Fractal Modeling of Gas Transport in Gas Diffusion Layers (GDLs) for Enhanced Electrochemical Performance of PEMFCs

Abstract

Proton exchange membrane fuel cells (PEMFCs) are among the most promising technologies for advancing the energy transition, particularly in clean transportation and decentralised power generation. However, improving their performance requires a detailed understanding of mass-transport processes within gas diffusion layers (GDLs), which play a key role in supplying reactants to electrochemically active sites and managing transport limitations. This study proposes a coupled multiscale and multiphysics approach that links the fractal microstructure of the GDL to the macroscopic electrochemical performance of the fuel cell. The objective is to identify optimisation criteria for the design of high-performance GDLs, with particular emphasis on selecting an optimal fractal tortuosity dimension. The numerical framework, implemented in Python, combines the generation of fractal tortuosity characteristics, the estimation of effective transport properties, and the simulation of polarisation and power-density curves. The results show that for a fractal tortuosity dimension (DT < 1.5), gas transport is enhanced, although this improvement occurs at the expense of the available electrochemically active surface area. A value of (DT = 1.53) therefore appears to provide an optimal compromise, leading to a peak power of 0.86 W/cm² and a voltage efficiency of approximately 57.8%. Conversely, for (DT > 1.7), the increase in catalytic surface area is associated with stronger limitations in gaseous species transport. These findings demonstrate the relevance of fractal modelling as a useful tool for guiding the design and optimisation of gas diffusion layers in PEMFCs.