A Novel Approach to Fabricate Membrane Electrode Assembly by Directly Coating the Nafion Ionomer on Catalyst Layers for Proton-Exchange Membrane Fuel Cells

The fabrication art of the membrane electrode assembly (MEA) in a proton-exchange membrane (PEM) fuel cell strongly correlates to the cell performance. It has been recognized that defects, for example, high interfacial resistance between the catalyst layers (CLs) and the membrane or cracks in the CLs, may occur during the MEA manufacturing process. These defects could greatly influence the electrochemical performance of the fuel cell. To eliminate those defects and improve the cell performance, in this study, a novel fabrication approach of the MEA for PEM fuel cells is developed. With this method, the Nafion ionomer, employed as a PEM, is directly coated onto both the cathode and anode CLs. As a result, not only an excellent interfacial connection between the PEM and CLs is achieved with a low interfacial resistance, but also cracks are eliminated due to Nafion ionomer penetration into the cracks, forming hydrophilic channels with ionic conduction. Those ionic conduction channels improve the water management, lower the mass transport loss, and facilitate the proton transfer, thus maximizing the three-phase boundary and enhancing the utilization of Pt/C catalysts. By adding an expanded polytetrafluoroethylene film, a favorable mechanical property of the MEA is also achieved. This novel MEA exhibits excellent cell performance under low humidity conditions. Under the H-2/air operation, the cell performance reaches a high maximum power density of 1.35 W cm(-2).