Optimal hydrogen storage in sodium substituted lithium fullerides

Through the substitution of Li with Na in Li6C60, we synthesized a series of mixed alkali cluster
intercalated fullerides, NaxLi6-xC60. These compounds share lattices of Na6C60 and Li6C60 with a cubic
parameter linearly dependent on x. H2 absorption and desorption were studied by means of charge/
discharge kinetic measurements and coupled calorimetric–manometric evaluation. By varying the stoichiometry,
we found the best compromise between the absorption rate, temperature and amount of
hydrogen for x = 0.5 and 1. Small concentrations of Na substituted to Li significantly lower the absorption
temperature of Li6C60, improving the hydrogenation capacity, the kinetics, and the dehydrogenation
enthalpy, the latter being 43.8 kJ mol/ H2 for x = 1. This study moves further toward the utilization of
intercalated fullerides for hydrogen storage applications.