Effects of porosity and porosity distribution in gas diffusion layer on the performances of proton exchange membrane fuel cell

Abstract

The transmission capability of the gas diffusion layer directly impacts electrochemical reaction and water drainage, consequently, the comprehensive performance and lifetime of the proton exchange membrane fuel cell. The gas diffusion layer's porosity and distribution must be designed effectively as a porous component. This study focuses on experimentally validated models to investigate the effects of porosity and distribution in the gas diffusion layer using three-dimensional numerical simulation. A porosity of 0.6, with a unitary distribution, provides comprehensive improvements in power density while minimizing pressure drops. Additionally, four different distribution patterns of porosity (28 cases) are studied while maintaining an overall porosity of 0.6. The linear porosity distribution (along the flow path) with positive slopes outperforms the alternant distribution due to the cumulative effects on the micro-subsection of the gas diffusion layer. The stepped and/or the sinusoidal distribution can also improve the performances, but just when the step gradient and/or the amplitude are sufficiently small. The adverse effects on the uniformity of current density cause the sinusoidal distribution to be inferior to linear and stepped distribution patterns. The transmission of oxygen significantly affects the dynamic performances, with the distribution patterns of porosity critically influencing sensitivity.