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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Surface-Enhanced Raman Spectroscopy Studies on the Adsorption and Electrooxidation of Carbon Monoxide at the Platinum-Formic Acid Interface
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Surface-Enhanced Raman Spectroscopy Studies on the Adsorption and Electrooxidation of Carbon Monoxide at the Platinum-Formic Acid Interface

机译：表面增强拉曼光谱研究一氧化碳在铂-甲酸界面处的吸附和电氧化

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摘要

The vibrational spectrum of carbon monoxide, exerted by dissociation of formic aid, has been investigated at the platinum electrode as a function of applied potential by using the surface-enhanced Raman spectroscopy (SERS) technique. The electrolyte is 0.1 M LiClO_4. Two typical SERS features observed at 475-490 and 2055-2080 cm~(-1) are attributed to the platinum-CO (v_(Pt)-C) and intramolecular C-O (v_(C-O)) stretching vibration, respectively, indicating linearly adsorbed CO on platinum. Comparisons of the present data with previous studies in aqueous solutions show that solution components, particularly the dielectric in the inner double layer, may significantly influence the interaction of CO with platinum, especially the CO intramolecular mode. Electrooxidation of CO was observed to occur at potentials more positive than 0.6 V, being slightly negative relative to previous studies for CO on smooth platinum, suggestive of a higher electrocatalytic activity for the present highly roughened platinum surface. At positive and moderately negative potentials (-0.2 to 0.6 V), the Pt-C and CO intramolecular bands exhibit opposite frequency changes with decreasing potential, with Stark tuning rate being -6 and 24 cm~(-1)/V, respectively. At more negative potentials, both Pt-C and CO exhibit nonmonotonic potential dependences. The gradually decreasing slope for v_(Pt-C) can be explained in terms of the nearly offsetting contributions from the π-back-donation and σ-bonding, along with increasing steric repulsion from negatively charged surfaces. The nearly potential-invariant frequencies for v_(CO) were observed at potentials more negative than -1.0 V, indicating the key role of increasing concentration of H~+ in the inner double layer, possibly weakening the electron density back-donated from platinum to CO 2π~* orbitals.
机译：通过使用表面增强拉曼光谱（SERS）技术研究了在甲酸铂电极上由甲酸辅助剂解离产生的一氧化碳的振动光谱。电解质是0.1M LiClO_4。在475-490和2055-2080 cm〜（-1）处观察到的两个典型SERS特征分别归因于铂-CO（v_（Pt）-C）和分子内CO（v_（CO））的拉伸振动，线性表明将CO吸附在铂上。本数据与水溶液中先前研究的比较表明，溶液成分，尤其是内部双层中的电介质，可能会显着影响CO与铂的相互作用，尤其是CO分子内模式。观察到CO的电氧化发生在大于0.6 V的正电势，相对于先前在光滑铂上进行的CO的研究而言，它的电负性稍弱，这表明目前高度粗糙的铂表面具有更高的电催化活性。在正电势和中度负电势（-0.2至0.6 V）下，Pt-C和CO分子内带显示相反的频率变化，且电势降低，Stark调谐速率分别为-6和24 cm〜（-1）/ V。在更多负电势下，Pt-C和CO均表现出非单调电势依赖性。 v_（Pt-C）的逐渐减小的斜率可以用π返给和σ键几乎抵消的贡献以及带负电荷的表面增加的空间排斥来解释。在大于-1.0 V的负电势下观察到v_（CO）的几乎不变的频率，这表明增加内部双层中H〜+的浓度的关键作用，可能削弱了从铂返还给电子的电子密度。 CO2π〜*轨道。

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