Why (1 0 0) Terraces Break and Make Bonds: Oxidation of Dimethyl Ether on Platinum Single-Crystal Electrodes

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• 作者：Hongjiao Li ; Federico Calle-Vallejo ; Manuel J. Kolb ; Youngkook Kwon ; Yongdan Li ; Marc T.M. Koper
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：September 25, 2013
• 年：2013
• 卷：135
• 期：38
• 页码：14329-14338
• 全文大小：527K
• 年卷期：v.135,no.38(September 25, 2013)
• ISSN：1520-5126

文摘

A surface structural preference for (1 0 0) terraces of fcc metals is displayed by many bond-breaking or bond-making reactions in electrocatalysis. Here, this phenomenon is explored in the electrochemical oxidation of dimethyl ether (DME) on platinum. The elementary C鈥揙 bond-breaking step is identified and clarified by combining information obtained from single-crystal experiments and density functional theory (DFT) calculations. Experiments on Pt(1 0 0), Pt(5 1 0), and Pt(10 1 0) surfaces show that the surface structure sensitivity is due to the bond-breaking step, which is unfavorable on step sites. DFT calculations suggest that the precursor for the bond-breaking step is a CHOC adsorbate that preferentially adsorbs on a square ensemble of four neighboring atoms on Pt(1 0 0) terraces, named as 鈥渢he active site鈥? Step sites fail to strongly adsorb CHOC and are, therefore, ineffective in breaking C鈥揙 bonds, resulting in a decrease in activity on surfaces with increasing step density. Our combined experimental and computational results allow the formulation of a new mechanism for the electro-oxidation of DME as well as a simple general formula for the activity of different surfaces toward electrocatalytic reactions that prefer (1 0 0) terrace active sites.