Enabling one-step regeneration of LiBH4 with self-sustaining hydrogen in its spent fuel – One pathway to storing renewable hydrogen

LiBH 4 (LB in short) with a hydrogen capacity as high as 18.5 wt% and a low molecular weight (21.78 g mol −1 ) is among the most promising candidates for the hydrogen-based economy. However, current major technologies in (re)generation of LB rely heavily on energy-intensive processes, which greatly prohibits practical scaling-up of applications. Here we report a sustainable and effective approach to (re)generate LB via converting renewable H + in crystalline water into H - , achieving a desirable yield of ∼50%. This one-step synthesis method relies on the reaction between spent fuels, specifically LiBO 2 · x H 2 O, and Mg-based alloys to form LB under ambient atmosphere. Notably, our approach surpasses the efficiency of other conventional method, such as LiH-B-H 2 and MgH 2 -LiBO 2 systems, which not only bypasses the energy-intensive dehydration procedure of LiBO 2 · x H 2 O (∼470 ℃) but also eliminates the use of costly hydrides or high-pressure H 2 . Our findings indicate that Mg participated in the regeneration process prior to Al in Mg-Al alloys and [BH 4 ] - is gradually evolved from other intermediate species [BH x (OH) 4- x ] - ( x = 0, 1, 2, 3). By combining hydrogen release and efficient storage of hydrogen-rich substrate in a closed materials cycle, this study may shed light on a promising step toward application of renewable hydrogen in a fuel cell-based hydrogen economy.