Sodium alanates for reversible hydrogen storage

In this paper we show that sodium alanates may be used for reversible hydrogen storage, with the advantage of having high storage capacity combined with low cost. Both NaAlH4 and Na3AlH6 have been investigated for this application, and two complementary techniques have been used: improvement of the reaction kinetics by mechanical grinding, and chemical modification of the alloys. By these methods remarkable desorption/absorption kinetics are obtained. Sodium alanates so modified are capable of reversible hydrogen storage at the relatively low temperatures of around 80-140 degrees C, with a capacity of between 2.5 and 3.0 wt.%. The hydrides have an even higher reversible capacity of about 4.5-5 wt.% when operated at temperatures around 150-180 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.