由於全球暖化在近幾十年內日益嚴重，所以一直以來對於將溫室氣體，如：甲烷、二氧化碳、氮氧化物...等物質轉化為低毒性、高附加值的經濟產物的議題不論在學界還是工業界皆備受關注，其中金屬合金、金屬氧化物和有機金屬骨架(MOF)對甲烷轉化展現良好的催化性能。然而，這樣的甲烷活化過程普遍需要在高溫(400–800°C)的環境下才得以進行。使得催化劑在應用於工業上時會因製造成本、有限的催化性能、選擇性、轉化率、可回收性等方面受到限制。因此，開發具有無毒、低溫下可轉化甲烷等特性的催化劑是必須的。在本研究中，我們考慮赤鐵礦(α-Fe2O3) (104)表面作為我們的催化劑，因為赤鐵礦具有載氧量高、結構穩定、對環境影響低、成本低、原料豐富並自然存在於自然界中等特點，並且已被廣泛應用於實驗當中，但是對於甲烷轉化反應機制在赤鐵礦(104)表面的理論研究尚缺乏，所以本文使用密度泛函理論(DFT)來計算赤鐵礦(104)表面氧配位對於甲烷直接轉化為甲醇和甲醛反應機制的理論研究。
從計算結果中顯示，甲醇的合成過程中，氧二配位表面(two-fold oxygen terminated)速率決定步驟為甲醇的脫附，而氧三配位表面(three-fold oxygen terminated)的速率決定步驟為C-O耦合反應。而在甲醛的合成過程中，氧二配位表面(two-fold oxygen terminated)速率決定步驟為甲醛的脫附，而氧三配位表面(three-fold oxygen terminated)的速率決定步驟為CH3*脫氫形成甲醛。氧二配位表面不管是在甲醇還是甲醛的合成上皆具有較低的反應勢壘，我們進一步考慮了溫度效應在系統中，以接近甲醇及甲醛真實的合成反應環境，並成功驗證了溫度在400℃以上將有利於產物脫附。
此外，我們考慮通過化學循環燃燒(CLC)技術生產二氧化碳和一氧化碳。在我們的計算結果中顯示，生成二氧化碳和一氧化碳的活化勢壘皆遠大於生成甲醇和甲醛的活化勢壘。並且在考慮溫度效應以後對於活化勢壘的改善並不顯著，顯示在動力學上CO/CO2在赤鐵礦氧二配位表面上的形成是不利的。這使得赤鐵礦成為一種合適且具有競爭力的催化劑並且能夠生產高附加價值的產物。另外，本研究考慮到甲烷轉化為C1產物以後，表面會留下氧空缺，所以我們進一步計算赤鐵礦(104)表面活性位點的再生，本研究利用氧氣吸附到已被還原的赤鐵礦表面來填補氧空缺，使催化劑可以完成循環利用，並且避免赤鐵礦在循環反應過程中越來越還原。最後，本研究透過原子級的理論研究來闡釋甲烷轉化的反應機制，並提供證據表明赤鐵礦(α-Fe2O3) (104)表面是一種具有潛力的催化劑並應用於甲烷轉化成高值化產物。

The ever-increasing global warming and methane dispersion require a novel catalyst to transform it into easily condensable energy carriers integrated into valuable chemical products. In this context, various metals and metal alloys, metal oxides, and some metal–organic-frameworks showing some specific catalytic performance for methane conversion. However, implementing these proposed catalysts often needs high temperatures (400–800 °C) to activate methane. Moreover, they are incompetent at the industrial level regarding their manufactured cost, limited catalytic properties, selectivity, turnover frequency (TOF), conversion, recyclability, etc. Therefore, it is necessary to develop nontoxic and low-temperature catalysts to activate and convert methane efficiently. Hence, in this study, one of the iron oxide surfaces, hematite (α-Fe2O3) (104) surface, is considered and explored its reactivity towards methane activation and conversion to methanol, formaldehyde using the density functional theory calculation in coupled with the correction of the on-site coulomb interaction (DFT + U). The reaction pathways of methane conversion on both two- and three-fold oxygen terminated hematite surfaces are considered. Besides, the CO/CO2 formation on these surfaces is also examined. The results indicate that the rate determined steps in methanol formation over two- and three-fold oxygen terminated surfaces are methanol desorption and C-O coupling, respectively. The thermodynamic analysis indicates that methane conversion is possible at a relatively higher temperature over two-fold oxygen terminated hematite surface than the three-fold oxygen terminated surface. It has been observed that the rate-determining step in formaldehyde formation over those two surfaces are formaldehyde desorption and CH3* dehydrogenation, respectively. The thermodynamic analysis showed that methane conversion into formaldehyde is possible higher than 400℃ over two-fold oxygen. For the methane conversion to value-added products, comparing the calculated energy profiles for all the reaction pathways considered in this study, it is seen that the rate-determining steps of both CO and CO2 formation steps' activation barriers are too high, suggesting that the CO/CO2 formation over two-fold oxygen terminated hematite surface is kinetically unfavorable evet at a higher temperature. The regeneration of the oxygen vacancy in both two-and three-fold oxygen terminated hematite surfaces using O2 is also considered. Finally, this theoretical study helps to understand the methane conversion mechanism over the hematite (α-Fe2O3) (104) surface at the atomic level and serves as guidance for developing cost-effective catalysts.

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