面臨能源短缺和環境汙染問題，發展永續能源是當務之急。太陽能驅動的水裂解反應(Water splitting)是解決能源危機和環境污染問題的一個理想途徑。其中，水氧化步驟為此反應過程的瓶頸反應，所以如何製備出高效能水氧化催化劑(Water oxidation catalysts, WOCs)是一個重要的議題。因此，在本研究中，我們運用理論計算方法建構一個氮參雜單層奈米碳管(N-doped single wall carbon nanotube)的化學分子模型，並探討此催化劑在水裂解反應過程中的催化效果。
首先，我們利用自旋極化密度泛函理論(spin-polarized DFT)來探討不同曲率之碳管模型的穩定性以及其水分子吸附能。此外，在電化學催化部分，除了使用密度泛函理論之外並加入凡德瓦爾(Van der Waals)作用力(DFT-D3)作計算。我們預想模型中的兩個活化位皆發生氧化反應，則可得知在水氧化過程中中間物(intermediate)的自由能大小及反應過電壓。
管徑為(5,5)、(6,6)、(7,7)、(8,8)、(10,10)之奈米碳管皆可進行水氧化反應，其過電壓大約在0.477至0.605伏特之間，比大部分的金屬塊材與金屬氧化物來的小。因此，這類的奈米碳管有較好的水氧化催化效果。然而，管徑為(12,12)之奈米碳管無法形成1212_1_2O的模型。在本研究中，我們成功地建構出高效能的水氧化催化劑——氮參雜單層奈米碳管。此模擬結果對未來水氧化催化劑的合成與應用具有重要的意義。

Considering the present challenges of energy shortage and environment pollution, it is necessary to investigate sustainable sources of energy. Solar energy power-driven water splitting is one ideal route for addressing these problems. In the process of water splitting, water oxidation reaction is a bottleneck step. Thus, developing a highly efficient water oxidation catalyst is an important issue. In this study, we utilize computational quantum mechanical modeling to construct an N-doped single wall carbon nanotube (CNT) model, and further investigate its catalytic efficiency for water splitting applying different structures.
We initially utilize spin-polarized density functional theory (DFT) to investigate the stability of the CNT model with different curvatures. Further, for the electrochemistry section of this thesis, we utilize spin-polarized DFT as well as van der Waals’ (DFT-D3) for calculations. We suppose that both active sites in the model perform oxidation reaction. The free energy of intermediates and the voltage required for overcoming energy barriers during water oxidation are investigated.
The CNTs with chirality (5, 5), (6, 6), (7, 7), (8, 8) and (10, 10) can perform oxidation reactions. The respective over-potentials are between 0.477 and 0.605 V. The values are smaller in comparison with most bulk metal and metal oxides (organometallic catalyst) materials. This indicates that the constructed CNTs have better catalytic effect for water oxidation. However, CNTs with chirality (12, 12) cannot form 1212_1_2O model for water oxidation reaction. In this manner, we successfully construct a highly efficient water oxidation catalyst, N-doped single-wall CNT. These simulation results can have significant impacts on the syntheses and applications of oxidation catalysts.

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