The fast electrochemical reduction of iodine in the RTIL l-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 4min][NTf2], is reported and the kinetics and mechanism of the process elucidated. Two reduction peaks were observed. The first reduction peak is assigned to the process 3I2+ 2e-⇌2I 3- The second reduction peak is assigned to the process I3- + 2e- ⇌3I- A diffusion coefficient of 6.6 × 10-11 m2 s_1 (298 K) is inferred for I2 in [C4mim][NTf2] with a solubility of 1.70 mM. A mechanistic study was undertaken using a digital simulation program based on the mechanism I2 + 2e -⇌k′a⇌k′b 2I - I- +I2 ⇌k f,hom⇌kb,homI3- and simulation of the first reduction wave allowed extraction of various kinetic parameters including the diffusion coefficients for I2, I 3-, and I-, rate constants for the homogeneous process (kf,hom and kb,hom), and the heterogeneous rate constants k′a and k′b, and the associated transfer coefficients. The electrode process was found to be consistent with the following form of Butler-Volmer kinetics DI2∂[I 2]/∂z= k′ae-α-F/RT E[I 2] - k′beβF/RT E[I-] The mechanistic basis for this rate law is discussed. © 2008 American Chemical Society.
