化学学报 ›› 2024, Vol. 82 ›› Issue (12): 1202-1208.DOI: 10.6023/A24090260 上一篇    下一篇

研究论文

电化学SERS研究离子液体/金属界面水吸附行为的阳离子亲水性效应

贺乾军, 张晨杰, 徐敏敏, 袁亚仙*(), 姚建林*()   

  1. 苏州大学 材料与化学化工学部 苏州 215123
  • 投稿日期:2024-09-03 发布日期:2024-11-28
  • 基金资助:
    国家自然科学基金(22172109); 国家自然科学基金(21773166)

Electrochemical-SERS Investigation for Cationic Hydrophilic Effects on the Adsorption Behaviors of Water at Ionic Liquid/Metal Interface

Qianjun He, Chenjie Zhang, Minmin Xu, Yaxian Yuan(), Jianlin Yao()   

  1. College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
  • Received:2024-09-03 Published:2024-11-28
  • Contact: E-mail: yuanyaxian@suda.edu.cn; jlyao@suda.edu.cn; Tel.: 0512-65880359; Fax: 0512-65880089
  • Supported by:
    National Natural Science Foundation of China(22172109); National Natural Science Foundation of China(21773166)

离子液体因其独特的性质而有望成为理想的电解液材料. 然而, 离子液体极易吸水, 吸收的水倾向于在电极界面富集, 削弱其工作性能. 本工作发展一种基于电化学表面增强拉曼光谱(EC-SERS)结合探针反应的技术, 并应用于离子液体/金属界面水分子吸附行为的研究. 以对界面水高度敏感的对二巯基偶氮苯(DMAB)的电化学还原反应为探针, 结合EC-SERS技术, 将具有良好均匀性和可靠性的Au纳米粒子单层膜转移至玻碳电极表面作为SERS膜电极, 提高光谱数据横向对比的可靠性, 深入研究了具有不同阳离子的离子液体界面水吸附行为. 研究发现, 随水含量增加, DMAB的还原程度明显提高, 当水含量低于1%时(体积分数), 1-丁基-3-甲基咪唑四氟硼酸盐([BMIm]BF4)和N-丁基吡啶四氟硼酸盐([BPy]BF4)中DMAB的还原程度几乎一致, 这是由于水含量较低, 体相中的阴阳离子的吸水性与界面阳离子的吸水性达到平衡所致. 水含量高于1%时, [BMIm]BF4中DMAB的还原程度均高于[BPy]BF4, 与阳离子的亲水性能力顺序一致. 结果表明离子液体/电极界面水吸附行为与离子液体阳离子亲水性密切相关, [BMIm]+亲水性更强, 导致较负电位区间内[BMIm]BF4中水分子较[BPy]BF4体系中更易吸附于界面, 从而对水敏感的界面反应的影响更为显著, 该研究为界面水及相关行为的测定提供了新路径.

关键词: 离子液体, 表面增强拉曼光谱, 探针反应, 界面水, 亲水性

Ionic liquid has emerged as ideal electrolyte due to its unique properties. However, the previous studies have shown that ionic liquid was very easy to absorb water, and the water in the ionic liquid is trended to enrich at the electrode interface, resulting the significant influence on the performance of ionic liquid. In this paper, an electrochemical surface-enhanced Raman spectroscopy (EC-SERS) combined with probe reaction technique was developed to study adsorption behavior of water at ionic liquid/metal interface. The electrochemical reduction reaction of p-dimercaptoazobenzene (DMAB), which is highly sensitive to interfacial water, was explored as a probe. The Au nanoparticle monolayer film (Au MLF) with good uniformity and reliability was transferred to the surface of glassy carbon electrode as SERS film electrode to improve the reliability of horizontal comparison of spectral result. The interfacial water adsorption behavior in ionic liquid with different cations was studied accordingly. The activity and homogeneity of the SERS substrate have emerged as pivotal in both fundamental researches and practical applications. Herein, Au MLF was successfully fabricated through a self-assembly process at the air-water interface, with the aid of polyvinylpyrrolidone (PVP) as an auxiliary agent. It was found that the reduction efficiency of DMAB increased significantly with the increase of water content. The reduction efficiencies of DMAB in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) and 1-butylpyridinium tetrafluoroborate ([BPy]BF4) were almost the same in the solution with the water content less than 1% (volume fraction). It was mainly contributed by the balance in the water adsorption between the anions and cations of bulk phase and the interfacial cations. With the increase of water content to higher than 1%, the reduction efficiency of DMAB in [BMIm]BF4 is higher than that in [BPy]BF4, which is consistent with the hydrophilic ability of cations. The results demonstrate that the water adsorption behavior of the ionic liquid/electrode interface is critically dependent on the hydrophilicity of the ionic liquid cation. More hydrophilicity of [BMIm]+ allowed the water molecules in [BMIm]BF4 to reach at the interface with more molecules than that in the [BPy]BF4 system in the negative potential range. It produced a more significant effect on the water-sensitive interfacial reaction. The present study provides a new approach for the determination of interfacial water and its related behaviors.

Key words: ionic liquid, surface-enhanced raman spectroscopy, probe reaction, interfacial water, hydrophilicity