Membrane electrode assembly performance of a standalone microporous layer on a metallic gas diffusion layer

Abstract

Metallic gas diffusion layers (MGDLs) with controlled micro-porosity, offer mechanical and thermal stability in proton exchange membrane fuel cells. The MGDLs require tailored microporous layers (MPLs) to facilitate optimal gas diffusion and water management. In this study, a MGDL surface was first treated with PTFE and then coated with a standalone MPL (sa-MPL). The sa-MPL was made using a wet kneading method with a high aspect ratio of graphite flakes as filler. Conventional wet-coated MPLs (WC-MPLs) were produced with and without graphite flakes and coated onto MGDLs for physical and electrochemical comparison. SEM images showed degrees of macropore intrusion of the MPL into the MGDL which facilitate water removal and gas diffusion. Compared to the WC-MPLs, the produced sa-MPLs (20 μm) had a homogeneous surface with no cracking and uniform porosity due to the mechanical strength provided by the graphite filler. The sa-MPL/MGDL membrane electrode assembly (MEA) outperformed the commercial carbon GDL reaching 3.0 A cm−2 at 100% relative humidity (RH) with a low high frequency resistance (HFR). This study showed that the internal morphology and external form of the sa-MPL allowed for efficient capillary water removal and increased gas diffusion resulting in superior MEA performance.