Study of the decomposition of a 0.62LiBH(4)-0.38NaBH(4) mixture

摘要

This work highlights the dehydrogenation mechanisms of a 0.62LiBH(4)-0.38NaBH(4) mixture in the range of 25-650 degrees C in flowing Ar. The dehydrogenation starts from 287 degrees C followed by two decomposition steps at 488 degrees C and 540 degrees C. These peak temperatures are in the range of 470 degrees C (for pure LiBH4)-580 degrees C (for pure NaBH4) due to different Pauling electronegativity values for Li+ (0.98) and Na+ (0.93) that affects the stability and decomposition temperatures. The 1St step of dehydrogenation is accompanied with precipitation of LiH, Li2B12H12 and B in between 287 and 520 degrees C; whilst the 2nd step of dehydrogenation is mainly accompanied by the precipitation of Na and B when temperature is higher than 520 degrees C. The total amount of H-2 released is 10.8 wt.% that exceeds the estimated amount (8.9 wt.%), indicating less metal dodecaborate (than that for pure LiBH4) is formed during the decomposition. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.