Research On Mathematical Model Of Passive Direct Methanol Fuel Cell

Micro direct methanol fuel cell (μDMFC) with the advantages in terms of long lasting time, low operating temperature, plentiful sources as well as convenient storage of methanol, easy miniaturization and integration, low pollution and so on, has been identified as one of the most promising candidates substituting conventional power sources applied in portable electronic devices.Theoretically researching mass transportation and process of electrochemical reaction in fuel cell with mathematical simulation to provide instructions for the optimum of electrode structure and the selection of operating conditions is beneficial to reduce the cost and period of design of fuel cell. Hence, studying mathematical model of two-phase flow, mass transportation and process of electrochemical reaction in direct methanol fuel cell (DMFC) has important engineering senses and academic significances.This paper set up a one-dimensional and a two-dimensional two-phase mathematical model with the two-phase theory in porous media, validated the precision of models with experimental data, analyzed two-phase mass transportation, electron and proton transportation as well as process of electrochemical reaction in porous media, and studied phenomenon of methanol permeation as well as water permeation in proton exchange membrane. The conclusions are as follows: methanol transport in anode is a dominate factor which affects cell performance while oxygen transport in cathode is just an insignificant factor; a negative overpotential is produced by methanol permeating to cathode, which decreases cell performance; methanol crossover by diffusion plays the dominant role, which decreases with current density; methanol crossover by electro-osmosis is affected by both methanol concentration and current density at the interface of anode catalyst layer and proton exchange membrane; methanol crossover is enhanced with the increase of methanol concentration leading to the decrease of fuel utilization efficiency and cell efficiency; fuel utilization efficiency decreases with the increase of operating temperature, while cell efficiency decreases under low current density and increases under high current density with the increase of operating temperature; CO2 and water are prone to block under the current collector, resulting in lack of methanol or"water flood"in the area under current collector; liquid pressure in cathode is higher than that in anode, which is beneficial to promote liquid convection from cathode to anode to reduce methanol permeation and water permeation in proton exchange membrane.