Improved gas diffusion electrodes for hybrid polymer electrolyte fuel cells

In this study, the performance of the anionic electrodes for hybrid polymer electrolyte fuel cells was improved. The anion exchange membrane (AEM) electrodes were initially characterized as the cathode on a proton exchange membrane (PEM) anode/membrane half-assembly (i.e. hybrid polymer electrolyte fuel cell). The electrode performance was improved by tailoring the ionomer distribution within the electrode structure so as to better balance the electronic, ionic, and reactant transport within the catalyst layer. An ionomer impregnation method was used to achieve a non-uniform ionomer distribution and higher performance. Traditional electrode fabrication methods (i.e. thin-film method) lead to a uniform ionomer distribution. The peak power density at 70 °C for a H2/O2 hybrid fuel cell was 44 mW cm−2 using the thin-film electrode, and 120 mW cm−2 using the ionomer impregnated electrode. A hydrophobic additive used in the catalyst layer further improved the electrode performance, giving a peak power density of 315 mW cm−2 for H2/O2 at 70 °C. Electrochemical impedance spectroscopy was used as an in situ diagnostic tool to help understand the origin of the electrode improvements. The increase in performance was attributed to improved catalyst utilization due to the creation of facile gas transport domains in the AEM electrode structure. Similarly, the AEM anode prepared by ionomer impregnation with polytetrafluoroethylene resulted in a three-fold increase in the peak power density compared to ones made by the thin-film method, which has no polytetrafluoroethylene.

Research highlights► Performance of alkaline electrodes was improved by changing ionomer distribution. ► Ionomer impregnation method led to higher performance than thin-film method. ► The use of a hydrophobic additive improves the catalyst utilization. ► Physical properties of polymer electrolytes dictates electrode architectures.