基于X(X=Sc,Ce,Pr,Sm)单质原位球磨合成的NaAlH4储氢性能

Hydrogen Storage Properties of NaAlH4 Prepared Via in-situ Ball-milling Method Based on X(X=Sc,Ce,Pr,Sm) Additive

关键词:  铝氢化钠  储氢材料  配位氢化物  原位合成  催化效果  稀土元素

Key words:  sodium aluminium hydride  hydrogen storage materials  complex hydrides  in-situ synthesis  catalytic effects  rare earth elements

摘要:

为改善铝氢化钠（NaAlH₄）的储氢性能，以过渡元素和稀土元素X单质（X=Sc，Ce，Pr，Sm）、NaH和Al为反应物，基于预球磨和加氢球磨两步制备方法，原位合成被掺杂的NaAlH₄。XRD分析结果显示NaAlH₄合成效果很好，放氢也很彻底。吸放氢性能测试显示，添加Sc情况下首次放氢量最高（达5.2 wt%，达到理论容量的99%），并且有最好的吸氢动力学。添加稀土单质时的容量保持率都明显高于添加Sc的情况，其中添加Sm情况最好；添加Ce情况下起始放氢温度（90℃）最低，吸氢动力学是3种稀土元素中最好的，但其最大放氢量最低。这4种单质没有一种能在所有性能都位居最优。基于本文所采用低剂量单质掺杂剂原位合成的NaAlH₄表现出良好的储氢性能，主要是因为球磨过程中单质添加剂能与基体产生反应，原位产物能与基体形成紧密耦合，甚至从体内激活基体，从而获得良好的催化效果。

Abstract:

To improve the hydrogen storage properties of sodium aluminohydride (NaAlH₄),a transitional and rare earth element X element (X=Sc,Ce,Pr,Sm),NaH and Al were used as reactants.The doped NaAlH₄ was synthesized in situ based on a two-step preparation method of pre-ball milling and hydrogenation ball milling.The results of XRD analysis showed that the synthesis effect of NaAlH₄ was very good,and dehydrogenation was also carried out thoroughly.Under Sc-doped situation,the hydrogen absorption and desorption performance test showed that the first hydrogen release amount was the highest (up to 5.2 wt%,reaching 99% of the theoretical capacity),and there was the best hydrogen absorption kinetics.The capacity retention rate when adding rare earth element was significantly higher than that of adding Sc.When Sm was added,the capacity retention rate was the best.Under Ce-doped situation,the initial dehydrogenation temperature (90℃) was the lowest,and the kinetics of hydrogen absorption was the best among the three rare earth elements,but the maximum dehydrogenation capacity was the lowest.None of the four elements could rank the best in all performance.In this paper,doped low-dose element,NaAlH₄ synthesized with in-situ method exhibits good hydrogen storage performance.The main reason is that the elemental additive can react with the matrix during the ball milling process,the in situ product can form a tight coupling with the matrix and even activate the matrix from the body to obtain a good catalytic effect.