Materials for State-of-the-Art PEM Fuel Cells, and Their Suitability for Operation Above 100°C

This review gives an overview of proton exchange membrane (PEM) fuel cells on the materials level. Materials for proton conducting mesmbranes, electrodes and bipolar plates are described from the perspective of their suitability for long-term operation in automotive and stationary applications. The state-of-the-art PEM fuel cells consisting of perfluorosulfonic acid membranes, platinum-based electrodes and graphite(-composite)-based bipolar plates are in a well advanced state of development. Although the main constituents are in use for many years, impressive improvements in performance and lifetime have been realized, leading to cost reduction, size reduction, improved robustness and mass manufacturing. For the sake of system simplification, increasing the temperature of operation of the proton exchange membrane fuel cells (PEMFC) would be beneficial. New materials are needed to enable operation at higher tem- peratures, and not less important, lower relative humidities. The suitability of present state-of-the-art materials for operation above 100°C is discussed, as well as a critical review of the suitability of emerging concepts. No alternative material that combines the virtues of the present materials with the ability of operation above 100°C has been developed so far. Therefore, the first commercial introduction of PEM fuel cells is likely to be based on the components that are at present in use, making use of perfluorosulfonic acid membranes.