Superior catalytic activity of in situ reduced metallic Co for hydrogen storage in a Co(OH)(2)-containing LiBH4/2LiNH(2) composite

Cobalt hydroxide (Co(OH)(2)) is introduced into the LiBH4/2LiNH(2) composite to improve its hydrogen storage properties. The 0.05Co(OH)(2)-containing sample exhibits a significantly reduced dehydrogenation temperature and improved hydrogen storage reversibility. Its dehydrogenation onset temperature is as low as 70 degrees C, representing the lowest onset dehydrogenation temperature for the known catalyst-added LiBH4/2LiNH(2) system. At 200 degrees C, approximately 9.1 wt% of hydrogen is rapidly released from the 0.05Co(OH)(2)-containing sample within 15 min, greatly superior to the pristine sample because nearly no hydrogen release from it is observed under identical conditions. More importantly, the dehydrogenated sample absorbs 1.1 wt% of hydrogen at 350 degrees C, achieving partial reversibility for hydrogen storage in the Li-B-N-H system. Structural investigations reveal that the added Co(OH)(2) is first reduced to metallic Co during ball milling, and the Co thus formed in situ serves as the active catalyst in improving the hydrogen storage properties of the LiBH4/2LiNH(2) sample.