Edge Effects on Reference Electrode Measurements in PEM Fuel Cells

A reference electrode specifically designed for proton exchange membrane (PEM) fuel cells (FCs) was developed. By using the Nafion membrane material as the electrolyte, this reference electrode eliminates the needs to modify the normal FC setup and can be easily integrated into FC systems. Experimental and modeling studies had been conducted to further understand the effects of misalignment in the main electrodes on the reference electrode signals. It was found that the reference sensing point is greatly affected by the relative geometry and alignment of the two electrodes on the main membrane and electrode assembly (MEA) and the nature of electrode kinetics. Even with a perfect alignment, the reference sensing point is no longer fixed at the middle of the membrane due to difference in the kinetic characteristics at the anode and the cathode. When the misalignment is greater than the membrane thickness, the potential that the reference electrode measures is overwhelmingly masked by the edge potential of the protruding electrode. Slow electrode kinetics can significantly magnify edge effects. Generally the reference sensing point varies significantly with the change of misalignment factor and cell voltage or current. The use of reference electrode as a qualitative tool to detect electrode flooding is also discussed.

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