One electron oxygen reduction in room temperature ionic liquids: A comparative study of Butler-Volmer and Symmetric Marcus-Hush theories using microdisc electrodes

摘要

The voltammetry for the reduction of oxygen at a microdisc electrode isreported in two room temperature ionic liquids: 1-butyl-1-methylpyyrolidiniumbis(trifluoromethylsulfonyl) imide ([Bmpyrr][NTf2]) andtrihexyltetradecylphosphonium bis9trifluoromethylsulfonyl) imide([P14,6,6,6][NTf2]) at 298 K. Simulated voltammograms using Butler-Volmertheory and Symmetric Marcus-Hush (SMH) theory were compared with experimentaldata. Butler-Volmer theory consistently provided experimental parameters with ahigher level of certainty than SMH theory. A value of solvent reorganisationenergy for oxygen reduction in ionic liquids was inferred for the first time as0.4-0.5 eV, which is attributable to inner-sphere reorganisation with anegligible contribution from solvent reorganisation. The developedButler-Volmer and Symmetric Marcus-Hush programs are also used to theoreticallystudy the possibility of kinetically limited steady state currents, and toestablish an approximate equivalence relationship between microdisc electrodesand spherical electrodes resting on a surface for steady state voltammetry forboth Butler-Volmer and Symmetric Marcus-Hush theory.