Extended Data Fig. 4: Influence of the scan rate.

(a) CV scan at different scan rates on P-825 after activations. (b) Potential at a current density of 5 mA.cm⁻² reported from the CV scans at different scan rates. The scan rate has a minimal impact on the potential measured at a current density of 5 mA cm⁻² (one of the activity markers considered in this study); the potential only varies by a few mV depending on the scan rate, which overall denotes for the minimal impact of the potential scan rate with the kinetic markers chosen herein. This is ascribed to the fact that (i) only smooth polished surfaces were tested (this was deliberate, so to minimize the capacitive behaviour of the electrodes) and (ii) they display very high faradaic OER activity; as a result, the faradaic contribution overwhelms the capacitive one. 50 mV.s⁻¹ was chosen (20 mV.s⁻¹ in the RRDE experiments), so to limit as much as possible hindrance by the evolved oxygen bubbles, which becomes more prevalent at lower potential scan rate.