Composite polymer electrolyte membranes based on Mg–Al layered double hydroxide (LDH) platelets for H2/air-fed fuel cells

• Mg/Al-Layered double hydroxides used as nanofillers in Nafion-based composites.
• LDHs with different Mg/Al metal ratios and intercalated anions are compared.
• Completely exfoliated and homogeneous nanocomposites membranes were achieved.
• Proton dynamic properties were studied by conductivity and NMR methods (PFG and T1).
• Remarkable water retention ability and proton conductivity at high T.

Layered double hydroxides (LDH) were incorporated into Nafion polymer for the development of innovative hybrid nanocomposites exploitable in the high temperature PEM fuel cells. Mg2 +/Al3 + LDHs (at two metal ratios, 2:1 and 3:1) with different countervailing anions in the interlayer space (CO32 −, ClO4−, NO3−) were synthesized, while fully exfoliated composite membranes were prepared by solution intercalation method. NMR technique (diffusion and relaxation) was used to investigate the transport properties of water confined in membranes. The protons dynamics appears to be influenced from the Mg2 +/Al3 + metal ratios of the nanoadditives, while the type of anion affects the electrochemical measurements. Compared to filler-free Nafion, both water absorption and diffusion in the hybrid membranes are increased with a noteworthy behavior at high temperature, proving the exceptional water retention property of these materials together with superior mechanical properties. The proton conductivity reaches 2.7 × 10− 2 S cm− 1 at 100 °C and 50% RH, as the best value for the composite based on Naf-LDH-Mg2 +/Al3 +(2/1)-NO3−.