| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 104 === In the attempt of membrane electrolyte for high-temperature proton
exchange membrane fuel cell, we have synthesized Poly(2,5-
benzimidazole), the so-called ABPBI. A few organic/inorganic membranes
are prepared through doped with phosphoric acid (PA) and one of antimony,
tin, or iron chlorides. And their proton conductivities are measured between
80 and 240 C, their mechanical properties are measured in tensil testing.
Under the unhumdified conditions, with partial pressure of water vapor =0.03 atm, the composite membrane, doped with PA and SbCl5, exhibits the highest conductivities, measured 6.7×10-2 S cm-1 at 160 C. In contrast, the composite membrane, doped with PA and SnCl4, shows the proton conductivity 4.5×10-2 S cm-1 at 200 C. The composite membrane, doped with PA and FeCl3, displays the proton conductivity 3.5×10-2 S cm-1 at 180 C. The highest conductivities of these three membranes are higher than that the membrane doped with PA alone, which shows the highest conductivity 2.0×10-2 S cm-1 at 180 C. SbCl5 appears to be the best co-dopant with PA for ABPBI, just like in case of PBI.
Intriguingly, the three composite membranes demonstrate their unique mechanical properties. Consistent with the literature knowledge on PBI membrane, the undoped ABPBI membrane displays brittle characteristics with Young modulus 3.67±0.61 GPa, while the PA doped ABPBI shows plasticity and a smaller Young modulus 0.16±0.04 GPa. The composite membranes of PA and SnCl4 or FeCl3 also show ductile properties, with Young modulus 0.17±0.03 GPa and 0.065±0.017 GPa. The composite membrane of PA and SbCl5 shows brittle characteristics at small strains, but ductile features at large strains. Its Young modulus is measured 0.22±0.01 GPa.
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