DFT Study of Oxygen Dissociation in Molten Carbonate

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• 作者：Xueling Lei ; Kahla Haines ; Kevin Huang ; Changyong Qin
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：8806-8812
• 全文大小：491K
• ISSN：1520-5215

文摘

Using density functional theory method, we have studied the oxygen dissociation in alkali molten carbonate at the B3LYP/6-31G(d) level. The calculated energies were then verified by MP4 and CCSD(T). A four-formula cluster (M₂CO₃)₄, M = Li, Na, and K was used to describe the molten carbonate. It was found that the adsorption of oxygen to molten carbonate is of a chemical type and leads to the formation of CO₅^{2鈥?/sup> in MC, which was confirmed for the first time by DFT calculations. The energy barrier for its dissociation is calculated to be 197.9, 116.7, and 170.3 kJ/mol in the (M₂CO₃)₄ cluster, M = Li, Na, and K, respectively. If the reaction of O₂ + 2CO₃2鈥?/sup> 鈫?2CO₄2鈥?/sup> is approximated as a one-step reaction, the activation energy is estimated to be 96.2, 15.1, and 68.6 kJ/mol, respectively. The reaction rate is first order to the pressure of oxygen. Surprisingly, the reaction of oxygen dissociation has the lowest energy barrier in sodium carbonate, which is consistent with the recent experimental findings. It is very clear that the molten carbonate salt has directly participated in the ORR process and plays an important role as a catalyst in the cathode of SOFCs. The oxygen reduction has been facilitated by MC and enhanced cell performance has been observed.}