Enhancing sulfonated polyethersulfone performance by incorporating TiO 2 -decorated MWCNTs: A viable solution for high-temperature polymer electrolyte fuel cell applications

In an era marked by escalating environmental concerns and increasing energy demands, the development of advanced, cost-effective polymer electrolyte membrane (PEM) materials is essential to accelerating the widespread adoption of fuel cell technology as a viable and environmentally sustainable alternative to traditional energy sources. To address this challenge, we integrated a novel hybrid nanofiller—fabricated by directly growing TiO 2 nanoparticles on the surface of multi-walled carbon nanotubes (MWCNTs)—into a readily available, cost-efficient polyaromatic polymer, specifically sulfonated polyethersulfone (sPES). The incorporation of the MWCNTs-TiO 2 nanohybrid resulted in significant improvements in the thermo-mechanical stability, swelling capacity, and transport properties of sPES. Ex-situ through-plane proton conductivity measurements demonstrated a peak value of 5.54 mS/cm at 120 °C and 20% RH for PM 5, representing a tenfold increase compared to unmodified sPES. This enhancement has ascribed to the synergistic effect of the elongated carbon nanotubes and hygroscopic TiO 2 nanoparticles, which fostered the formation of additional proton-conductive pathways within the sPES, maintaining their activity even under dehydrating conditions. Furthermore, the PM 5 nanocomposite exhibited a remarkable peak power density of 87.2 mW/cm 2 in the fuel cell (H 2 /air, 120 °C, 30% RH), exceeding the performance of the Nafion benchmark.