Initial Atmospheric Corrosion of Zinc Exposed to Formic Acid, Investigated by in Situ Vibrational Sum Frequency Spectroscopy and Density Functional Theory Calculations

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• 作者：Jonas Hedberg ; Jaime Henriquez ; Steven Baldelli ; C. Magnus Johnson ; Christofer Leygraf
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：February 12, 2009
• 年：2009
• 卷：113
• 期：6
• 页码：2088-2095
• 全文大小：349K
• 年卷期：v.113,no.6(February 12, 2009)
• ISSN：1932-7455

文摘

Vibrational sum frequency spectroscopy (VSFS) and ab initio density functional theory (DFT) calculations of formic acid on ZnO/Zn have been performed in order to understand the first step of atmospheric corrosion on zinc initiated by formic acid. In addition, infrared reflection absorption spectroscopy (IRAS) has been employed to complement the surface sensitive VSFS results to identify the corrosion products. Oxidized polycrystalline zinc samples were exposed to 120 ppb formic acid in either humid or dry air where, the formic acid adsorption on ZnO/Zn is observed to have a low dependence on the humidity, as deduced by VSFS. Formate is formed on the surface in both dry and humid air and stabilized in configuration after about 90 min exposure in 120 ppb formic acid as seen in the VSFS results. This is evidenced by the occurrence of the CH and symmetric COO⁻ vibrations of the formate ion. The DFT calculations support the VSFS results, showing a coordination of the formate to zinc ions without participation from water molecules.