Optimized gradient polytetrafluoroethylene layout to enhance liquid water transport of catalyst layers for anion exchange membrane fuel cells

A coupled experimental and numerical study is undertaken to elucidate the fundamental effects of polytetrafluoroethylene (PTFE) distribution within the anode catalyst layer on transport phenomena and electrochemical performance of anion exchange membrane fuel cells (AEMFCs). A comprehensive multiphysics model is developed to optimize the layout and content of PTFE, guiding the preparation of high-performance multilayer electrodes. We find that a non-gradient PTFE distribution at 10 wt% content achieves a tradeoff between mass transport and charge transport. The optimized gradient distribution of PTFE is observed to further mitigate water flooding without increasing ohmic impedance, enhancing peak power density by 213.6 mW/cm2 and cell voltage by 163 mV at 2,000 mA/cm2, compared to the membrane electrode assembly without PTFE. These electrochemical performance enhancements are validated with experimental polarization curves. Furthermore, the influence of PTFE layout on mass transport behavior is identified through electrochemical impedance spectroscopy and mercury intrusion porosimetry, revealing that adding PTFE binder to the catalyst layer enhances liquid water transport. This comprehensive study offers vital insights and pragmatic guidelines for designing gradient electrode structures in AEMFCs under high current density conditions, facilitating the development of more efficient and robust fuel cell technologies.