Ce2Mg17及其氢化物添加剂对LiBH4的放氢作用机理研究

为改善LiBH4体系的可逆吸放氢性能,将Ce2Mg17合金(简称为CM)及其氢化物(CeH2.51和MgH2,简称为CMH)分别与LiBH4球磨4 h制得LiBH4-0.02CM和LiBH4-0.02CMH复合储氢体系,采用MS、TPD、XRD和FT-IR等测试手段研究了不同状态Ce-Mg添加剂对复合储氢体系可逆吸放氢性能的影响及其作用机制。结果表明:Ce2Mg17合金本身对改善LiBH4吸放氢性能没有明显作用;而Ce2Mg17氢化物(即MgH2和CeH2.51)可降低复合体系中LiBH4的放氢温度和提高LiBH4的放氢速率,并可明显改善体系的可逆吸放氢性能。进一步分析表明,MgH2和CeH2.51对LiBH4的协同改性作用是有效降低LiBH4热力学稳定性、提高LiBH4-Ce-Mg复合体系可逆吸放氢性能的主要原因。

Dehydrogenation Behavior and Mechanism of LiBH4 Doped with Ce2Mg17 and Its Hydride

LiBH4 was ball milled for 4 h with Ce2Mg17 (CM) and its hydride (CeH2.51 and MgH2, CMH) to prepared LiBH4-0.02CM and LiBH4-0.02CMH samples, respectively. Their dehydrogenation behavior and mechanism were experimentally investigated by MS, TPD, XRD and FT-IR techniques. It is found that Ce2Mg17-hydride of MgH2 and CeH2.51 effectively reduces the hydrogen desorption temperature and improves the dehydriding kinetics of LiBH4. However, Ce2Mg17 alloy exerts few favorable effects to the dehydrogenation behavior of LiBH4. In addition, partial reversibility is achieved for the LiBH4-0.02CMH system. The enhancement of the dehydrogenation and rehydrogenation is ascribed to the synergistic effect of MgH2 and CeH2.51, which reduces the thermodynamics stability of the system.