高等学校化学学报 ›› 2016, Vol. 37 ›› Issue (1): 94.doi: 10.7503/cjcu20150514

• 物理化学 • 上一篇    下一篇

离子液体在CO2电还原反应过程中的催化作用与机理研究

杨冬伟, 李露, 王琴, 王晓春, 李青远, 施锦()   

  1. 昆明理工大学省部共建复杂有色金属资源清洁利用国家重点实验室, 冶金与能源工程学院, 昆明 650093
  • 收稿日期:2015-07-02 出版日期:2016-01-10 发布日期:2015-12-20
  • 基金资助:
    国家自然科学基金(批准号: 51164020)和教育部留学回国人员科研启动基金资助

Catalytic Mechanism of Ionic Liquid for CO2 Electrochemical Reduction

YANG Dongwei, LI Lu, WANG Qin, WANG Xiaochun, LI Qingyuan, SHI Jin*()   

  1. State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China
  • Received:2015-07-02 Online:2016-01-10 Published:2015-12-20
  • Contact: SHI Jin E-mail:shijin1118@163.com
  • Supported by:
    † Supported by the National Natural Science Foundation of China(No.51164020) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars

摘要:

在1-丁基3-甲基咪唑三氟甲基磺酸盐([Bmim][CF3SO3])/碳酸丙烯酯(PC)溶液中, 采用循环伏安曲线、 交流阻抗谱及阻抗模拟方法, 研究了CO2在Au上发生电还原反应的速率控制步骤与离子液体的催化作用. 结果表明, 在CO2电还原反应过程中, 吸附态CO2经单电子还原生成C自由基是速率控制步骤. 由于离子液体的催化作用, CO2在[Bmim][CF3SO3]/PC溶液中电还原的过电位比在四丁基三氟甲基磺酸铵([Bu4N][CF3SO3])/PC溶液中降低了239 mV. 交流阻抗测试结果表明, 离子液体中的阳离子[Bmim]+吸附在Au电极表面, 形成离子液体吸附层, 吸附态的CO2分子经单电子还原后生成C自由基, 与周围离子液体发生相互作用, 形成中间体[Bmim-CO2]ad, 降低了C的能量状态, 使得CO2电还原反应的过电位大幅度降低.

关键词: 二氧化碳, 电化学还原, 离子液体, 交流阻抗, 催化机理

Abstract:

In 1-butyl-3-methylimidazolium trifluoromethanesulfonate([Bmim][CF3SO3])/propylene carbo-nate(PC) solution, the rate-determining step and catalytic mechanism of ionic liquid for CO2 electrochemical reduction on gold electrode were studied by cyclic voltammetry, electrochemical impedance spectroscopy and impedance simulation. Experimental results show that the rate-determining step for CO2 reduction is the formation of C radical by one-electron transfer. Due to the catalytic effect of ionic liquid, the onset potential of CO2 reduction in [Bmim][CF3SO3]/PC shifts positively by 239 mV comparing to that occurred in tetrabuty-lammonium trifluoromethanesulfonate([Bu4N][CF3SO3])/PC catholyte. The catalytic mechanism of ionic liquid is proposed as follows: firstly, the cation of ionic liquid([Bmim]+) adsorbed on the Au electrode and lead to the formation of ionic liquid film; then, CO2 in catholyte diffuses from the bulk solution to the surface of cathode. After transfer through the ionic liquid film adsorbed on the surface of Au electrode, CO2 is reduced to C radical via single electron transfer. The generated C radical further react with cation [Bmim]+ and induce the formation of [Bmim-CO2]ad. Through this route, the activation energy of CO2 electrochemical reduction is reduced. Hence the overpotential of CO2 electrochemical reduction is reduced substantially.

Key words: Carbon dioxide, Electrochemical reduction, Ionic liquid, Electrochemical impedance, Catalytic mechanism

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