Model Development And Numerical Simulation Of Microbial Fuel Cell Based On Redox Mediator

Microbial fuel cell （MFC） is a new technologies used in energy andenvironment field recent years, and has a relatively high development rate. CurrentMFC research oriented either improving microbial reaction rate ofelectrochemically active microorganisms, or to develop more efficient andversatile MFC configurations. Few research concentrated on MFC mechanism andinternal operation. This study uses numerical simulation to study MFC, aiming toexplain the mechanism of MFC and provide a simulation model for MFC research.This Model built basing on redox mediators that widely exit in MFC andconduct electron. By solving the metabolic metrology equation, Fick’s Law,microbial metabolic rate equation, electrochemical potential equation, the circuitOhm’s Law equation, model simulates MFC operation process like, material masstransfer, metabolism, energy transfer, electrochemical reaction rate,power loss etc.A suitable MFC numerical simulation model is built in this study.The output current change in different external resistance condition alongrunning time is divided into three categories. Comparing the change regular ofredox mediator concentration and organic substrate concentration, we summarizedthe redox mediator on anode surface is a symbol for the sustains of MFC outputcurrent. When the reduced mediator form is less than10^-2mmol/L,output currentbegin decline. This is caused by system doesn’t have enough oxidized mediator tosustain microbial metabolic active, the microbial metabolic activity decline withthe consumption of organic substrate.Anode surface, mass transfer diffusion coefficient, redox mediatorconcentration and thermodynamic properties are selected as key factors in deeperstudy of MFC energy produce based on redox mediator. The increase of anodesurface improves the current production capacity of MFC, but unit microbialmetabolism falls, which may lead microorganism participate in current productioncompetition at a disadvantage with those don’t participate in current production. Ifthe mediator molecules becomes smaller and diffusion ability enhances, currentcapacity of MFC is remarkably improved, it provides model support for searchsuitable mediator. Total redox mediator concentration and thermodynamicproperties also affects the production capacity of the MFC system. The totalmediator concentration increases, MFC gets more reduced mediator for currentproduction, and also more oxidized mediator to sustain microbial metabolismactivities. In MFC system, redox mediator thermodynamic properties isrepresented by standard electrode potential, when redox mediator impetus increases, MFC current production capacity relatively increases. This provides asimulation method for study on redox mediator thermodynamic affects on MFCoperation.