Fuel cells have been shown to provide an environmentally sustainable clean source of energy. Recently Anion Exchange Membrane fuel cells (AEMFCs) have achieved a great deal of attention since a broader range of non-PGM catalysts can be employed to achieve the ion transport reactions. The problems facing this newer technology are that the power output achieved is still less than that reported for the traditional Proton Exchange Membrane fuel cells (PEMFCs), and more disturbing the stability of the membranes is much shorter. We have shown previously that nanoparticle platelets can synergize with the membrane of the PEMFCs and achieve a significant increase in power output as well as increase stability. The mechanism of degradation of the output in AEMFCs is not well understood. Here we applied the same strategy for the AEMFC in order to determine if GO was instrumental in catalyzing reactions on the membrane surfaces.
Fuel cell performance was compared between untreated Sustainion X37-50 grade RT membranes and those treated by spraying either GO or prGO. The Membrane electrode assembly (MEA) had a 5 cm² active area of Sustainion X37-50 grade RT membrane with 0.76 mg/cm² Pt nanoparticle catalyst. The maximum power density obtained on the MEA with the untreated membranes was 0.42W/cm²and 0.45 W/cm² following treatment with GO, which was not a significant improvement. On the other hand, the MEA which had an additional 1 μg/cm² prGO, generated a maximum power density of more than 0.60 W/cm².
The chemical stability test was performed under a constant current density of 0.15 A/cm2, where the untreated sustainion membrane lasted around 70 hours before being completely depleted. In contrast, no attenuation of the power was discerned for the MEA on the membranes containing prGO. In order to determine the cause of failure, Raman spectroscopy was first performed on the membranes which indicated that the polymer was not the likely source of the degradation. X-ray computed tomography (XCT) was then performed to determine if any morphological decline had occurred. After 70 hours the Pt had completely penetrated into the membrane forming a lattice network connecting both surfaces essentially producing a short circuit across the membrane. XCT examination of the membrane coated with the prGO demonstrated sharp interfaces between the membrane and the Pt/C catalyst layer, indicating that the prGO formed a physical block preventing diffusion of the Pt layer lasting 150 hrs.

Rebecca Isseroff

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