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Superior Reversible Hydrogen Storage Properties and Mechanism of LiBH4–MgH2–Al Doped with NbF5 Additive
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-03-21 00:00:00 , DOI: 10.1021/acs.jpcc.8b00959 Changjun Cheng , Man Chen , Xuezhang Xiao , Xu Huang , Jiaguang Zheng , Lixin Chen 1
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-03-21 00:00:00 , DOI: 10.1021/acs.jpcc.8b00959 Changjun Cheng , Man Chen , Xuezhang Xiao , Xu Huang , Jiaguang Zheng , Lixin Chen 1
Affiliation
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LiBH4 is one of the most potential candidates for hydrogen storage materials among several sorts of complex borohydrides. Utilizing reactive hydride composites on LiBH4 could destabilize the thermodynamics and improve dehydrogenation behaviors, such as the excellent reversibility of LiBH4–MgH2 and the fast dehydrogenation of LiBH4–Al. The strategy of combining both outstanding effects of MgH2 and Al to form LiBH4–MgH2–Al system has been proposed. However, reduction of hydrogen capacity during cycles has not been solved for the LiBH4–MgH2–Al system, which is considered as the principal problem. In this work, we investigated the reversible hydrogen storage performance and reaction mechanism of LiBH4–MgH2–Al doped with/without NbF5 additive. It can be found that the dehydrogenation of 4LiBH4–MgH2–Al can release about 9.0 wt % H2 quickly without incubation period, compared with 2LiBH4–MgH2. Moreover, it is the first time to achieve completely reversible hydrogen desorption property of LiBH4–MgH2–Al by doping with NbF5 and dehydrogenating under hydrogen back pressure in experiment. Microstructure analysis shows that the formation of Mg–Al alloys could result in the formation of Li2B12H12 and subsequently lead to the capacity degradation. With the additive NbF5, it shows a totally different pathway and a significant inhibition effect on the alloying between Mg and Al, leading to an improved de/rehydrogenation behavior without the byproduct Li2B12H12. Meanwhile, NbF5 could be hydrogenated into NbH2 and react with element B to form NbB2, promoting the reaction between Mg/Al metals and B element to form MgAlB4. On the other hand, those niobium compounds could facilitate the products MgAlB4 and LiH to be fully rehydrogenated into LiBH4, MgH2, and Al, which contributes to the complete reversibility of LiBH4–MgH2–Al. A better understanding of the capacity fade mechanism of LiBH4–MgH2–Al system and the effects of additives might promote further development of high-capacity hydrogen storage materials.
中文翻译：
高级可逆储氢性能及的LiBH机制4 -MgH 2与NBF -Al掺杂5添加剂
LiBH 4是几种复杂的硼氢化物中最有潜力的储氢材料之一。在LiBH 4上使用反应性氢化物复合物会破坏热力学并改善脱氢性能，例如LiBH 4 -MgH 2的优异可逆性和LiBH 4 -Al的快速脱氢。提出了将MgH 2和Al的显着效果相结合以形成LiBH 4 -MgH 2 -Al体系的策略。但是，对于LiBH 4 –MgH 2，循环中氢容量的降低尚未解决-铝系统，这被认为是主要问题。在这项工作中，我们研究了掺入或不掺入NbF 5的LiBH 4 -MgH 2 -Al的可逆储氢性能和反应机理。可以发现，4LiBH脱氢4 -MgH 2 -Al可以释放大约9.0重量％的H 2迅速而不潜伏期，与2LiBH相比4 -MgH 2。此外，这是第一次通过掺杂NbF 5来实现LiBH 4 -MgH 2 -Al的完全可逆的氢解吸性能。实验中在氢气背压下进行脱氢。显微组织分析表明，Mg-Al合金的形成可能导致Li 2 B 12 H 12的形成，从而导致容量下降。使用添加剂NbF 5时，它显示出完全不同的途径，并且对Mg和Al之间的合金化具有显着的抑制作用，从而在没有副产物Li 2 B 12 H 12的情况下改善了脱氢/再氢化行为。同时，NbF 5可以被氢化成NbH 2并与元素B反应形成NbB 2，促进Mg / Al金属与B元素之间的反应以形成MgAlB 4。另一方面，这些铌化合物可以促进产物MgAlB 4和LiH完全重氢化为LiBH 4，MgH 2和Al，这有助于LiBH 4 -MgH 2 -Al的完全可逆性。更好地了解LiBH 4 -MgH 2 -Al体系的容量衰减机理以及添加剂的作用可能会促进高容量储氢材料的进一步发展。
更新日期：2018-03-21
中文翻译：
高级可逆储氢性能及的LiBH机制4 -MgH 2与NBF -Al掺杂5添加剂
LiBH 4是几种复杂的硼氢化物中最有潜力的储氢材料之一。在LiBH 4上使用反应性氢化物复合物会破坏热力学并改善脱氢性能，例如LiBH 4 -MgH 2的优异可逆性和LiBH 4 -Al的快速脱氢。提出了将MgH 2和Al的显着效果相结合以形成LiBH 4 -MgH 2 -Al体系的策略。但是，对于LiBH 4 –MgH 2，循环中氢容量的降低尚未解决-铝系统，这被认为是主要问题。在这项工作中，我们研究了掺入或不掺入NbF 5的LiBH 4 -MgH 2 -Al的可逆储氢性能和反应机理。可以发现，4LiBH脱氢4 -MgH 2 -Al可以释放大约9.0重量％的H 2迅速而不潜伏期，与2LiBH相比4 -MgH 2。此外，这是第一次通过掺杂NbF 5来实现LiBH 4 -MgH 2 -Al的完全可逆的氢解吸性能。实验中在氢气背压下进行脱氢。显微组织分析表明，Mg-Al合金的形成可能导致Li 2 B 12 H 12的形成，从而导致容量下降。使用添加剂NbF 5时，它显示出完全不同的途径，并且对Mg和Al之间的合金化具有显着的抑制作用，从而在没有副产物Li 2 B 12 H 12的情况下改善了脱氢/再氢化行为。同时，NbF 5可以被氢化成NbH 2并与元素B反应形成NbB 2，促进Mg / Al金属与B元素之间的反应以形成MgAlB 4。另一方面，这些铌化合物可以促进产物MgAlB 4和LiH完全重氢化为LiBH 4，MgH 2和Al，这有助于LiBH 4 -MgH 2 -Al的完全可逆性。更好地了解LiBH 4 -MgH 2 -Al体系的容量衰减机理以及添加剂的作用可能会促进高容量储氢材料的进一步发展。
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