Does the thermal conductivity of gas diffusion layer matter in polymer electrolyte fuel cells?

Water management is a highly critical parameter for improving the performance of polymer electrolyte fuel cells (PEFCs) at high current densities. The microstructure and properties of the gas diffusion layer (GDL) play an important role in the distribution of the reactant gases and drainage of the liquid water produced in the catalyst layer during PEFC operation. In this context, the community still debates on the role and optimum values of the GDL's thermal conductivity and if it is even the decisive factor for water management. This study presents insight into this fundamental question by reporting experimental performance and thermal modeling data of GDLs with identical, ordered microstructure but different thermal conductivities. Results show that lower GDL thermal conductivity produces higher temperature gradients in the GDL, which are, however, partially compensated by a heat pipe cooling mechanism. Even with an order of magnitude different thermal conductivity, the ordered, deterministic GDLs surpass the performance of a conventional carbon GDL. Our findings suggest that the thermal conductivity should not be a decisive criterion for future materials developments of optimized GDLs to improve fuel cell performance at high current densities, but rather the GDL structure.ISSN:0378-7753ISSN:1873-275