Study of Morphological Variation on SiO2/Nafion Composite Membrane Under Different Hydration Condition

Passive air breathing proton exchange membranes fuel cells (AB-PEMFC) have a unique advantage such as remarkably reducing stack weight by minimizing balance of plant (BOP). However, the performance of the AB-PEMFC is worse than general PEMFC because it is difficult to controlling humidification and stack temperature. Thus, the proton exchange membranes (PEMs) which are used to AB-PEMFC have to stably work under various humidification and temperature. A lot of research groups are reported that inorganic fillers (SiO2, TiO2, ZrO2) and Nafion composite membrane show high performance under low relative humidity by increasing water retention on the membrane. In this study, we synthesize SiO2/Nafion composite membrane for compensating the weakness of AB-PEMFC.

The performance of membrane electrode assembly (MEA) with SiO2/Nafion composite membrane is tested under different hydration and temperature conditions. For more detailed characterization, morphological variations of the composite membrane under hydration conditions are studied by using dynamic mode atomic force microscopy (DMAFM). DMAFM can map amplitude and phase distribution on the specimen surface. The phase lag, which is mechanical vibration changing of a cantilever, is resulting of tip-sample interaction, which is induced by microscopic mechanical property of sample. Thus, the DMAFM is best tool for characterizing heterogeneous materials such as composite membrane. The morphological structure variation on the composite membrane by water retention elevation is systematically studied by using phase lag changing under different humidification condition.

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