Prospects for the Application of Scanning Electrochemical Microscopy in Ionic Liquids

摘要

Prospects have been assessed for the application of the technique of scanning electrochemical microscopy (SECM)in viscous ionic liquids.Use of the Fc~(0/+)redox couple (Fc =ferrocene)to obtain microelectrode approach curves revealed that the required steady state behaviour needed for analysis of data relevant to conducting platinum and insulating glass substrates is moderately easy to achieve in a l-butyl-3-methylimidazoliurn tetrafluoroborate ([BMIM][BF4])ionic liquid.However,in the more highly viscous 1 -butyl-3-methylimidazolium hexafluorophosphate ionic liquid,where significantly lower diffusion coefficients are encountered,approach-curve data that conform to steady state theory are only found with very small microelectrodes (e.g.,<2u,m diameter),very slow electrode-substrate approach rates (e.g.,<=0.05 mu m s~(-1)),and long equilibration times (e.g.,50 s).A comparison is provided with SECM approach curves acquired in aqueous media.SECM images of an Ag substrate in contact with [BMIM][BF4]also are presented and are of only slightly inferior quality to images obtained in water.