High performance gas diffusion layers with added deterministic structures

Abstract

Polymer electrolyte fuel cells are a key technology for future green energy systems for transport applications and for balancing the intermittency of renewable energies. For wider application, material enhancements of all functional fuel cell components to increase the power density and reduce fuel cell cost are required. Gas diffusion layers (GDLs) with deterministic structures, reducing mass transport overpotentials and enabling high current density operation, play a vital role in this development. Adding deterministic structures to the random GDL structure in the form of perforated slits, connecting flow field lands and channels, facilitates water transport and can drain saturated pore space. Here we investigate a large range of laser-structured GDL patterns to optimize water management. An optimal pattern that increases the power density by up to 20% was identified. The perforations increase the through-plane diffusivity and reduce, together with the improved water transport, the oxygen transport resistance. Membrane water evaporation through perforations at the anode, increasing the membrane resistance, was identified as the antagonist to these effects, limiting the performance gain at about 5% perforation area. Asymmetric GDL assemblies and the use of micro-porous layers indicate ways to solve these issues. The large investigated parameter space provides guidelines for other GDL substrates and/or flow field geometries.