A Comprehensive Study on Oxygen Reduction and Evolution from Lithium Containing DMSO Based Electrolytes at Gold Electrodes

Abstract

© 2016 The Electrochemical Society. All rights reserved. In the present study, we investigated the reduction and the evolution of oxygen from lithium containing DMSO based electrolytes at gold. The number of electrons that are transferred per O 2 (z-value) during oxygen reduction depends on the structure of the electrode: Despite the presence of Li + , O 2 is reduced electrochemically to superoxide at smooth gold electrodes and at low overpotentials. At porous electrodes a z-value close to 2 e - /O 2 indicates Li 2 O 2 -formation even at low overpotentials. This is ascribed to a reaction of superoxide, which is catalyzed by gold-particles at open circuit. This behavior is also responsible for the non-proportionality between reduced and evolved amounts of oxygen. Furthermore, we observed a linear relationship between evolved amounts of CO 2 and reduced amounts of oxygen, indicative for electrolyte decomposition during oxygen reduction. Combined electrochemical quartz crystal microbalance (eQCMB) and Differential electrochemical mass spectroscopy (DEMS) measurements reveal that mass changes that occur in the anodic sweep are due to the evolution of CO 2 , whereas oxygen evolution takes place without any mass changes. The observed m.p.e-values (mass changes per transferred electron) are affected by convection due to the formation of soluble reduction products which observed in rotating ring disc electrode measurements.