Phosphoric acid clustering in porous composite membranes for high temperature fuel cell

High-temperature PEM fuel cells (HT-PEMFCs) are crucial for achieving net-zero emissions by efficiently converting hydrogen and oxygen into electricity, with only water as a byproduct. Operating at 120-200°C, these fuel cells rely on phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes to deliver high power density and durability. Unlike low-temperature fuel cells where water conducts protons, PA is the proton conductor in HT-PEMFCs. However, PA leaching from PBI membranes reduces performance, accelerates catalyst migration, and shortens the cell’s lifespan.
Our research addresses this by developing composite membranes made from cardo polymers of intrinsic microporosity (cPIM-1) and polyvinylpyrrolidone (PVP). These membranes show improved electrochemical performance over commercial alternatives due to their microporous structure, which retains PA through capillary forces and hydrogen bonds, reducing acid loss. Small-angle and wide-angle X-ray scattering (SAXS and WAXS) experiments show that PA clusters in these composite membranes are smaller and more uniformly distributed, enhancing stability and efficiency.
To deepen our understanding of the PA interactions within the membranes, we plan to use neutron scattering techniques. This will offer insights into hydrogen bonding and microstructural behavior, aiding in the design of more efficient, durable fuel cells.