Comparative Electrochemical Investigations in Ionic Liquids and Molecular Solvents of a Carbon Surface Modified by a Redox Monolayer
Résumé
Electrochemical properties of carbon surfaces modified by a covalently attached redox monolayer (alkyl-ferrocenyl) have been investigated in three different classical room temperature ionic liquids (RTILs): BMIPF6, BMINTf2, Me3BuNNTf2, and in two common molecular solvents (ethanol and CH2Cl2) for evidencing special aspects of the electronic transfer in RTILs. If the redox activity and the stability of the layer are globally preserved in the RTILs, a considerable decrease of the amount of active redox groups is observed when the layer is examined in the RTILs. The oxidation potentials are only slightly higher in the RTILs contrarily to the charge transfer kinetics that decrease by a factor of 10–20 as measured for the rates between the attached redox moieties and the substrate. These behaviors that appear as possible limitations for practical applications of such systems in RTILs could be ascribed to specific ionic associations and a large reorganization of the layer during its charging process.