Investigation of performance and microstructure of membrane-electrode-assembly in PEMFC

Abstract

In this study, a carbon-filled gas diffusion layer (CFGDL), and a novel selfhumidifying membrane electrode assembly (MEA) for proton exchange membrane fuel cell (PEMFC) were developed for improvement of the performance of PEMFC. The studies are included in detail as follows: 1. A new structural design of gas diffusion layer (GDL)-CFGDL is made of electrical conductive macro-porous carbon paper filled with a mixture of conductive carbon powder and hydrophobic polymer (PTFE). The systematic study on the properties of CFGDLs and their electrodes with various physical analysis techniques and electrochemical characterizations were carried out in comparison with conventional one-layer GDL, dual-layer GDL, and gained an insight into the relationship between the electrode performance and GDL structure. 2. The effects of material composition in CFGDL on the microstructure and performance of CFGDL were studied. The experimental results showed that the carbon loading in the CFGDL plays a critical role in the electrode performance and Pt utilization, but the PTFE content in the CFGDL has lesser influence. 3. The effect of PTFE content on the mass transport in the CFGDL was studied. It was found that the PTFE content in CFGDL significantly affected the contact angle (hydrophobic property) and water uptake (immobile liquid saturation) of CFGDL. The analysis by a theoretical model developed for cathode flooding, in which the water saturation is incorporated, shows that the mass transport limitation of fuel cells at high current density is attributed to the water flooding when using CFGDL with a lower PTFE content.