Electroreduction of oxygen in a series of room temperature ionic liquids composed of group 15-centered cations and anions
Electroreduction of oxygen in a series of room temperature ionic liquids composed of group 15-centered cations and anions
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DOI：
10.1021/jp031309i
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发表时间：
2004-06-10
影响因子：
3.3
通讯作者：
Compton, RG
中科院分区：
文献类型：
--
作者：
Evans, RG;Klymenko, OV;Compton, RG
报道了四种基于四种室温离子液体(RTIL)中氧的电化学还原反应，这些离子液体的中心原子是氮或磷。用循环伏安法和电位阶跃计时安培法在微米尺寸的金、铂和玻璃碳盘电极上收集数据，在受控温度下的无水条件下进行。然后对适当的理论方程进行拟合分析，以获得与所观察到的电化学过程有关的动力学和热力学信息。在季铵盐电解液中，氧发生可逆还原，生成稳定的超氧化物，类似于传统的非质子化溶剂，如二甲基亚砜和乙腈。最显著的区别是相对扩散速度；氧在RTILs中的扩散系数比在普通有机溶剂中低一个数量级，而对于超氧化物，这些值又降低了10倍。然而，在季膦离子液体中，观察到更复杂的伏安法，类似于酸化有机介质中氧的还原。这与初始电子转移后电生超氧化物与季烷基膦阳离子之间发生的质子提取反应是一致的。
The electrochemical reduction of oxygen is reported in four room temperature ionic liquids (RTILs) based on quaternary alkyl -onium cations and heavily fluorinated anions in which the central atom is either nitrogen or phosphorus. Data were collected using cyclic voltammetry and potential step chronoamperometry at gold, platinum, and glassy carbon disk electrodes of micrometer dimension under water-free conditions at a controlled temperature. Analysis via fitting, to appropriate theoretical equations was then carried out to obtain kinetic and thermodynamic information pertaining to the electrochemical processes observed. In the quaternary ammonium electrolytes, reduction of oxygen was found to occur reversibly to give stable superoxide, in an analogous manner to that seen in conventional aprotic solvents such as dimethyl sufoxide and acetonitrile. The most significant difference is in the relative rate of diffusion; the diffusion coefficients of oxygen in the RTILs are an order of magnitude lower than in common organic solvents, and for superoxide these values are reduced by a further factor of 10. In the quaternary phosphonium ionic liquids, however, more complex voltammetry is observed, akin to that expected for the reduction of oxygen in acidified organic media. This is shown to be consistent with the occurrence of a proton abstraction reaction between the electrogenerated superoxide and quaternary alkyl phosphonium cations following the initial electron transfer.