Modeling of Crossover Phenomenon in Liquid Feed Direct Methanol Fuel Cells

Increasing energy consumption and global warming problem make use of renewal energies inevitable. Among these energy resources, fuel cells are interesting due to almostinexpensive raw materials and high performance. In recent years, the Direct Methanol Fuel Cells (DMFC) have been increasingly interesting because of its low temperature over theother fuel cells, removing problems due to storage and conversion of hydrogen, ease ofoperating and simplicity for transportation applications. In the first section of this study, 3-D modeling of DMFC is solved by use of the finite element method. The obtained results showgood agreement with experimental data which are reported in their paper. In this study, a two dimensional, isothermal, steady-state model is developed for DMFC. The model is accounting for mass balances, the charge balances, electrochemical reactions and the masstransport phenomena. Diffusion and convective effects as well as crossover of methanol are considered in this model. The governing equations are solved using COMSOL software. The results are reported as methanol concentration profile and methanol flux in gas diffusion,catalyst and membrane layers; oxygen concentration profile in cathodic catalyst layer; anodic and cathodic overpotentials changes through catalyst layer, and finally, the cell voltage versus different current densities. The results show that methanol concentration reduces through thelayers and reaches zero in the interface of the membrane and catalyst layer. At lower methanol concentrations, the profiles have the same concentration gradient and increasethrough the layers as current density increases. Furthermore, anodic and cathodic overpotentials increase as current density increases. Oxygen concentration decreases through catalyst cathodic layers.

Keywords:

DMFC , Fuel Cell Modeling , Methanol Crossover