Solvent co-deposition during oxygen reduction on Au in DMSO LiPF6

Rotating ring disk electrode (RRDE) and electrochemical quartz crystal microbalance (EQCM) have been employed for chronoamperometry of the oxygen reduction reaction (ORR) on gold electrodes in O2 saturated LiPF6/DMSO electrolyte. The Au ring electrode (ER = 3.0 V) detects a small fraction of soluble superoxide generated at the disk while EQCM detects the mass of ORR insoluble products. By integration of the ORR current transient the mass to charge plots exhibit mass per electron (mpe) values which largely exceed those expected for simple O2 to O2Li or Li2O2 reactions. Therefore the co-deposition of solvent and/or side reactions such as electrolyte degradation should be taken into consideration to explain the experimental evidence.