Magnesium is one of the potential candidates for on-board hydrogen storage, but slow hydrogenation kinetics and unfavourable thermodynamics limits its practical implementation. To improve the hydrogenation characteristics, nanocrystalline magnesium was prepared by a simple wet milling method without addition of heavy metal catalyst. Compared to micro-crystalline Mg, developed nanocrystalline Mg exhibits improved hydrogen storage properties showing extended plateau region in the pressure-composition-temperature curves with higher hydrogen storage capacity (6.24 wt% at 300°C). Hydrogenation and dehydrogenation kinetics is found to follow Kolmogorov−Johnson−Mehl−Avrami activation energy model confirming the involvement of nucleation-growth-impingement mechanism. Prolonged ball milling leads to quite fast hydrogenation kinetics (upto 90% of the saturation value in 15.5 minutes at 250°C) and leads to substantial decrease in the activation barrier. The activation energy for hydrogenation is found to be 68.88 kJ mol⁻¹ for 8 hours ball milled sample. Present study established a simple and scalable method for nanocrystalline Mg, which can undergo reversible hydrogen absorption and desorption with improved performance without using any additional catalyst.

中文翻译：

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湿磨法制备无催化剂镁纳米颗粒储氢特性的改善

镁是车载储氢的潜在候选者之一，但缓慢的氢化动力学和不利的热力学限制了其实际应用。为了改善加氢特性，纳米晶镁通过简单的湿磨法制备，不添加重金属催化剂。与微晶镁相比，开发的纳米晶镁表现出改善的储氢性能，在压力-成分-温度曲线中显示出扩展的平台区域，具有更高的储氢容量（300°C 时为 6.24 wt%）。发现加氢和脱氢动力学遵循 Kolmogorov-Johnson-Mehl-Avrami 活化能模型，证实了成核-生长-冲击机制的参与。长时间的球磨会导致非常快的氢化动力学（在 250°C 下 15.5 分钟内达到饱和值的 90%）并导致活化势垒的显着降低。发现加氢活化能为 68.88 kJ mol^-1 8 小时球磨样品。目前的研究建立了一种简单且可扩展的纳米晶镁方法，该方法可以在不使用任何额外催化剂的情况下进行可逆的氢吸收和解吸，并提高性能。