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

Abstract

Nanoscale CeAl4 was directly synthesized by the thermal reaction between CeH2 and nano-aluminum at 300 °C. Then nano CeAl4-doped sodium alanate (NaAlH4) was synthesized by ball milling NaH/Al with 0.04CeAl4 under hydrogen atmosphere at room temperature, and the catalytic efficiency of nanoscale CeAl4 for hydrogen storage of NaAlH4 was systematically investigated. It is shown that CeAl4 can effectively improve the dehydrogenation properties of sodium alanate system. The 0.04CeAl4-doped NaAlH4 system starts to release hydrogen below 80 °C, completes dehydrogenation within 10 min at 170 °C, and exhibits good cycling de/hydrogenation kinetics at relatively lower temperature (100–140 °C). Apparent activation energy of the dehydrogenation of NaAlH4 can be effectively reduced by addition of CeAl4, resulting in the decrease in desorption temperatures. Moreover, by analyzing the reaction kinetics of nano CeAl4-doped NaAlH4 sample, 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. Nanoscale CeAl4 was successfully synthesized and doped into NaAlH4 system ball milling NaH/Al + 0.04CeAl4. The addition of CeAl4 can effectively improve the dehydrogenation properties of NaAIH4, which starts to release hydrogen below 80 °C, completes dehydrogenation within 10 min at 170 °C, and exhibits good cycling de/hydrogenation kinetics at relatively lower temperature.