Effects of graded-porosity gas diffusion layers used in polymer electrolyte fuel cells

Abstract

Optimising the design of gas diffusion layers (GDLs) is essential to enhance water management and reactant transport in polymer electrolyte fuel cells (PEFCs), which are critical renewable energy conversion technologies required to decarbonise electricity. In this work, a comprehensive three-dimensional model of a PEFC has been developed to analyse the sensitivity of fuel cell performance to graded-porosity cathode GDLs under various humidity conditions and GDL thicknesses. The results show that, for most humidity conditions, the fuel cell performs best when the cathode GDL has low porosity at the catalyst interface and high porosity at the bipolar plate interface. Under relatively low humidity conditions, fuel cell performance deteriorates when using graded-porosity GDLs with higher porosity near the catalyst layer. On the other hand, under high humidity conditions, a cathode GDL with a porosity gradient improves performance compared to a GDL with uniform porosity. Further, when the GDL thickness is reduced from 300 μm to 200 μm, the best performance is achieved with a GDL that has higher porosity near the catalyst layer. These findings are discussed and justified in the study providing valuable guidance for designing advanced GDL structures to improve PEFC efficiency, supporting their wider adoption in renewable energy systems.