A rotating ring disk electrode study of the oxygen reduction reaction in lithium containing non aqueous electrolyte

Abstract

We show the effect of a very small addition of LiClO4 to tetraethyl ammonium perchlorate (TEAP) in acetonitrile on the electro-reduction of molecular oxygen (ORR) at a rotating ring (Pt) glassy carbon (GC) disk electrode. While TEA+ cations stabilize the first electron reduction product in acetonitrile, superoxide O2−, in the absence of Li+ the ORR proceeds by two one-electron sequential steps to the stabilized peroxide. Addition of 10μM LiClO4 (<1:800 Li+ to TEA+ ratio) strongly affects the ORR mechanism: Both disk (ID) and ring (IR) currents strongly decrease, with less than 0.5% O2− produced at the GC disk reaching the ring electrode, but still IR follows the same potential dependence as ID. On the other hand, addition of DMSO to acetonitrile 0.1M LiClO4 stabilizes soluble O2− detected at the ring since DMSO preferentially solvates Li+ preventing disproportionation of LiO2 into O2 and passivating Li2O2.