Combinations of V2C and Ti3C2 MXenes for Boosting the Hydrogen Storage Performances of MgH2
Combinations of V2C and Ti3C2 MXenes for Boosting the Hydrogen Storage Performances of MgH2
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DOI：
10.1021/acsami.0c23150
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发表时间：
2021-03-15
影响因子：
9.5
通讯作者：
Guo, Jin
中科院分区：
文献类型：
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作者：
Liu, Haizhen;Lu, Chenglin;Guo, Jin
首先通过剥离 V2AlC 或 Ti3AlC2 合成二维碳化钒 (V2C) 和碳化钛 (Ti3C2) MXene，然后将其共同引入氢化镁 (MgH2) 中以调整 MgH2 的氢解吸/吸收性能。所制备的 MgH2-V2C-Ti3C2 复合材料表现出比纯 MgH2 更好的储氢性能。添加 10 wt% 2V(2)C/Ti3C2 的 MgH2 在 180 摄氏度左右引发氢解吸； 225℃下60min内解吸出5.1wt%的氢气，300℃下2min内解吸出5.8wt%的氢气。在6MPa H-2下，脱水后的MgH2-2V(2)C/Ti3C2在室温下即可开始回收氢气，在20s恒温下，可在20s内得到5.1wt%的H-2。 40℃。可逆容量（6.3wt%）长达10次循环不下降，表现出优异的循环稳定性。 2V(2)C/Ti3C2的添加可使MgH2的氢解吸反应活化能显着降低37%，并略微降低氢解吸反应热函2 kJ mol(-1) H-2。结果表明，与仅添加V2C或Ti3C2相比，V2C和Ti3C2的组合促进了MgH2的放氢过程，而在室温下MgH2的吸氢过程中，Ti3C2对MgH2的影响比V2C更显着。提出了MgH2-V2C-Ti3C2体系释放和吸收氢的可能机制：氢原子或分子在解吸过程中可能优先通过MgH2/V2C/Ti3C2三晶界迁移，在吸收过程中优先通过Mg/Ti3C2界面迁移。微观结构研究表明V2C和Ti3C2主要充当MgH2的有效催化剂。这项工作深入了解了两种 MXene 组合增强的 MgH2 的储氢行为和机制。
Two-dimensional vanadium carbide (V2C) and titanium carbide (Ti3C2) MXenes were first synthesized by exfoliating V2AlC or Ti3AlC2 and then introduced jointly into magnesium hydride (MgH2) to tailor the hydrogen desorption/absorption performances of MgH2. The as-prepared MgH2-V2C-Ti3C2 composites show much better hydrogen storage performances than pure MgH2. MgH2 with addition of 10 wt % of 2V(2)C/Ti3C2 initiates hydrogen desorption at around 180 degrees C; 5.1 wt % of hydrogen was desorbed within 60 min at 225 degrees C, while 5.8 wt % was desorbed within 2 min at 300 degrees C. Under 6 MPa H-2, the dehydrided MgH2-2V(2)C/Ti3C2 can start to recover hydrogen at room temperature, and 5.1 wt % of H-2 is obtained within 20 s at a constant temperature of 40 degrees C. The reversible capacity (6.3 wt %) does not decline for up to 10 cycles, which shows excellent cycling stability. The addition of 2V(2)C/Ti3C2 can remarkably lower the activation energy for the hydrogen desorption reaction of MgH2 by 37% and slightly reduce the hydrogen desorption reaction enthalpy by 2 kJ mol(-1) H-2. It was demonstrated that the combination of V2C and Ti3C2 promotes the hydrogen-releasing process of MgH2 compared with addition of only V2C or Ti3C2, while Ti3C2 impacts MgH2 more significantly than V2C in the hydrogen absorption process of MgH2 at ambient temperatures. A possible mechanism in the hydrogen release and uptake of the MgH2-V2C-Ti3C2 system was proposed as follows: hydrogen atoms or molecules may preferentially transfer through the MgH2/V2C/Ti3C2 triple-grain boundaries during the desorption process and through the Mg/ Ti3C2 interfaces during the absorption process. Microstructure studies indicated that V2C and Ti3C2 mainly act as efficient catalysts for MgH2. This work provides an insight into the hydrogen storage behaviors and mechanisms of MgH2 boosted by a combination of two MXenes.