State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China.
Dalton Trans. 2012 Aug 28;41(36):10980-7. doi: 10.1039/c2dt30945a.
A significant improvement of hydrogen storage properties was achieved by introducing MgH(2) into the 6LiBH(4)-CaH(2) system. It was found that ~8.0 wt% of hydrogen could be reversibly stored in a 6LiBH(4)-CaH(2)-3MgH(2) composite below 400 °C and 100 bar of hydrogen pressure with a stepwise reaction, which is superior to the pristine 6LiBH(4)-CaH(2) and LiBH(4) samples. Upon dehydriding, MgH(2) first decomposed to convert to Mg and liberate hydrogen with an on-set temperature of ~290 °C. Subsequently, LiBH(4) reacted with CaH(2) to form CaB(6) and LiH in addition to further hydrogen release. Hydrogen desorption from the 6LiBH(4)-CaH(2)-3MgH(2) composite finished at ~430 °C in non-isothermal model, a 160 °C reduction relative to the 6LiBH(4)-CaH(2) sample. JMA analyses revealed that hydrogen desorption was a diffusion-controlled reaction rather than an interface reaction-controlled process. The newly produced Mg of the first-step dehydrogenation possibly acts as the heterogeneous nucleation center of the resultant products of the second-step dehydrogenation, which diminishes the energy barrier and facilitates nucleation and growth, consequently reducing the operating temperature and improving the kinetics of hydrogen storage.
通过将 MgH(2) 引入 6LiBH(4)-CaH(2) 体系，实现了储氢性能的显著提高。研究发现，在 400°C 和 100 巴氢气压力下，6LiBH(4)-CaH(2)-3MgH(2) 复合材料可可逆储存约 8.0 重量%的氢气，优于原始的 6LiBH(4)-CaH(2) 和 LiBH(4) 样品。在脱氢过程中，MgH(2) 首先分解，在约 290°C 的起始温度下转化为 Mg 并释放氢气。随后，LiBH(4) 与 CaH(2) 反应，除了进一步释放氢气外，还形成了 CaB(6) 和 LiH。在非等温模型中，6LiBH(4)-CaH(2)-3MgH(2) 复合材料的氢气释放在约 430°C 时完成，与 6LiBH(4)-CaH(2) 样品相比，降低了 160°C。JMA 分析表明，氢气释放是扩散控制反应，而不是界面反应控制过程。第一步脱氢生成的新 Mg 可能作为第二步脱氢生成产物的非均相形核中心，降低了能量势垒，促进了形核和生长，从而降低了操作温度，提高了储氢动力学性能。
