In this study, MXene-derived VO@C nanosheets are successfully synthesized as an efficient catalyst for enhancing the hydrogen storage performance of MgH. MgH-VO@C exhibits exceptional kinetic and cyclic performance. It desorbs 3.59 wt.% H within 120 min at 200 °C and adsorbs 3.9 wt.% H within 2.7 h at room temperature after complete dehydrogenation. Moreover, even after 251 cycles at 300 °C, it maintains a hydrogen capacity of 5.45 wt.%, which accounted for 90.5% of the maximum hydrogen capacity. In addition, an activation mechanism for Mg hydrogenation driven by phase transition from VO to VO is firstly clarified through experimental and theoretical analysis. DFT calculations show that the hydrogenation energy barrier of VO (1.01 eV) is significantly lower than that of VO (1.82 eV). The phase transition from VO to VO forms abundant strong hydrogenation sites, effectively reducing the hydrogenation energy barrier of magnesium and activating the hydrogenation ability of deactivated magnesium. Therefore, benefited from the activation mechanism driven by the VO/VO interface, the hydrogen storage capacity of magnesium increased from 4.28 wt.% at 46th cycle to 5.45 wt.% at 251st cycle.

中文翻译：

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构建VO/V2O3界面增强MgH2储氢性能

在这项研究中，成功​​合成了 MXene 衍生的 VO@C 纳米片作为增强 MgH 储氢性能的有效催化剂。MgH-VO@C 表现出优异的动力学和循环性能。完全脱氢后，在200℃下120分钟内脱附3.59wt.%H2，并在室温下2.7h内吸附3.9wt.%H2。此外，即使在300℃下循环251次后，其氢容量仍保持在5.45wt.%，占最大氢容量的90.5%。此外，通过实验和理论分析，首次阐明了由 VO 到 VO 相变驱动的 Mg 加氢活化机制。DFT计算表明，VO的加氢能垒（1.01 eV）明显低于VO的加氢能垒（1.82 eV）。VO到VO的相变形成丰富的强加氢位点，有效降低镁的加氢能垒，激活失活镁的加氢能力。因此，受益于VO/VO界面驱动的活化机制，镁的储氢能力从第46次循环时的4.28wt.%增加到第251次循环时的5.45wt.%。