Impact of Cationic Impurities on Low-Pt Loading PEFC Cathodes
To test the real world condition and obtain the consistent data, the commercially available the low loading catalyst (Pt: 0.1 mg /cm2) coated membrane (GORE Inc.) was used. During the contaminant test, cell was maintained at 80◦C with anode H2 and cathode air flow rates of 1.75 slpm and 1.66 slpm, respectively. The CaSO4 solution of 5 ppm of total concentration was injected (130 µl/min) at the cathode inlet using nebulizer . Overall, the anode/cathode RH was maintained at 25%/125%, and the anode/cathode outlet back pressure was maintained at 10 kPa/100 kPa gauge pressure (∼1.5 psig/15 psig, ambient pressure 1 atm), respectively. Figure 1 shows the cell voltage decay during the constant-current hold tests (1 A cm-2) with and without Ca 2+ solution injection. It is observed that during the initial injection of water there is no significant performance loss, whereas while injecting the CaSO4 solution (5 ppm) steep fall in cell voltage is observed. In order to get a clear understanding on factors that contribute to the severe voltage loss during the CaSO4 injection, pressure of the cathode inlet and outlet are monitored (Figure 1 (b)). These data reveal that the increased pressure over the time is due to salt precipitation in the cathode gas diffusion layer and the flow field, and the pressure gain trend is correlated with the voltage degradation. The cell test was stopped after 350 h of CaSO4injection due to blocking of the cathode outlet.
The polarization curves were obtained before and after the injection of CaSO4(Figure 2), a sharp fall in voltage was observed in the case of end of test (EOT ) curve, which indicates a very severe mass transport loss due to blocking of the cathode outlet [1-3]. These studies confirm that apart from the contaminant effect in polymer electrolyte membranes and catalyst layer’s ionomer, there is a severe impact that comes from the salt precipitation at gas diffusion layer and flow field plates. In addition, the effect of contaminant on catalyst support corrosion, membrane conductivity loss over the time also performed.
Financial support from the Department of Energy (DOE)-EERE, DE-EE0000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI) is greatly acknowledged.
- X. Wang, J. Qi, O. Ozdemir, A. Uddin, U. Pasaogullari, L. Bonville, and T. Molter, J. Electrochem. Soc., 161, F1006 (2014).
- M. A. Uddin, X. Wang, J. Qi, M. O. Ozdemir, L. Bonville, U. Pasaogullari, and T. Molter, ECS Trans., 61(12), 49 (2014).
- M. A. Uddin, J. Qi, M. O. Ozdemir, L. Bonville, U. Pasaogullari, and T. Molter, ECS Trans., 61(12), 37 (2014).