SulfoMg organophyllosilicate − infused nafion membranes: overcoming hydration and stability challenges in HT-PEMFCs

• SulfoMgPS nanofiller enhances HT-PEMFC Nafion membrane hydration and conductivity. • High EIC (12.5 mmol/g) ensures hydration and 7x proton conductivity at low RH/120 °C. • Uniform nanofiller dispersion reinforces mechanical strength and thermal stability of PEMs . • Single-cell tests yield 1100 mW/cm 2 at 80 °C (100 % RH) and 800 mW/cm 2 at 110 °C (25 % RH). • Nanocomposite design meets DOE targets for efficiency and durability in harsh conditions. High-temperature Proton Exchange Membrane Fuel Cells (HT-PEMFCs) are crucial for advancing hydrogen energy technologies, particularly in automotive applications. This study introduces sulfo-functionalized magnesium organophyllosilicate (SulfoMgPS) as a novel nanofiller for enhancing Nafion-based hybrid membranes. SulfoMgPS nanoparticles, synthesized via a co-condensation method, exhibit a unique layered structure with sulfonic acid (−SO 3 H) groups grafted onto brucite-like layers. These nanoparticles demonstrate exceptional hydrophilicity, with water uptake reaching 252 % at 100 % RH , and a high ion exchange capacity of 12.5 mmol g −1 , supporting efficient proton conduction through the Grotthuss mechanism. Incorporating SulfoMgPS into Nafion produces nanocomposite membranes with remarkable structural and functional properties. The hybrid membrane with 3 % of filler loading (N-L3) achieved exceptional proton conductivity, up to sevenfold greater than filler-free Nafion under low humidity (30 % RH) across 30–120 °C. Single-cell tests revealed peak power densities of 1100 mW cm −2 under 100 % RH and 800 mW cm −2 under 25 % RH at 110 °C, outperforming many benchmarks. These results highlight the potential of SulfoMgPS nanofillers to overcome dehydration and thermal stability challenges in HT-PEMFCs, meeting stringent DOE targets for efficiency and durability.