Enhanced biocathode performance through surface charge induced microbial adhesion

Biocathode performance is often constrained by low biomass accumulation on the electrode surface due to electrostatic repulsion between negatively charged cells and negatively polarized electrodes. A strategy known as polarity reversal is typically applied to overcome this limitation, initially growing bacteria under anodic conditions and subsequently switching the electrode polarity to cathodic. This approach requires substantial time and requires bacteria capable of bidirectional extracellular electron transfer. In this work, biocathode enhancement is achieved by suppressing electrostatic repulsion between bacteria and the electrode during adhesion stage, via the generation of a positive charge on the electrode through polarization above the potential of zero charge (PZC). Bacterial adhesion kinetics to electrodes polarized at different potentials and subsequent current generation were systematically investigated using a real-time, in situ approach. A fivefold increase in the number of irreversibly adhered bacteria during the first 90 min of polarization was observed on positively charged electrodes compared with negatively charged ones. Kinetic analysis revealed a 63% higher attachment rate in the former case. Subsequent biofilm formation was also enhanced, resulting in cathodic current densities higher than those typically reported for pure cultures. The effectiveness of this strategy was confirmed on gold and carbon-based graphite electrodes, indicating that the underlying mechanism is not material-specific. These findings demonstrate that biocathode development can be improved by a strategy termed here as Surface Charge-Induced Microbial Adhesion (SCIMA), providing a mechanistic framework for optimizing its performance in microbial electrochemical technologies.