To further confirm the nature of the chemical species forming in the process, rotating ring disk electrode (RRDE) based experiments are conducted with Zn as the disc electrode, Pt as the outer (ring) electrode, Ag/AgCl (sat.) as a reference electrode, platinum mesh as the counter electrode, and 1 M KOH as electrolyte. Schematic of the O2 reduction process on the Zn surface in RRDE set up is given in Fig. C. The disc electrode is kept at the OCP, where the OCP was found to be ~-1.6 V in the N2 supplied system while the OCP is decreased to -1.5 V with the O2 supply. The rotation speed is kept constant at 1600 rpm. The Pt ring is set at a potential of 0.5 V vs Ag/AgCl (sat. KCl) to oxidize the species formed at the disc electrode, if any. The experimental setup is given in SI Appendix, Fig. . It is important to note that a notable ring current is observed in O2 in comparison to that in the N2 supplied system, as shown in Fig. . This suggests the formation of reduced O2 species (radicals or anions) at the disc electrode when the supplied O2 encounters the zinc. Negligible ring or disc current are observed when bare glassy carbon disc electrodes or iron powder (another transition metal where its rechargeable alkaline batteries are demonstrated) are taken onto the disc keeping all the other conditions the same (SI Appendix, Fig. ). This confirms the unique reduction process of O2 molecules happening at the zinc surface.