Numerical anodic mass transfer of redox mediators in microbial fuel cell

In order to address the role of redox mediator mass transfer in microbial fuel cell (MFC), numerical simulation models are developed on the basis of Monod equation, Fick´s second law, Ohm´s law and Butler-Volmer equation in this study. In the models, microbial metabolizing kinetics, substrate diffusion, electrochemical reaction kinetics and circuit behavior are taken into consideration. Electricity generation and mass transfer process is simulated as function of reaction time under various external resistance conditions (100Ω, 1000Ω, 10000Ω). Besides, spatial mass transfer process of acetate and mediator is also displayed. To further investigate the impact of redox mediator mass transfer on MFC performance, polarization and power-current behavior are obtained at initial acetate concentration of 1000mg/l. The simulation shows that the mass transfer resistance is mainly caused by the diffusion of redox mediator rather than acetate inside the anophilic biofilm. In particular, the mass transfer resistance tends to become the rate-limiting step when the reduced mediator concentration is descended to a low magnitude of 10^-2mmol/l.