電化學沉積與陽極化處理不同製程，形成不同型態的二氧化鈦奈米薄膜，再分別進行300°C/3h氫化處理，最後再選擇最佳光催化效果之二階處理奈米管進行鎳粒子覆載研究。以XRD 或GIXRD 分析薄膜相結構、SEM/EDS觀察表面圍觀結構與成份分析、XPS 分析表面化學成份鑑定，最後再利用太陽光模擬器(AM 1.5)進行光電流轉換效率測試。 將一階陽極處理後之奈米管利用超音波震盪器將鈦管震離基板，再進行60V/1h二次陽極處理，相較於一階陽極處理試片，二階陽極處擁有表面平坦與規則排列之奈米鈦管。在光電流測試中，電弧蒸鍍、雙極式電化學沉積、一階陽極與二階陽極處理二氧化鈦奈米薄膜，經過退火處理後其光電流轉換效率分別為0.367%、0.095%、0.388% 與0.528%，若再進行300°C/3h氫化處理後其光電流轉換效率分別為0.36%、0.153%、0.62%與0.77%。僅有電弧蒸鍍二氧化鈦奈米薄膜轉換效率呈現下降，其餘皆有1.5倍以上的提升。 二階陽極處理二氧化鈦奈米管，分別浸泡於0.05%、0.1%、2%與4% 鎳還原溶液，其光電流轉換效率皆呈現下降趨勢。若再以300°C/3h氫化處理，由GIXRD 與XPS 圖譜所示，還原後鎳粒子，大部分為鎳金屬，少部分為其他鎳化合物。由SEM 觀察，浸泡於2%鎳還原溶液，奈米管表面佈滿鎳粒子，導致在光電流測試中，2% 樣品光催化效果最低。在本實驗中，覆載氧化鎳與金屬鎳於二氧化鈦奈米管表面，光電流轉換效率皆呈現下降趨勢，故鎳粒子對於二氧化鈦奈米管光裂水解研究中並無輔助效果。

In this study, TiO2 thin films were prepared by arc deposition, electrodeposition and anodization method. When TiO2 thin films were hydrogenated at 300 °C for 3 h, the photoconversion efficiency for TiO2 nanotubes was measured as 0.77 %. The TiO2 nanotubes were loaded with nickle particles. The modified TiO2 thin films have been characterized with GIXRD, SEM, EDS, XPS and AM 1.5 solar simulator. In order to enhance the photoconversion efficiency of TiO2 nanotubes, two step growth of TiO2 nanotubes has been performed. The 1-step TiO2 nanotubes on the titanium foils formed by anodization were removed by sonicating in deionized water and then the titanium foils was anodized at 60 V/1 h for the formation of TiO2 nanotubes. The 2-step TiO2 nanotubes with more regular and highly smooth surfaces. The arc deposition, Electrodeposition, 1-step and 2-step TiO2 nanotubes showed maximum efficiencies of 0.367 %, 0.095 %, 0.388 % and 0.528 %. When arc deposition, Electrodeposition, 1-step and 2-step TiO2 nanotubes were hydrogenated at 300 °C for 3 h, the photoconversion efficiency were measured as 0.36 %, 0.153 %, 0.62 % and 0.77 %, respectively. The arc deposition TiO2 thin film was hydrogenated, which not useful for PEC water splitting. However, the photoconversion efficiency of the others films were enhanced by hydrogenation with over 1.5 times. The 2-step TiO2 nanotubes were immersed in Ni solution with concentrations of 0.05%, 0.1%, 2% and 4% for 10 min, in order to obtain Ni nanoparticles on surface of TiO2 NTs, Ni-Loaded TiO2 NTs of the sample the process of by H2 reduction at 300 °C/3 h. The XPS pattern, Ni(OH)2, NiO and Ni, but only signal of nickel can be observed in the GIXRD pattern. Most of Nickle oxide were transformed to Nickle metal by hydrogenating. The 2% Ni-Loaded TiO2 had the lowest photoconversion efficiency, because the surface of the sample was almost covered by nickle particles in SEM image. All Ni-Loaded TiO2 nanotubes have lower efficiencies than 2-step TiO2 nanotubes. They are not useful for TiO2 nanotubes in PEC water splitting.