Figure demonstrates that the disproportionation rate, 𝑘 𝑓,3 , primarily affects the limiting current densities but not the halfwave voltage of oxygen reduction, where low disproportionation rates result in only a single electron transfer (corresponding to exclusively superoxide formation) while high disproportionation rates push the electron transfer number towards n = 2 due to the feedback loop of generated O2. Thus, the catalytic disproportionation of superoxide helps to rationalize the difference in observed oxygen reduction current between the p(NDI-T2 P75) coated electrode and the bare glassy carbon electrode-which shares the same E1/2 but only generates half of the limiting current in 0.1 M KOH (Figure ). On glassy carbon, which is apparently less catalytic for superoxide disproportionation, the limiting current density corresponds to a single electron transfer to form superoxide which builds up at the electrode surface excluding O2 resulting in a decrease in current density with increasing potential. While the side chains for the tested OMIECs are not identical, they all contain a polar (hydrophilic) portion, which is essential for bulk ion-insertion redox in aqueous electrolytes. In contrast, an NDI-T2 polymer with entirely nonpolar side chains was found to be incapable of electrochemical activation and oxygen reduction in aqueous electrolytes (Figure ). The