应用扫描电化学显微镜研究电子在室温离子液体与1,2-二氯乙烷混合溶液/水相界面上的转移反应

应用扫描电化学显微镜研究了室温离子液体(Omim·Tf2N)与1,2-二氯乙烷(DCE)混合溶液/水界面上的电子转移反应. 在保持共同离子(Tf2N-)的浓度比恒定及异相电子转移反应由界面电势差所决定的条件下, 研究了离子液体和DCE混合溶液中二茂铁(Fc)与水相中亚铁氰化钾[K4Fe(CN)6]之间异相电子转移反应. 探讨了混合溶液中离子液体的体积分数(xRTIL)的变化对混合溶液/水界面上电子转移反应的影响. 结果表明, 随着xRTIL的减小(从1减小到0.1), Fc在混合溶液中的扩散系数单调递增(从2.730×10-7 cm2·s-1增加到9.131×10-6 cm2·s-1); 而异相电子转移反应速率常数(k)则先逐渐减小(从8.0 mol-1·cm·s-1减小到0.32 mol-1·cm·s-1), 之后又略有增大(从0.32 mol-1·cm·s-1增大到0.48 mol-1·cm·s-1). 对这种现象可能的原因进行了较详细探讨.

Studies of Electron Transfer Reactions at the Interface Between Room-temperature Ionic Liquid+1,2-Dichloroethane Solutions and Water by Scanning Electrochemical Microscopy

The kinetic behavior of electron transfer(ET) reactions at the interface between room-temperature ionic liquid(RTIL, Omim·Tf2N) + 1,2-dichloroethane(DCE) solutions and water was studied by scanning electrochemical microscopy(SECM). The tip was positioned in the top RTIL+DCE solutions containing ferrocene(Fc), and potassium ferrocyanide[K4Fe(CN)6] was employed as the mediator in water(bottom phase). The effects of RTIL with different volume fractions(xRTIL) in the mixtures on the apparent heterogeneous ET rate constants(k) were investigated at the same concentration ratio of the common ion(Tf2N-) by fitting the experimental approach curves to the theoretical values. The results showed that with xRTIL decreasing from 1 to 0.1, the diffusion coefficient of Fc(DFc) in the mixtures increased from 2.730×10-7 to 9.131×10-6 cm2·s-1 monotonously, but k decreased firstly(from 8.0 to 0.32 mol-1·cm·s-1), and then increased a little(from 0.32 to 0.48 mol-1·cm·s-1). The possible reasons for observation of these behavior were discussed in details.