Self-assembled network polymer electrolyte membranes for application in fuel cells at 250 °C

Abstract

Operating polymer electrolyte membrane (PEM) fuel cells at high temperatures can simplify water management and allow integration with high-purity fuel processing units. However, existing polybenzimidazole (PBI)-based PEM fuel cells face challenges due to the instability of proton transport above 160 degrees C. Here we report a PEM composed of para-PBI (p-PBI) and cerium hydrogen phosphate (CeHP) that can be used in a fuel cell at up to 250 degrees C. During fabrication, echinoid-shaped CeHP particles form a well-dispersed and interconnected self-assembled network within the PBI matrix (SAN-CeHP-PBI), allowing them to outperform p-PBI and conventional CeHP-PBI PEMs in terms of proton transport above 200 degrees C. We report a SAN-CeHP-PBI-based fuel cell that reaches a maximum power density of 2.35 W cm-2 (at 250 degrees C in dry H2/O2) with negligible degradation over 500 h during thermal cycling (at 160-240 degrees C, H2/air). SAN-CeHP-PBI also demonstrates excellent CO tolerance, showing promise for integration with liquid hydrogen carrier systems. High-temperature operation of polymer electrolyte membrane fuel cells has some advantages but is also challenging due to the instability of proton transport above 160 degrees C. Here the authors report a polymer electrolyte membrane comprising well-dispersed and interconnected cerium hydrogen phosphate particles within a polymer matrix that performs well in a fuel cell at up to 250 degrees C.