Why (100) Terraces Break and Make Bonds: Oxidation of Dimethyl Ether on Platinum Single-Crystal Electrodes
Why (100) Terraces Break and Make Bonds: Oxidation of Dimethyl Ether on Platinum Single-Crystal Electrodes
复制标题
DOI：
10.1021/ja406655q
复制
发表时间：
2013-09-25
影响因子：
15
通讯作者：
Koper, Marc T. M.
中科院分区：
文献类型：
--
作者：
Li, Hongjiao;Calle-Vallejo, Federico;Koper, Marc T. M.
在电催化中，许多断键或成键反应显示出(100)面心立方金属的表面结构择优。本文以二甲醚(DME)在铂上的电化学氧化为例，探讨了这一现象。结合从单晶实验获得的信息和密度泛函理论(DFT)计算，确定并澄清了基本的C-O键断裂步骤。在铂(1 0 0)，铂(5 1 0)和铂(10 1 0)表面上的实验表明，表面结构敏感性是由断键步骤引起的，这对台阶位是不利的。密度泛函理论计算表明，断键步骤的先驱物是优先吸附在铂(100)平台上的四个相邻原子的方形系综上的CHOC吸附物，被称为“活性中心”。阶梯中心不能强烈吸附CHOC，因此不能有效地破坏C-O键，导致随着阶梯密度的增加，表面的活性降低。我们的实验和计算结果相结合，提出了DME电氧化的新机理，以及不同表面对(100)平台活性中心的电催化反应的活性的简单通用公式。
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-O 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 "the active site". Step sites fail to strongly adsorb CHOC and are, therefore, ineffective in breaking C-O 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.