Catalytic CO Oxidation Using Bimetallic MxAu25–x Clusters: A Combined Experimental and Computational Study on Doping Effects

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• 作者：Weili Li ; Chao Liu ; Hadi Abroshan ; Qingjie Ge ; Xiujuan Yang ; Hengyong Xu ; Gao Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：May 19, 2016
• 年：2016
• 卷：120
• 期：19
• 页码：10261-10267
• 全文大小：449K
• 年卷期：0
• ISSN：1932-7455

文摘

Heteroatom-doped gold clusters have been of great interest to modify the catalytic performance of the clusters, although the structure–activity correlation is rarely discussed. Herein, we explore the catalytic activity of bimetallic gold-based M_xAu_25–x(SR)₁₈ (M = Cu and Ag, and SR = SC₂H₄Ph) clusters and compare with that of homogold Au₂₅(SR)₁₈ in the CO oxidation reaction. It is found that the CeO₂-supported clusters show catalytic activity for the reaction in the order Cu_xAu_25–x(SR)₁₈ > Au₂₅(SR)₁₈ > Ag_xAu_25–x(SR)₁₈. The supported clusters exhibit excellent catalytic activity and durability for prolonged conversion of CO into CO₂ (98% in the case of Cu_xAu_25–x(SR)₁₈ at 120 °C for 110 h). Fourier-transform infrared (FT–IR) analyses as well as the density functional theory (DFT) calculations suggest that the thiolate ligands are partially removed under reaction conditions (T > 120 °C). The metal atoms thus exposed (Au, Ag, and Cu) are deemed as the catalytic active sites. DFT calculations suggest that metal exchange between the icosahedral core and the staple motif of the clusters at elevated temperature plays an important role on the conversion rate of CO oxidation. The adsorption of CO on the clusters would be more preferable to occur in the order Cu₂Au₂₃(SCH₃)₁₅ > Au₂₅(SCH₃)₁₅ > Ag₂Au₂₃(SCH₃)₁₅, which is in line with the experimental results on the CO oxidation catalyzed by the bimetallic clusters.