Enhanced water management in the cathode of an air-breathing PEMFC using a dual catalyst layer and optimizing the gas diffusion and microporous layers

Abstract

In an air-breathing proton exchange membrane fuel cell (ab-PEMFC), large amounts of water are generated and condensed on the cathode at high current densities due to the low operating temperature. Water management for ab-PEMFCs remains a challenge. In this paper, a cathode with a dual catalyst layer structure is designed, and the gas diffusion layer (GDL) and microporous layer (MPL) are optimized to improve the water management of an ab-PEMFC. A thin hydrophilic layer using perfluorosulfonate (Nafion) as the catalyst binder is coated on the electrolyte membrane to form an inner layer that maintains a good proton transfer rate, while a hydrophobic outer layer is prepared using a mixture of Nafion and polytetrafluoroethylene as the binder, preventing the removal of water under low-humidity conditions and expelling the excess water generated in the high current density area. A membrane electrode assembly (MEA) with this dual catalyst layer cathode exhibits excellent air-breathing performance, as the MEA's water management is greatly improved by the dual layer structure. We also find that the thickness of the MPL and the hydrophobicity of the GDL significantly affect the air-breathing performance of the MEA, and we attempt to optimize these parameters.