Synthesis of nanoscale CeAl4 and its high catalytic efficiency for hydrogen storage of sodium alanate

摘要

Nanoscale CeAl_4 was directly synthesized by the thermal reaction between CeH_2 and nano-aluminum at300℃.Then nano CeAl_4-doped sodium alanate(NaAlH_4)was synthesized by ball milling NaH/Al with 0.04CeAl_4under hydrogen atmosphere at room temperature,and the catalytic efficiency of nanoscale CeAl_4 for hydrogen storage of NaAlH_4 was systematically investigated.It is shown that CeAl_4 can effectively improve the dehydrogenation properties of sodium alanate system.The 0.04CeAl_4-doped NaAlH_4 system starts to release hydrogen below 80℃,completes dehydrogenation within 10 min at 170℃,and exhibits good cycling de/hydrogenation kinetics at relatively lower temperature(100-140℃).Apparent activation energy of the dehydrogenation of NaAlH_4 can be effectively reduced by addition of CeAl_4,resulting in the decrease in desorption temperatures.Moreover,by analyzing the reaction kinetics of nano CeAl_4-doped NaAlH_4sample,both of the decomposition steps are conformed to a two-dimensional phase-boundary growth mechanism.The mechanistic investigations gained here can help to understand the de-/rehydrogenation behaviors of catalyzed complex metal hydride systems.