氫氣是一種可再生的環保能源，經由燃料電池(fuel cell)不但可產生出電能、熱、和水，轉換效率也高且無污染。但目前這項技術仍存在著許多瓶頸，其中之一就是在攜帶型電力系統的發展上，仍然缺乏一種安全、便利、效率高、質量輕的儲氫媒介，對於氫能源的發展有很大的阻礙。根據文獻記載奈米碳管是較具發展潛力的儲氫材料。目前雖有一些文獻記載了其儲氫特性的研究，但尚無完整的理論可以推導並印證其可靠度，因而導致實驗的可重複性尚低，不同的實驗結果易產生不同的誤差，阻礙了相關領域的研究進展。為了解決此困境，應用分子動力學架構一套理論，藉以描述奈米碳管的吸氫行為是本文研究的主要方向。

本研究以微觀分子力學模型為基礎，探討奈米碳管儲氫過程之作用機制，並建構一套完整的儲氫模擬模型。首先採用分子力學研究粒子間非鍵節力作用情形，並完成粒子運動軌跡之推導，藉由分子動力學模擬的方式掌握在特定環境以及碳管結構下，氫氣流場於系統中的運動狀態，觀察在穩定狀態下所存在的氫氣分子數量，以了解在儲氫過程中碳管之儲氫機制與總體的儲氫能力。最後，將文獻實驗資料與微觀模擬結果相互印證，並以印證後可靠之模型進行儲氫能力之預估以及系統優化等應用。

由本文所建構的奈米碳管儲氫模型所估算出的結果，與文獻中模擬結果趨勢相同，且誤差在可接受範圍內。此外為了找出最大的儲氫量，本文應用遺傳演算法架構出最佳化儲氫容量法則，不但對於實際應用上有所幫助，更可以提供未來設計上一個明確的方向。唯若要套用在實際的實驗中，尚需考慮到壓力對於碳管束的影響、碳管試片純化的程度…等問題，才能夠達到較佳的可靠性。

Hydrogen is expected to become an important energy carrier in the 21st century, supplementing electricity as a non-polluting method of delivering energy. Hydrogen usage is particularly beneficial to the transportation sector, since hydrogen can be stored onboard a moving vehicle more readily than electricity. Zero emission electric or hydrogen vehicles would help to clean the air we breathe and reduce our dependence on foreign resources. However, the most important of which is lack of safe and efficient ways of hydrogen storage. Targets for gravimetric (6.5wt%) and volumetric (62%) density for storage and transportation were recently standardized in the Department of Energy US as a “DOE Hydrogen Plan”. Several research groups have focused on experimental studies on hydrogen adsorption by using graphitic sorbents. Notwithstanding there are no existing adsorbents that satisfy the DOE target so far. Carbon Nanotube are now considered as the most promising hydrogen store system for future use. Some research groups have reported high values of the hydrogen content in the nanotubes but as a rule they could not be confirmed independently. It should be stressed that the progress in this domain is hampered by its novelty and poor reproducibility or misinterpretation of the results obtained by various research groups. In order to solve this problem, model calculation of physisorption by the nanotubes were of great urgency.

In this paper, the hydrogen storage in carbon nanotube is studied by molecular dynamics simulation. The particle-particle interactions between hydrogen are modeled with Lennard-Jones potential, and the interactions between hydrogen molecules are well modeled by the three-parameter potential function of Williams. This project will establish a molecular model for hydrogen storage, which shall integrate intermolecular reaction forces, external operating forces and membrane resistance forces together. The microscopic molecular dynamics approach will be used to characterize the behaviors of hydrogen storage processes. The results are further verified by experimental data.

Good agreement between the computed solutions and existing data obtained from the literature indicates that the theory and modeling procedure that are presented in this paper is theoretically sound and practically applicable for the analysis of nanotube hydrogen storage systems. They can be used not only to compute the hydrogen storage capacity with a designated response characteristic, but also to provide a clear direction in further studies in design practice.

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