Effect of anisotropy in cathode diffusion layers on direct methanol fuel cell

Abstract The diffusion layer in direct methanol fuel cells features strong anisotropic characteristics, which has large effect on complex transport phenomena and hence the cell performance. In this study, a comprehensive three-dimensional numerical model of direct methanol fuel cell is developed using Eulerian-Eulerian model describing the multiphase flow. Using this model, the effects of anisotropy properties in diffusion layer on performance and transport characteristics in direct methanol fuel cell are investigated in detail. In particular, the anisotropic electric and thermal conductivities, gas diffusion coefficients and permeability are studied. The comparison of polarization curves with isotropic and anisotropic diffusion layer shows that cell performance with isotropic diffusion layer assumption is overestimated and the deviation is as much as 48%, especially the electric conductivity. In addition, anisotropic electric conductivity is helpful to predict accurate current density spatial distribution. The simulation results also reveal that high permeability in all three directions can help promote water management. The water distribution in in-plane direction is largely affected by the in-plane permeability. The lower the in-plane permeability is, the more water accumulated under the rib.