Adsorption of Acetonitrile on Platinum and its Effects on Oxygen Reduction Reaction in Acidic Aqueous Solutions—Combined Theoretical and Experimental Study
Adsorption of Acetonitrile on Platinum and its Effects on Oxygen Reduction Reaction in Acidic Aqueous Solutions—Combined Theoretical and Experimental Study
复制标题
乙腈对铂的吸附及其对酸性水溶液中氧还原反应的影响——理论与实验相结合的研究
作者：
I. Pašti;A. Markovic;N. Gavrilov;S. Mentus
对乙腈(ACN)在铂表面的吸附进行了理论和实验相结合的研究，考察了其对HClO4和H2SO4溶液中氧还原反应动力学的影响。用周期密度泛函理论计算表明，ACN分子可以通过不饱和的π电子系统或通过氮原子的单电子对与铂表面相互作用。在这两种情况下，随着覆盖度的增加，吸附能降低，而铂表面电子结构的改变局限于吸附位置。结合密度泛函理论计算结果以及氧饱和溶液中空白循环伏安法和旋转圆盘电极伏安法的结果，得出ACN对铂表面化学和ORR动力学的影响主要是空间位阻效应。在ACN存在下测得的多晶铂的ORR活性是由于(I)抑制(Bi)硫酸盐吸附(在H_2SO_4溶液中)，(Ii)抑制表面氧化(在H_2SO_4和HClO_4溶液中)和(Iii)被吸附的ACN(或其电化学转化产物)位堵塞的综合结果。
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AbstractCombined theoretical and experimental study of acetonitrile (AcN) adsorption on platinum was performed and its effects on the kinetics of oxygen reduction reaction in HClO4 and H2SO4 solutions were examined. Using periodic density functional theory calculations, it was shown that AcN molecule can interact with Pt surface either through the unsaturated π electron system or via lone electron pair of nitrogen atom. In both cases, adsorption energy decreases upon increasing coverage, while the modification of electronic structure of Pt surface is localized to the adsorption site. By combining the results of the DFT calculations with the results of blank cyclic voltammetry and rotating disk electrode voltammetry in O2-saturated solutions, it was concluded that the effects of AcN on Pt surface chemistry and ORR kinetics are primarily steric in nature. Resulting measured ORR activities of polycrystalline platinum in the presence of AcN are due to the combination of (i) suppression of (bi)sulfate adsorption (in H2SO4 solution), (ii) suppression of surface oxidation (in both H2SO4 an HClO4 solution), and (iii) site blockage by adsorbed AcN (or products of its electrochemical transformations).
Graphical Abstractᅟ