Three-layered electrolyte membranes with acid reservoir for prolonged lifetime of high-temperature polymer electrolyte membrane fuel cells

High-temperature polymer electrolyte membrane fuel cells with phosphoric acid doped polybenzimidazole (PBI) are made with three-layered membranes. The central membrane layer is meant as an acid reservoir made from direct cast PBI with a higher acid content than the outermost layers, which are post doped membranes acting as barrier layers to limit the acid transport out of the central layer. Cells with three-layered membranes and others with normal single layered membranes are tested at 170 and 180 °C. At both temperatures, the cells with three-layered membranes show significantly lower voltage decay rates than the corresponding cells with single-layered membranes. Post doped PBI membranes based on linear or thermally crosslinked PBI are used for the barrier layers of the three-layered membranes and for the single-layered membranes in the test series at 180 °C. The acid loss rates assessed by acid collection at the fuel cell exhaust, are rather comparable. At 180 °C, the cells are tested for up to 10,000 h and voltage decay rates of 2.3 and 4.1 μVh-1 are measured for the cells with three-layered membranes and 14 and 11 μVh-1 for cells with single-layered membranes.