Role of Reduced CeO2(110) Surface for CO2 Reduction to CO and Methanol

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• 作者：Neetu Kumari ; M. Ali Haider ; Manish Agarwal ; Nishant Sinha ; Suddhasatwa Basu
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 4, 2016
• 年：2016
• 卷：120
• 期：30
• 页码：16626-16635
• 全文大小：811K
• 年卷期：0
• ISSN：1932-7455

文摘

Density functional theory (DFT) calculations were performed to study the mechanism of carbon dioxide (CO₂) reduction to carbon monoxide (CO) and methanol (CH₃OH) on CeO₂(110) surface. CO₂ dissociates to CO on interacting with the oxygen vacancy on reduced ceria surface. The oxygen atom heals the vacancy site and regenerates the stoichiometric surface via a redox mechanism with intrinsic activation and reaction energies of 259.2 and 238.6 kJ/mol, respectively. Lateral interaction of oxygen vacancies were studied by the generation of two oxygen vacancies per unit of CeO₂ surface. Compared to a single isolated vacancy, the activation and reaction energies of CO₂ dissociation on a divacancy were approximately reduced to half of its value. Hydrogen atom coadsorbed on the surface was observed to assist CO₂ dissociation by forming a carboxyl intermediate, CO₂+H → COOH (ΔE_act = 39.0 kJ/mol, ΔH = −69.2 kJ/mol) which on subsequent dissociation produces CO via the redox mechanism. On hydrogenation, CO is likely to produce methanol. The energetics of CO hydrogenation to produce methanol showed exothermic steps with activation barriers comparable to the DFT calculations reported for Cu (111) and CeO_2–x/Cu(111) interface. While on the stoichiometric surface, COOH dissociation COOH → CO+OH (ΔE_act = 55.6 kJ/mol, ΔH = 5.7 kJ/mol) is likely to be difficult as compared to rest of the elementary steps, whereas on the reduced surface the energetics of the same step were significantly lowered (ΔE_act = 47.4 kJ/mol, ΔH = −80.4 kJ/mol). In comparison, hydrogenation of methoxy, H₃CO+H → H₃COH, appears to be relatively difficult (ΔE_act = 58.7 kJ/mol) on the reduced surface.