context: The potential of the respective working electrode Ewe and the electrolyte redox potential Esol as function of charge/discharge cycles are shown in Fig. 8a and c. Averaged overpotentials (, see eqn (3)) and CE per cycle for [FeII/III-racEDDHA] and [FeII/III(CN)6] are shown in Fig. 8b and d. In case of [FeII/III(CN)6] a time stable value for was obtained. In case of the [Fe-racEDDHA] complex even a slight decrease in was observed. Thus, no deactivation of the carbon electrode surface was measured during repetitive cycling. Excellent CE was observed for both redox systems, indicating the absence of parasitic side reactions and suggesting a good electrochemical stability of all electrochemically active species. The applied procedure of desizing and anodic activation of the CRLE lead to formation of a stable and active carbon surface, which is not degraded or passivated during extended electrolysis. Independent on electrode potential, passivation was not observed in the potential window between +800 mV and −1200 mV vs. Ag/AgCl, which demonstrates the high chemical stability of the surface towards electrochemical degradation processes at the chosen experimental conditions.