Using light metal hydrides as hydrogen carriers is of particular interest for safe and compact storage of hydrogen. Magnesium hydride (MgH₂) has attracted significant attention due to its 7.6 wt% hydrogen content and the natural abundance of Mg. However, bulk MgH₂ is stable (ΔH_f ∼ 76 kJ mol⁻¹) and releases hydrogen only at impractically high temperatures (>300 °C). Herein, we demonstrate a first attempt to achieve ambient-temperature reversibility of hydrogen storage for MgH₂ by fabricating non-confined ultrafine nanoparticles. Taking advantage of the big discrepancies in the solubility of metal hydrides and chlorides in THF, a novel metathesis process of liquid–solid phase driven by ultrasound was proposed. Ultrafine MgH₂ nanoparticles predominantly of around 4–5 nm in size were successfully obtained without scaffolds or supports. A reversible hydrogen storage capacity of 6.7 wt% at 30 °C was measured, which has never been achieved before, thanks to thermodynamic destabilization and decreased kinetic barriers. The bare nanoparticles exhibited a stable and rapid hydrogen cycling behaviour in 50 cycles at 150 °C, a remarkable improvement compared with bulk MgH₂. Our finding brings MgH₂ a step closer to practical applications and the methodology presented here opens new pathways for fabricating sensitive nanoparticles.

中文翻译：

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使用无限制的超细氢化镁在环境温度下可实现6.7 wt％的氢可逆存储

对于安全和紧凑地存储氢而言，使用轻金属氢化物作为氢载体特别受关注。氢化镁（MgH ₂）由于其7.6 wt％的氢含量和Mg的自然丰度而备受关注。然而，散装的MgH ₂是稳定的（Δ ħ _˚F〜76千焦耳摩尔^-1）和释放氢仅在不切实际高温（> 300℃）。本文中，我们展示了实现MgH ₂储氢的环境温度可逆性的首次尝试。通过制造无限制的超细纳米颗粒。利用金属氢化物和氯化物在THF中溶解度的巨大差异，提出了一种由超声驱动的液相固相复分解的新方法。在没有支架或支架的情况下，成功获得了大小约为4–5 nm的超细MgH ₂纳米颗粒。由于热力学不稳定和动力学障碍的减少，在30°C下测得的可逆储氢能力为6.7 wt％，这是前所未有的。裸露的纳米颗粒在150°C下的50个循环中表现出稳定且快速的氢循环行为，与块状MgH ₂相比有显着改善。我们的发现带来了MgH ₂ 接近实际应用的一步，此处介绍的方法为制造敏感的纳米粒子开辟了新途径。