Significant contribution of three-phase boundary for the oxygen reduction current in DMSO solution at a gold disk electrode in hanging meniscus configuration

Significant contribution of three-phase boundary for oxygen reduction reaction at a gold disk electrode in hanging meniscus configuration in dimethyl sulfoxide (DMSO) solution was demonstrated. While cyclic voltammograms (CVs) with symmetrical shape representing quasi-reversible kinetics were obtained for oxygen reduction reaction (ORR) at a Au disk electrode in an ordinary configuration when it was fully immersed in an O2 saturated 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) DMSO solution, asymmetric CVs with enhanced ORR current were obtained at a Au disk electrode in the hanging meniscus configuration. Origin of this feature was investigated at a gold wire electrode, which was immersed partly in the solution, in detail by changing the concentrations of O2 in the gas phase and in solution independently as well as the immersion depth. All the results confirm that the ORR at the three-phase, O2 gas/Au electrode/electrolyte solution, boundary contributes dominantly to the observed current in the hanging meniscus configuration.