To evaluate the impact of Na + doping on electrical conductivity in 2, we studied its impedance spectra (Figure ). The semicircle is related to the charge-transfer resistance (Rct) of the cathode materials. The electrochemical impedance spectroscopy (EIS) spectra show that the charge-transfer resistance of 2 (Rct =16.01 Ω) is lower than 1 (Rct = 20.89 Ω) and much lower than the commercial IrO2 (72.8 Ω), indicating a better electron transfer capability across the electrode/electrolyte interface, thereby indicating a superior OER kinetics and an improved overall electrochemical performance (Figure ).