Conformational distortion of the ionomer backbone for reinforcing the catalyst layer under dynamic operation

Abstract

The design of robust catalyst layers (CLs) applicable under realistic conditions is an essential concern for anion exchange membrane fuel cells (AEMFCs). Ionomers act as “transport bridges” for electrochemical reactions involving water, gas, and ions within CLs, and play a crucial role in CL stability and performance. Here, quaternary ammonium polymers with meta- or para-terphenyl were compared as anion exchange ionomers (AEIs), to study the relationship between AEI molecular conformation and CL parameters under dynamic operating conditions. The meta-AEI exhibits a lower swelling ratio compared with the para-AEI, endowing the CL with high water retention ability, which remarkably enhances the CL stability under an accelerated stress test (AST). The power density attenuation of the membrane electrode assembly prepared with meta-AEI is only 49.5%, which is much lower than that based on para-AEI (69.5%) after 100 dry/wet N₂ cycles. These insights lead to improvements in AEI design and consequently, the operational stability of AEMFCs.