Novel PTFE-Reinforced Composite PEMs for Fuel Cell Applications

Over the past decade, significant R&D progress has been made toward two challenging targets of cost and performance required for proton exchange membrane (PEM) fuel cells in transportation application. The development of two key materials (PEMs and the electro-catalysts) should be given highly emphasis on. However, the high cost of popular perfluorinated sulfonic acid (PFSA) membranes becomes one of the major obstacles for the commercialization of PEM fuel cells. Fortunately, the successfully commercial Gore-select® membranes gave an indication that porous PTFE reinforcement technology could be an effective means to develop ultra thin PEMs for fuel cells. In this paper, we fabricated three types of PTFE-reinforced PEMs for fuel cell applications. On the one hand, the Nafion-impregnated PTFE membrane (Nafion/PTFE) and the sulfonated poly arylene sulfone (SPSU)-impregnated PTFE membrane (SPSU/PTFE) were developed for fuel cells under external humidification. On the other hand, a novel PTFE-reinforced multiplayer self-humidifying membrane (Pt-SiO2/NP) was studied for dry operation mode of PEM fuel cells. Preliminary results indicate that Nafion/PTFE membrane (20µm, thick) have almost twice mechanical property values relative to that of Nafion®112 (50µm, thick) due to the PTFE reinforcement effect. Moreover, the Nafion/PTFE membrane shows superior cell performance as compared to that for the commercial Nafion®211 and the Nafion®112 membranes. Since SPSU is a fluorine-free ionomer, the development of PTFE-reinforced hydrocarbon PEMs could result in low cost and high performance and should be more attractive and competitive. Inspiringly, our novel SPSU/PTFE membrane shows better PEM fuel cell performance than that of the Nafion/PTFE membrane on the basis of 20 µm in thickness. The peak power density of the former reaches as high as 2.4 W/cm2 at 5 A/cm2 of current density. The novel Pt-SiO2/NP membrane was prepared with a sandwich structure constituting of Nafion/PTFE composite as the central layer and silicon oxide supported platinum (Pt-SiO2) catalyst imbedded in Nafion as the two side layers. Under dry operation, the fuel cell employing Pt-SiO2/NP membrane gives 1.4 W/cm2 of peak power density and 1.032 V of open circuit voltage (OCV). The high performance is ascribed to hygroscopic property of the Pt-SiO2 catalyst inside the membrane, which improves anode self-humidification