Analysis of Mass Transport of Methanol at the Anode of a Direct Methanol Fuel Cell

We present an analysis of the mass transport of methanol at the anode of a direct methanol fuel cell (DMFC) and show that the overall mass-transfer coefficient can be determined by measuring the cell limiting current density. We measured the cell limiting current density of an in-house-fabricated DMFC with different flow fields for various methanol concentrations and flow rates of methanol solution. The experimental data showed that the overall mass-transfer coefficient was nearly independent of current density, although the rate of gas bubble liberation changed with current density. We found that the overall methanol-transfer coefficient in the serpentine flow field could be significantly increased with increased methanol flow rate due to the enhanced under-rib convection. We developed the correlation equations predicting the overall methanol transfer coefficient in terms of the methanol flow rate for a given DMFC hardware. Finally, we showed that the polarization curves predicted based on the correlation equation of the overall mass-transfer coefficient in the DMFC with the serpentine flow field for different flow rates were in fairly good agreement with the experimental data.