Construction of PTFE/Nafion Composite Membrane with Ultrathin Graphene Oxide Layer for Durable Fuel Cells

The long-term operation of polymer electrolyte membrane fuel cells (PEMFCs) relies heavily on the durability of the perfluorinated sulfonic acid (PFSA, e.g., Nafion) membrane against chemical and mechanical degradation. To mitigate mechanical degradation, the introduction of a reinforcing matrix, such as a porous PTFE sheet, is employed. However, completely impregnating the PFSA ionomer into the PTFE sheet through the conventional blade-coating method using a highly viscous ionomer solution proves challenging. This limitation results in decreased mechanical and proton transport properties. To reduce proton transport resistance, thinner membrane thickness is desirable, although it increases the amount of gas crossover, which generates radicals and accelerates the chemical degradation of the membrane. In this study, a spraying process utilizing a low viscous-solvent-rich ionomer solution is experimentally optimized to construct a well-impregnated PTFE/Nafion membrane and analyzed using a simple theoretical droplet-spreading model. Furthermore, an ultrathin graphene oxide (GO) layer is introduced during the membrane fabrication process with the same spraying technique for reducing gas crossover while minimizing performance loss. The membrane electrode assembly (MEA) with the prepared PTFE/Nafion membrane-incorporated ultrathin GO layer shows significantly greater durability and initial performance compared to the conventional MEA. The construction of PTFE/Nafion composite membrane with ultrathin graphene oxide layer for durable and high-performance fuel cells by spray coating system. The optimized conditions for the ionomer impregnation into a porous PTFE sheet are experimentally and theoretically investigated; the graphene oxide thickness is also optimized. The improved durable reinforced membrane is compared with Nafion 211 using the DOE durability protocol.image