High catalytic efficiency of amorphous TiB2 and NbB2 nanoparticles for hydrogen storage using the 2LiBH4-MgH2 system
High catalytic efficiency of amorphous TiB2 and NbB2 nanoparticles for hydrogen storage using the 2LiBH4-MgH2 system
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DOI：
10.1039/c3ta12401k
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发表时间：
2013-01-01
影响因子：
11.9
通讯作者：
Wang, Qidong
中科院分区：
文献类型：
--
作者：
Fan, Xiulin;Xiao, Xuezhang;Wang, Qidong
LiBH4-MgH2体系以2：1的摩尔比构成了一种具有代表性的反应性氢化物复合材料(RHC)。但反应动力学速度慢、可逆性差等问题阻碍了其实际应用。为了缓解这些问题，合成了非晶态的TiB2和NbB2纳米粒子，并将其用于2LiBH(4)-MgH2体系的催化剂。等温脱氢和程序升温质谱分析表明，非晶态TiB_2和Nb_2纳米粒子能够显著提高2LiBH(4)-MgH_2体系的储氢性能。掺杂纳米TiB(2)的2LiBH(4)-MgH2仅在6min内释放出9wt%的氢，而未掺杂的复合体系在400℃下300min内释放出3.9wt%的限氢量。掺杂纳米TiB(2)后，第一步和第二步的脱氢活化能分别降低了40.4kJ mol(-1)和35.2kJ mol(-1)。认为TiB_2和Nb_2纳米粒子可以首先催化氢化镁的脱氢，然后诱导LiBH_4的分解，同时作为氢化镁的成核剂，从而大大提高脱氢动力学。这项研究为过渡金属硼化物物种在掺杂RHC中的显著性能提供了明确的证据，这对于理解RHC的机理和进一步提高RHC的储氢性能是至关重要的。
LiBH4-MgH2 system in a 2 : 1 molar ratio constitutes a representative reactive hydride composite (RHC) for hydrogen storage. However, sluggish kinetics and poor reversibility hinder the practical applications. To ease these problems, amorphous TiB2 and NbB2 nanoparticles were synthesized and employed as catalysts for the 2LiBH(4)-MgH2 system. Isothermal de-/rehydrogenation and temperature programmed mass spectrometry (MS) measurements show that amorphous TiB2 and NbB2 nanoparticles can significantly improve the hydrogen storage performance of the 2LiBH(4)-MgH2 system. 9 wt% hydrogen can be released within only 6 min for nanoTiB(2)-doped 2LiBH(4)-MgH2, while for the undoped composite limited hydrogen of 3.9 wt% is released in 300 min at 400 degrees C. The dehydrogenation activation energies for the first and second steps are dramatically reduced by 40.4 kJ mol(-1) and 35.2 kJ mol(-1) after doping with nanoTiB(2). It is believed that TiB2 and NbB2 nanoparticles can first catalyze the dehydrogenation of MgH2, and then induce the decomposition of LiBH4 and meanwhile act as nucleation agents for MgB2, thereby greatly enhancing the kinetics of dehydrogenation. The present study gives clear evidence for the significant performance of transition metal boride species in doped RHCs, which is critically important for understanding the mechanism and further improving the hydrogen storage properties of RHCs.