LiMn(BH4)3/2LiCl复合物的反应球磨制备及其脱氢性能

以LiBH₄和MnCl₂为初始原料, 采用反应球磨法制备了LiMn(BH₄)₃/2LiCl复合物, 并系统地研究了该复合物的脱氢性能及含钛催化剂的掺杂对其脱氢性能的影响. 结果表明: LiMn(BH₄)₃/2LiCl复合物是由非晶态的LiMn(BH₄)₃和晶态的LiCl组成, 在135-190 °C分解, 分解反应的活化能为114.0 kJ·mol^-1; LiMn(BH₄)₃/2LiCl复合物分解失重约7.0% (w). 组分分析表明除H₂外, 释放的气体中还含有4.0% (摩尔分数, x)的B₂H₆. B₂H₆的生成是该复合物失重超过其理论储氢容量6.3% (w)的原因; 进一步研究发现, 含钛催化剂(TiF₃、TiC、TiN和TiO₂)中, 仅TiF₃能够催化LiMn(BH₄)₃/2LiCl复合物的分解反应, 使其起始分解温度和分解反应活化能分别降低至125 °C和104.0 kJ·mol^-1. 这主要归因于TiF₃中的Ti原子取代了LiMn(BH₄)₃中的部分Li原子, 并在局域形成了易于分解的Ti(BH₄)₃.

LiMn(BH4)3/2LiCl Composite Synthesized by Reactive Ball-Milling and Its Dehydrogenation Properties

A LiMn(BH₄)₃/2LiCl composite was prepared by reactive ball-milling a mixture of LiBH₄ and MnCl₂, and its dehydrogenation properties were investigated. The results indicate that the LiMn(BH₄)₃/2LiCl composite consists of crystalline LiCl and amorphous LiMn(BH₄)₃, and decomposes at 135-190 °C with an activation energy of 114.0 kJ·mol^-1, resulting in an emission of 7.0% (w) gas. The released gases contain 96.0% H₂ and 4.0% B₂H₆ (mole fraction, x), which is the reason for why the mass loss of the LiMn(BH₄)₃/2LiCl composite is larger than that of theoretical hydrogen capacity of 6.3% (w). Moreover, the influence of various Ti-containing dopants on the decomposition of the LiMn(BH₄)₃/2LiCl composite was studied. We found that among TiF₃, TiC, TiN, and TiO₂, only TiF₃ achieved a reduction in decomposition temperature. Compared with the undoped LiMn(BH₄)₃/2LiCl composite, the onset decomposition temperature and the activation energy of the TiF₃-doped composite are reduced to 125 °C and to 104.0 kJ·mol^-1, respectively. These are attributed to the formation of Ti(BH₄)₃ in some local regions of the TiF₃-doped composite by the partial substitution of Ti for Li in LiMn(BH₄)₃.