Synergistic Promotion of NO-CO Reaction Cycle by Gold and Nickel Elucidated using a Well-Defined Model Bimetallic Catalyst Surface

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• 作者：Atsushi Beniya ; Yasuhiro Ikuta ; Noritake Isomura ; Hirohito Hirata ; Yoshihide Watanabe
• 刊名：ACS Catalysis
• 出版年：2017
• 出版时间：February 3, 2017
• 年：2017
• 卷：7
• 期：2
• 页码：1369-1377
• 全文大小：582K
• ISSN：2155-5435

文摘

A bimetallic catalyst of Au and Ni significantly increased the catalytic activity of the NO-CO reaction in comparison to monometallic Au and Ni catalysts. Unraveling the roles of Au and Ni atoms in the each of the NO-CO reaction steps occurring on the Au-Ni catalyst surface is crucial to reveal the origin of the increased activity. For this purpose, a well-defined Au/Ni(111) model catalyst was prepared, on which CO and NO adsorption, their coadsorption, NO dissociation, CO₂ formation, and N₂ formation were investigated using infrared reflection absorption spectroscopy, temperature-programmed desorption/reaction, and density functional theory calculations. In the reaction process, the catalyst surface would be dominantly covered by N and O atoms, which would be removed from the surface by N₂ formation and CO₂ formation. O atoms preferentially occupy the Ni hollow sites by segregating N atoms to the adsorption sites made up of Au and Ni atoms. Thus, only the N₂ formation step was affected by the Au atoms. The activation energy for the N₂ formation step, which was assigned as a rate-limiting step, was significantly lowered by the Au atoms, and this effect will contribute to the decrease of the activation energy of the overall NO-CO reaction. These results suggest that, by utilizing the adsorption site preferences among the coadsorbates on the bimetallic surface, the activation energy of a rate-limiting step would be significantly decreased; this could be useful in the development of advanced NO_x reduction catalysts.