| 摘要: | 二氧化碳是造成現今地球暖化的主因。由於甲醇可作為替代燃料，又用於甲醇電池，因此回收二氧化碳並將之氫化合成甲醇 (CO2 + 3H2 CH3OH + H2O) 已是一個重要的課題。本篇研究的目的，為利用不同基板，具體心立方晶格的金屬面，如 Fe(111)，W@Fe(111)等的奈米粒子催化模型，並藉由CO2氫化反應形成甲醇之過程來探討吸附行為、反應機制，同時對該反應系統做詳細的電子分析。經由這些研究結果我們可以提供產業界設計出更有效率的表面基板，並提供較完整並且穩定的反應機制來將二氧化碳轉化成可用的酒精燃料，以減少溫室氣體。結果顯示在Fe(111)及W@Fe(111)表面有相似的吸附結構，在反應路徑中均不傾向將H原子氫化到O原子上。而Fe(111)與W@Fe(111)反應路徑不相同，在Fe(111)表面主要是經由產生中間物甲酸鹽類(HCOO)的路徑進行加氫合成甲醇，而在W@Fe(111)表面有利於二氧化碳的分解，也有較穩定的吸附能量。在Fe(111)和W@Fe(111)表面上最大的活化能分別是27.84和39.57 kcal/mol。為了瞭解吸附物和表面的交互作用，我們也提出電子結構等相關資訊來討論。
Carbon dioxide is an important role to the greenhouse gas, but it is renewable. The methanol could be synthesis via CO2 hydrogenation (CO2 + 3H2 CH3OH + H2O). The methanol is a significant alternative fuels in the future, and also could be a material of Direct-methanol fuel cells. In our study, we investigated CO2 hydrogenation on the different metal surface of the body-center cubic lattices, such as Fe(111) and W@Fe(111). The reaction mechanisms, activation barrier energies, and adsorption energies of the CO2 hydrogenation are studied by VASP program. The results show the reaction processes is different on the two surface. For the Fe(111) surface, the CO2 favored to form intermediate, formate (HCOO), in the first step. However, for the W@Fe(111) surface, the carbon dioxide favored to decompose to fragments, CO + O. In the reaction process, the highest activation barrier energy is 27.84 and 39.57 kcal/mol for Fe(111) and W@F(111) surface, respectively. Although the activity energy on W@Fe(111) is higher than on Fe(111) by11.73 kcal/mol, the intermediate on the W@Fe(111) is more stable than on the Fe(111). To explore this phenomenon in detail, we study with the electron localization function (ELF), charge densite difference, and electronic local density of states (LDOS). According to our work, we expected to provide the more efficient CO2 hydrogenation method and surface for the industry and to reduce CO2 concentration in the atmosphere. |
