利用密度泛函理論計算二氧化碳還原反應在銅與銅合金上的反應機構
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2018
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在本研究中，我們應用密度泛函理論計算研究了二氧化碳還原反應的機理，在具有前景的銅基材料催化劑中，該反應最常見的產物生成了甲醇。系統性的檢查發現，生成甲酸根 (HCOO) 和羧基(COOH) 是關鍵的兩個反應步驟。為了顯示結構效應，我們首先檢查Cu(100) 和Cu(111) 表面上的還原反應以揭示結構效應；此外，為了研究電子效應，我們還研究了在純銅、銅銀和銅金合金表面上的反應，其中銅表面25％的原子被其他元素原子替代。結構效應研究發現Cu(100) 表面上的中間體有比Cu(111) 表面更強的吸附能，誘發更多的放熱反應能量和更低的活化屏障，表示在鬆弛的Cu(100) 表面上具有更好的活性。電子效應結果表明，用銀和金取代表面銅可進一步降低能量，提高還原反應活性，而銀的取代稍好於金。在所有研究的表面上，甲酸根和羧基途徑中的速率決定步驟分別是HOCOH→COH + OH。最後，分析這些表面的狀態密度(DOS) 和相關的吸附情況，以揭示能量預測背後的化學反應。
In the present study, we applied density functional theory (DFT) calculation to investigate the mechanism of carbon dioxide reduction reaction forming the most common product of methanol on the promising materials of copper-based catalysts. Two key reaction pathways through carboxyl (COOH) and formate (HCOO) were systematically examined, denoted as Pathway I and II, respectively. We initially examine the reduction reaction on Cu(100) and Cu(111) surfaces to reveal the structural effects; additionally, we examine the reaction on pure Cu, CuAg and CuAu bimetallic surfaces, in which 25% of surface Cu was replaced with the foreign elements, to study the electronic effect. The structural effect study found that Cu(100) surface has more exothermic reaction energy and lower activation barriers on Pathway I, while Cu(111) has lower energetic on Pathway II, attributable to the difference of the adsorption energies on those two surfaces. The energetic results suggest that the structural effect might change the reaction pathway, but less likely alter the overall activity. The electronic effect result showed that substituting surface Cu with both Ag and Au can further lower the energetics and enhance the reduction reaction activity, while the substitution of Ag is somewhat better than that of Au. The rate determining steps in the formate and carboxyl pathways are HOCOH COH + OH, respectively, on all the studied surfaces. Finally, density of state (DOS) of those surfaces and the related adsorptions were analyzed to reveal the chemistry behind the energetic prediction.
In the present study, we applied density functional theory (DFT) calculation to investigate the mechanism of carbon dioxide reduction reaction forming the most common product of methanol on the promising materials of copper-based catalysts. Two key reaction pathways through carboxyl (COOH) and formate (HCOO) were systematically examined, denoted as Pathway I and II, respectively. We initially examine the reduction reaction on Cu(100) and Cu(111) surfaces to reveal the structural effects; additionally, we examine the reaction on pure Cu, CuAg and CuAu bimetallic surfaces, in which 25% of surface Cu was replaced with the foreign elements, to study the electronic effect. The structural effect study found that Cu(100) surface has more exothermic reaction energy and lower activation barriers on Pathway I, while Cu(111) has lower energetic on Pathway II, attributable to the difference of the adsorption energies on those two surfaces. The energetic results suggest that the structural effect might change the reaction pathway, but less likely alter the overall activity. The electronic effect result showed that substituting surface Cu with both Ag and Au can further lower the energetics and enhance the reduction reaction activity, while the substitution of Ag is somewhat better than that of Au. The rate determining steps in the formate and carboxyl pathways are HOCOH COH + OH, respectively, on all the studied surfaces. Finally, density of state (DOS) of those surfaces and the related adsorptions were analyzed to reveal the chemistry behind the energetic prediction.
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密度泛函理論, 二氧化碳還原反應, 甲醇, 反應機構, DFT, carbon dioxide reduction reaction, methanol, mechanism