Three-electrode electrochemical measurements were conducted in an alkaline-resistant PTFE cell (AF01CKT1001, Pine Research Instrumentation) using a VSP-300 potentiostat (Biologic), with a leakless Ag/AgCl reference electrode (ET069, eDAQ), a coiled Pt wire counter electrode, and the RRDE with the dropcast or spin cast fims p(NDI-T2 P75) film. All voltages are referenced versus the reversible hydrogen electrode (RHE), where the RHE voltage of the Ag/AgCl reference for each experiment was standardized against a bulk RHE electrode (Hydroflex Hydrogen Reference Electrode, eDAQ) in each electrolyte prior to testing. The 0.1 M KOH electrolytes were prepared using KOH and ultrapure de-ionized water ("DI water", 18.2 MΩ resistance, MilliQ). The electrolytes for the pH series were made by mixing varying ratios of 1 M KHCO3 and 1 M KOH stock solutions, where each stock solution was prepared in advance with ultrapure de-ionized water. Prior to electrochemical characterization, Ar gas was allowed to bubble through the solution for at least 30 minutes. For each experiment, the uncompensated resistance, R, was measured at open circuit voltage (polymer is in the pristine, neutral state) through electrochemical impedance spectroscopy (EIS) at the high frequency intercept and iR correction was completed manually during the data analysis phase. In the 1 M [K + ] electrolytes, The R values in the 1 M [K + ] 0.1 M [K + ] electrolytes were about 15 Ω and 58 Ω, respectively. In Ar-saturated solution, the Pt ring was electrochemically cleaned according to the procedure outlined by Chen et al. The p(NDI-T2 P75) film was then cycled five times between 0.2 V and -0.5 V vs. Ag/AgCl and another five times between 0.2 V and -1.0 V vs. Ag/AgCl at 5 mV s -1 scan rate. O2 gas was then bubbled through solution for at least 30 minutes to saturate the electrolyte. In O2-saturated solution, RRDE measurements were completed at different rotation rates (400, 900, 1200, and 1600 r.p.m., MSR Rotator, Pine Research) while the p(NDI-T2 P75) was cycled between 0.2 V and -1.0 V at 5 mV s -1 and the ring was held constant at 1.2 V vs. RHE. At 1600 r.p.m., an extra RRDE measurement was completed following the same procedure as before, with a changed scan rate of 0.5 mV s -1 . All the measured disk and ring currents were normalized by the disk electrode area (~0.196 cm 2 ).