臺灣博碩士論文加值系統

本文利用第一原理分子動力學研究奈米碳材儲氫機制與特性，研究內容主要分為甲基自由基對奈米碳管儲氫之影響與富勒稀膠囊儲氫二大類，由結構差異、參數設定、溫度調節、電子密度、過渡態搜尋等輔助方法進行模擬研究。奈米碳管儲氫研究中，結果顯示在甲基自由基的影響下，奈米碳管對氫氣的吸附能由1.94 eV下降至0.54 eV，由五種催化劑(鉑、鈣、鈀、鈧及鈦)的模擬中，均會因甲基自由基而降低吸附能，利用電子密度分佈亦可得知催化劑與氫氣之間的電子，因甲基自由基存在而重新分配，造成吸附能力降低，而奈米碳管使用催化劑鉑的儲氫量亦由3.35 wt%降至1.36 wt%。富勒烯儲氫模型計算之結果，與文獻中結果趨勢相同，並明確定義四種不同富勒烯(碳60、碳70、碳80及碳100)之儲氫能力，此外使用分子動力學模擬表明，提升溫度能有效降低過渡態之能障，提升富勒烯儲氫之能力，而富勒烯膠囊儲氫能量最高可達7.5 wt%，此方法可提供未來儲氫設計上一個新穎的研究方向。

In this paper, we use first-principles molecular dynamics studies of the mechanisms and characteristics of hydrogen storage in carbon nanomaterials. This research is divided into two categories: the effect of methyl radical on hydrogen storage of carbon nanotube and fullerene cage hydrogen storage. The simulate study include: structural differences, parameter setting, temperature regulation, electron density, and transition state. For calculations on hydrogen molecule adsorption on carbon nanotubes, the results indicate when a methyl radical in the space, that absorption energy of H2 on carbon nanotubes is decreased from 1.51eV to 0.49eV. We also comparison of the platinum catalyst and the four kinds of transition metal used as catalyst (such as: Ca, Pd, Sc, Ti) on the carbon nanotubes. The adsorption decreases significantly with the existence methyl radical. The electronic density shows that when the methyl radicals near the vicinity of hydrogen molecules, the hydrogen molecules and the catalyst for the charge density will be redistribution. Part of the electron transfer from the catalyst to the methyl radicals. This phenomenon will cause the catalysts to decrease influence of hydrogen molecule. The adsorption decreases significantly with the existence methyl radical. The hydrogen storage capacity also decreased from 3.35 wt% to 1.36 wt%. For calculation results on fullerene cage hydrogen storage, good agreement the computed existing data obtained from literature indicates that are presented in this paper is theoretically sound and practically applicable for the analysis of fullerene cage hydrogen storage systems. We clear and definite define the hydrogen storage capacity of four different fullerenes (such as: C60, C70, C80, C100). In addition, the molecular dynamics simulation results indicate. Fullerene elevated temperatures can reduce the transition state barrier high and the enhanced hydrogen storage capacity. Our calculations revealed that the most hydrogen storage capacity is 7.5 wt%. The results of these studies can provide new research directions for design of future hydrogen storage.

致謝 I
摘要 II
ABSTRACT III
目錄 IV
表目錄 VI
圖目錄 VII
符號說明 VIII
第一章 緒論 1
1-1 前言 1
1-2 研究動機與目的 1
1-3 本文架構 2
第二章 背景介紹與文獻回顧 4
2-1 氫氣的儲存 4
2-2 奈米碳管的介紹 5
2-2.1 奈米碳管的簡介與製作 5
2-2.2 奈米碳管儲氫之文獻回顧 6
2-3 富勒烯的介紹 7
2-3.1 富勒烯的簡介與特性 7
2-3.2 富勒烯儲氫之文獻回顧 7
第三章 理論計算與方法 11
3-1 密度泛函理論 11
3-1.1 Hohenberg-Kohn Theorem 11
3-1.2 Kohn-Sham Equation 12
3-1.3 Local Density Approximation 13
3-2 分子動力學 14
3-3 過渡態理論 15
3-4 吸附理論 16
3-5 計算細節 17
3-5.1 計算流程 17
3-5.2 模型建構 17
第四章 甲基自由基對奈米碳管儲氫之理論研究 23
4-1 五種催化劑的吸附能力研究 23
4-2 不同位置的催化劑之影響 24
4-3 電子密度分佈 25
4-4 五組氫分子的吸附能與儲氫量 25
第五章 富勒烯儲氫之量子理論研究 36
5-1 過渡態搜尋與氫氣擴散路徑 36
5-2 溫度對膠囊儲氫之影響 37
5-3 富勒烯與儲氫量之關係 37
第六章 結論 50
參考文獻 51

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