Investigation of layered double hydroxide (LDH) Nafion-based nanocomposite membranes for high temperature PEFCs

Hydrogen/air Polymer Electrolyte Fuel Cell (PEFC) are highly attractive as energy source for mobile applications, improving electrochemical kinetics rates, waste heat recovery and overcoming catalyst tolerance for reformed hydrogen at operating temperatures above 80 °C. Layered double hydroxide (LDH) nanoparticles with Mg2+/Al3+ metal cations (metal ratio 2:1) and different countervailing anions (CO2- 3 , ClO- 4, NO- 3 ) in the interlayer space were synthesized and tested as fillers for the creation of hybrid Nafion nanocomposites using a standardized casting method. The development of such nanocomposites will lead to a highly efficient H2/air polymer electrolyte fuel cell operating at high temperatures. The produced hybrid membranes were characterized by a combination of powder X-ray diffraction, FTIR spectroscopy, and thermal analysis (DTA/TGA) that revealed the creation of homogeneous exfoliated nanocomposites. The water-transport properties were investigated by NMR spectroscopy (diffusion and relaxation time). Interlayer anions affect the lambda value (mol H2O/mol SO3H) showing better hydration with higher values compared to recast Nafion. Fuel cell tests performed in drastic conditions (1.5 abs. bar and 50% RH) at 100°C highlighted the influence of the different interlayer anions in composite membranes. A good performance was obtained for membranes containing LDH-ClO- 4 with a power density of 300mW cm-2 at 0.6 V at 100 °C.