Study of the Constrained Expansion of Nafion within the Hardware of a PEMFC
In this communication a study is presented about the influence of Nafion expansion on the response of a proton exchange membrane fuel cell (PEMFC). First, the constrained expansion of the membrane is analyzed within the flow field of a cell, and compared with its free expansion. The study has been carried out by means of a specially designed cell that allows for the observation of morphology changes in cross section with optical microscopy. Minimal changes are observed in the morphology of the free expanded MEAs when clamping pressure and/or humidification is applied within the cell hardware (Fig. 1b). MEAs expanded within the cell hardware (Fig. 1a), however, lead to a zig-zag morphology.
In a second part, free and constrained expanded Nafion have been tested in single cells. The responses of both types of expansion have been analyzed by polarization curves (Fig. 1c), active area measurements, and impedance spectroscopy. First results indicate better behavior of free expanded Nafion, due to lower internal resistance of the cell. Durability issues under expansion-contraction cycles, and cell voltage cycles will also be analyzed.
This work is financed by the project ELECTROFILM, MAT2011-27151 from Ministry of Science and Innovation of Spain.