Numerical simulation of methanol crossover in flowing electrolyte-direct methanol fuel cell

Abstract

A two-dimensional, comprehensive model for flowing electrode direct methanol fuel cell (FEDMFC) is developed to investigate cell performance and prevention of methanol crossover. Governing equations consists of the electron and proton transfer equations, mass and momentum conservation equation, energy transfer equations, species transfer of gas and liquid equations, dissolved water equations, as well as modified Tafel equations. The influence of operating parameters (such as flow rate and inlet temperature) and porous properties (such as porosity and permeability) of flowing electrode channel (FEC) on cell performance and methanol crossover are discussed in details. The results show that FEDMFC effectively reduces the methanol crossover rate with no significant reduction of power densities compared with direct methanol fuel cell (DMFC) under the same conditions. The Increase of the FEC flow rate can further reduce the methanol crossover rate. However, a higher flow rate will lead to a decrease in cell efficiency and stability. The FEC flow rate controlled at 1-3 sccm is more appropriate. Additionally, the lower inlet temperature of FEC is associated with lower methanol crossover rate and better cooling effect. The lower porosity is more conducive to reducing the effective diffusion coefficient of methanol, thus decreasing the methanol crossover rate.