Superior catalytic activity of in situ reduced metallic Co for hydrogen storage in a Co(OH)2-containing LiBH4/2LiNH2 composite

- Co(OH)2 is used to improve hydrogen storage properties of the LiBH4-2LiNH2 system.
- The LiBH4-2LiNH2-0.05Co(OH)2 sample exhibited optimal hydrogen storage properties.
- The 0.05Co(OH)2-containing sample starts releasing hydrogen at only 70 °C.
- 9.1 wt% of H2 was released from the 0.05Co(OH)2-added sample in 15 min at 200 °C.
- The metallic Co formed in situ during BM was identified to be the active catalyst.

Cobalt hydroxide (Co(OH)2) is introduced into the LiBH4/2LiNH2 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 °C, representing the lowest onset dehydrogenation temperature for the known catalyst-added LiBH4/2LiNH2 system. At 200 °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 °C, achieving partial reversibility for hydrogen storage in the LiBNH 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 LiBH4/2LiNH2 sample.

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