Fundamental investigation of de/rehydrogenation of metal borhydrides-mechanistic clarification and performance improvement

本文系统地研究了金属硼氢化物脱氢/再加氢的机理澄清和性能改进，重点研究了中间产物。由[BH4]生成的多原子阴离子[B12H12]2-是通过B-H阴离子的逐渐演化形成的，如[BH4]-→[B2H6]2-→[B5H9]2-→[B12H12]2-。反应性复合氢化物2LiBH4 + mgh2的脱氢在很大程度上取决于氢的压力，中间产物Li2B12H12的形成只有在低于1.0 MPa的压力下才会形成。脱氢后的Mg(BH4)2和Ca(BH4)2的再加氢性能不同，Ca(BH4)2的再加氢性能优于Mg(BH4)2。综上所述，控制金属硼氢化物脱氢过程中中间体的形成对于大幅度提高储氢性能具有重要意义。

Mechanistic clarification and performance improvement of de/rehydrogenation of metal borohydrides with a focus on intermediates have been systematically investigated. The formation of polyatomic anion [B12H12]2-from [BH4]-was found to occur via the gradual evolution of the B-H anion, such as [BH4]-→ [B2H6]2-→[B5H9]2-→ [B12H12]2-. Dehydrogenation of reactive composite hydrides 2LiBH4 + MgH2largely depends on the hydrogen pressure and the formation of intermediate Li2B12H12 was found to form only at pressures lower than 1.0 MPa. The different boron-related species between the dehydrogenated Mg(BH4)2 and Ca(BH4)2 would afford different rehydrogenation performance, i.e. Ca(BH4)2 showed better rehydrogenation than Mg(BH4)2.In conclusion, controlling of the formation of intermediates during the dehydrogenation of metal borohydrides would be of great importance for substantial improvement of hydrogen storage properties.