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Sodium catalytic effect in the NaxLi6-xC60 hydrogen storage process

We report on the hydrogen sorption investigation of the mixed alkali cluster intercalated fulleride series NaxLi6-xC60. These compounds are isostructural to Na6C60 and Li6C60 while the cubic lattice parameter is linearly dependent on x. The H2 absorption/desorption was studied by means of charge/discharge kinetic and coupled calorimetric - manometric measurements. By varying the stoichiometry, we found the best compromise between absorption rate, temperature and amount of hydrogen in Na1Li5C60. This system is able to reversibly absorb up to 4.3 wt% H2 at 280 °C, which is 70 °C lower in temperature than its parent compound Li6C60. Furthermore, the kinetics is improved of 67% with respect Li6C60 and the dehydrogenation enthalpy is 13 kJ/mol H2 lower.