Hydrogenation of CO2 to Methanol on CeOx/Cu(111) and ZnO/Cu(111) Catalysts: Role of the Metal–Oxide Interface and Importance of Ce3+ Sites

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• 作者：Sanjaya D. Senanayake ; Pedro J. Ramírez ; Iradwikanari Waluyo ; Shankhamala Kundu ; Kumudu Mudiyanselage ; Zongyuan Liu ; Zhi Liu ; Stephanus Axnanda ; Dario J. Stacchiola ; Jaime Evans ; José A. Rodriguez
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 28, 2016
• 年：2016
• 卷：120
• 期：3
• 页码：1778-1784
• 全文大小：436K
• ISSN：1932-7455

文摘

The role of the interface between a metal and oxide (CeO_x–Cu and ZnO–Cu) is critical to the production of methanol through the hydrogenation of CO₂ (CO₂ + 3H₂ → CH₃OH + H₂O). The deposition of nanoparticles of CeO_x or ZnO on Cu(111), θ_oxi < 0.3 monolayer, produces highly active catalysts for methanol synthesis. The catalytic activity of these systems increases in the sequence: Cu(111) < ZnO/Cu(111) < CeO_x/Cu(111). The apparent activation energy for the CO₂ → CH₃OH conversion decreases from 25 kcal/mol on Cu(111) to 16 kcal/mol on ZnO/Cu(111) and 13 kcal/mol on CeO_x/Cu(111). The surface chemistry of the highly active CeO_x–Cu(111) interface was investigated using ambient pressure X-ray photoemission spectroscopy (AP-XPS) and infrared reflection absorption spectroscopy (AP-IRRAS). Both techniques point to the formation of formates (HCOO^–) and carboxylates (CO₂^δ?) during the reaction. Our results show an active state of the catalyst rich in Ce³⁺ sites which stabilize a CO₂^δ? species that is an essential intermediate for the production of methanol. The inverse oxide/metal configuration favors strong metal–oxide interactions and makes possible reaction channels not seen in conventional metal/oxide catalysts.