| 초록 |
Technical advances in polymer electrolyte membrane (PEM) design and performance have increased demand for thin membranes produced at production rates that will meet the lower conversion cost goals required for fuel cell applications. In a number of Companies, Research Institutions and Universities, ongoing polymer and membrane improvement programs are focused on providing the required performance, mechanical durability, and chemical stability necessary for successful PEM fuel cell applications. Fundamental research has enabled processing advancements for various PEM candidate materials as well as formulation choices for improved fuel cell membrane fabrication and performance. Research efforts have targeted several areas: (1) reduction of cost through the use of entirely hydrocarbon based polymers, (2) reduction of humidification requirements to yield overall system simplifications, (3) increasing thermal stability so as to enable warm temperature operation, especially for automotive applications, and (4) decreasing methanol crossover. Improving mechanical properties under high levels of hydration has also received some attention. Here a few selected strategies and promising membrane materials will be highlighted here. For instance, high chemical and thermal stability are typically features of aromatic hydrocarbon polymers that incorporate benzene into their structures. The conductivities of sulfonated hydrocarbons tend to be lower than that of perfluorinated materials, but with appropriate medications improvements may be attained. Sulfonation can be carried out directly on the polymer back-bone, or short, sulfonate-terminated side-groups can be introduced. The latter appears to provide increased thermal stability. To improve provide water retention, which decreases sensitivity to humidity and enables high temperature operation, and to reduce the swelling, others have used inorganic additives such as complex clays, silica, and phosphotungstic acid. In addition, in order to avoid completely the many difficulties associated with water-saturated polymers, others are pursuing acid-base polymer complexes, in which a strong acid is coupled to a highly basic polymer. Thus, we will review briefly the most recent development of PEM for fuel cell applications. |
