Polydopamine-Modified Halloysite Nanotube Blended Sulfonated Poly(ether Ether Ketone) Cross-Linked Composite Membrane for Fuel Cells

This study addresses the swelling issue in highly sulfonated poly(ether ether ketone) (SPEEK) membranes for fuel cells through a dual-strategy approach: functionalized nanofiller blending and thermal cross-linking. Poly(dopamine)-modified halloysite nanotubes (DHNTs) were incorporated into SPEEK to create composite membranes, which were then thermally cross-linked. The amine groups on DHNTs form acid–base pairs with SPEEK’s sulfonic acid groups, preserving these functional sites while facilitating proton transport via the Grotthuss mechanism. This interaction extends the proton conduction pathway, limiting water penetration and membrane swelling. As a result, the SPEEK/DHNTs composite membranes exhibit a higher sulfonic acid group density and enhanced proton conductivity (182 mS cm–1 vs 132 mS cm–1 for pristine SPEEK). Fuel cell tests demonstrated a peak power density of 406 mW cm–2 at 80 °C and 100% relative humidity, significantly outperforming pristine SPEEK (308 mW cm–2). This work advances SPEEK-based membrane technology by simultaneously improving proton conductivity and structural stability, which are crucial for high-performance fuel cells.