隨著溫室效應等問題存在多年，近期許多國家轉而積極推廣再生能源。固態氧化物燃料電池(SOFC)可視為具有發現潛力的新興能源之一。不僅因其擁有比其他同類型的燃料電池較高的能量密度，也包括高轉換效率及零污染等優點。雖然Ni/ZrO2是常見的固態氧化物燃料電池陽極材料，但在實驗上針對晶格取向影響的討論卻相對較少，因此在本研究中將以此作為討論主軸。
在本研究中利用第一原理計算Ni/ZrO2異質界面結構，探討在不同的旋轉介面角度下電子結構及特性的變化，藉由計算態密度及電子傳導係數等相關特性比較各種異質界面結構間的優劣性。根據優化後的結構中會發現介面都出現Ni原子及O原子間的鍵長比初始結構的鍵長短，且介面間距也有縮小的現象，代表在介面的原子可能存在交互作用，且由態密度的結果判斷，電荷是在Ni的d軌域、O的p軌域與Zr的d軌域之間進行傳輸。比較在不同旋轉角度下結構之傳輸係數及局部態密度分析圖結果發現，旋轉角度為30o的結構在費米能處擁有較高的傳輸係數。此外，在介面處的LDOS顯示，其中部分的Ni原子及Zr原子是相連結的，代表介面之間有偶合，且可能是由Ni-Zr的軌域混成所造成。若是延伸到應用上，我們以常見的氫氣及甲烷燃料作為參考，其開路電壓分別為1.05 V及1.15 V，對應到穿隧能譜中的能量位置，都會以旋轉角度90o的結構會具有較高的傳輸係數。若繪製此能量下的LDOS圖，可以看到當旋轉角度為90o之電荷密度等效平面都較其他結構大，且在介面處的原子態密度也有相偶合的狀況，推測可能是Ni-Zr之間發生軌域混成，提升結構的電荷傳輸特性，因此90o的結構在應用到SOFC的陽極材料上會具有較佳的電荷傳輸特性。綜觀以上結果說明介面的方向對於系統的導電性的確有影響。

With the greenhouse effect existing for many years, many countries have tried to promote renewable energies. Solid oxide fuel cells (SOFC) can be regarded as one of the talented energy. Not only does it have a higher energy density than other types of fuel cells, but also it has advantages of high conversion efficiency and non-pollution. Although Ni/ZrO2 is a classical anode material of SOFC, there has been little discussion on the effect of structure orientations.
In this study, we investigate the geometric and electronic properties of Ni/ZrO2 heterostructures from first-principle calculations, focusing on the effect of different orientation angles at the interface. We compare density of states and the transmission spectra of six heterostructures. After optimization, the Ni-O bond and the interfacial spacing decrease, indicating that there might be an interaction at the interface. Also, in density of states, the charge transferred between Ni d orbitals, O p orbitals and Zr d orbitals can be observed. Comparing the transmission coefficients and the local density of states (LDOS) of the heterostructures at the Fermi energy with different orientations, the structure of 30o shows a higher transmission coefficient, and there is LDOS overlaps between Ni and Zr atoms, attributed to the hybridization of Ni-Zr. If we consider application, hydrogen and methane are the common fuels in the usage of SOFC. The open circuit voltages (OCV) are 1.05 V and 1.15 V, respectively. Corresponding to the transmission spectrum and LDOS, the 90o structure shows a higher transmission coefficient. Also there is a hybridization between the interface, which provides the structure a good transport characteristic. In summary, 90o structure shows a better transmission peroperty in application. Overall, the orientation of the interface indeed has effects on the electronic transport properties of the Ni/ZrO2 systems.

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