Acta Chimica Sinica ›› 2013, Vol. 71 ›› Issue (07): 1059-1063.

Article

### 离子液体中Fe电极界面结构的SERS光谱研究

1. 苏州大学材料与化学化工学部 苏州 215123
• 投稿日期:2013-02-19 发布日期:2013-05-02
• 通讯作者: 袁亚仙, yuanyaxian@suda.edu.cn; 姚建林, jlyao@suda.edu.cn E-mail:yuanyaxian@suda.edu.cn; jlyao@suda.edu.cn
• 基金资助:

项目受国家自然科学基金(Nos. 21073128, 21033007, 21173155)和江苏省自然科学基金(No. BK2012187)资助.

### SERS Investigation of the Interfacial Structure at Fe Electrode in Ionic Liquids

Mei Jinhua, Xu Minmin, Yuan Yaxian, Yang Fengzhu, Gu Ren'ao, Yao Jianlin

1. College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123
• Received:2013-02-19 Published:2013-05-02
• Supported by:

Project supported by the National Natural Science Foundation of China (Nos. 21073128, 21033007, 21173155) and the Natural Science Foundation of Jiangsu Province (No. BK2012187).

The surface enhanced factor, potential zero charge (pzc), surface adsorption and structures of electrostatic double layer were electrochemically investigated at ionic liquids/Fe electrode interfaces through high sensitive surface enhanced Raman spectroscopy (SERS) combined with probe molecules of various lengths. In order to improve the intensity of Raman signals from adsorbed species and decrease the influences from the bulk ionic liquids, Au@SiO2 nanoparticles were spread over the Fe electrode, that is, shell-isolated nanoparticles-enhanced Raman spectroscopy (SHINERS) was employed. Based on the SHINERS technology, the adsorption behaviors of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) on a Au@SiO2 modified Fe electrode were investigated. It was found that the adsorption behaviors depended on the applied potentials. When the potentials were positive than-1.3 V[vs. a Pt quasireference electrode (PQRE)],[BMIm]BF4 was adsorbed with the imidazolium ring nearly perpendicular to the surface. While it kept tilted or even parallel as the potentials negative to-1.3 V. At a extremely negative potential (-2.3 V), the imidazolium cation was reduced to carbene. In addition, SCN- and 4-cyanopyridine (4-CNPy) with different molecular lengths were employed as probes. Electrochemical Stark effects of C≡N stretching band was measured to monitor the double structures at ionic liquids/Fe electrode interfaces. It was resulted that SCN- and 4-CNPy were adsorbed through N atom and N atom of pyridine ring, respectively. The results revealed that the C≡N stretching band of SCN- was shifted to low frequency with the negative moved potentials. The electrochemical Stark coefficient was about 17 cm-1/V. However, the C≡N stretching band of 4-CNPy nearly kept constant, that is, Stark coefficient was 0 cm-1/V. It was suggested that there were big differences comparing with aqueous systems. The surface electric field was mainly distributed in the compact layer of ionic liquids/Fe electrode interface. Moreover, through the calculation based on the SERS of SCN-, the surface enhancement factor of rough Fe electrode in[BMIm]BF4 was about 1.5×102.