Hydrogen sorption properties of nanocrystalline Mg2FeH6-based complex and catalytic effect of TiO2

The diversities of hydrogen sorption properties of Mg₂FeH₆-based complexes with and without TiO₂ were investigated. Mg₂FeH₆-based complexes with and without TiO₂ were synthesized respectively by reactive mechanical alloying, and hydrogen sorption properties of the complexes were examined by Sieverts-type apparatus. The results show that the sample without TiO₂ releases 4.43 % (mass fraction) hydrogen in 1.5 ks at 653 K under 0.1 MPa H₂ pressure and absorbs 90% of the total 4.43 % (mass fraction) hydrogen absorbed in 85 s at 623 K under 4.0 MPa H₂ pressure. But for the sample with TiO₂ addition under the same condition, it only needs 400 s to release all of the stored hydrogen and 60 s to absorb 90% of the total hydrogen absorbed. The activation energies for desorption process of the samples with and without TiO₂ are determined to be 71.2 and 80.3 kJ/(mol·K), respectively. The improvement in hydrogen sorption rate and and reduction in activation energy can be attributed to the addition of TiO₂.     

LaNi_5对机械合金化合成Mg_2FeH_6基复合物放氢性能的影响

放氢性能是镁基储氢材料应用的关键。该研究采用机械合金化和熔炼的方法分别合成Mg2FeH6基复合物和LaNi5,然后将70%(质量分数)的Mg2FeH6基复合物和30%的LaNi5进行球磨复合,得到Mg2FeH6基复合物,研究LaNi5对Mg2FeH6基复合物放氢性能的影响。研究结果显示该复合物具有良好的放氢动力学性能,在553 K放氢量可达到1.46%(质量分数);在653 K下120 s内可释放总放氢量的80%,最终放氢量为3.6%。LaNi5的添加可降低Mg2FeH6基复合物的放氢温度,提高放氢速率。