离子液体在CO_2电还原反应过程中的催化作用与机理研究  

Catalytic Mechanism of Ionic Liquid for CO_2 Electrochemical Reduction

作　　者：杨冬伟[1] 李露[1] 王琴[1] 王晓春[1] 李青远[1] 施锦[1] 

机构地区：[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

出　　处：《高等学校化学学报》2016年第1期94-99,共6页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:51164020);教育部留学回国人员科研启动基金资助~~

摘　　要：在1-丁基3-甲基咪唑三氟甲基磺酸盐([Bnlim][CF_3SO_3])/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CO_2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CO_2电还原反应过程中,吸附态CO_2经单电子还原生成CO_2^-自由基是速率控制步骤.由于离子液体的催化作用,CO_2在[Bmim][CF_3SO_3]/PC溶液中电还原的过电位比在四丁基三氟甲基磺酸铵([Bu_4N][CF_3SO_3])/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CO_2分子经单电子还原后生成CO_2~·-)自由基,与周围离子液体发生相互作用,形成中间体[Bmim-CO_2]_(ad),降低了CO_2^(·-)的能量状态,使得CO_2电还原反应的过电位大幅度降低.In 1-butyl-3-methylimidazolium trifluoromethanesulfonate（[Bmim][CF3SO3]） /propylene carbonate（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 CO2^（·-） 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 tetrabutylammonium 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 CO2^·- radical via single electron transfer.The generated CO2^·- 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.

关 键 词：二氧化碳 电化学还原 离子液体 交流阻抗 催化机理 

分 类 号：O646[理学—物理化学]