SCHEDULED MAINTENANCE
Achieving ambient temperature hydrogen storage in ultrafine nanocrystalline TiO2@C-doped NaAlH4†
Abstract
Sodium alanate (NaAlH4) has attracted tremendous interest as a prototypical high-density complex hydride for on-board hydrogen storage. However, poor reversibility and slow kinetics limit its practical application. In this paper, we propose a novel strategy for the preparation of an ultrafine nanocrystalline TiO2@C-doped NaAlH4 system by first calcining the furfuryl alcohol-filled MIL-125(Ti) at 900 °C and then ball milling with NaAlH4 followed by a low-temperature activation process at 150 °C under 100 bar H2. The as-prepared NaAlH4-9 wt% TiO2@C sample releases hydrogen starting from 63 °C and re-absorbs starting from 31 °C, which are reduced by 114 °C and 54 °C relative to those of pristine NaAlH4, respectively. At 140 °C, approximately 4.2 wt% of hydrogen is released within 10 min, representing the fastest dehydrogenation kinetics of any presently known NaAlH4 system. More importantly, the dehydrogenated sample can be fully hydrogenated under 100 bar H2 even at temperatures as low as 50 °C, thus achieving ambient-temperature hydrogen storage. The synergetic effect of the Al–Ti active species and carbon contributes to the significantly reduced operating temperatures and enhanced kinetics.
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