Periodic polarization duty cycle tunes performance and adhesion of anodic electroactive biofilms

Periodic polarization can improve the performance of anodic electroactive biofilms (EABs). The impact of the half-period duration was previously investigated at constant duty cycle (50%), i.e., the proportion of a period during which the electrode is polarized. Here, we cultured eight EABs on glassy carbon electrodes at four different duty cycles (50%, 67%, 80% and 91%) by varying the time interval under open circuit conditions, while keeping the polarization duration at 10 s. The shorter duty cycles slightly slowed initial growth but produced EABs generating higher faradaic currents. The total charge recovery over 38 days increased with decreasing duty cycles from 0.53 kC.cm^-2 (duty cycle of 91%) to 1.65 kC.cm^-2 (50%). EABs with the shortest duty cycle fully detached twice from the electrode surface, but detachments were quickly followed by the formation of more efficient EABs. We then carried out controlled removal of some aged and low current-producing EABs by applying a 30 s cathodic current (H₂ evolution at -15 mA.cm^-2) and observed the subsequent rapid development of fresh EABs displaying better electrochemical performance. Our results illustrate that well-chosen dynamic controls of electrode potentials can substantially improve the average current production of EABs, or allow a simple replacement of underperforming EABs.