Influence and Optimization of Gas Diffusion Layer Porosity Distribution along the Flow Direction on the Performance of Proton Exchange Membrane Fuel Cells

Abstract

The longevity of proton exchange membrane fuel cells (PEMFCs), as a promising new energy technology, is a critical factor in achieving their market viability. However, the nonuniform distribution of reactants within fuel cells, resulting from their complex porous structure and reaction mechanisms, can lead to localized catalyst degradation and consequently reduce their lifespan. Moreover, the condensation of water vapor exacerbates this phenomenon. To address this challenge, this study proposes an optimization approach focused on the pore distribution of the gas diffusion layer (GDL) to enhance the uniformity of the reactant distribution and mitigate catalyst degradation. Initially, a three-dimensional (3D) model is established to describe the two-phase flow dynamics within PEMFCs. Subsequently, parameter models are developed for three different distributions of GDL pore density, namely, uniform, curved, and parabolic distributions, while ensuring that the average porosity of the GDL remains constant. The performance of PEMFCs under these distinct GDL pore density distributions is comprehensively analyzed including current density, oxygen concentration, and liquid water behavior. Compared to the uniform distribution, both the curved and parabolic distributions of GDL pore density exhibit an improved current density distribution and enhanced liquid water removal. Numerical analysis of performance characteristics elucidates the underlying mechanism by which the GDL pore density distribution influences the cell’s performance. Specifically, variations in the pore density distribution alter the interfacial area for mass transfer between the catalyst layer and GDL, resulting in a more even distribution of current density and mitigating localized catalyst degradation. Furthermore, an optimization process is implemented to determine the optimal parameters for the GDL pore density distributions. Comparative analysis of the three GDL pore density distributions under optimal conditions reveals that the parabolic distribution offers advantages in promoting a uniform distribution of the current density within PEMFCs. In summary, this research proposes an innovative approach to improve the longevity of PEMFCs by optimizing the pore distribution of the GDL. The findings highlight the significance of GDL pore density distribution in enhancing reactant uniformity and mitigating catalyst degradation, ultimately contributing to the advancement and commercialization of PEMFC technology.