Properties of SPEEK based PEMs for fuel cell application

Peer reviewed: YesNRC publication: Ye

Impact of ionomer content on proton exchange membrane fuel cell performance

The effect of Nafion ionomer content on performance of a proton exchange membrane (PEM) fuel cell operated with home-made anodic and cathodic electrodes fabricated from a novel metal organic framework (MOF) derived Pt-based electrocatalyst was investigated via numerical simulation and experimental measurement. First, the parameter sensitivity analysis was performed to identify the most influential parameters of the model. Then, these parameters were calibrated for different fuel cell designs investigated in the current study by employing the corresponding experimental data. Afterwards, the calibrated model was used to examine the impact of Nafion content in the catalyst layer of home-made electrodes. Finally, the qualitative trend predicted by this model was experimentally surveyed by varying the Nafion content between 10–50 wt.% in the catalyst layer of home-made electrodes. At the anode side, the performance of home-made electrode in a PEM fuel cell demonstrated small dependency on Nafion content. For the cathodic home-made electrode, Nafion content was found to affect the PEM fuel cell performance more strongly. Although the model could correctly capture the impact of Nafion content on calculated polarization curves, the model predicted optimum values significantly deviate from the experimental results. This was related to the several simplifications made during model development

Measurements of PEM conductivity by impedance spectroscopy

The methodology of PEM conductivity measurements is discussed for examples of literature data and results of the experiments, carried out in this study. It is shown here that a simple two-electrode cell proposed in this work, operated at frequencies of 1 to 107 Hz reproducibly gives a response typical for a solid electrolyte, and therefore is easily rationalised in terms of equivalent circuits. The obtained impedance diagrams are compared with the ones described in the literature for 4-probe experiments. It appears from this comparison that the cell geometry and electrode arrangement play important roles in the formation of the frequency dependent response. In some cases, two-electrode cells may have an advantage over the four-probe technique, as they are less complicated and therefore involve less stray effects in the resulting impedance spectra. In this study, the proposed configuration, which we have previously utilized for some of our measurements, proved to be efficient at producing reproducible, reasonable and reliable results, related to the expected values of PEM conductivity.NRC publication: Ye