Bioelectrode Healing via Engineered Electrode Reconstruction on Biofilms under Strong Acid and Ultrahigh Current Density

Abstract

Novel bioelectrodes are being developed to advance the applications of bioelectrocatalytic technology in various energy and environmental scenarios. However, concerns about the sustainability of engineered electrodes during prolonged operation is keeping raised. This study proposes a novel bioelectrode healing strategy via in situ electrode reconstruction on biofilms. The amount of viable cells in healed bioelectrode decreases by 24.23% because of the extreme conditions of strong acid (pH 0.1) and ultrahigh current density (−4.4 to 8.5 × 10⁵ mA m^–2) during the redeposition of sponge-like polyaniline@carbon nanotube; however, it quickly recovers to 1.88-fold that of the unhealed bioelectrode. Compared with the control, the healed bioelectrode attains a 2.61-fold toluene degradation kinetics (2.71 h^–1), a 1.36-fold power density (401.4 mW m^–2), and a 1.09-fold Coulombic efficiency (14.69%), which are also considerably higher than the literature results. The energy cost for electrode healing (19.05 J) accounted for ∼4.7% of the energy recovered in the following operation, thus confirming the energy efficiency of the healing strategy. In addition, the output voltage of the healed bioelectrode decreases by 17.1% at the end of a 60-day operation, with the corresponding decrement being 41.0% for the unhealed control. Furthermore, the elevated concentrations of ATP, NADH, and c-type cytochromes, along with the upregulated genes related to intracellular and extracellular electron transfer, are found to be the driving forces behind the superior and durable performance.