Performance hysteresis phenomena of anion exchange membrane fuel cells using an Fe–N–C cathode catalyst and an in-house-developed polymer electrolyte

We focus on the water management challenges and report on the improvements of cell performance for anion exchange membrane fuel cells (AEMFCs) using a non-PGM catalyst (Fe–N–C) for the cathode and an in-house-developed anion exchange ionomer (quaternized poly(arylene perfluoroalkylene), QPAF-4) for both the membrane and the catalyst layers (CLs) binder under practical gas flow rates conditions. The cell using the Fe–N–C cathode exhibited similar current-voltage (I–V) performance compared with those using Pt catalyst supported on carbon black. The cell using the Fe–N–C catalyst showed I–V hysteresis between increasing and decreasing current. The hysteresis decreased with increasing back-pressure. Based on the results of various I–V measurements, we conclude that the hysteresis is related to water supplied to the cathode using the Fe–N–C catalyst. Tafel slope component analysis revealed that a severe polarization occurred, amounting to slope octupling, with increasing current density, most likely due to the addition of water transport to the usual combination of gas and ionic transport. This severe polarization was alleviated after the cathode layer became sufficiently hydrated. We found from these results that water management is essential, due to the role of water as a reactant in the cathode reaction, for high-performance AEMFCs.