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

Layered double hydroxides (LDH) were incorporated into Nafion polymer for the development of innovativehybrid nanocomposites exploitable in the high temperature PEMfuel cells.Mg2+/Al3+ LDHs (at two metal ratios,2:1 and 3:1) with different countervailing anions in the interlayer space (CO3 2 -, 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, whilethe type of anion affects the electrochemical measurements. Compared to filler-free Nafion, both waterabsorption and diffusion in the hybrid membranes are increased with a noteworthy behavior at hightemperature, proving the exceptional water retention property of these materials together with superiormechanical properties. The proton conductivity reaches 2.7 × 10-2 S cm-1 at 100 °C and 50% RH, as the bestvalue for the composite based on Naf-LDH-Mg2+/Al3+(2/1)-NO3