Scanning electrochemical Microscopy in nonusual solvents: Inequality of diffusion coefficients problem
Scanning electrochemical Microscopy in nonusual solvents: Inequality of diffusion coefficients problem
复制标题
DOI：
10.1021/ac071195x
复制
发表时间：
2007-10-01
影响因子：
7.4
通讯作者：
Hapiot, Philippe
中科院分区：
文献类型：
--
作者：
Ghilane, Jaial;Lagrost, Corinne;Hapiot, Philippe
扫描电化学显微镜为研究室温离子液体（RTILs）中的传输性质以及在离子液体/基底界面发生的反应提供了有趣的可能性。除了由于RTILs较高的粘度导致溶解在其中的物质扩散系数较低所带来的预期困难外，主要问题来自用于探测界面的氧化还原介质的氧化态和还原态之间扩散系数的不相等。这个问题通过对最初由马丁和昂温提出的模型（Martin, R. D.; Unwin, P. R. J. Electroanal Chem. 1997, 439, 123）进行扩展来处理，并适应了离子液体中扫描电化学显微镜（SECM）的特定方面。扩散系数的不相等导致电流响应出现很大的异常，在极端情况下会阻碍稳态接近曲线的记录。研究了在离子液体中记录稳态接近曲线的条件以及错误数据处理的后果。这些与简单模型（当扩散系数被视为相等时）的差异可以转化为一种表征溶解在RTIL中物质传输性质的便捷方法。该分析基于瞬态SECM实验以及从明确的无量纲参数进行的测定。基于在常见RTILs中使用O₂/O₂(·⁻) 电对的SECM实验实例，结合所提出的模型进行了分析。
Scanning electrochemical microscopy offers interesting possibilities for investigating both transport properties in room-temperature ionic liquids (RTILs) and reactions occurring at the ionic liquid/substrate interface. Besides the expected difficulties related to the lower diffusion coefficients for species dissolved in RTILs arising from the higher viscosity of RTILs, the major problem comes from the inequality of the diffusion coefficients between the oxidized and reduced forms of the redox mediator used to probe the interfaces. This question was treated by an extension of the model originally presented by Martin and Unwin (Martin, R. D.; Unwin, P. R. J. Electroanal Chem. 1997, 439, 123) and was adapted to the specific aspects of SECM in ionic liquids. The inequalities of diffusion coefficients lead to large anomalies in the current responses, which in extreme cases impede the recording of stationary approach curves. Conditions for recording steady-state approach curves into ionic liquids and consequences of erroneous data treatment were examined. These discrepancies with the simple models (when diffusion coefficients have been taken as equal), could be transformed in a convenient method for characterizing the transport properties of species dissolved in RTIL. The analysis is based on transient SECM experiments and determinations from nonambiguous dimensionless parameters. Experimental examples based on SECM in common RTILs, using the O-2/O-2(center dot-) couple, were analyzed taking into account the presented model.