Simulation of mass transfer in a passive direct methanol fuel cell cathode with perforated current collector

Abstract

The current collector offers passages for mass transport and is one of the key components of the passive direct methanol fuel cell (DMFC). The effect of perforated current collector design on mass transport is studied based on a three-dimensional (3D), unsteady-state, two-phase mass transport model of a passive DMFC cathode. The model is implemented via the mixture multiphase model, which solves the continuity and momentum equations for the mixture and the volume fraction equation for the secondary phases. Numerical results indicate that the distributions of oxygen in both cathode catalyst layer (CCL) and cathode diffusion layer (CDL) are non-uniform because of the effect of the perforated current collector plate (CCP) structure. Liquid water produced by an electrochemical reaction in the CCL accumulates significantly at the bottom. Clearly, the distribution of liquid water in the cathode catalyst and diffusion layers is affected by gravity. The size of the circular holes and the distance between them are taken into account to investigate the effect of the CCP structure. Small uniformly arrayed circular holes in the entire active area of CCP are advantageous to the transfer of gas and liquid water in the cathode side of a passive DMFC.