Confined NaAlH4 nanoparticles inside CeO2 hollow nanotubes towards enhanced hydrogen storage

Abstract

NaAlH₄ has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO₂ hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH₄ nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH₄ inside CeO₂ HNTs, synthesized via the infiltration of molten NaAlH₄ into the CeO₂ HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO₂ HNTs-catalyzed NaAlH₄. The onset dehydrogenation temperature of the NaAlH₄@CeO₂ composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO₂ HNTs-catalyzed NaAlH₄, respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH₄ under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO₂ HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH₄ NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH₄.