Multiphysics simulation analysis of microbial fuel cell coupling microbial electrolysis cell to enhance liquid-phase mass transfer

Microbial fuel cells (MFCs) are renewable energy technologies that convert chemical energy from organic waste into electrical energy. However, the low power output of MFCs limits their commercial application. Although our previous studies confirm that MFC-microbial electrolysis cells (MECs) coupled with an electric field as a link can effectively improve the performance of MFCs, liquid-phase transfer (LPMT) as the rate-limiting step remains relatively unexplored. Therefore, in this study, based on the MFC-MEC system, the effect of the electric field on the LPMT is investigated via experiments and multiphysics field simulations. The results show that the maximum power output and the average electromigration flux of the experimental group are as high as 529.73 mW/m³ and 1.68 × 10⁻⁴ mol/(m²·s), which are approximately 2- and 8-fold higher than those of the control group, respectively. Notably, in the LPMT process, electric field-driven electromigration dominates the electrode region. The enhancement of the LPMT favors an increase in the reaction rate and a decrease in the internal resistance, which, in turn, increases the power output of the MFCs. This study emphasizes the key role of LPMT in the energy conversion of MFCs and provides new solutions for further improving their energy-conversion efficiency.