由於碳酸二甲酯(DMC)含有甲氧基(CH3O)、甲基(CH3)、羰基(C=O)等官能基，且具有低毒性、可生物降解的特性，因此常被視為環境友善試劑並應用於各種反應當中。此外，近年來二氧化鈰(CeO2)催化劑廣泛地被應用在各種催化領域之中，科學家們發現其不同切面或者不同表面型態會具有不同的反應選擇性。在本研究中，我們藉由密度泛函理論(DFT)計算來探討DMC在CeO2(100)表面上的分解機制。結果顯示，表面上會產生OCH3、CO3、CO2等物種，而CH3OH及CO則會在後續的OCH3氫化及脫氫反應中產生，最終在表面上殘留許多難以移除的氫原子。對此，我們額外考慮了表面存在額外氫原子的系統，發現額外的氫原子可以有效降低生成CH3OH的活化能。此外，我們也發現在較高的氫原子覆蓋率及氧缺陷的系統中可能使氫氣生成變得更加容易。微觀反應動力學的模擬則說明了CH3OH與CO2會於大約395K時產生、CO會於560K附近產生，這些動力學模擬數據也與我們合作的實驗團隊結果幾乎一致。另外，模擬結果顯示可以藉由控制系統溫度來改變CeO2(100)表面上的官能基。在230-300K時，表面上主要會存在CH3O基團，可以進行甲氧基化的加成反應；400-500K時，表面存在HCO基團與H原子，能夠進行反應物的氫化或者HCO的直接加成；溫度600K以上時，表面剩下大量的H原子，只能夠進行氫化反應。本篇計算結果能夠給予實驗學家更多關於溫度對CeO2(100)上基團選擇性的影響，並對後續研究有所幫助。

Due to its low toxicity, biodegradability, and various types of fragments, dimethyl carbonate (DMC) has been seen as an environment-friendly reagent in many applications. Recently, the CeO2 catalysts have been widely used in different territories and are reported to have different reaction selectivity with varying surface conditions. In this study, we use the density functional theory (DFT) calculations to explore the DMC decomposition reactions on the CeO2(100). The results show that the DMC can decompose into OCH3, CO3, and CO2 fragments with low activation energies. The CH3OH and the CO can be produced by the further hydrogenation or dehydrogenation of OCH3. Finally, only the H atoms are left on the surface and are hard to remove. The H-CeO2(100) system shows that methanol can be produced with lower activation energies. We also observe that the higher H coverage or oxygen vacancy amounts may lead to easier H2 formation. Furthermore, the microkinetic simulations reveal that the products can appear at the temperature of 395K (CH3OH and CO2) and 560K (CO). The microkinetic simulation data are also consistent with the observation of experiments from our collaborators. In addition, the simulation results show that the functional groups on the CeO2(100) surface can be altered by controlling the temperature of the system. The main species on the surface is OCH3 in the temperature range of 230-300K, which might continue the methoxylation reaction to other chemicals; within the temperature of 400-500K, the main species are HCO and H, which may apply to the hydrogenation or the HCO addition reactions of other reactants; when the temperature reaches over 600K, only the hydrogenation can occur due to a large number of H atoms on the surface. Our calculation results could give experimentalists more information about the effect of temperature on the intermediate selectivity of CeO2(100) and will be helpful for subsequent research.

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